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Drill core and outcrop samples of pure marine chemical sediments (banded iron formation (BIF), manganese formation (MnF), jaspilites, lutites, and cherts) from the transition of the ~2426 Ma old Ongeluk Formation into the 2413 Ma old Hotazel Formation, Transvaal Supergroup, South Africa, reveal remarkable changes of seawater chemistry in the Transvaal Ocean. Similar to pre-Ongeluk chemical sediments, the shale-normalized rare earths and yttrium (REYSN) patterns of jaspilites intercalated with the volcanic rocks of the Ongeluk large igneous province and directly overlying cherts do not show positive EuSN anomalies, indicating that high-temperature (>250 °C) hydrothermal fluids did not contribute significantly to the REY budget of ambient waters. However, a 10 cm drill core section in the lower Hotazel Formation is characterized by conspicuous positive EuSN anomalies, revealing temporary inflow of water masses strongly affected by high-temperature hydrothermal fluids. After this short episode, the REYSN pattern of Transvaal seawater returned to that of pre-Ongeluk times, showing heavy REYSN enrichment, positive LaSN, GdSN and YSN anomalies, but no CeSN or EuSN anomalies. Higher up in the stratigraphy, the Hotazel Formation shows negative CeSN anomalies in some of the lutites, BIFs and MnFs, reflecting Ce depletion in ambient seawater. All Hotazel lutite, BIF, and MnF samples studied show unradiogenic eNd(t) values (−0.5 ± 0.2 to −2.4 ± 0.2), indicating a mostly continental REY source. The REY distribution and Nd isotope data combined suggest that oxidative terrestrial weathering of this continental crustal source supplied most of the dissolved REY to local “Transvaal seawater”. Precipitation of the Hotazel lutites, BIFs and MnFs with negative CeSN anomalies, therefore, suggests that oxic conditions prevailed on the Kaapvaal Craton and in Hotazel seawater already at ~2.413 Ga, i.e. 80 m.y. before the disappearance of mass-independent sulfur isotope fractionation (MIF-S) that defines the Great Oxidation Event at ~2.33 Ga.

We provide new data on the Black Sea evolution during the preconnection and reconnection stages with the Mediterranean, based on sedimentology, geochemistry, calcareous nannoplankton and ostracods analysis, in 13 cores placed between 141 m and 1315 m water depths. Unit 1 – The Coccolith Mud, Unit 2 - The Sapropel Mud and Unit 3 – The Lacustrine Lutite, including red-brownish depositional intervals, were identified in all studied deep-water cores. These units are not present in a shallow setting, i.e., above 166.7 m water depth, being replaced by sandy levels and shell debris. The red-brownish layers are interpreted as hyperpycnites, but some of the red successions show turbidite features, especially the ones situated on canyon sides, at a water depth below 600 m. In the oldest intercepted Unit 3 of the Neoeuxinian lake, CaCO3 values are constantly low, but towards the top of this unit they show two distinct peaks, interpreted as signals of Bolling–Allerod and Preboreal interstadials. In between, a significant decrease in CaCO3 values, linked to the setting of the Younger Dryas, is coincident in the deep cores with diatom blooms and high frequency of ostracods related to cooler waters. The scarce but continuous occurrence of Emiliania huxleyi nannoplankton species from the top of Unit 3 indicates that the salinity was at least 10–11‰ prior the Sapropel Mud deposition and increase at a least 17‰ within the lower part of Unit. 2. In the same interval, the Ponto-Caspian ostracods are still present. The Mediterranean ostracods consistently occur from the top of Unit 2, when bottom water salinity reached values for allowing their survival. The first bloom of E. huxleyi is placed at the base of Unit 2, where coccolith laminae occur, while the second bloom is placed in Unit 1 that contains exclusively Mediterranean ostracods and consistent assemblages of benthonic foraminifers, similar with the ones present today.

The Pico do Itapeva Formation is a key metasedimentary unit to the understanding of the extensional events that occurred between the late stage of the southern Brasilia Orogen collision and the main collision in the central Ribeira Orogen. The formation crops out in a 20 km long NE-trending narrow belt in the Mantiqueira mountain range in eastern Sao Paulo State, Brazil. It is located in the interference zone of the southern Brasilia and the central Ribeira orogens and records deformation and greenschist facies metamorphism (biotite zone) related to the Brasiliano orogeny. The Pico do Itapeva Formation rests unconformably on a metaigneous substratum of the Socorro-Guaxupe Nappe/Embu Terrane and, on the southern side, is truncated by a steep SE-dipping dextral reverse shear zone. It consists of a coarsening- and thickening-upward succession, with minimum thickness of 800 m, composed of lutite, arkose and conglomerate. These rocks constitute three distinct lithofacies associations: LAI- arkose, arkose-lutite composite beds, lutite and fine conglomerate beds; LAII- arkose, pebbly arkose and scarce lutite and; LAIII- conglomerate and pebbly arkose. Most of the beds are massive; graded beds, dish and convolute structures occur locally. Bed thickness varies from thin to very thick and amalgamated bodies constitute up to 30m thick strata. Three mappable units at scale 1:20,000 were recognized based on different proportions of the three lithofacies associations. The deposits are interpreted as the record of mass flows and associated processes in a fan delta setting developed in an intermontane rift basin. U-Pb LA-ICP-MS detrital zircon ages suggest the maximum depositional age at ca. 611 Ma and the basin evolution is interpreted in the range between 611 and 580 Ma during an inter-orogenic stage between the Brasilia and Ribeira orogenies.

