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The East Asian summer monsoon (EASM) variability on orbital time scale has been extensively investigated in Quaternary loess and speleothems. However, EASM variability during pre‐Quaternary time remains poorly understood. Here we report a continuous upper Miocene cyclostratigraphic record from lake deposits of the Tianshui basin, Northeast Tibet, to reconstruct past variations of the regional hydrological cycle. Our results, combined with previously published cyclostratigraphic records from Northeast Tibet, show that regional lake expansion cycles have been consistently dominated by ~100‐kyr eccentricity forcing over most of the middle to late Miocene. These ~100 kyr cycles corroborate a significant forcing of the East Asian hydrological cycle by Antarctic ice sheet variations at that time. It is, however, unclear if this forcing affected EASM intensity or westerly derived moisture supply to the far east. Regardless of the nature of the main source of precipitation in Northeast Tibet during the Miocene, these results emphasize the existence of a strong teleconnection between Antarctic ice sheet modulations and the continental climate of Asia. Key Points: Regional lake expansion cycles have been consistently dominated by 100‐kyr eccentricity forcing over most of the middle to late MioceneThese 100 kyr cycles corroborate with a significant forcing of the East Asian hydrological cycle by Antarctic ice sheet variationsThis study emphasizes the existence of a strong teleconnection between Antarctic ice sheet modulations and the continental climate of Asia [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Global Miocene last tectonic uplifts influenced sandstone-style uranium mineralization. • The tectonic uplift were 20–5 Ma while that of the uranium mineralization at 20–0.1 Ma. • The subtropical high pressure belts formed influenced the sandstone-style uranium deposits. Abstract The formation of sandstone-style uranium deposits are significantly controlled by the latest tectonic uplift events, especially those generated in an open system by the infiltration of meteoritic water. This study explores the spatiotemporal relationship between global Miocene tectonics and sandstone-style uranium deposits to evaluate the link between tectonic uplift and metallogenic ages. In general, modern landforms were shaped by diverse global tectonic events that began in the Middle and Late Miocene. This includes the formation of continental-scale faults and fold belts, including the uplift of the three broadly contemporaneous ranges, the Alpine–Himalayan Belt, the Cordillera, and the East African Rift. These events were accompanied by intense magmatic activity, as well as an increase in the spreading rates of oceanic ridges and higher sedimentation rates in the Pacific, Indian, and Atlantic oceans. Modern global climate patterns are a direct consequence of these Miocene tectonic events. Studies on sandstone-style uranium deposits report that though their stratigraphic ages extend from the Proterozoic to the Cenozoic, they notably occur from the Late Mesozoic to the Neogene. Uranium mineralization ages are concentrated between 20 and 0.1 Ma, clustering mainly in the Miocene although remobilizations are known to have occurred subsequently, some even in the Holocene. Global tectonics in the Miocene, between 20 and 5 Ma, resulting in the regional uplift of mountain ranges and continental tilts, may have exerted significant control over the migration directions of uranium-bearing fluids that formed these sandstone-style uranium deposits. Climate patterns in the Miocene, specifically subtropical high-pressure belts on both sides of the equator controlled the creation of arid and semi-arid areas, creating characteristic rainfall patterns which would also have influenced the spatial distribution of these uranium deposits. Thus, the spatiotemporal characteristics of most sandstone-style uranium deposits in the world were controlled by global tectonics in the Miocene that uplifted mountain ranges and tilted continents, generating subtropical high-pressure belts and the Asian high pressure region. In addition to new ideas adding greater research value to the study of global sandstone-style uranium mineralization, this paper also provides a new exploration indicator for sandstone-style uranium deposits. [ABSTRACT FROM AUTHOR]

Abstract The fossil crocodylomorph fauna of the Cenozoic of South America is very rich and diverse. Historically, few publications have been dedicated to providing an overall review of this fauna, with most reviews focusing on specific areas. However, the fact that many new species, taxonomic reviews and description of new specimens have been proposed in the last decade makes a comprehensive review of the fossil crocodylomorph fauna of the South American Cenozoic necessary. The only crocodylomorph lineages to have a fossil record comprising Late Cretaceous and Cenozoic deposits in South America is the Dyrosauridae. Sebecidae or its predecessors, however, are very likely to have inhabited the continent during the Cretaceous-Paleogene transition as well; both Dyrosauridae and Sebecidae are considered here to have survived the Cretaceous-Paleogene extinction while inhabiting South America. Caimaninae (Alligatoroidea) arrived either in the late Cretaceous or in the early Paleocene coming from North America. The fossil record of Caimaninae is present, however, only from the Paleocene. By the Eocene, there are no records of Dyrosauridae in South America; this group was globally extinct after the Eocene, possibly due to the global cooling that occurred by the end of the epoch. Sebecids and caimanines solely comprised the crocodylomorph fauna of the continent until the Miocene, where there are the first records of Gavialoidea (Gryposuchinae) and a possible first dispersion of Crocodyloidea, through the tentative tomistomines Charactosuchus and Brasilosuchus. Gryposuchinae likely arrived in the continent from Africa or from Asia during the Oligocene. Charactosuchus and Brasilosuchus may have come from North America where tomistomines lived from the Oligocene to the Pliocene. Sebecids were extinct after the middle Miocene; Charactosuchus , Gryposuchinae, Purussaurus , Mourasuchus and durophagous caimanines such as Gnatusuchus were extinct after the late Miocene. These extinctions are related to changes in the drainage basins caused by elevation of the Andes mountain range. Only the extant caimanine Caiman , Melanosuchus and Paleosuchus would survive the Miocene, being enriched by Crocodylus from the Pliocene onwards, which is likely that Crocodylus arrived in the American continents from Africa. The current fossil record indicates that these four genera comprise the extant crocodylian fauna of the continent since the Pliocene. Although our knowledge on crocodylomorph fossil fauna of the South American Cenozoic has increased continuosly, especially in the last decade, much yet must be done, especially on the taxonomy and phylogeny of Brasilosuchus and Charactosuchus , fieldworks in Paleogene and Pliocene localities, and the evolution of the specialized Caimaninae morphotypes. Highlights • This paper is a review of the South American fossil crocodylomorph fauna. • The fauna is comprised mainly by Dyrosauride, Sebecidae and Caimanine during the Paleogene. • Gavialoids arrived between the Paleogene and the Neogene. • End of Miocene: geomorphological changes in the continent caused the extinction of many taxa. • Caiman, Melanosuchus, Paleosuchus and Crocodylus solely comprise the fauna from the Pliocene onwards. [ABSTRACT FROM AUTHOR]

Abstract The Eastern Marlim oilfield, located in the northeastern offshore of the Campos Basin, is a portion of the Marlim Complex, one of the most important oil accumulations ever found in Brazil. This paper presents findings from lithofacies, sequence stratigraphy and petrophysical analyses for the Oligocene-Miocene section of the Eastern Marlim oilfield. Here, we evaluate at least four main lithofacies associations and three major zones recognized in the latter section, presenting sedimentological and stratigraphical interpretations based on stratigraphic correlations, distribution and sand proportion maps, and accompanying petrophysical analysis. Our findings suggest at least two bipartite turbiditic flows representing different stages of deposition associated with a deep-water turbidite sequence, composing the elements of a submarine lobe complex. Massive unconsolidated amalgamated sandstone bodies, displaying very good porosity, lateral and vertical continuity, reflecting excellent reservoirs. The final depositional model of the studied Oligocene-Miocene interval in this work is part of the first-order Highstand System Tract (HST) of the Campos Basin, which in turn represents a second-order, exploration-scale depositional sequence. Finally, the sequence stratigraphic model of the Oligocene-Miocene section of the Eastern Marlim oilfield has an architecture similar to those that have been developed from Oligocene-Miocene global sea level changes. Highlights • A lithofacies, sequence stratigraphic and petrophysical evaluation is proposed for the Eastern Marlim oilfield. • Four main lithofacies and three major zones were recognized. • Two-bipartite turbiditic flows represent different stages of deposition. • A deep-water submarine lobe complex was identified. • The studied section represent a first order HST and a second order depositional sequence. [ABSTRACT FROM AUTHOR]

During the 2007 ANtarctic geological DRILLing (ANDRILL) campaign in the Ross Sea, Antarctica, the AND‐2A core was recovered through a stratigraphic succession spanning 1,138.54 m of Neogene sedimentary rocks that include an expanded early to middle Miocene sequence. The study reported here focuses on the magnetic properties of the interval from 778.63 m below sea floor (mbsf) to 1,138.54 mbsf, which comprises a time interval spanning 1.5 Myr, from ~18.7 to ~20.2 Ma. We recognize three main pulses of increased input of magnetic materials to the drill site between 778.34–903.06, 950.55–995.78, and 1,040–1,103.96 mbsf. Trends in the magnetic mineral concentration dependent parameters mirror changes in the proportion of sediments derived from McMurdo Volcanic Group rocks. We suggest that these pulses in magnetic mineral concentration reflect changes in sediment transport processes associated with changing glacial conditions at the drill site that included (1) subglacial and grounding zone proximal settings, (2) hemipelagic and neritic conditions with abundant sediment‐rich icebergs, and (3) grounding zone‐distal environment that was covered by land‐fast multiyear sea ice or a fringing ice shelf. The magnetic minerals record preserved in the AND‐2A core supports other data that indicate a highly dynamic and variable coastal environment during the early Miocene, where glaciers retreated inland under warm climatic conditions and advanced beyond the drill site across the continental shelf when cold climate prevailed. Key Points: We investigate Miocene glacial dynamics recorded by variations in magnetic properties in the ANDRILL‐2A drill corePulses in magnetic mineral concentration reflect changes in sediment transport processes associated with changing glacial conditionsWe refine previous environmental interpretations and delineate a complex early Miocene paleoenvironment in the southern McMurdo Sound [ABSTRACT FROM AUTHOR]

