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The fluctuating climatic conditions of the Saharo-Arabian desert belt are increasingly important for both palaeoclimatic and palaeoanthropological debates. Currently, Saharo-Arabia acts as a vast biogeographic barrier between the Afrotropical and Palaearctic realms. On orbital timescales, northward incursions of the African (ASM) and Indian (ISM) Summer Monsoons activated fluvio-lacustrine systems and led to the formation of grassland habitats. The formation of these habitats has been considered a crucial factor in Homo sapiens dispersals into the Saharo-Arabian deserts and beyond. The so-called “northern route” favours a terrestrial dispersal through green palaeohydrological corridors. However, a maritime “southern route” during the sea-level low-stand of Glacial Termination-II (T-II) has also been proposed. The precise phasing between the onset of wetter conditions and rising sea-levels may thus be a crucial factor for testing these alternative hypotheses. Here, we present a precisely dated high-resolution (

In Arabia, the first half of the sixth century CE was marked by the demise of Himyar, the dominant power in Arabia until 525 CE. Important social and political changes followed, which promoted the disintegration of the major Arabian polities. Here, we present hydroclimate records from around Southern Arabia, including a new high-resolution stalagmite record from northern Oman. These records clearly indicate unprecedented droughts during the sixth century CE, with the most severe aridity persisting between ~500 and 530 CE. We suggest that such droughts undermined the resilience of Himyar and thereby contributed to the societal changes from which Islam emerged.

Homo sapiens dispersals out of Africa are often linked to intensifications of the African Summer Monsoon and Indian Summer Monsoon. Current dispersal models advocate that dispersals along the "sout...

Homo sapiens dispersals out of Africa are often linked to intensifications of the African and Indian Summer Monsoons. Current models advocate that dispersals along the “southern-route” into Arabia occurred during Glacial Termination-II (T-II), when lower sea-level and reduced Bab-al-Mandab width increased the likelihood of crossing. The precise phasing between sea-level and monsoon precipitation is thus key to assess the likelihood of a successful crossing or the behavioural and technological capacities that facilitated crossing. Based on a precisely-dated stalagmite record from Yemen, we reveal a distinct phase-lag of several thousand years between sea-level rise and major monsoon intensification. Pluvial conditions in Southern Arabia during MIS 5e lasted from ∼127.7 to ∼121.1 ka BP and occurred when sea-levels were already higher than at present. Based on our observations, we propose three models for the dispersal of H. sapiens which all have pertinent implications for our understanding of human technological and behavioural capacities during MIS 5e.

The ~ 5.5 km sized Jabal Rayah ring structure located at 28° 390 N/37° 120 E in Saudi-Arabia has been classified as a possible complex impact structure located in flat-lying-Paleozoic clastic sediments. Previous, detailed mapping showed that erosional processes led-to a relief inversion, with displaced, folded, and faulted blocks of Silurian to Early-Devonian strata, interpreted to form a ring syncline, now forming a topographically-outstanding, 150 m high ring crest. The drainage toward the center of the structure seems-controlled by a set of radial faults. This central part is eroded to the level of the-surrounding plateau and partially covered with gravel. Analysis of 28 Qusaiba Formation-sandstones showed that at the present outcrop level, the sediments seem devoid of shock-features. Measurement of fold axes in the central part of the structure shows radially-outward plunging fold axes, becoming steeper toward the center, and also fold axes of other-orientation, and folded folds. This fold axis pattern is interpreted as an upward-pointing,-kilometer-sized sheath fold. Assuming an impact scenario and using the present size of the-structure, the minimum central structural uplift is estimated at ~ 500 m, which is consistent-with Qusaiba Formation occupying the center of the ring structure.

Enzel et al. (2015) reassess sedimentary records of Early to Mid-Holocene lake sites in Arabia based on a reinterpretation of published multiproxy data and a qualitative analysis of satellite imagery. The authors conclude that these sites represent palaeo-wetland environments rather than palaeolakes and that the majority of the Arabian Peninsula experienced no or, if at all, only a very minor increase of rainfall at that time mainly due to eastward expansion of the East African Summer Monsoon. We disagree with their reassessment and identify several cases where unequivocal evidence for early Late Pleistocene and Early to Mid-Holocene perennial lake environments in Arabia, lasting for centuries to millennia, was neglected by Enzel et al. (2015). Here we summarize findings which indicate the presence of lakes from the sites of Jubbah, Tayma, Mundafan (all Saudi Arabia), Wahalah, Awafi (both UAE), and the Wahiba Sands (Oman), supported by evidence including occurrence of barnacle colonies in living position, remnant bioclastic shoreline deposits, undisturbed varve formation, shallowing-up lacustrine sequences, various aquatic freshwater, brackish and saline micro- and macrofossils, such as ichnofaunal remains, which are the result of prolonged field-based research. While the precise depth, hydrology and ecology of these water bodies is still not entirely resolved, their perennial nature is indicative of a markedly increased precipitation regime, which, in combination with more abundant groundwater and increased spring outflow in terminal basins fed by charged aquifers, was sufficient to overcome evaporative losses. The palaeolakes' influence on sustaining prehistoric populations is corroborated by the presence of rich archaeological evidence.

In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate dependent DCF values. For M1-5 an average DCF of 56.2 ± 3.4 % is observed between 27 and 18 kyr BP. Such high DCF values indicate a high influence of aged soil organic matter (SOM) and nearly completely closed system carbonate dissolution conditions. Towards the end of the last glacial period decreasing Mg/Ca ratios suggest an increase in precipitation which caused a marked change in the soil carbon cycling as indicated by sharply decreasing DCF. This is in contrast to the relation of soil infiltration and reservoir age observed in stalagmites from temperate zones. For Socotra Island, which is influenced by the East African–Indian monsoon, we propose that more humid conditions and enhanced net-infiltration after the LGM led to denser vegetation and thus lowered the DCF by increased 14CO2 input into the soil zone. The onset of the Younger Dryas (YD) is represented in the record by the end of DCF decrease with a sudden change to much higher and extremely variable reservoir ages. Our study highlights the dramatic variability of soil carbon cycling processes and vegetation feedback on Socotra Island manifested in stalagmite reservoir ages on both long-term trends and sub-centennial timescales, thus providing evidence for climate influence on stalagmite radiocarbon. This is of particular importance for studies focussing on 14C calibration and atmospheric reconstruction through stalagmites which relies on largely climate independent soil carbon cycling above the cave.