The stratigraphic reinterpretation of the palynologically analysed Miocene succession of the Wijshagen borehole along the southern margin of the North Sea Basin allowed an age assessment – late Burdigalian to early Serravalian – for the Genk Sand Member of the Bolderberg Formation. The depositional environment varied during Burdigalian to Serravalian times from continental (peat formation) to open marine (glauconitic sands), respectively from south to north in the Roer Valley Rift System. The study area of the Wijshagen borehole is located in the central part of the Roer Valley Rift System between these extreme environments. During the Burdigalian, the glauconitic fine clayey sands of the Houthalen Sand Member were deposited in the study area. From the late Burdigalian onwards, the glauconite content decreased and lignite content increased as a result of high influx of clastic material in the Roer Valley Rift System, and marked the start of the deposition of the Genk Sand Member. The Genk Sand Member shows an overall coarsening-upwards trend, which is consistent with the gradual infill of the available accommodation space in the Roer Valley Rift System by northwest-prograding clastic delta sequences. Dinoflagellate cyst analyses indicate that the Genk Sand Member was largely deposited in a marginal marine environment with only short pulses of continental input. These pulses of continental input increase in a southerly or landward direction where they led to the development of thick lignite seams. [ABSTRACT FROM AUTHOR]

The morphological variability of two biostratigraphically important diatom species of the Russian Far East, Alveolophora areolata (Moisseeva) Moisseeva and Alveolophora bifaria Nevretdinova et Moisseeva,was studied using light and scanning electron microscopy. High variability was found in mantle height, diameter, stria organization, areola location on the valve face, alveolus structure and costae of A. bifaria, but less variability in A. areolata. Separation valves of A. areolata lack spines, and rimoportulae were found on the valve face for the first time. Based on the new morphological data, descriptions for these taxa have been emended. [ABSTRACT FROM AUTHOR]

Abstract The origin of magma at Libya's volcanic provinces is still poorly understood. In order to constrain these sources we report results of the first P-to-S receiver function investigation of the 410 km and 660 km depth discontinuities bounding the mantle transition zone (MTZ) beneath Libya. The dataset used by this study is a combination of eighteen seismic stations belonging to the Libyan Center for Remote Sensing and Space Science and the Incorporated Research Institutions for Seismology Data Management Center. The average thickness of the MTZ is found to be 249 ± 14 km, which is similar to the global average. A 10 km thinning of the MTZ was observed beneath the Miocene – Holocene volcanic provinces in central Libya, suggesting higher-than-normal temperatures in those parts of the MTZ. Our preferred model suggests that the origin of volcanism in Libya is due to higher temperatures in the MTZ beneath this region. However, in Eastern Libya, the thickness of the MTZ increases from 249 km to 270 km which indicates a colder-than-normal MTZ which may relate to ancient subducted slabs due to the Africa-Europe convergence since the late Mesozoic. [ABSTRACT FROM AUTHOR]

Highlights • Miocene coarse clastic formation in Israel is correlated with truncated doming in Southern Jordan. • Both point to rift related doming in Southern Jordan, starting at 18 Ma, which failed to develop further. • Rift failure probably happened due to final suturing on the orthogonal to plate movement continental collision zone in the Zagros Mountains. • As a result, the Arabian plate shifted to a more northerly direction of movement and the Dead Sea Transform was initiated. • Mantle Hot spot activity is presently located in West Central Jordan, as evidenced by higher Moho and P wave anomalies. Abstract Development of the Red Sea and the Dead Sea Rift is preceded by regional scale uplift and erosional truncation. Associated with this regional uplift, towards its final stages at the early Miocene, are volcanic fields and mafic dike intrusion. On top of the regional uplift, near its northern edge, we recognize in Southern Jordan-Northwestern Saudi Arabia evidence for local smaller scale swell (200 km by 400 km) developing in the Mid Miocene (starting around 18 Ma) which are interpreted as related to the initial stages of rifting in this area, as continental breakup progresses to the north from the Red Sea. Presence of thick Neogene clastic formations in southern Israel and Jordan whose base is dated to 17.9 Ma, is taken as indication for the presence of Neogene (ca 18–8 Ma) rift related doming in Southern Jordan and NW Saudi Arabia. This incipient rifting failed to develop due to the final stages of continental collision in the Zagros mountains in Iran which occurred at the same time. Similar explanation is proposed for the NW-SE trending Gulf of Suez which was abandoned as strongly active rift at the Serravalian (13.7–11.6 Ma, Bosworth et al., 2005). In place of this failed rifting, plate movement re-adjustment took place and plate movement on the Dead Sea Transform (DST) was initiated between 20 Ma (Nuriel et al., 2017) and 14 Ma (Bosworth et al., 2005). Evidence from Neogene stratigraphy, basement structural maps, distribution of fracture zones, timing of volcanism, presence of mud volcanoes, changes in Arabia plate movement directions and geophysical data are presented in support of this interpretation. Present day anomalies in moho elevations, P wave velocities and asymmetries in S wave responses in the north part of this zone are added as support for continuation of mantle plume activity in this area, which started in the early Miocene. We propose this plume evolved independently from the activity in Saudi Arabia and the Red Sea, preceding it by 3–4 Ma, with doming initiated at 18 Ma and volcanism at 13 Ma. [ABSTRACT FROM AUTHOR]

Abstract During the Messinian Salinity Crisis (MSC), between 5.97 and 5.33 Ma, the marine connections between the Atlantic Ocean and the Mediterranean Sea were temporarily restricted. The post-MSC reflooding of the Mediterranean Sea by the Atlantic waters and its sedimentary record are debated. The Boudinar basin (North-Morocco) provides an exceptional record of this period between ca 5.32–5.27 and 4.37 Ma at youngest (Zanclean - Zone PL1). The sedimentary succession of this basin comprises seven facies associations corresponding to depositional settings ranging from continental to open marine environments. We provide a new sequence stratigraphic framework, based on twelve stratigraphic sections. Two orders of depositional sequences (4th, 3rd order), related to base-level changes during the Late-Messinian Early-Pliocene time interval, are correlated at the basin scale. According to our reconstruction, the post-MSC base level rise and the Zanclean reflooding lasted from a minimum of several tens up to hundreds thousands years, suggesting a gradual, not catastrophic event indicative of a progressive transgression. Highligths • Two orders of sequences (4th, 3rd order) were correlated during the Late-Messinian Early-Pliocene. • The sea-level drop during the Messinian Salinity Crisis (MSC) was of limited amplitude. • The post-MSC transgression does not match with the rapid and sudden reflooding scenario. [ABSTRACT FROM AUTHOR]

The paper deals with the structure and evolution of the Pieniny Klippen Belt in its classic area in western Slovakia. The so-called Peri-Klippen Zone provides a transition from the Pieniny Klippen Belt s.s. built up by Jurassic to Eocene Oravic units (Šariš, Subpieniny and Pieniny from bottom to top) to the outer margin of the Central Western Carpathians composed of Triassic to mid-Cretaceous successions of the Fatric and Hronic cover nappe systems. The Peri-Klippen Zone attains a considerable width of 15 km in the Middle Váh River Valley, where it is composed of the supposedly Fatric Manín, Klape and Drietoma units, as well as their post-emplacement, Gosau-type sedimentary cover. All these units are tightly folded and imbricated. The complex sedimentary and structural rock records indicate the late Turonian emplacement of the frontal Fatric nappes in a position adjacent to or above the inner Oravic elements, whereby they became constituents of an accretionary wedge developing in response of subduction of the South Penninic– Vahic oceanic realm separating the Central Western Carpathians and the Oravic domain. Evolution of the wedge-top Gosau depressions and the trench-foredeep basins of the foreland Oravic area exhibit close mutual relationships controlled by the wedge dynamics. The kinematic and palaeostress analyses of fold and fault structures revealed only one dominating stress system coeval with development of the accretionary wedge, which is characterized by the generally NW–SE oriented main compression axis operating in a pure compressional to dextral transpressional regime, interrupted by short-term extensional events related to the wedge collapse stages. Younger, Miocene to Quaternary palaeostress fields correspond to those widely recorded in the entire Western Carpathians. Relying on the regional tectonostratigraphic and structural data, the problematic issues of the palaeogeographic settings of the Manín and Klape units, presumably affiliated with the Fatric cover nappe system, and of the provenance of numerous olistoliths occurring at different stratigraphic levels are then discussed in a broader context. [ABSTRACT FROM AUTHOR]

The preservation of conglomerates far from mountainous sources is commonly interpreted in terms of tectonic or climatic forcing. To relate a depositional signal to changing conditions in source areas, the process and duration of sediment routing from source to sink need to be determined. For the first time, we quantified sediment transport histories using cosmogenic 21Ne in quartzite pebbles from modern river gravels and Neogene conglomerates from the modern and ancient North Platte River of the Great Plains of Nebraska, United States. We demonstrate that at ~400 km distance from the Front Ranges of the Rocky Mountains, the majority of pebbles were stored in older channel deposits for up to several millions of years before being recycled; this was enabled by very slow to zero basin subsidence rates. This implies that upstream tectonic or climatic controls on surface processes were decoupled from the downstream depositional record--a result supported by the similarities in cosmogenic 21Ne values among Miocene, Pliocene, and modern river channel pebbles despite known changes in tectonic and climatic forcing. [ABSTRACT FROM AUTHOR]

Abstract The Mid-Miocene Climatic Optimum (MMCO) is one of Earth's most recent prolonged warming events, recorded in both the deep ocean and mid- to high-latitude continents. Thick Cenozoic deposits in the Longzhong Basin, Northwest China, provide great potential for characterizing the MMCO, but have not been well documented. In this study, we carry out clay mineralogical and geochemical analyses of the Miocene red clay succession from the eastern Longzhong Basin, employing X-ray diffraction and geochemistry, and discuss the climatic characteristics of the MMCO. The results reveal that the MMCO occurred at 16–14 Ma and is associated with relatively high kaolinite and smectite contents, high illite crystallinity values and kaolinite/(illite + chlorite) ratio, and lower chlorite and illite contents. These clay mineral assemblages confirm a warm and moist climate during the MMCO. Furthermore, the SiO 2 /Al 2 O 3 ratio declined with increasing Al 2 O 3 , indicative of greater precipitation and intensified weathering during this period. When compared with local and global records, we find that our clay mineral records reflect regional climatic change superimposed upon global climatic trends during the MMCO. It is suggested that a high concentration of CO 2 , and associated global warming, may have been responsible for the MMCO, rather than the uplift of the Tibetan Plateau. Highlights • Mid-Miocene Climatic Optimum (MMCO) at 16–14 Ma recorded by clay minerals • MMCO in the Longzhong basin characterized by a warm and moist climatic environment • High CO 2 and global warming, rather than tectonic activity, may have caused the MMCO event. [ABSTRACT FROM AUTHOR]

Core study of two wells drilled in the southeastern part of the Nile Delta reveals a sub-basin in northern Egypt from the Carboniferous-Permian up to the post-Miocene. The drilled sections are approximately 2600 m thick in the Ubur well in the east and about 3238 m thick in the Orabi well to the west. Basement rocks are recorded in the eastern side of the sub-basin, whereas drilling reached only Lower Cretaceous rocks in the west. The faulting movements played the most important factor determining the distribution, lateral facies changes and unconformities between the different rock units across the sub-basin. The reversal of the faulted blocks over time led to different thicknesses of the drilled units. During the Paleogene, the downfaulted western Orabi part of the sub-basin received up to 1163 m of Paleocene-Eocene sediments, whereas only 203 m were deposited in the eastern uplifted Ubur part. During the Miocene, reversal of the sub-basin taphonomy took place leading to deposition of a thick Miocene section (898 m) in the downfaulted Ubur eastern part, whereas minor thickness (387 m) of the Miocene sediments were laid down in the high Orabi western part of the sub-basin. The stratigraphy of sections drilled is more related to the north Eastern Desert and Sinai rather than to the Western Desert facies. During the Miocene, stratigraphy of the rock units and their facies are a continuation of the Mediterranean subsurface in northern Sinai and eastern Nile Delta facies. [ABSTRACT FROM AUTHOR]

Abstract In the southern Gulf of Mexico, deepwater sediments were affected during deposition by contractional and extensional deformation events and halokinesis. The Miocene reservoirs in this area were deposited in slope and basinal settings during the falling-stage systems tracts and the lowstand systems tracts, where channel and frontal splay depositional elements were the most important. The integration of the structural analysis with seismic data, seismic attributes and isochron maps allows us to evaluate how the deformational events (especially the contractional event D3) controlled the distribution of sediments and the external geometry of their deposits. This interplay between deformation and sedimentation mainly occurred in two ways. First, the structural elements modified the paleobathymetry of the basin and created an accommodation space for clastic deposition. Second, the structural features controlled the entry of sediments. During the Oligocene and early Miocene, the depocenters were bounded by diapirs, salt sheets and structural highs formed by older salt anticlines. On the other hand, for the middle Miocene, the depocenters were controlled by the presence of folds in the southern part of the study area and by shortened diapirs and salt sheets in the periphery. The formation of these depocenters provided the accommodation space for sediment deposition; as a result, during the early and middle Miocene, the frontal splays were confined to these depocenters. At the end of the middle Miocene, these depocenters were filled, and channel levee systems and frontal splay complexes predominated. Finally, during the late Miocene, the depocenters formation was controlled by the extensional event, which provided the accommodation space for sediment deposition in half-grabens, where frontal splays complexes and channel levee systems were the most important depositional elements. All of these structural elements had significant implications for the architecture and internal organization of the turbidite systems. Highlights • Reservoirs were deposited in the slope during the falling-stage and lowstand systems tracts. • Structural elements modified the paleotopography of the basin creating accommodation space. • Structural elements controlled the entry of sediments. • Deformation events had implications in the architecture and organization of turbidites. [ABSTRACT FROM AUTHOR]

Abstract Old and new specimens from the early Miocene middle member of the Mariño Formation (Mendoza, Argentina) allow for a reinterpretation of a controversial Mesotheriidae taxon. Earlier known remains come from the Divisadero Largo locality and were, depending on the specimen, either previously described as Trachytherus? mendocensis or referred to a coeval taxon from Chile, Altitypotherium chucalensis. Based on new specimens, here described in detail for the first time, we propose that all mesotheriid material from Divisadero Largo, as well as new material from the Potrerillos locality belong to a new mesotheriid taxon. Recognition of the same taxon from these two localities establishes a sound biostratigraphic correlation. The combination of morphological characters leads to the proposal of a new generic name, Rusconitherium , for Trachytherus? mendocensis , establishing Rusconitherium mendocense New genus and New Combination. This nomenclatural act is due to the fact that T.? mendocensis , formerly thought as a Trachytheriinae from the Paleogene Divisadero Largo Formation, actually comes from the Mariño Formation and belongs to the same taxon as the new material. The missing holotype of T.? mendocensis prompts us to propose a neotype and a new diagnosis for this species, which better characterize the Santacrucian mesotheriids from Mendoza. A phylogenetic analysis does not support a close relationship between this species and Altitypotherium (or any other mesotheriine genus) counter to a previous hypothesis. An unnamed new taxon from the Chinches Formation (San Juan Province) could belong to Rusconitherium , but its full description is pending, as well as a thorough revision of most Mesotheriinae members. Sediments at Potrerillos reveal two paleoenvironmental scenarios: dune fields, influenced by volcanic events, and capillary water that provided humid conditions encouraging vegetation and fauna. Highlights • A new mesotheriid genus from the Miocene Mariño Formation, NW Argentina, is described. • A new taxonomic combination and a neotype are proposed. • Sedimentary and paleoenvironmental approaches are provided for the Potrerillos locality. [ABSTRACT FROM AUTHOR]

Abstract The Gualcamayo Igneous Complex is located over the Pampean flat-slab segment (28–33°S), ∼110 km eastward from the Upper Miocene front arc position. It consists of subvolcanic rocks that are affected by porphyry-type hydrothermal alteration, and are genetically linked to a cluster of Carlin-type, skarn and epithermal gold deposits at the Gualcamayo mining district. The petrogenetic analysis of these volcanic rocks allows suggesting that this late Miocene (∼9 Ma) arc-related magmatism with an adakitic signature derives from asthenospheric mantle magmas that under thickened crust conditions, evolved through amphibole fractionation with lower crust melting, probably involving Grenvillian amphibolites from the basement of the Precordillera. These melts evolved towards shallower magma chambers, where they fractionated amphibole and plagioclase, leading to a variable adakitic signal. Graphical abstract Image 1 Highlights • The volcanic rocks of the Gualcamayo mining district represent the late Miocene (∼ 9 Ma) arc mineralizing magmatism ∼ 110 km eastward from the Upper Miocene front arc position. • They come from, hydrous and oxidized magmas with a variable adakite signature which is recognizable despite the hydrothermal alteration that affects these rocks. • The magmas that ultimately derived from an asthenospheric mantle evolved, under thickened crust through an amphibole fractionation with lower crust melting (wich probably involved Grenvillian amphibolites) complementing the high-pressure conditions. [ABSTRACT FROM AUTHOR]

The Oligocene–Miocene carbonate record of the Zagros Mountains, known as the Asmari Formation, constitutes an important hydrocarbon reservoir in southern Iran. This marine carbonate succession, which developed under tropical conditions, is explored in terms of larger foraminiferal biostratigraphy, facies analysis and sequence stratigraphy in a new section at Papoon cropping out in the western Fars sub‐basin, in the south‐east of the Zagros belt. Facies analysis shows evidence of re‐working and transport of skeletal components throughout the depositional system, interpreted here as a carbonate ramp. The foraminifera‐based biozones identified include the Globigerina–Turborotalia cerroazulensis–Hantkenina Zone and Nummulites vascus–Nummulites fichteli Zone, both of Rupelian age, the Archaias asmaricus–Archaias hensoni–Miogypsinoides complanatus Zone of Chattian age and the 'Indeterminate' Zone of Aquitanian age. The vertical sedimentary evolution of the formation exhibits a progressive shallowing of the facies belts and thus the succession is interpreted as a high‐rank low‐order regressive systems tract. This long‐lasting Rupelian–Aquitanian regressive event is in accordance with accepted global long‐term eustatic curves. Accordingly, long‐term eustatic trends would have been a factor controlling accommodation during the deposition of the Asmari Formation studied in the western Fars sub‐basin. [ABSTRACT FROM AUTHOR]

The Xining basin is located in the northeastern margin of the Qinghai‐Tibet Plateau. It is a rift basin formed in Mesozoic and Cenozoic and structurally belongs to the intersection of Kunlun and Qilian Mountains. Cenozoic fluvial and lacustrine sedimentary strata are continuous in the Xining basin, with a thickness of more than 800 m, completely recording the deformation uplifting, weathering and denudation history and climate change process of the northeastern plateau. Currently, early Miocene Xijia fauna, early Middle Miocene Danshuilu fauna and late Middle Miocene Diaogou fauna are discovered in the Xining basin, which provide an important basis for the stratigraphic correlation of the Cenozoic strata in the Xining basin. However, in the next few decades, there are no reports about the large mammal fossils in the Xining basin, especially about late Miocene fauna. The author discovered a large amount of mammal fossils in the Neogene sedimentary strata in Huzhu area, Xining basin. According to the identification results of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, these fossils mainly included Hipparion dongxiangense, Chilotherium sp., Parelasmotherium sp., Stephanocemas sp. and Kubanochoerus sp. and their age was early Late Miocene. Since the discovery of this set of fossils directly filled the blank that there were no large mammal fossils in the Xining basin in Late Miocene, it was very important for studying the magnetic stratigraphic chronology of fossil‐forming strata and establishing the paleomagnetic chronology scale plate of mammal fossils. In this paper, the paleomagnetic data of the fossil‐forming stratigraphic profile, Banyan profile, were measured and the paleomagnetic records were collected through high density sampling, and finally the paleomagnetic polarity column of the profile was established. The results showed that five positive and five negative polarity segments were recorded in Banyan profile, which corresponded well to the polarity between C3Br.1n‐C4n.2n in the standard polarity column. The age of profile top was about 7.25 Ma and profile bottom was about 8.4 Ma, with an age range of 1.15 Ma. The mammal fossils discovered this time were exposed between positive and negative polarities N5 and R5 at the bottom of the profile, corresponding to C4r.1r at negative polarity and C4n.2n at positive polarity in the standard polarity column. The age of mammal fossils was about 8.3 Ma. The paleomagnetic chronology of the strata and paleontological fossils determined the absolute age of late Miocene mammal fossils and expanded the upper age of late Miocene Xianshuihe Formation (N1xn) in the Xining basin, which had provided new basic data for further studying the stratigraphic deposition and correlation of late Cenozoic strata and regional environmental evolution. [ABSTRACT FROM AUTHOR]