Late Carboniferous to early Permian glacigenic Al Khlata Formation reservoirs account for one of the largest hydrocarbon productions in the Sultanate of Oman. Tectonic activities caused a varied subsidence, uplift, and erosion history resulting in present-day formation depths between surface exposure and approximately 4000 m (13,125 ft). Furthermore, tectonism caused fluid incursions leading to mineral reactions and porosity-modifying processes. Since deposition, the pore water evolved from low-salinity and negative δ18OVSMOW value to a high-salinity brine with a positive δ18OVSMOW value. This change is related to Ara salt halokinesis beginning at approximately 200 Ma. At the eastern flank of the Ghaba Salt Basin, low saline intervals occurred isochronously with the obduction of the Hawasina Nappes-Samail Ophiolite. Dilution event(s) and changes to negative δ18OVSMOW values occurred between 60 and 50 Ma because of intraplate deformation creating new fluid pathways. Reservoir quality deterioration results from compactional porosity loss and heavy quartz cementation. Authigenic quartz precipitated as zoned syntaxial overgrowths cogenetically with calcite, Fe-dolomite, anhydrite, and kaolinite. Hydrochemical modeling of kaolinite precipitation indicates a link to CO2 migration rather than meteoric water infiltration. The onset of quartz cementation was contemporaneous with the obduction of the Hawasina Nappes–Samail Ophiolite irrespective of burial temperature, thus indicating a tectonic rather than a purely kinetic control.

The Wadi ad Dawasir fluvial system in central Saudi Arabia is investigated using remote sensing and sedimentology, in combination with bio-proxy analyses (molluscs and ostracods). Age control is provided by radiocarbon as well as luminescence dating, using both quartz and feldspar grains. It is shown that the fluvial system was active from the Asir Mountains across the partially sand-covered interior of the Arabian Peninsula to the Arabian Gulf during the Holocene humid period. Sedimentology and faunal analysis reveal the presence of perennial streams and a permanent freshwater lake in the distal reach of the Dawasir system that are synchronous with fluvial accumulation in the headwaters of its major tributary, Wadi Tathlith. The increased runoff during the Holocene led to a re-activation of streams that largely followed pre-existing Late Pleistocene courses and eroded into older sediments. The absence of Holocene lakes in most of the Rub' al-Khali implies that trans-Arabian rivers were mainly fed by precipitation in the Asir Mountains. Monsoonal rainfall was apparently stronger there as well as in the northern, south-eastern and southern part of the Arabian Peninsula (southern Yemen and Oman), but it apparently did not directly affect the interior during the Holocene. The palaeoenvironmental reconstruction shows a narrow trans-Arabian green freshwater corridor as the result of phases of sustained flow lasting up to several centuries. The permanent availability of water and subsistence for wildlife provided a favourable environment for human occupation as documented by Neolithic stone tools that are found all along Wadi ad Dawasir.

Past climates and environments experienced by the Saharo-Arabian desert belt are of prime importance for palaeoclimatic and palaeoanthropological research. On orbital timescales transformations of the desert into a grassland landscape in response to higher precipitation provided “windows of opportunity” for hominin dispersal from Africa into Eurasia. On long timescales, palaeoenvironmental reconstructions for the region are predominantly derived from marine sediments and available terrestrial records from the Arabian Peninsula are limited to 450 ka before present (BP). Here, we present a new stalagmite-based palaeoclimate record from Mukalla Cave in Yemen which extends back to ∼1.1 million years BP or Marine Isotope Stage (MIS) 31, as determined by Uranium-lead dating. Stalagmite Y99 grew only during peak interglacial periods and warm substages back to ∼1.1 Ma. Stalagmite calcite oxygen isotope (δ18O) values show that every past interglacial humid period was wetter than the Holocene, a period in which large lakes formed in the now arid areas of southern Arabia. Carbon isotope (δ13C) values indicate habitable grassland environments developed during these pluvial periods. A total of 21 pluvial periods with precipitation of more than 300 mm yr−1 occurred since ∼1.1 Ma and thus numerous opportunities for hominin dispersals occurred throughout the Pleistocene. New determinations of hydrogen (δDFI) and oxygen (δ18OFI) isotopes in stalagmite fluid inclusion water demonstrates that enhanced precipitation in Southern Arabia was brought by the African and Indian Summer Monsoons. When combined with sub-annual calcite analysis of δ18O and δ13C, these data reveal a distinct wet (summer) and dry (winter) seasonality.

Shallow lakes and sabkha deposits are evidence of past periods of higher groundwater table than today, and hence reflect increased humidity in the Rub' al-Khali, the large desert in the southern part of the Arabian Peninsula. Reported here are the observations made during four expeditions into this remote area in combination with luminescence dating constraining the age of the deposits. The results presented extend the spatial coverage of evidence and show that most of the deposits correlate to MIS 5 (ca. 130–70 ka) and the Early/Mid Holocene (ca. 11–5.5 ka). A single sample points towards potentially more humid conditions during the transition MIS 4/3 (ca. 65–55 ka). The presence of the mussel Unio in some of the deposits attributed to MIS 5 is indirect evidence for the presence of fish in the lakes, which must have supported a rich and diverse fauna (and probably also flora). Together with other evidence, this demonstrates that a number of small persistent lakes were spread across the Rub' al-Khali for at least some of the time. These lakes would not only have been a potential source of freshwater but could also have provided an additional and easy accessible food source via the fish for humans migrating through the area. The presented palaeoenvironmental data underlines that parts of MIS 5 represent a time window of opportunity for a potential expansion of modern humans across Arabia.

We have investigated the Ash Shutbah circular structure in central Saudi Arabia (21 degrees 37N 45 degrees 39E) using satellite imagery, field mapping, thin-section petrography, and X-ray diffraction of collected samples. The approximately 2.1km sized structure located in flat-lying Jurassic Tuwaiq Mountain Limestone has been nearly peneplained by erosional processes. Satellite and structural data show a central area consisting of Dhruma Formation sandstones with steep bedding and tight folds plunging radially outward. Open folding occurs in displaced, younger Tuwaiq Mountain Limestone Formation blocks surrounding the central area, but is absent outside the circular structure. An approximately 60cm thick, unique folded and disrupted orthoquartzitic sandstone marker bed occurring in the central area of the structure is found 140m deeper in undisturbed escarpment outcrops located a few hundred meters west of the structure. With exception of a possible concave shatter cone found in the orthoquartzite of the central area, other diagnostic shock features are lacking. Some quartz-rich sandstones from the central area show pervasive fracturing of quartz grains with common concussion fractures. This deformation was followed by an event of quartz dissolution and calcite precipitation consistent with local sea- or groundwater heating. The combination of central stratigraphic uplift of 140m, concussion features in discolored sandstone, outward-dipping concentric folds in the central area, deformation restricted to the rocks of the ring structure, a complex circular structure of 2.1km diameter that appears broadly consistent with what one would expect from an impact structure in sedimentary targets, and a possible shatter cone all point to an impact origin of the Ash Shutbah structure. In fact, the Ash Shutbah structure appears to be a textbook example of an eroded, complex impact crater located in flat-lying sedimentary rocks, where the undisturbed stratigraphic section can be studied in escarpment outcrops in the vicinity of the structure. (Less)