Highlights • Seep carbonates are hotsted in Miocene marine mudstone of the Kuohsing area, Taiwan. • Carbon isotope signals were strongly altered, but REE compositions remain unaffected. • Negative δ13C of −47.6‰ was recognized as a near-primary isotopic signature. • Carbonates show MREE enrichment, no La and Ce anomalies, and supra-chondritic Y/Ho. • Carbonates were formed in reducing seep fluids with limited admixture of seawater. Abstract Hydrocarbon-seep carbonates were discovered to be hosted within Miocene marine mudstone in the central Western Foothills near the Kuohsing area, Central Taiwan. Here, we present field observations, petrography, mineralogy, stable carbon isotope data, as well as rare earth element compositions. We evaluate the role of diagenetic alteration on the Kuohsing seep carbonates and constrain their fluid sources and formation conditions. Four main morphologies in the field were observed, including cylindrical columns, massive forms, lenticular nodules, and stratiform bodies. Petrographically, the carbonates are predominantly composed of partially recrystallized calcite and dolomite, with abundant amounts of biogenic detritus, pyrite aggregations and unidentified filaments. Isotopic analyses show that carbon isotope values inversely vary with oxygen isotope values, indicating substantial modification of the carbon isotope compositions of the carbonates by diagenetic processes. Extremely negative δ13C values as low as −47.6‰ recognized as a near-primary isotopic signature recorded in the carbonates, an end member of the trend, reveals that methane was incorporated during the carbonate precipitation. On the other hand, the carbonates have well preserved primary REE compositions, exhibiting MREE enrichment, no La and Ce anomalies, and supra-chondritic Y/Ho ratios. These REE patterns suggest that the Kuohsing authigenic carbonates were precipitated from reducing seep fluids with limited admixture of seawater. [ABSTRACT FROM AUTHOR]

Abstract: Planktonic and benthic foraminiferal assemblages from the upper Tortonian-lower Messinian part of the Gibliscemi section (Sicily, Italy), are described. The major stratigraphic markers recorded in the section are (1) the first occurrence of Globigerinoides extremus marking the lower boundary of the corresponding upper Tortonian zone, (2) first occurrence of Globorotalia miotumida that previously was considered as an index form of the Tortonian-Messinian boundary, and (3) the first regular occurrence of Globorotalia conomiozea recording this boundary. The distribution in the section of keeled Globorotalia and Globorotalia miotumida group is traced. The composition of the Globorotalia scitula group is analyzed and the group is proposed to be identified as one species G. praescitula. It is assumed that the Mediterranean in the Middle and Late Miocene was the site where Globigerinoides ruber survived during its complete disappearance in the Atlantic and Pacific. [ABSTRACT FROM AUTHOR]

The Adana Basin is one of the major Neogene basins situated in SW Turkey with sedimentary successions providing good records of the paleoenvironmental changes that affected the Mediterranean area. Since a detailed biochronostratigraphic framework has not been properly established in the Adana Basin yet, this study will be the first multidisciplinary approach carried out in this region. In addition, a detailed biozonation based on marine palynomorphs was the first ever documented from the Köpekli Formation deposited during the Miocene (from late Burdigalian to Langhian) and the established biozones were correlated with those of planktonic foraminifera and calcareous nannofossils. According to the first occurrences (FOs) and the last occurrences (LOs) of selected taxa, five biozones (P-1, P-2, P-3, P-4 and P-5) based on dinoflagellate cysts; five biozones (M4a, M4b, M5a, M5b and M6) based on planktonic foraminifera; and two biozones (NN4 and NN5) based on calcareous nannofossils were established in the Miocene Köpekli Formation. In order to achieve a worldwide biostratigraphic perspective based on dinoflagellate cysts, the present biozones were compared with those described from NW Europe (Denmark, Germany, the Netherlands), the East Coast of the US and Egypt. After calibration to the established Turkish foraminifera and nannofossils standard, the palynological analysis shows that the recorded dinoflagellate cysts events (e.g. FO of Labyrinthodinium truncatum, Cerebrocysta poulsenii and Unipontidinium aquaeductus and LO of Palaeocystodinium ventricosum) occurred chronostratigraphically earlier in SE Turkey than in NW Europe and on the East Coast of the US. [ABSTRACT FROM AUTHOR]

This study documents soft-sediment deformation structures in the lacustrine Bigadiç Basin, one of the early Miocene terrestrial basins in the extensional tectonomagmatic province of northwestern Anatolia. The focus is on the Upper Borate Unit of the basin-fill succession, which consists of sedimentary facies including massive conglomerates, stratified sandstones, siltstones, organic-rich claystones, laminated limestones, organic-rich limestones, marlstones, borates and volcaniclastics. Their deposition, including borates, occurred in a deep lacustrine environment. Possible phases of lake shallowing are represented by stratified sandstones facies. Soft-sediment deformation features include small-scale folds formed by convolution with occasional basal décollement (minor slumps); load casts and related flame structures; fragmented and mixed beds, brecciated by pore-water explusion; shallow- and deep-rooted synsedimentary extensional faults with related neptunian dykes; and large slump sheets of thick bed packages with recumbent folds. These deformation features are interpreted to be of seismo-tectonic and seismo-volcanic origin, related to syndepositional strike-slip faulting and volcanic eruptions. Seismic tremors combined with the basin floor updoming by magma intrusions caused deep-rooted normal faults and intra-basinal slumps tens of metres thick. The study may serve as a guide to similar deformation structures in the underlying part of the Bigadiç lake-fill succession and in the other Neogene basins of northwestern Anatolia – which shared the region's seismo-tectonic, magmatic, palaeogeographic and sedimentation history. [ABSTRACT FROM AUTHOR]

The Pajares calcrete in Central Spain, a modern calcrete, consists of an accumulation of powder carbonate around the roots of living trees and bushes which penetrates Miocene deposits by more than 3 m. Calcrete development is mostly vertical and oblique, but thinner horizontal calcified root mats also occur. Carbonate accumulation, up to 15 cm thick, is made up of micrite with some etched clasts, alveolar septal structures, calcified rootlets, coated grains and micrite grains. In detail many of these features are composed of needle fibre calcite and micro-rods. Accumulation of carbonate was produced both by roots through direct calcification of their cells and also by microbial activity within the rhizosphere. This case study provides a good example of how carbonate is accumulating around roots at present and may allow better understanding of ancient calcretes, especially those which formed directly around roots in direct contact with the host rock. In addition the calcrete's setting, and its occurrence around roots belonging to various types of plants, suggest that carbonate accumulation in modern landscapes may be a relatively rapid, common process even in erosive regimes, and unrelated to specific vegetation types. [ABSTRACT FROM AUTHOR]

Abstract The Turkana Depression is a structurally complex and long-lived segment of the East African Rift System (EARS), with associated magmatism and strain nucleating there in the late Paleogene. The anomalously wide, ~N-S rift zone defines the topographic lowlands separating the Ethiopian and East African Domes. The atypical architecture and morphology of the Turkana Depression has often been attributed to the influence of an oblique, pre-existing lithospheric heterogeneity speculated to result from earlier Cretaceous-early Paleogene Anza-South Sudan rifting. However, this hypothesized period of earlier rifting is poorly constrained due to the obscuring effects of extensive Cenozoic rifting and volcanism. Similarly, the extent and timing of basin formation during the initial stages of EARS extension in Turkana is not well understood. Seismic reflection studies in Turkana have revealed the presence of older, possibly late Paleogene sub-basins, predating the Neogene onset of major faulting elsewhere in the EARS. One example, the Lothidok Basin, has previously been imaged beneath the late Miocene-Pliocene North Lokichar Basin. Its age, however, is unconstrained due to a lack of well controls, geochronological constraints and outcrop of its basal unit. Here, we present a multiple low-temperature thermochronometer [apatite fission track, apatite (U-Th-Sm)/He and zircon (U-Th)/He] study performed on Precambrian basement samples from the western margin of the overlying North Lokichar Basin. Thermal history modelling reveals a polyphase Late Cretaceous-Recent tectono-thermal evolution providing new insights into pre-EARS tectonism in Turkana and subsequent, late Paleogene ~E-W extension. Pronounced Late Cretaceous-Paleogene denudational cooling challenges the theorized linkage of the Anza-South Sudan Rifts in Turkana, perhaps suggesting later Paleogene tectonism played a more critical role in modifying the lithosphere. Subsequent Oligocene-early Miocene reheating is interpreted as resulting from burial beneath ~200–800 m of overburden, accordant with the proposed formation of the Lothidok Basin and/or coeval emplacement of thick lava flows in the region. Highlights • Marked Late Cretaceous-Paleogene denudation of southern Turkana • Inconsistent with linkage of Cretaceous Anza-South Sudan Rifts in Turkana • ~30–10 Ma reheating related to burial during formation of Lothidok Basin • Late Miocene-Pliocene cooling marks formation of North Lokichar Basin. [ABSTRACT FROM AUTHOR]

The Sarajevo-Zenica Basin of Bosnia-Herzegovina was part of the Dinaride Lake System, a large network of Miocene long-lived freshwater basins in southeastern Europe. The basin contains a thick sedimentary succession of carbonates, coals and mixed siliciclastic deposits that reflects the paleoclimatic and tectonic evolution of the region. In this study, we present novel integrated (magneto-bio)stratigraphic and sedimentological data and reconstruct the paleoenvironmental evolution of the Sarajevo-Zenica Basin during its two main evolutionary phases (thrusting and extension). The basal “Oligo-Miocene” freshwater paleoenvironments are characterized by alternating palustrine, shallow lacustrine and distal fluvial phases. The base level fluctuations are largely controlled by syn-sedimentary pulses of tectonic loading during the final phase of thrusting in the Internal Dinarides. The majority of this succession is considered early Miocene in age, which contrasts with previous Oligocene age estimates. The subsequent extensional phase initiated not later than ~18.4 Ma. This coarsening upward sequence of lacustrine carbonates, silts, sands and conglomerates is correlated between 17.2 and 15 Ma (C5Cr-C5Br) by means of integrated bio-magnetostratigraphy. During this upper extensional phase, subsidence and sediment influx was generally controlled by activity along the basin bounding normal fault, overruling smaller scale climatic influences. We conclude that the existence of the long-lived Sarajevo lake is coeval with other Dinaric and southern Pannonian lakes, and overlaps in time with the Miocene Climatic Optimum. Sedimentation in the Sarajevo-Zenica basin terminated at ~15–14 Ma which concurs with both the end of the climatic optimum as well as the cessation of extension in the Dinarides. These results will help to better quantify the paleoclimatic changes in the Dinaride Lake System as well as the regional tectono-sedimentary events, such as potential migrations of deformation across the Dinarides. [ABSTRACT FROM AUTHOR]

Lower Miocene deposits of the Güneyce Formation formerly described as the Elmalı Formation of Lutetian-Burdigalian age are located near the villages of Gökçebağ (Burdur) and Yakaören (Isparta), (southwestern Turkey), Eastern Mediterranean, and overlie the pre-Neogene tectonostratigraphic units of the Isparta Angle. The purpose of this study is to discuss new biostratigraphic data calibrated to originally classified nannofossil records. Three Early Miocene nannofossil biozones, NN1 - Triquetrorhabdulus carinatus Zone, NN2 - Discoaster druggii Zone and NN3 - Sphenolithus belemnos Zone, were defined in clastic sediments of the Güneyce Formation. In addition, one Lutetian biozone, NP16 - Discoaster tanii nodifer Zone, was recognized in the remaining outcrops of the Isparta Formation unconformably underlying the Güneyce Formation. Nannofossil assemblages of shallow marine deposits in the Güneyce Formation contain high amounts of reworked (Palaeogene and Cretaceous) specimens. New biostratigraphic data and sedimentary features of the Güneyce Formation clastics indicate shallow marine deposition and the beginning of the transgression, spreading over an erosional surface on the ophiolitic melange and Cretaceous to Eocene marine successions rising to the west of the region. [ABSTRACT FROM AUTHOR]

The Cenozoic spore-pollen zonation scheme of southeastern Australia is used to constrain the ages of marine and terrestrial strata throughout Australasia. New palynological, strontium isotope and foraminiferal data from the Torquay and Gippsland basins in southeastern Australia are here used to revise and chronologically calibrate the Oligocene and Miocene portions of this scheme. The revised age assigned to the Upper Nothofagidites asperus /Lower Proteacidites tuberculatus zonal boundary is 30.5–31.2 Ma, the Lower/Middle P. tuberculatus zonal boundary is 23.03 Ma, the Middle/Upper P. tuberculatus zonal boundary is approximately 21.1 Ma and the Upper P. tuberculatus/Triporopollenites bellus zonal boundary is 17.54 Ma. This revision confirms that a near-continuous Early Miocene neritic sequence is present in the Torquay Basin. The new ages also suggest that the timing of coal seam deposition in the Latrobe Valley was episodic, rather than continuous as has previously been interpreted. We propose that abrupt changes in moisture content across seam boundaries are associated with stratigraphic gaps. The new age controls facilitate more accurate comparisons of time-equivalent paleobotanical material throughout the southern hemisphere. The refinements presented will improve future Cenozoic paleoclimatic and paleobotanical reconstructions concerning Australia, New Zealand, South America and Antarctica. [ABSTRACT FROM AUTHOR]

A Sr-isotope chronostratigraphy is presented for Miocene sediments deposited by the “Paranense” Sea along 1200 km of the southwestern Atlantic coast of Argentina and Uruguay. Numerical ages were obtained for shells of Aequipecten paranensis from the Argentinean Puerto Madryn Formation, Facies Balneario La Lobería, “Entrerriense Beds” of the Salado Basin, and Paraná Formation, and from the Camacho Formation (Uruguay). The 87 Sr/ 86 Sr ages fall into five age-groups that encompass the “Paranense” flooding in the latest Serravalian-Messinian interval. For the Puerto Madryn Formation, the ages span the latest Serravalian to the Tortonian and are stratigraphically coherent with the transgressive phase (11.9–10.4 Ma) and the regressive phase (10.2–9.82 Ma and 9.40–9.05 Ma) of that unit. Ages of 8.85–7.95 Ma for the “Entrerriense Beds” show them to be Tortonian while the Facies Balneario La Lobería, and the Paraná and Camacho formations span the age-range 7.50–6.00 Ma, comprising the Tortonian-Messinian interval. The regressive phase of the Puerto Madryn Formation, and the Facies Balneario La Lobería are respectively correlated with the basal and middle beds of the cliffs at Barranca Final, where the uppermost horizons of the Barranca Final Formation are exposed. The “Entrerriense Beds” are correlated with the “Cape Fairwheater Beds”. Dating the “Paranense” marine incursion permits a reappraisal of its paleogeography and differentiation of its deposits from those of the “Patagoniense” Sea. The flooding area was smaller than previously thought, with its northwestern-most boundary in the surroundings of the Santa Fe Province and its southernmost boundary in southern Santa Cruz Province. Moreover, the Paranaian Molluscan Bioprovince was coeval with the Valdesian Molluscan Bioprovince for 2.35 Ma and species included in the Aequipecten paranensis Zone lived for at least 5.90 Ma. [ABSTRACT FROM AUTHOR]

Understanding the history, causes, and impact of sea-level changes is a challenge for our societies that face accelerated global sea-level rise. In this context, improvement of our knowledge of sea-level changes and shoreline migration at geological time scales is critical. The preserved, laterally correlative sedimentary record of continental erosion on passive margins has been used to reconstruct past sea level. However, the detailed nature of a basic clinothem progradational pattern observed on many of these margins is still poorly known. This paper describes the sedimentary facies and interprets the depositional environments and the architecture of the clinothems of the New Jersey shelf (offshore northeastern USA) to depict the origin and controls of the distribution of the sediment on the margin. We analyze 612 cores totaling 1311 m in length collected at three sites 60 km offshore Atlantic City, New Jersey, during International Ocean Discovery Program-International Continental Scientific Drilling Program (IODP-ICDP) Expedition 313. The three sites sampled the lower to middle Miocene passive margin sediments of the New Jersey shelf clinothems. We also collected wireline logs at the three sites and tied the sedimentary architecture to the geometry observed on seismic profiles. The observed sediment distribution in the clinoform complex differs from that of current models based on seismic data, which predict a progressive increase in mud and decrease in sand contents in a seaward direction. In contrast, we observe that the clinoforms are largely composed of muds, with sands and coarser material concentrated at the rollover, the bottomset, and the toe of the slope. The shelf clinothem topsets are storm-influenced mud whereas the foreset slope is composed of a mud wedge largely dominated by density current deposits (e.g., low-density turbidites and debrites). The architecture of the clinothem complex includes a composite stack of ~30-m-thick clinothem units each made up of four systems tracts (Transgressive, Highstand, Forced-Regressive, and Lowstand Systems Tract) building individual transgressiveregressive sequences. The presence of mud-rich facies deposited during highstands on the topset of the clinoform, 40-60 km offshore from the sand-prone shoreface deposit (observed in the New Jersey onshore delta plain), and the lack of subaerial erosion (and continental depositional environments) point to a depositional model involving a subaerial delta (onshore) feeding a distant subaqueous delta. During forced regressions, shelf-edge deltas periodically overstep the stacks of flood-influenced, offshore-marine mud wedges of the New Jersey subaqueous delta, bringing sand to the rollover and building up the large-scale shelf-prism clinothems. The clinothem complex develops on a gently dipping platform with a ramp-like morphology (apparent dip of 0.75°-0.5°) below mean storm wave base, in 30-50 m of water depth, 40-60 km seaward of the coastal area. Its shape depends on the balance between accommodation and sedimentation rates. Subaqueous deltas show higher accumulation rates than their subaerial counterparts and prograde three times further and faster than their contemporaneous shoreline. The increase in the intensity of waves (height and recurrence intervals) favors the separation between subaqueous and subaerial deltas, and as a consequence, the formation of a flat topset geometry, a decrease in flood events and fluvial discharge, an overall progressive decrease in sediment grain size (from sequence m5.45, ca. 17.8-17.7 Ma, onwards), as well as an increase in sedimentation rates on the foresets of the clinoforms. All of these are recognized as preliminary signals that might characterize the entry into the Neogene icehouse world. [ABSTRACT FROM AUTHOR]