Present climate in the Nafud desert of northern Saudi Arabia is hyper-arid and moisture brought by north-westerly winds scarcely reaches the region. The existence of abundant palaeolake sediments provides evidence for a considerably wetter climate in the past. However, the existing chronological framework of these deposits is solely based on radiocarbon dating of questionable reliability, due to potential post-depositional contamination with younger 14C. By using luminescence dating, we show that the lake deposits were not formed between 40 and 20 ka as suggested previously, but approximately ca 410 ka, 320 ka, 200 ka, 125 ka, and 100 ka ago. All of these humid phases are in good agreement with those recorded in lake sediments and speleothems from southern Arabia. Surprisingly, no Holocene lake deposits were identified. Geological characteristics of the deposits and diatom analysis suggest that a single, perennial lake covered the entire south-western Nafud ca 320 ka ago. In contrast, lakes of the 200 ka, 125 ka, and 100 ka humid intervals were smaller and restricted to interdune depressions of a pre-existing dune relief. The concurrent occurrence of humid phases in the Nafud, southern Arabia and the eastern Mediterranean suggests that moisture in northern Arabia originated either from the Mediterranean due to more frequent frontal depression systems or from stronger Indian monsoon circulation, respectively. However, based on previously published climate model simulations and palaecolimate evidence from central Arabia and the Negev desert, we argue that humid climate conditions in the Nafud were probably caused by a stronger African monsoon and a distinct change in zonal atmospheric circulation.

Four stalagmites covering the last 7.0 ka were sampled on Socotra, an island in the northern Indian Ocean to investigate the evolution of the northeast Indian Ocean Monsoon (IOM) since the mid Holocene. On Socotra, rain is delivered at the start of the southwest IOM in May–June and at the start of the northeast IOM from September to December. The Haggeher Mountains act as a barrier forcing precipitation brought by the northeast winds to fall preferentially on the eastern side of the island, where the studied caves are located. δ18O and δ13C and Mg/Ca and Sr/Ca signals in the stalagmites reflect precipitation amounts brought by the northeast winds. For stalagmite STM6, this amount effect is amplified by kinetic effects during calcite deposition. Combined interpretation of the stalagmites' signals suggest a weakening of the northeast precipitation between 6.0 and 3.8 ka. After 3.8 ka precipitation intensities remain constant with two superimposed drier periods, between 0 and 0.6 ka and from 2.2 to 3.8 ka. No link can be established with Greenland ice cores and with the summer IOM variability. In contrast to the stable northeast rainy season suggested by the records in this study, speleothem records from western Socotra indicate a wettening of the southwest rainy season on Socotra after 4.4 ka. The local wettening of western Socotra could relate to a more southerly path (more over the Indian Ocean) taken by the southwest winds. Stalagmite STM5, sampled at the fringe between both rain areas displays intermediate δ18O values. After 6.2 ka, similar precipitation changes are seen between eastern Socotra and northern Oman indicating that both regions are affected similarly by the monsoon. Different palaeoclimatologic records from the Arabian Peninsula currently located outside the ITCZ migration pathway display an abrupt drying around 6 ka due to their disconnection from the southwest rain influence. Records that are nowadays still receiving rain by the southwest winds, suggest a more gradual drying reflecting the weakening of the southwest monsoon.

Relict fluvial and lacustrine deposits in the interior of Oman near Saiwan consist of waterlain breccias with pebble imbrications and current ripples, covered by algal laminites containing calcified reeds and charcoal pieces. Geomorphological evidence suggests that the palaeolake covered a maximum surface of 1400 km2 and had a maximum depth of about 25 m. Optically stimulated luminescence (OSL) and thermally transferred OSL dating indicate that this palaeolake existed sometime between 132 and 104 ka. The rich archaeological evidence in the area suggests substantial human occupation, possibly at the time when Palaeolake Saiwan existed. Interestingly, the lithic traditions of the archaeological material show no clear relation to coeval findings from neighbouring areas, putting a question mark on the origin of the culture found at Saiwan. This finding raises questions concerning the origin of the population inhabiting Saiwan, as the site lies along one possible route for the dispersal of anatomically modern humans out-of-Africa. Copyright © 2011 John Wiley & Sons, Ltd.

Arabia is a key area for the dispersal of anatomically modern humans (AMH, Homo sapiens) out of Africa. Given its modern hostile environment, the question of the timing of dispersal is also a question of climatic conditions. Fresh water and food were crucial factors facilitating AMH expansions into Arabia. By dating relict lake deposits, four periods of lake formation were identified: one during the early Holocene and three during the late Pleistocene centered ca. 80, ca. 100, and ca. 125 ka. Favorable environmental conditions during these periods allowed AMH to migrate across southern Arabia. Between ca. 75 and 10.5 ka, arid conditions prevailed and turned southern Arabia into a natural barrier for human dispersal. Thus, expansion of AMH through the southern corridor into Asia must have taken place before 75 ka, possibly in multiple dispersals.

Arabia is an important potential pathway for the dispersal of Homo sapiens (“out of Africa”). Yet, because of its arid to hyper-arid climate humans could only migrate across southern Arabia during pluvial periods when environmental conditions were favorable. However, knowledge on the timing of Arabian pluvial periods prior to the Holocene is mainly based on a single and possibly incomplete speleothem record from Hoti Cave in Northern Oman. Additional terrestrial records from the Arabian Peninsula are needed to confirm the Hoti Cave record. Here we present a new speleothem record from Mukalla Cave in southern Yemen. The Mukalla Cave and Hoti Cave records clearly reveal that speleothems growth occurred solely during peak interglacial periods, corresponding to Marine Isotope Stages (MIS) 1 (early to mid-Holocene), 5.1, 5.3, 5.5 (Eemian), 7.1, 7.5 and 9. Of these humid periods, highest precipitation occurred during MIS 5.5 and lowest during early to middle Holocene.

Glacial deposits are found in the Ayn Formation and Shareef Formation of the Mirbat Group close to Mirbat in Dhofar, southern Oman. The Mirbat Group is most likely a correlative of the Abu Mahara Group of the Huqf Supergroup of northern Oman. The Ayn Formation, the main subject of this chapter, comprises 8-km-wide N- to NW-oriented palaeovalleys eroded into crystalline basement, with few or no deposits preserved on intervening palaeohighs. The Shareef Formation occurs as thin, lenticular, erosional remnants beneath the unconformably overlying Cretaceous. The Ayn Formation is overlain by a thin ( The Ayn Formation is younger than its youngest detrital zircons and the youngest late plutons in crystalline basement, constraining it to c . 720 Ma, but its exact age is unknown. The detrital zircon population comprises exclusively Neoproterozoic sources, suggesting derivation from the juvenile Neoproterozoic crust of the Arabian area. The composition of fine-grained matrix in glaciogenic diamictite units and of non-glacial mudstones, plotted using the chemical index of alteration (CIA), suggests strong variations in the intensity of palaeoweathering on contemporary land surfaces between the mechanical weathering-dominated Ayn Formation, and the chemical weathering-dominated overlying Arkahawl Formation, which supports the notion of major glaciation followed by rapid climatic transit as basin margins were flooded and buried with sediment during post-glacial transgression. The carbon isotopic ratio (δ 13 C) of the post-glacial carbonate is strongly variable from −3.5‰ to +5.8‰, whereas carbonate fissures in the underlying basement range between +4.1‰ and +5.7‰. Two independent palaeomagnetic studies have yielded low palaeomagnetic latitudes for the Mirbat Group.

Oxygen isotope records of stalagmites from China and Oman reveal a weak summer monsoon event, with a double-plunging structure, that started 8.21 ± 0.02 kyr B.P. An identical but antiphased pattern is also evident in two stalagmite records from eastern Brazil, indicating that the South American Summer Monsoon was intensifi ed during the 8.2 kyr B.P. event. These records demonstrate that the event was of global extent and synchronous within dating errors of

Two new graphoglyptid ichnogenera were found in the Upper Triassic turbiditic deep-sea fan deposits in Oman. Omanichnus virgatus igen. nov. et isp. nov. represents a burrow having a central axis from which branches deviate alternating to each side, the axis being at the same level of branching or very close to it. Vitichnus nizwaensis igen. nov. et isp. nov. represents a V-shaped structure composed of narrow-spaced, biserially arranged tubes alternating to each other side forming a plait-like pattern. Behaviorally it contains elements of Saerichnites beskidensis (formerly Hormosiroidea beskidensis) such as the plait-like arranged elements, that is, narrow-spaced, biserially arranged tubes directed alternating to each other side, but differs in the overall V-shape. These new trace fossils represent some of the earliest uniramous graphoglyptids in deep-marine deposits, which became diverse since the Late Cretaceous.

Uranium-series dated stalagmites from Oman indicate that pluvial conditions prevailed from 6.3 to 10.5, 78 to 82, 120 to 130, 180 to 200 and 300 to 330 kyr B.P.; all of these periods coincide with peak interglacials. Oxygen (δ18O) and hydrogen (δD) isotope ratios of speleothem calcite and fluid inclusions reveal the source of moisture and provide information on the amount of precipitation, respectively. δ18O and δD values of stalagmites deposited during peak interglacials vary between −8 and −4 ‰ (VPDB) and −53 and −20‰ (Vienna Standard Mean Ocean Water [VSMOW]) respectively, whereas modern stalagmites range from −2.6 to −1.1‰ in δ18O (VPDB) and −7.6 and −3.3‰ in δD (VSMOW), respectively. The growth and isotopic records indicate that during peak interglacial periods, the limit of the monsoon rainfall was shifted far north of its present location and each pluvial period was coinciding with an interglacial stage of the marine oxygen isotope record.

Stalagmite M1-5 from Socotra Island, Yemen in the northwest Indian Ocean provides a robust, high-resolution paleoclimate record from ∼ 27.4–11.1 ka based on 717 stable isotope and 28 230 Th measurements. Variations in M1-5 oxygen isotope ratios ( δ 18 O) are interpreted to be primarily driven by an amount effect related to changes in the mean position and/or intensity of convection of the intertropical convergence zone, the island's only source of precipitation. The M1-5 δ 18 O time series is strongly correlated to the Greenland ice cores, similar to an older Socotra speleothem deposited from 53–40 ka [S.J. Burns, D. Fleitmann, A. Matter, J. Kramers, A. Al-Subbary, Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13, Science 301 (2003) 1365–1367], indicating that a North Atlantic–Indian Ocean cold-dry/warm-wet teleconnection persisted through the end of the last glacial period. Peak aridification occurred at ∼ 23 ka and a gradual increase in moisture thereafter was interrupted by an abrupt drying event at ∼ 16.4 ka, perhaps related to Heinrich event 1. Indian Ocean rainfall increased dramatically during the Bolling period and then decreased continuously and gradually through the Allerod and Younger Dryas. The Holocene began abruptly with increased precipitation at 11.4 ka and was followed by a major but short-lived drying during the Preboreal Oscillation at ∼ 11.2 ka. M1-5 is highly correlated to the Dongge Cave record from 15.5–11 ka, suggesting much of the Indian Ocean monsoon region responded similarly to the major climate changes of the last deglaciation. The transitions into the Younger Dryas and to a lesser extent the Bolling are remarkably gradual in M1-5, as they are in all other Asian speleothem records, occurring over several centuries. These gradual transitions are in striking contrast to high-resolution records from around the North Atlantic basin where the transitions are extremely abrupt and generally occur in under a century. This spatially variable pattern of climate change is consistent with an Atlantic origin for these deglacial climate events.

The Ediacaran–Early Cambrian Ara Group in the South Oman Salt Basin consists of six evaporite–carbonate cycles (A0/A1 to A6) that record tectono-eustatic sea-level changes. The A4 cycle developed at the Precambrian–Cambrian boundary (∼ 542 Ma). It forms a single depositional sequence with evaporites deposited in a lowstand systems tract (LST). Overlying carbonates represent an open-marine shallowing-upward ramp succession that developed in transgressive (TST) and highstand systems tracts (HST). The low-energy carbonate ramp occupied a relatively protected site between a large shelf and an exposed paleogeographical high. The TST facies include sulfates, evaporite–carbonate laminites, and organic-rich carbonate laminites that record initial flooding, deepening of the basin, and establishment of an outer ramp depositional environment. Carbonate sediment flux was low and the environment was partly subject to cyclically elevated salinity. Subsequent HST facies comprise mostly fine-grained clastic carbonates and stromatolites that formed in middle and inner ramp settings. These facies show evidence of shoaling and establishment of a carbonate factory that probably operated over most of the middle and inner ramp. Sediment was redistributed in suspension, by muddy turbidity currents, muddy debris flows, storm and shallow-water currents. During the late HST, carbonate facies were affected by elevated salinity and recorded the gradual transition to the overlying LST evaporite unit. A combination of strong tectonic subsidence and transient flooding caused significant shallow-water evaporite deposition to occur not only down dip, but also on top of the former carbonate platform, where several hundreds of meters of evaporites accumulated. The transgressive carbonate laminites are the main reservoir facies and thus represent a relatively unusual reservoir unit. The presence of organic material and the relative scarcity of carbonate mud influenced diagenesis and reservoir properties. Distribution of organic material and carbonate mud can be linked to specific environmental conditions (low physical and biogenic disturbance of sediment and stratified water mass) and the sequence stratigraphic position (low flux of fine-grained carbonate during TST). In contrast, diagenetic evaporite formation has largely degraded reservoir quality in porous shallow-water facies near the top of the A4C.