Low-temperature thermochronology is used widely in the Tibet plateau uplift. Some researches, however, have defined the time of rapid denudation as simply rock uplift and have neglected the fact that the rock denudation recorded by fission track (FT) data was controlled by both surface incision and rock uplift. The incision of the Yarlung Zangbo River had a significant influence on uplift history inversion in Southern Tibet. This paper simulated the bedrock denudation and river incision histories using apatite fission track (AFT) data sampled from the Gangdese conglomerate belt, which is located in the middle of Southern Tibet, and analyzed the geological meaning of the AFT age of each sample. The results showed the following: (1) In the early Miocene (22–16 Ma), both the value of the denudation rate and the incision rate were high (0.56 mm/yr and 0.24 mm/yr). (2) In the middle-late Miocene, the incision rate (0.12 mm/yr) was similar to the denudation rate (0.09–0.11 mm/yr). (3) The historical model between river incision and bedrock denudation revealed a significant difference in the denudation rate during the period ca. 8–6 Ma. Combining these data with previously published thermochronological ages and synthesizing these ages with regional geological, we arrived at the following conclusions: (1) In the early Miocene, the denudation event probably was caused by a combined result of Indian plate rollback and the incision of the Yarlung Zangbo River. (2) In the middle-late Miocene, the denudation rate was consistent with the incision rate, which suggested that the denudation episode was caused by climate change associated with Asian monsoon intensification. (3) After 8 Ma, the stable and slow incision rate indicated that regional drastic uplift had ceased. The paleo-elevation of the research area had approached, and even exceeded, the present-day elevation in the late Miocene. [ABSTRACT FROM AUTHOR]

The objective of this study is to interpret the regularities in distribution of surface geochemical anomalies observed in a fragment of the contact zone between the Carpathian Fold-and-Thrust Belt and the Carpathian Foredeep (SE Poland). The surface geochemical survey included a total of 670 soil gas samples analyzed by gas chromatography, integrated with seismic cross sections, and supplemented by production data from wells. Maximum concentrations of methane, total alkanes C2-C5, total alkenes C2-C4, H2, and CO2 measured in soil gas samples were 27.1 vol.%, 45.3 ppm, 0.49 ppm, 0.232 vol.%, and 6.29 vol.%, respectively. Traces of alkanes detected in samples are the result of microseepage from a few accumulations of various compositions. Methane and ethane migrate primarily from relative shallow Miocene strata, and higher alkanes from deeper Miocene strata and from Paleozoic-Mesozoic basement. We found relatively high positive correlation between the distribution of surface geochemical anomalies and the relative intensity of hydrocarbon shows recorded in the wells. The location and range of 13 anomalous zones are controlled by the patterns of both the Dębno and the Wojnicz slice-folds. Most of the anomalies occur over the Wojnicz Trough, suggesting the presence of conventional accumulations and/or the sites where the Miocene mudstone and heterolithic formations are saturated with gas. [ABSTRACT FROM AUTHOR]

Nearly 72% world's borate reserves are in western part of Turkey. The Emet (Kütahya) deposit is one of these deposits. The Emet borate deposit, like other deposits in western Anatolia, was deposited in Miocene lacustrine environment whose formation coincides with volcanic activity started in Paleogene and lasted to the beginning of Quaternary. The borate ore displaying lenticular structure is alternated with claystone, marl, tuff and thin bedded limestone. The mineral paragenesis is composed of colemanite, hydroboracite, Veatchite, dolomite, calcite, montmorillonite and illite. The Emet borate deposit has been the subject of various geologic and mineralogical studies. In the present study major and trace element contents of 60 borate samples from this deposit are discussed. Among the trace elements, significant enrichment was found in As, Se, Sr, Cs, Sb and Li. Element correlations indicate volcanic source for boron (exhalations and hydrothermal solutions) whilst other elements are found to be derived from a terrestrial source. According to REE data, high Ce concentrations and anomalies are generally indicative of oxygenated depositional environment whilst low Ce contents facilitated the lake waters to be low oxygenated as a result of H 2 S-rich hydrothermal solutions. The weak negative anomaly detected only in the Hisarcık region is attributed to lacking of Eu contribution to the lake due to insufficient alteration on the continent. [ABSTRACT FROM AUTHOR]

Atmospheric CO 2 starvation, aridity, fire and warm season precipitation have all been proposed as major contributors to C 4 plant expansion during the Late Miocene. However, the driving factors responsible for the distribution of C 4 plants in the early and mid-Miocene still remain enigmatic. Here we report pedogenic carbon and oxygen isotope data (δ 13 C pedo , δ 18 O pedo ), along with magnetic susceptibility (MS) results, from the Zhuang Lang drilling core on the Chinese Loess Plateau (CLP). Elevated δ 13 C pedo values (>−5‰) signal a prominent C 4 expansion and substantially increased δ 18 O pedo and MS values indicate enhanced Asian summer monsoon (ASM) precipitation. Both of these conditions are observed during the Mid-Miocene Climatic Optimum (MMCO), 14.5–17 million years ago. The marked increase in C 4 plants, associated with warm temperatures and increased precipitation, strongly suggests the control of an enhanced ASM on C 4 expansion on the CLP during the MMCO. This finding contrasts with the late-Miocene C 4 expansion associated with cooling and drying conditions observed in low latitudes and argues for regionally specific control of C 4 plant distribution/expansion. [ABSTRACT FROM AUTHOR]

The Early Miocene Taşkapı-Mecitli granitoid that is located in the northern section of the Eastern Anatolia Collision Zone has typical I-type, metaluminous and calk-alkaline characteristics. It also contains mafic microgranular / magmatic enclaves (MMEs). New Ar-Ar dating results show that the age of the Taşkapı-Mecitli granitoid is ∼23 Ma and it crystallised in the Early Miocene, in contrast to its previously known Cretaceous age. Identical crystallisation ages (∼23 Ma), similar mineral assemblages and geochemical compositions, and indistinguishable isotopic compositions of MMEs and host rocks imply that the MMEs are most consistent with a cumulate origin formed at earlier stages of the same magmatic system that produced the Taşkapı-Mecitli granitoid. MELTS modelling suggests that magma of the Taşkapı-Mecitli granitoid was the result of fractionation under a crustal pressure of 4 kbar, with a H 2 O content of 1.5%. EC-AFC model calculation reveals that the Taşkapı-Mecitli granitoid includes from 0.5% to 2% crustal assimilation rates. These rates indicate that crustal contamination can be negligible when compared to fractional crystallisation in the evolution of the magma beneath the Taşkapı-Mecitli granitoid. The partial melting model calculations and MORB-normalised trace element concentrations of the least evolved samples of the Taşkapı-Mecitli granitoid are consistent with those of mafic melts obtained from partial melting of interacting mantle- lower crust with a melting degree of 18%. The age (23 Ma) of the post- or syn-collisional Taşkapı-Mecitli granitoid suggests that the collision between Arabian and Eurasian plates could be before/around ∼23 Ma (Late Oligocene to Early Miocene). [ABSTRACT FROM AUTHOR]

Detailed stratigraphic and facies analyses were conducted and combined with seismic facies and 3D seismic‐derived plan view images to interpret the depositional environments, processes and depositional elements during the Miocene for an area located in the southern Gulf of Mexico. The results showed that deposition during the Miocene mainly occurred in a slope setting, with bathymetric changes associated with highs and mini‐basins related to salt features. From the sedimentological interpretation, 13 sedimentary facies were identified. The abundant lithofacies were structureless (massive) sandstone and massive mudstone. Ripple‐ , parallel and cross‐laminated sandstone and siltstone were found in minor proportions. The main depositional processes were related to turbidity currents, including high‐density and low‐density currents; debris flows (mud flows and grain flows) were of secondary importance, as was deposition from fallout of suspended hemipelagic mud particles. The vertical and lateral distributions of facies revealed seven facies associations linked to depositional environments. These facies associations were the building blocks that were used to characterize the depositional elements recognized on seismic data. The main depositional elements identified were mass‐transport complexes, submarine channels, and frontal splays. Finally, interpretations from different data sets enabled the conclusion that, during the Miocene in this area were submarine fans deposited on an irregular paleotopography, with topographic lows and highs controlled by salt tectonics. [ABSTRACT FROM AUTHOR]

After the formalization of the base of the Miocene in the Lemme‐Carrosio section (Italy) at the base of Subchron C6Cn.2n, the calcareous plankton biostratigraphy was refined in several open ocean Deep Sea Drilling Project/Ocean Drilling Program sites. However, high‐resolution quantitative biostratigraphic studies, integrating planktonic foraminifera and calcareous nannofossils, are still lacking for the time interval spanning the Oligocene–Miocene transition. Here, we present a reinvestigation of Deep Sea Drilling Project Hole 516F (Rio Grande Rise) and 4 oil wells drilled by Petróbras Brasileiro SA in the Campos Basin (SW Atlantic Ocean). We identified 12 planktonic foraminiferal and 18 calcareous nannofossil bioevents that have been integrated with an updated magnetostratigraphy of Hole 516F allowing the correlation with the GPTS and the identification of the Oligocene/Miocene boundary (base of Subchron C6Cn.2n) between the Top of Sphenolithus delphix and the Base of common Paragloborotalia kugleri. Furthermore, our results give new insights on the reliability of major calcareous plankton events across the Oligocene–Miocene transition: (a) the Sphenolithus ciperoensis Top, the S. delphix Base and Top, and the Sphenolithus cometa Base are reliable events at a global scale; (b) the Bases of Globoquadrina dehiscens and Sphenolithus disbelemnos > 4 μm are correlatable events only within the study sector of the SW Atlantic Ocean; and (c) the Globoturborotalita ciperoensis Top, Globoturborotalita angulisuturalis Top, and Sphenolithus procerus Base are diachronous. Finally, previously unreported biostratigraphic data, such as the distribution range of S. disbelemnos < 4 μm and Sphenolithus cf. S. pseudoheteromorphus, the Tenuitellinata praestainforthi acme interval, and the Top of common Globigerinoides primordius were identified in the Campos Basin. [ABSTRACT FROM AUTHOR]