Invertebrate and trace fossil assemblages in wet interdune deposits of the Wahiba Sand Sea record environmental changes associated with the Indian Ocean Monsoon system during the Early Holocene wet period. This period is dated locally by infrared stimulated luminescence (IRSL) from ca. 9300 to 5500 years ago. Lacustrine deposits from interdune areas of the central sand sea developed during peak precipitation 9300 years (IRSL) ago. The deposits represent short-lived but permanent lakes characterized by salinity tolerant freshwater snails and ostracodes. Diverse trace fossils exposed on the present-day surface show that the dried out lake sediments became substrates for the dwelling, feeding, and reproductive activities of insects. This period of continued moist conditions with pronounced vegetation cover is recorded in post-lacustrine, wet interdune deposits from the coastal Wahiba Sand Sea. A 4-m thick succession of interdune deposits was dated to ca. 8500–5500 years (IRSL). This interdune succession shows intense bioturbation by rhizocretions and insect burrows and nests. Both sites of wet interdune deposits show that changes of moist conditions during the Early Holocene wet period can be monitored by a variety of biological indicators. The ecological information of in situ animal species and trace fossil assemblages adds to the understanding how climatic changes are expressed in continental environments.

Sandstones of the Early Paleozoic Miqrat Formation and Barik Sandstone Member (Haima Supergroup) are the most prolific gas/condensate containing units in the northern part of the Interior Oman Sedimentary Basin (IOSB). The reservoir-quality of these sandstones, buried to depths exceeding 5 km, is critically related to the depositional environment, burial-related diagenetic reactions, the timing of liquid hydrocarbon charge and the replacement of liquid hydrocarbon by gas/condensate.The depositional environment of the sandstones controls the net-sand distribution which results in poorer reservoir properties northwards parallel to the axis of the Ghaba Salt Basin. The sandy delta deposits of the Barik Sandstone Member have a complex diagenetic history, with early dolomite cementation, followed by compaction, chlorite formation, hydrocarbon charge, quartz and anhydrite precipitation and the formation of pore-filling and pore-lining bitumen. In the Miqrat Formation sandstone, which is comprised of inland sabkha deposits, similar authigenic minerals occur, but with higher abundances of dolomite and anhydrite, and less quartz cement. The deduced pore water evolution from deposition to recent, in both the Miqrat Formation and the Barik Sandstone Member, reflects an early addition of saline continental waters and hydrocarbon-burial related mineral reactions with the likely influx of lower-saline waters during the obduction of the Oman Mountains.Four structural provinces are recognized in the IOSB based on regional differences in the subsidence/uplift history: the Eastern Flank, the Ghaba and Fahud Salt Basins and the Mabrouk-Makarem High. In the Fahud Salt Basin, biodegradation of an early oil charge during Late Paleozoic uplift resulted in reservoir-quality degradation by bitumen clogging of the pore space. On the Eastern Flank and the Mabrouk-Makarem High, however, the early oil bypassed the area. In contrast, post-Carboniferous liquid hydrocarbons were trapped in the Mabrouk-Makarem High, whereas on the Eastern Flank surface water infiltration and loss of hydrocarbons or biodegradation to pore occluding bitumen occurred. In the Ghaba Salt Basin, post-Carboniferous hydrocarbon charge induced a redox reaction to form porosity/permeability preserving chlorite in the reservoirs. The liquid hydrocarbons were replaced since the obduction of the Oman Mountains by gas/condensate which prevented the deep parts (>5,000 m) of the Ghaba Salt Basin from pore occluding pyrobitumen and thus deterioration of the reservoir quality.

Terminal Neoproterozoic and Cambrian evaporite rocks worldwide record a marked sulphur isotope excursion to very heavy δ 34 S isotopes that reflect a period of significant burial of reduced sulphur. New δ 34 S data from anhydrite and pyrite of the Ara Group in Oman extend this record to Arabia. Depositional history of the Ara Group spans c . 8 Ma across the terminal Neoproterozoic–Cambrian boundary. Therefore, these rocks provide a detailed record of sulphur isotopic evolution in this important time interval. Ara Group sulphur isotope values include a mean δ 34 S anhydrite of 39.4‰ ± 2.6‰ (1σ; range 32.4–46.4‰; n =61), and a mean δ 34 S pyrite of 1.4‰ ± 7.3‰ (1σ; range −10.8‰ to 11.4‰; n =12). The isotope signatures were not altered significantly during diagenesis and are representative of the isotopic composition of parent waters in the basin. Marine bromine concentrations in halite and marine fossils in associated carbonate rocks indicate that these waters had a marine origin. Bacterial sulphate reduction was the dominant process leading to the segregation between isotopically heavy sulphur incorporated in evaporite rocks and isotopically light sulphur buried in pyrite and organic matter. Strong sulphate reduction operated in a hypersaline and partly anoxic basin; these environmental conditions were also conducive to the preservation of organic material and make the Ara Group a prolific hydrocarbon province. Significant variation of the observed values is attributed to the inherent variability of bacterial sulphate reduction, including partially closed-system behaviour, disproportionation processes, limited diagenesis, and possibly secular variation of sulphur isotopes within the basin. Ara Group δ 34 S anhydrite values overlap with data from other terminal Neoproterozoic to Cambrian basins, but the mean δ 34 S anhydrite is highest in Oman. This observation cannot be attributed solely to the specific anoxic conditions and strong bacterial sulphate reduction in Oman, because such conditions were widespread in most evaporite basins of the terminal Neoproterozoic–Cambrian Periods. Instead, slight age differences between these basins can introduce a bias in the sulphur isotope curve. Excellent preservation of Ara Group deposits and in particular the precise age constraints make the Ara Group representative for the seawater sulphur isotopic composition at the terminal Neoproterozoic–Cambrian boundary. As a result of the inherent variability of bacterial sulphate reduction, δ 34 S values at the lower end of the spectrum should be most representative for the global signal. Based on results of this study, the global signal is estimated to be approximately 35–40‰.

High-resolution stable isotope profiles of three contemporaneously deposited stalagmites from a shallow cave in Southern Oman provide an annually resolved record of Indian Ocean monsoon rainfall variability for the past 780 years. Uranium-series age dating and counts of annual growth bands enable an excellent age calibration. Although modern speleothems do not grow in perfect isotopic equilibrium, oxygen isotope ratios (δ18O) are a proxy for the amount of monsoon rainfall. This is supported by the statistically significant correlation between δ18O and the thickness of annual bands, whereas δ18O is inversely correlated with annual band thickness. Additionally, overlapping δ18O profiles are very similar in pattern and range, indicating that sample specific noise did not blur the climatic signal. The longest oxygen isotope profile, derived from stalagmite S3, clearly shows the transition at ∼1320 AD from a generally wetter Medieval Warm Period to a drier Little Ice Age that lasted from approximately AD 1320–1660 in Southern Oman. The decrease in monsoon rainfall since the 1960s is also obvious in meteorological records from Northern Africa and India, indicating that our speleothem-based rainfall records do not only reflect local monsoon rainfall variability.

Six evaporite-carbonate sequences are recognized in the terminal Neoproterozoic-Early Cambrian Ara Group in the subsurface of Oman. Individual sequences consist of a lower, evaporitic part that formed mainly during a lowstand systems tract. Overlying platform carbonates contain minor amounts of evaporites and represent transgressive and highstand systems tracts. Detailed sedimentological and geochemical investigation of the evaporites allowed reconstruction of the depositional environment, source of brines and basin evolution. At the beginning of the evaporative phase (prograding succession), a shallow-water carbonate ramp gradually evolved into a series of shallow sulphate and halite salinas. Minor amounts of highly soluble salts locally record the last stage of basin desiccation. This gradual increase in salinity contrasts sharply with the ensuing retrograding succession in which two corrosion surfaces separate shallow-water halite from shallow-water sulphate, and shallow-water sulphate from relatively deeper water carbonate respectively. These surfaces record repeated flooding of the basin, dissolution of evaporites and stepwise reduction in salinity. Final flooding led to submergence of the basin and the establishment of an open-water carbonate ramp. Marine fossils in carbonates and bromine geochemistry of halite indicate a dominantly marine origin for the brines. The Ara Group sequences represent a time of relatively stable arid climate in a tectonically active basin. Strong subsidence allowed accommodation of evaporites with a cumulative thickness of several kilometres, while tectonic barriers simultaneously provided the required restricted conditions. Subsidence allowed evaporites to blanket basinal and platform areas. The study suggests a deep-basin/shallow-water model for the evaporites.

Exceptionally rich Permian fusulinid assemblages, varying in age from Yakhtashian to Dzhulfian, were found in reworked limestone blocks from conglomerates of the Aseelah Unit, recently defined in the Batain Plain and dated possibly as Upper Triassic. This paper only deals with the Middle Permian, Midian (= Capitanian) microfaunas from the conglomerates. The Aseelah Unit is found associated with the Triassic Sal Formation, tectonically overlying the Qarari Unit, and is dated as Middle to Late Permian based on ammonoid assemblages and conodonts. The boulders of the Aseelah Unit are composed of exclusively Permian skeletal limestones in a sandy matrix; the limestones were deposited on a shallow marine shelf environment from the southern Neotethys. The Qarari Unit is interpreted as a hemipelagic series deposited on the distal slope of the Arabian carbonate platform. The Midian foraminifers from the Batain Plain are similar to some assemblages of Transcaucasia, of the Abadeh area (Iran), of SW Turkey (Taurus Mountains), and some, especially the Neoschwagerinidae, exhibit affinities with microfaunas of the eastern Tethys terranes of Japan. However, similar Neoschwagerinid assemblages were not found in any significant area of the Arabian Peninsula (Oman Mountains, Huqf-Haushi area, and Khuff area).

Variations in the amount of solar radiation reaching the Earth are thought to influence climate, but the extent of this influence on timescales of millennia to decades is unclear. A number of climate records show correlations between solar cycles and climate, but the absolute changes in solar intensity over the range of decades to millennia are small and the influence of solar flux on climate is not well established. The formation of stalagmites in northern Oman has recorded past northward shifts of the intertropical convergence zone, whose northward migration stops near the southern shoreline of Arabia in the present climate. Here we present a high-resolution record of oxygen isotope variations, for the period from 9.6 to 6.1 kyr before present, in a Th-U-dated stalagmite from Oman. The delta18O record from the stalagmite, which serves as a proxy for variations in the tropical circulation and monsoon rainfall, allows us to make a direct comparison of the delta18O record with the Delta14C record from tree rings, which largely reflects changes in solar activity. The excellent correlation between the two records suggests that one of the primary controls on centennial- to decadal-scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation.

Shallow-marine, coastal-plain, and fluvial sediments of the Lower Permian Gharif Formation in the Interior Oman Sedimentary Basin presently range in depth from outcrop in the Huqf-Haushi area to almost 5000 m in the northwest. This large depth range results from a varied subsidence history with only minor uplift during the Late Triassic to Early Jurassic. The degree of diagenetic overprint varies, depending on burial history. Sandstone at shallow depth ( 2600 m) is highly compacted and tightly cemented by quartz, carbonate, and sulfate minerals. This varied diagenesis is caused by increasing temperature with burial, by surface-water infiltration during the Late Triassic to Early Jurassic, basin inversion and uplift in the Late Cretaceous along the southeastern basin margin, and obduction of the Oman Mountains in the Late Cretaceous. Depositional pore water was initially of low salinity (

An almost complete Permian sequence is reworked in the conglomerates and sandstones of the Aseelah Unit forming the lower part of the Batain Croup. This series of Late Permian to Earliest Triassic age overlies conformably the Qarari Unit, dated as Middle Permian by ammonoids. The bioclastic limestone pebbles and boulders deposited on shallow marine-shelf environments yield diversified assemblages of dasyclads, red algae, fusulinids and smaller foraminifers, indicating Yakhtashian, Bolorian, Kubergandian, Early Murgabian, Midian and Dzhulfian ages (systematic work in progress).

The Late Westphalian to Artinskian Haushi Group in the Sultanate of Oman consists of the glaciogenic A1 Khlata Formation and the Gharif Formation which contains marginal marine, coastal plain, and fluvial sediments. The sequence was deposited during a global-warming event following the Permo- Carboniferous glaciation of Gondwana. Because of a varied subsidence history, these sediments range from the surface in the SE to almost 5000 m in the NW of the basin. Mixed-layer illite-smectite (I-S) is an important constituent of the

This integrated study of the sedimentology, magnetostratigraphic chronology and petrography of the mostly continental clastics of the Oligocene to Miocene Swiss Molasse Basin underpins a reconstruction of facies architecture and delineates relationships between the depositional evolution of a foreland-basin margin and exhumation phases and orogenic events in the adjacent orogen. A biostratigraphically based high-resolution magnetostratigraphy provides a detailed temporal framework and covers nearly the whole stratigraphic record of the Molasse Basin (31.5–13 Ma). Three transverse alluvial fan systems evolved at the southern basin margin. They are characterized by distinct petrographic compositions and document the exhumation and denudation history of the growing eastern Swiss Alps. Enhanced northward propagation of the orogenic wedge is interpreted to have occurred between 31.5 and 26 Ma. During the period 24–19 Ma, intense in-sequence and out-of-sequence thrusting took place as Molasse strata were accreted to the orogenic wedge. A third active tectonic phase, possibly caused by backthrusting of the Plateau Molasse, probably occurred between ca. 15 and 13 Ma. Fan head migration between 31.5 and 13 Ma is probably controlled by the structural evolution of the thrust front due to Molasse accretion and backthrusting.