To clarify the taxonomy and biostratigraphy of Southwest Pacific populations currently identified as Fohsella peripheroronda a morphometric study is reported on the shape of its aperture in collections from DSDP Sites 588A and 593, and from the stratotype of the New Zealand Lillburnian Stage. This material is compared with Globorotalia partimlabiata from Serravallian strata in Sicily. Shape analyses use 50 equally-spaced coordinates along the margin of the apertural re-entrant of the last-preserved chamber. Data are aligned by the Procrustes algorithm and projected onto principal component axes. Canonical discriminant analysis of these scores shows that convexity of the margin increases clinally. The cline is interpreted as primary evidence for a previously unrecognized lineage for which a provisional taxonomy is advanced. Globorotalia partimlabiata , which has individuals with strongly convex margins, represents the climax of the cline. The highest occurrence of its ancestor, recognized here informally as Globorotalia cf. peripheroronda , is determined by the highest sample whose mean shape does not differ significantly from its earliest representative at Site 593. There and at Site 588A that datum is close to, or within, Miocene isotope event Mi-3b. The architectural history of the lineage differs from the tropical fohsellids and its relation to them is unresolved. [ABSTRACT FROM AUTHOR]

We present dinoflagellate assemblages contained in samples from the exploratory well Buenaventura 1-ST-P, located on the Colombian Pacific coast. The biostratigraphic model includes data from calcareous nannofossils and dinoflagellates studied from the same samples. The paleobathymetric evolution for the stratigraphic column is interpreted from its lithology, and content of benthic foraminifera and palynomorphs. We propose a chronostratigraphic framework based on the correlation of the integrated biostratigraphy, and this framework allows identification of regional tectonic and paleoceanographic events in the section studied. Our results indicate that the studied interval was deposited from early to late Miocene times (<17.9–5.33 Ma). The basal conglomeratic portion of the section was deposited between <17.9 and 13.4 Ma, and may reflect the collision of the Chocó Block with northwestern South America. These conglomerates contain very few dinoflagellates, calcareous nannofossils and benthic foraminifera. Overlying these conglomerates, ~1500 m of mainly shales, represent three complete transgressive-regressive (T-R) sedimentary cycles with environments ranging from transitional to upper bathyal. Autotrophic gonyaulacoid dinoflagellates dominate the lowest T-R cycle (~14.18 to <10.9 Ma), indicating warm and stratified superficial waters. The second T-R cycle (<10.9 to <9.53 Ma) is characterized by the lowest presence of marine microfossils, indicating low primary productivity. This cycle coincides with the Carbonate Crash event in the eastern tropical Pacific. Finally, the youngest T-R, from <9.53 to ~5.33 Ma, shows an increase in marine microfossils, and a dominance of heterotrophic peridinioid dinoflagellates, which indicate high productivity in cooler superficial waters. This cycle coincides with the late Miocene Global Biogenic Bloom event. [ABSTRACT FROM AUTHOR]

We use tectonic subsidence patterns from wells and stratigraphic sections to describe the mid-Miocene to present tectonic subsidence history of the Rio Grande rift. Tectonic subsidence and therefore rift opening were quite fast until ca. 8 Ma, with net subsidence rates (~25-65 mm/k.y.) comparable to those of the prerupture phase of rifted continental margins. The rapid subsidence was followed by a late Miocene-early Pliocene unconformity that developed mainly along the flanks of most rift basins. The age of its associated lacuna is spatially variable but falls within 8-3 Ma (mostly 7-5 Ma) and thus is synchronous with eastward tilting of the western Great Plains (ca. 6-4 Ma). Tectonic subsidence rates either remained similar or decreased after the Miocene-Pliocene unconformity. North of 35°N, our analysis of geoid-to-elevation ratios suggests that, at present, topography of the Rio Grande rift region is compensated by a component of mantle-driven dynamic uplift. Previous work has indicated that this dynamic uplift is caused by focused vertical flow in the upper mantle resulting from slab descent and fragmentation of the Farallon slab, and Rio Grande rift opening, which affected the Rio Grande rift area beginning in the late Miocene. The spatial distribution and timing of the unconformity, as well as eastward tilting of the western Great Plains, can be explained by this dynamic mantle uplift, with contributions from variations in rift opening tectonics and climate. The focused mantle upwelling is not associated with increased rift opening rates. [ABSTRACT FROM AUTHOR]

High-Mg diorites and/or ultrapotassic volcanic rocks are generally associated with postcollisional porphyry copper deposits, but their contribution to the formation of the mineralization remains unclear. A suite of Miocene postcollisional ultrapotassic-potassic lamprophyres, high-Mg diorites, and adakite-like intrusions have been recognized in the Zhunuo porphyry Cu deposit, located in a continental collisional zone within the Gangdese belt, southern Tibet. The post-mineralization ultrapotassic-potassic lamprophyres have zircon U-Pb ages of 12.2±2.1 Ma and contain abundant Proterozoic to Miocene inherited zircons. The ultrapotassic lamprophyres have high K2O (>8.5wt%) and MgO (>8.8wt %) contents, are enriched in light rare earth elements (LREE; La=123 ppm) and large ion lithophile elements (LILE; e.g. Ba=3102 ppm, Th=116.6 ppm, and Pb=140 ppm), and display high Th/Yb and Rb/Sr, and low Ba/Rb and Hf/Sm ratios. They have zircon εHf(t) values of -2.8 to 1.3, δ18O values of 6.5 to 7.4%0', and enriched bulk-rock Sr-Nd-Pb isotope compositions ((87Sr/86Sr)i=0.73134, εNd(t)=-13.7, (206Pb/204Pb)i=19.20). Their parental magmas were derived from partial melting of an enriched mantle source that had been metasomatized by fluids and sediment-derived melts associated with Neo-Tethyan oceanic subduction and subsequent Indian continental lithosphere subduction. The potassic lamprophyres have lower contents of K2O, MgO, REE and LILE than the ultrapotassic lamprophyres and (87Sr/86Sr)i of 0.710993 to 0.711139, εNd(t) of -12.3 to -12.4, and (206Pb/204Pb)i of 18.59 to 18.72. Taken together with observations of a negative trend between eNd(t) and MgO content; positive trends between (87Sr/87Sr)i, (206Pb/204 Pb)i and MgO content from ultrapotassic lamprophyres to potassic lamprophyres; the existence of abundant Miocene inherited zircons showing similar ages and εHf(t) values to the adakite-like intrusions; and variable Hf/Sm ratios with some Hf/Sm ratios similar to adakite-like intrusions, we propose that the potassic lamprophyres were formed by mixing of ultrapotassic lamprophyre magmas with adakitelike magmas. The syn-mineralization high-Mg diorites including diorite porphyry and enclaves hosted by the adakite-like intrusions at Zhunuo have zircon U-Pb ages of 13.0±0.2 Ma and 13·1±0·2 Ma. They show negative correlations between Y, Yb, Dy/Yb and SiO2, and positive correlations between Sr, Sr/Y and SiO2, among which some more evolved samples (such as diorite porphyry) show adakite-like geochemical signatures. The high-Mg diorites are enriched in LREE and LILE, depleted in high-field-strength elements (HFSE), and have (87Sr/86Sr)i of 0·709401 to 0·710362, εNd(t) of -11·1 to -9·9, and (206Pb/204Pb)i of 18·62 to 18·71. Taken together with petrographic observations that show magma mixing, we argue that the high-Mg diorites were derived from previously subduction-modified Tibetan lithospheric mantle with little or no input from Indian continental sediment. Mixing with adakite-like magmas and fractional crystallization of hornblende and/or titanite are also responsible for the differentiation of the high-Mg diorites. The ore-hosting, adakitelike granitic rocks at Zhunuo with zircon U-Pb ages of 14·7±0·3 Ma and 14·6±0·2 Ma have lower concentrations of REE, LILE and HFSE, much higher εNd(t) (-6·1 to -6·9) and lower (87Sr/86Sr)i (0·707325-0·707663) values than the ultrapotassic lamprophyres and the high-Mg diorites. They were derived from remelting of previously subduction-modified Tibetan lower crust with some involvement of hydrous high-Mg dioritic magmas during magma mixing. The postcollisional adakite-like intrusions in the Gangdese belt could be generated by remelting of previously subduction-modified lower crust and mixing with hydrous high-Mg dioritic magmas in a lower crustal MASH zone and/or in an upper-crustal adakite-like magma chamber. The metallogenic potential of postcollisional adakite-like intrusions largely depends on rejuvenation of subductionmodified lower crust by previous arc magmas, differentiation of hydrous high-Mg dioritic magmas, and magma mixing of high-Mg dioritic magmas with lower crustal magmas. [ABSTRACT FROM AUTHOR]

Abstract: The Chilean Frontal Cordillera, near 28°45′S, provides a remarkable example to explore the evolution of the Central Andes; this area provides conspicuous pediment surfaces and continental deposits, which allowed us to analyse the timing and propagation of deformation which controlled the Andes building during the Cenozoic using structural, geomorphological, sedimentological, stratigraphic and geochronological data. The study area is characterized by outcrops of the Cerro del Burro Gravels, a continental deposit which is surrounded by four morphostructural mountain systems. Based on a 46 Ma tuff affected by a syncline, which is sealed by a 44 Ma tuff, we recognized an Eocene fault activity that contributed to the uplift of the western and northern systems, which have remained inactive during the last 44 Ma. The deformed lithologies during the last pulse of activity of the western fault and the youngest lithology carved by pediment processes (21 Ma) indicate a pediment surface developed during the Late Eocene and Oligocene. This pediment extended below the Cerro del Burro Gravels associated to a base level which drained to the east. We also recognized Miocene fault activity that played a main role in the uplift of the eastern and southern systems. Geochronological, stratigraphic and geomorphological data suggest a first pulse of fault activity between 19 and 13 Ma, which interrupted the pedimentation processes, developed an intramontane depocenter, and forced the accumulation of the Laguna Grande Succession in an alluvial‐braided fluvial environment. After 13 Ma, an erosive event evidenced by the incision of valleys, resulted after the change in the extension and configuration of the hydric network. [ABSTRACT FROM AUTHOR]