The combined information about sedimentary petrography from the North Alpine Foreland Basin and structural geology from the Alps allows a qualitative reconstruction of the drainage network of the central Swiss Alps between 30 Ma and the present. This study suggests that crustal thickening and crustal thinning significantly controlled the location of the drainage divide. It also reveals the possible controls of crustal thickening/thinning on the change of the orientation of the drainage network from across-strike between 30 and 14 Ma to along-strike thereafter. Initial crustal thickening in the rear of the wedge is considered to have formed the drainage divide between north and south at 30 Ma. Because the location of crustal thickening shifted from east to west between ≈30–20 Ma, the catchment areas of the eastern dispersal systems reached further south than those of the western Alpine palaeorivers for the same time slice. Similarly, the same crustal dynamics appear to have controlled two phases of denudation that are reflected in the Molasse Basin by petrographic trends. Uplift in the rear of the wedge caused the Alpine palaeorivers to expand further southward. This is reflected in the foreland basin by increasing admixture of detritus from structurally higher units. However, tectonic quiescence in the rear of the wedge allowed the Alpine palaeorivers to cut down into the Alpine edifice, resulting in an increase of detritus from structurally lower units. Whereas uplift in the rear of the wedge was responsible for initiation of the Alpine drainage systems, underplating of the external massifs some 50 km further north is thought to have caused alongstrike deviation of the major Alpine palaeorivers. Besides crustal thickening, extension in the rear of the wedge appears to have significantly controlled the evolution of the drainage network of the western Swiss Alps. Slip along the Simplon detachment fault exposed the core of the Lepontine dome, and caused a 50-km northward shift of the drainage divide.

Magnetostratigraphic chronologies, together with lithostratigraphic, sedimentological, and petrological data enable detailed reconstruction of the Oligocene to Miocene history of the North Alpine foreland basin in relation to specific orogenic events and exhumation of the Alps. The Molasse of the study area was deposited by three major dispersal systems (Rigi, Hohronen, Napf). Distinguished by characteristic heavy mineral suites, conglomerate clast populations, and the presence of key clasts, these systems record three major phases of denudation of the Alpine edifice. The Rigi system eroded the Austroalpine and Penninic nappes of eastern Switzerland from 30 to 25.5 Ma as a result of backthrusting and uplift of these units along the Insubric Line. Subsequent uplift of the Aar massif some 40 km to the north appears to have controlled the duration of the Hohronen and Napf dispersal systems, spanning 24–22 Ma and 21.5–15 Ma, respectively. They record downcutting into the crystalline cores of the Penninic and Austroalpine nappes of eastern (Hohronen) and western (Napf) Switzerland. High-resolution reconstruction of the structural and geometrical evolution of the proximal Molasse reveals in-sequence and out-of-sequence thrusting events at the Alpine front and incorporation of the Molasse into the orogenic wedge by in-sequence thrusting and underplating. Furthermore, it reveals close relationships between periods of rapid denudation in the central Alps and phases of increased sediment accumulation rates at the proximal basin border. An initial increase in Molasse accumulation rates to >1 km/m.y. occurred between 30 and 25.5 Ma and coincides with the Insubric phase of backthrusting along the eastern Insubric Line, where >10 km of vertical displacement is interpreted. During the same time span, the Alpine wedge propagated forward along the basal Alpine thrust, as indicated by the coarsening- and thickening-upward megasequence and by occurrence of bajada fans derived from the Alpine border. The end of this tectonic event is marked by a basinwide unconformity, interpreted to have resulted from crustal rebound after initial loading. A subsequent increase in accumulation rates to >1 km/m.y. between 23 and 21.5 Ma coincides with initial uplift of the eastern Aar massif by at least 4 km. This phase of high accumulation rates is associated with incorporation of early Chattian conglomerates into the orogenic wedge. The third advance of the Alpine wedge between 21 and 15.5 Ma caused underplating of Molasse deposits, resulting in synsedimentary backthrusting of previously deposited Molasse sequences and in the development of a progressive unconformity. A rapid increase in accumulation rates from 0.35 to >1 km/m.y. between 15.5 and 15 Ma marks the final loading event in the wedge, which may be caused by further major displacement and loading of the Aar massif. This deformation is coeval with out-of-sequence thrusting of the Helvetic border chain and of the piggyback stack of North Penninic and Ultrahelvetic Flysch nappes along the basal Alpine thrust.

Four stalagmites covering the last 7.0 ka were sampled on Socotra, an island in the northern Indian Ocean to investigate the evolution of the northeast Indian Ocean Monsoon (IOM) since the mid Holocene. On Socotra, rain is delivered at the start of the southwest IOM in May–June and at the start of the northeast IOM from September to December. The Haggeher Mountains act as a barrier forcing precipitation brought by the northeast winds to fall preferentially on the eastern side of the island, where the studied caves are located. d18O and d13C and Mg/Ca and Sr/Ca signals in the stalagmites reflect precipitation amounts brought by the northeast winds. For stalagmite STM6, this amount effect is amplified by kinetic effects during calcite deposition. Combined interpretation of the stalagmites' signals suggest a weakening of the northeast precipitation between 6.0 and 3.8 ka. After 3.8 ka precipitation intensities remain constant with two superimposed drier periods, between 0 and 0.6 ka and from 2.2 to 3.8 ka. No link can be established with Greenland ice cores and with the summer IOM variability.In contrast to the stable northeast rainy season suggested by the records in this study, speleothem records from western Socotra indicate a wettening of the southwest rainy season on Socotra after 4.4 ka. The local wettening of western Socotra could relate to a more southerly path (more over the Indian Ocean) taken by the southwest winds. Stalagmite STM5, sampled at the fringe between both rain areas displays intermediate d18O values. After 6.2 ka, similar precipitation changes are seen between eastern Socotra and northern Oman indicating that both regions are affected similarly by the monsoon. Different palaeoclimatologic records from the Arabian Peninsula currently located outside the ITCZ migration pathway display an abrupt drying around 6 ka due to their disconnection from the southwest rain influence. Records that are nowadays still receiving rain by the southwest winds, suggest a more gradual drying reflecting the weakening of the southwest monsoon.

An organic-rich laminated chert (silicilyte) consisting of up to 90% microcrystalline quartz that formed at the Precambrian–Cambrian boundary acts as a light-oil reservoir in the subsurface of the South Oman Salt Basin, Sultanate of Oman. Fully encased in salt domes, it was first discovered during the 1990's hydrocarbon exploration activities of Petroleum Development Oman. Because of the economic significance and the unconventional reservoir characteristics, there is great interest in understanding the origin of the laminated chert, its source of silica and mode of precipitation in an anoxic, sulphur-rich, stagnant and highly saline basin. The homogeneous distribution and high values of stable Si isotope composition (avg. δ 30 Si = 0.83 ± 0.28) coupled with a low molar Ge/Si ratio ( −6 ) of the microcrystalline matrix quartz clearly reveal dissolved silica in the seawater as the Si source, whereas hydrothermal or biogenic (e.g. sponge-derived) silica can be excluded. Silica precipitation from seawater was likely the result of a dramatic increase in salinity in response to salt dissolution atop and adjacent to the edges of transtensional depressions on the deep basin floor, thus markedly reducing the solubility of amorphous silica in these brine-filled seawater depressions. This saturation triggered the formation of silica-gel, which accumulated at the basin floor forming a soft silica-rich layer on bacterial mats giving rise to a laminated sediment. The mean number of laminae is ca. 32 per year suggesting that layering is non-annual and controlled by processes such as fluctuations in nutrient supply, lunar driven re-mixing or diagenetic segregation. The transformation of the silica-gel to microcrystalline quartz occurred below 45 °C indicating a less than −4.5‰ δ 18 O composition of the pore-water during microcrystalline quartz formation.

Oxygen-isotope ratios of a stalagmite from Socotra Island in the Indian Ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present. The pattern of precipitation bears a striking resemblance to the oxygen-isotope record from Greenland ice cores, with increased tropical precipitation associated with warm periods in the high northern latitudes. The largest change, at the onset of interstadial 12, occurred very rapidly, in about 25 years. The chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period.

The strontium isotopic compositions of carbonates from the Huqf Group of Oman provide the first data on the Sr isotopic composition of seawater during the latest Precambrian. The data show that the isotopic composition of seawater was increasing relatively rapidly, from values of ∼ 0.7082 at ∼ 560 Ma, to values of ∼ 0.7090 at ∼ 540 Ma. When combined with data from older carbonates, the data verify a large change in the isotopic composition of late Precambrian seawater, from < 0.7070 at ∼ 680 Ma, to ⩾ 0.7090 in the early Cambrian. Thus, late Precambrian seawater Sr isotope ratios should eventually prove to be useful for stratigraphic correlation. The causes of the increase in seawater 87Sr86Sr are interpreted to be due in part to increased continental weathering associated with extensive tectonic activity of the Pan-African orogeny and the Varangian and Sinian glacial periods, which increased the riverine flux of Sr to the oceans and may also have increased the isotopic ratio of the riverine Sr flux. Massbalance calculations suggest that the change must have also in part been caused by a decrease in the hydrothermal flux of Sr to the oceans.

Aeolian deposits in the Wahiba Sands, Sultanate of Oman, reveal patterns of atmospheric circulation over the past 160,000 years. Luminescence dating indicates a correlation of dune activity with periods of low global sea level and decreased monsoon intensity. Evidence from dune orientation and sedimentary structures shows exclusively northbound transport of sand during times of high- latitude glaciation. These results are in contrast to the current paleocirculation model that assumes an increase of northwesterly winds because of a southward shift of the Intertropical Convergence Zone. Our results indicate that the circulation pattern during glacial times was comparable to that of the present.

Keuper (Upper Triassic) fluvial sandstones and nonmarine carbonate rocks form a major oil reservoir in the western Paris Basin at burial depths of nearly equal 2 km. Early-diagenetic processes comprise red-bed-type diagenesis (mechanical clay infiltration, iron-oxide precipitation) and extensive dolocrete formation both in fluvial channels and in fine-grained overbank sediments. Locally significant paleokarst created vuggy dissolution porosity in the carbonate units and probably also caused leaching of detrital alkali feldspar grains. Oxygen, carbon, and strontium isotope analyses of various eogenetic cements indicate a nonmarine pore-water composition. Ferroan carbonates, authigenic albite and potassium feldspar, quartz, sulfates, sulfides, and clay minerals formed subsequent to major mechanical compaction. Their isotopic compositions record significant changes in the chemistry of the parent pore water. Cl-Br relationships of the present-day pore water reveal that fluids saturated with respect to halite flushed the reservoir during burial. This is documented by the oxygen-isotope composition of the burial cements. Based on radiogenic dating of illite cements, influx of warm brines into the reservoir most likely occurred during the earliest Cretaceous. At this time the margins of the basin were uplifted by late Cimmerian tectonism, resulting in an unconformity at the Jurassic/Cretaceous boundary. We suggest that uplift of the Vosges crustal block created a hydraulic head in the eastern part of the basin and established a gravity-driven fluid flow system, displacing interstitial brines from the Keuper evaporites from the eastern part towards the western part of the basin. Fluid-inclusion studies indicate that brine-influenced cementation occurred at progressively higher temperatures, reaching peak temperatures of

A vast bajada consisting of coalescing low-gradient (

A 50 kyr-long exceptionally well-dated and highly resolved stalagmite oxygen (δ 18O) and carbon (δ 13C) isotope record from Sofular Cave in northwestern Turkey helps to further improve the dating of Greenland Interstadials (GI) 1, and 3–12. Timing of most GI in the Sofular record is consistent within ±10 to 300 years with the “iconic” Hulu Cave record. Larger divergences (>500 years) between Sofular and Hulu are only observed for GI 4 and 7. The Sofular record differs from the most recent NGRIP chronology by up to several centuries, whereas age offsets do not increase systematically with depth. The Sofular record also reveals a rapid and sensitive climate and ecosystem response in the eastern Mediterranean to GI, whereas a phase lag of ∼100 years between climate and full ecosystem response is evident. Finally, results of spectral analyses of the Sofular isotope records do not support a 1,470-year pacing of GI.

[1] The 8.2 ka event was triggered by a meltwater pulse (MWP) into the North Atlantic and resultant reduction of the thermohaline circulation (THC). This event was preceded by a series of at least 14 MWPs; their impact on early Holocene climate has remained almost unknown. A set of high-quality paleoclimate records from across the Northern Hemisphere shows evidence for a widespread and significant climatic anomaly at ∼9.2 ka B.P. This event has climatic anomaly patterns very similar to the 8.2 ka B.P. event, cooling occurred at high latitudes and midlatitudes and drying took place in the northern tropics, and is concurrent with an MWP of considerable volume (∼8100 km3). As the 9.2 ka MWP occurs at a time of enhanced baseline freshwater flow into the North Atlantic, this MWP may have been, despite its relatively small volume, sufficient to weaken THC and to induce the observed climate anomaly pattern.