The Dongsheng uranium district, located in the northern part of the Ordos Basin, contains the largest known sandstone-hosted uranium deposit in China. This district contains (from west to east) the Daying, Nalinggou, and Dongsheng uranium deposits that host tens of thousands of metric tonnes of estimated recoverable uranium resources at an average grade of 0.05% U. These uranium orebodies are generally hosted by the lower member of the Zhiluo Formation and are dominantly roll or tabular in shape. The uranium deposits in this district formed during two stages of mineralization (as evidenced by U–Pb dating) that occurred at 65–60 and 25 Ma. Both stages generated coffinite, pitchblende, anatase, pyrite, and quartz, with or without sericite, chlorite, calcite, fluorite, and hematite. The post-Late Cretaceous uplift of the Northern Ordos Basin exposed the northern margins of the Zhiluo Formation within the Hetao depression at 65–60 Ma, introducing groundwater into the formation and generating the first stage of uranium mineralization. The Oligocene (∼25 Ma) uplift of this northern margin exposed either the entirety of the southern flank of the Hetao depression or only the clastic sedimentary part of this region, causing a second gravitational influx of groundwater into the Zhiluo Formation and forming the second stage of uranium mineralization. [ABSTRACT FROM AUTHOR]

Thirty-five stratigraphic section exposed along the Mukah-Selangau road in the Mukah-Balingian area have been studied. Sedimentological and palynological data have been integrated to gain a better insight into the depositional architecture of the area. Broadly, the Mukah-Balingian area is dominated by fluvial, floodplain and estuarine related coal-bearing deposits. The Balingian, Begrih and Liang formations have been described and interpreted in terms of seven facies association. These are: FA1 – Fluvial-dominated channel facies association; FA2 – Tide-influenced channel facies association; FA3 – Tide-dominated channel facies association; FA4 – Floodplain facies association; FA5 – Estuarine central basin-mud flats facies association; FA6 – Tidal flat facies association and FA7 – Coastal swamps and marshes facies association. The Balingian Formation is characterised by the transgressive phase in the base, followed by a regressive phase in the upper part. On the basis of the occurrence of Florscheutzia trilobata with Florscheutzia levipoli , the Early to Middle Miocene age has been assigned to the Balingian Formation. The distinct facies pattern and foraminifera species found from the samples taken from the Begrih outcrop imply deposition in the intertidal flats having pronounced fluvio-tidal interactions along the paleo-margin. Foraminiferal data combined with the pronounced occurrence of Stenochlaena laurifolia suggest at least the Late Miocene age for the Begrih Formation. The internal stratigraphic architecture of the Liang Formation is a function of a combination of sea level, stable tectonic and autogenic control. Based on stratigraphic position, the Middle Pliocene to Pleistocene age for the Liang Formation is probable. The Balingian, Begrih and Liang formations display deposits of multiple regressive-transgressive cycles while the sediments were derived from the uplifted Penian high and Rajang group. [ABSTRACT FROM AUTHOR]

The Kailas conglomerates crop out ubiquitously along the southernmost boundary of the Gangdese batholith. They unconformably overlie the Gangdese batholith and are displaced by the Great Counter thrust (GCT) fault, forming a fault contact with the Xigaze forearc basin, the associated subduction complex and the Tethyan Himalayan sequence. These strata furnish a record of uplift and paleoenvironmental change in the Indus-Yarlung suture zone during the Oligocene-Miocene. Our new and previously published low-temperature thermochronometric data from the Gangdese batholith and the Kailas conglomerates indicate a period of rapid exhumation beginning approximately 17–15 Ma centered on the southern margin of the Gangdese batholith, whereas regional uplift commenced significantly earlier during the deposition of the Kailas conglomerates, based on the presence of an abrupt facies transition from deep-water lacustrine deposits to red alluvial fan or fluvial deposits. The period of rapid exhumation probably lagged behind the initiation of faster uplift, while the related changes in the depositional environment were most likely recorded immediately in the basin stratigraphy. Subsequently, the Kailas conglomerates were buried in association with the development of the north-directed Great Counter thrust, while rapid exhumation was facilitated by efficient incision by the paleo-Yarlung river at approximately 17–15 Ma. [ABSTRACT FROM AUTHOR]

The intermediate to low sulfidation epithermal gold deposit in Masara, Compostela Valley, Eastern Mindanao, Philippines, is associated with a diorite porphyry from the Late Miocene Lamingag Intrusive Complex. Detailed mineralogical investigation of the host rocks in the deposit reveals five major alteration zones and at least two mineralizing events. A potassic alteration zone characterized by stockwork magnetite veins, secondary biotite and magnetite and an early-stage chlorite-sericite alteration composed of quartz + chlorite + illite + sericite + pyrite ± biotite ± magnetite ± calcite assemblages are interpreted to be linked with an earlier porphyry copper system in the area. These were overprinted by late-stage chlorite-sericite alteration consisting of quartz + chlorite + illite + sericite + pyrite ± adularia ± magnetite ± epidote and sericite assemblages which generally contain quartz + illite + sericite + pyrite. These alteration overprints are inferred to be related to a younger low to intermediate-sulfidation epithermal gold mineralization which involved near-neutral fluids. Advanced argillic alteration comprising quartz + kaolinite + magnetite + dickite ± illite ± calcite was also observed in the area. Isocon analysis shows that alteration zones associated with epithermal mineralization are generally characterized by enrichment in SiO 2 and K 2 O and depletion of CaO and Na 2 O as well as additions of Au, Cu, Zn and Pb. Pearce Element Ratio (PER) analysis indicates high degrees of sericitization in the altered diorite porphyry, tuff and quartz diorite units. At least three major alteration centers are defined based on the spatial distribution of the Alteration Index of surface samples calculated from the PER analysis. The results of this study support the use of whole-rock geochemistry as a complement to traditional techniques in exploration geochemistry. [ABSTRACT FROM AUTHOR]

An intertidal shore platform in bathyal mudstones of the Late Miocene Pohutu Formation near East Cape, North Island, New Zealand, hosts many impressive dolomitic conduit concretions having predominantly doughnut morphologies up to 6 m across. Carbon isotope values (δ13C + 6 to + 9‰ PDB) are interpreted to show that the carbon for dolomite precipitation was derived from extensive anaerobic oxidation of thermogenic methane, while oxygen isotope values (δ18O + 2 to + 6‰ PDB) implicate the dissociation of gas hydrates at the time of carbonate precipitation. The concretions are inferred to mark the shallow sub-seafloor locations of upward migrating hydrocarbon-enriched fluids in a fossil cold seep system on a convergent margin. The distribution of concretions and faults are intimately associated. We propose that doughnut concretion growth was related to a periodically active fault-valve mechanism involving fluid pressure increase, fault rupture and fluid discharge, followed by fluid pressure decrease, mineral precipitation and fault sealing. [ABSTRACT FROM PUBLISHER]

Basin floor fans contain some of the largest deep-water hydrocarbon accumulations discovered, however they also demonstrate extremely complex stratigraphic architecture, understanding of which is crucial for maximum recovery. Here we develop a new method, based upon palynofacies analysis, for the distinction of the different depositional environments that are commonly associated with basin floor fans. Previous studies and our sedimentological analysis allow good confidence in the discrimination of the different depositional environments of the outcropping Marnoso-Arenacea Formation fan system. One hundred and thirty-five samples were collected from mudstones in conjunction with sedimentary logging of 871 m of outcrops. Six lithofacies associations are described and interpreted to represent lobe axis, lobe fringe, fan fringe, contained interlobe, basin plain, and starved high depositional sub-environments. Palynofacies of these elements demonstrate turbidites to be rich in terrestrial organic matter, with sixteen categories of matter recognised. The abundances and proportions of particles varies between sub-environments, with lobe axis deposits containing the largest, densest particles, with a transition to ever smaller and lighter particles moving toward the basin plain. Fuzzy C-means statistical analysis was used to explore this trend. Distribution of organic matter is not random, but is dominated by hydrodynamic sorting and sequential fall-out of particles as turbidity currents passed across the basin. This allows a palynofacies classification scheme to be constructed to assist the identification of depositional environments of submarine fans, which may be combined with subsurface data to assist reservoir characterisation. [ABSTRACT FROM AUTHOR]

A three-dimensional reconstruction of burial and palaeogeothermal conditions is presented for Miocene sediments of the Carpathian Foredeep beneath the Outer Western Carpathians fold and trust belt in the eastern part of the Czech Republic. The sedimentary units involved include autochthonous Paleozoic sequences, Miocene deposits of the Carpathian Foredeep and of the Western Carpathian nappe system. Reservoir rocks with economic oil and gas accumulations occur in the fractured crystalline basement and in the Neogene Carpathian Foredeep. The studied Vizovice area, is characterized by rocks representing both Variscan and Carpathian orogenic cycles. The 3D thermal maturity and subsidence model presented allows the significance of both tectonic events to be evaluated. The model, calibrated by vitrinite reflectance from eight boreholes proved that eroded units related to the Variscan orogeny approach, in amount, those eroded during the Carpathian orogeny. The thickness of the eroded rocks does not exceed 300 m in either case. Vitrinite reflectance data from representative core samples of the Miocene organic matter show that R r values increase with depth from 0.36 to 0.58%. A re-evaluation of archival data on the quantity and quality of organic matter shows that total organic carbon ranges from 0.20 to 2.92 wt%, and residual hydrocarbons (S 2 ) from 0.04 to 8.48 mg HC/g rock. These results lead to the conclusion that Neogene Unit II that was interpreted as coastline-through to shallow-marine deposition environment within the Carpathian Foredeep in the Czech Republic is potential source rock for hydrocarbon accumulations. [ABSTRACT FROM AUTHOR]