The Aptian Crato Member of the Araripe Basin is a 50-m-thick succession of laminated limestones alternated with siliciclastic rocks. This unit has been receiving attention worldwide mainly because it is one of the most famous fossil Konservat-Lagerstatten, where were identified well-preserved paleofauna and paleoflora. Clay mineralogy and lithogeochemical data have been widely used in paleoenvironmental, paleoclimatic and provenance reconstructions. However, these techniques were not systematically used to study the Crato Member rocks. This study reports the mineralogical and lithogeochemical characterization of the Crato Member lutites looking for paleoenvironmental, paleoclimatic, and provenance reconstructions. Facies analysis, X-ray diffractometry, lithogeochemical, and scanning electron microscopy studies were carried out on thirteen Crato Member lutite samples in the Tres Irmaos quarry, near Nova Olinda County. Regional arid paleoclimate conditions were identified using clay mineral assemblages and two paleoenvironmental models with subtle paleoprecipitation and provenance differences were interpreted. In the lower Tres Irmaos quarry, a tidal-dominated delta mouth bar facies succession coincident with a clay mineral association with lesser kaolinite contents was identified, which indicates drier conditions. Lithogeochemical data suggests provenance from Archean felsic rocks. In the upper Tres Irmaos quarry, a marginal paleolagoon facies succession coincident with a clay mineral association with higher kaolinite contents was recognized, which indicates wetter conditions. Lithogeochemical data indicate provenance from mixed Post-Archean to Archean felsic-mafic rocks. The paleolagoon water was interpreted as brackish and sudden paleosalinity increases indicated seawater inputs, which were also responsible for raising the paleolagoon water table in the marginal paleolagoon facies succession, which presented paleoenvironmental proxies suggesting a more expressive marine character.

A complex of inactive tufas, the thickness of which reaches 3.5 m, was studied in the lowermost segment of the Sąspowska Valley in the Krakow Upland (Ojcow National Park, Poland). Five fluvial tufa barrages were recognized. They are composed of moss tufa and stromatolitic tufa accompanied with oncoidal rudstone and detrital tufa. Interbarrage ponded areas were filled with detrital tufa, lutite, and subordinately oncoidal rudstone, limestone gravel and peat-like deposit. Radiocarbon dates suggest that the tufa formed during Subboreal, Boreal and Atlantic time. The main difference between the tufa in the Sąspowska Valley and contemporaneous tufas in other valleys of the Krakow Upland is the higher amount of non-carbonate fraction in the former. Other Lower and Middle Holocene tufas of the Krakow Upland are composed mainly or exclusively of carbonate fraction. The non-carbonate fraction in fluviatile tufas in the Sąspowska Valley resulted from erosion of loess cover in the upper part of the catchment. The erosion was related to local activity of Neolithic flint miners who cleared forest at a local scale, dug shafts in loess cover and exploited flints from underlying weathered residuum of Jurassic limestone. Consequently, they made copious amounts of loose material available for transport down the valley and subsequent trapping within the tufa depositional system.

The Ipubi Formation in the Araripe Basin (Northeast Brazil) has evaporite-lutite successions rich in gypsum, a mineral of great regional economic relevance, a highlighted stratigraphic mark, and also a natural boundary for underlying successions potentially analogous to “Pre-Salt” hydrocarbon reservoirs of the Brazilian coastal basins. In this study, syngenetic and diagenetic aspects of the Ipubi Formation at Santana do Cariri (Ceara State) were investigated by means of facies analysis, petrography, and mineralogical/chemical analyses of evaporites and shales. The results show that the contact relationship between evaporites and marly shales, without signs of subaerial exposure and laterally adjacent, was associated with shallow, calm and somewhat anoxic waterbodies, locally salt-supersaturated (brines) but under seasonal variations of water levels. This scenario could have shared place with hydrothermal phenomena in a playa lake depositional system. Regarding diagenesis, although there is evidence supporting pseudomorphic replacement of gypsum by anhydrite, the burial of the Ipubi Formation would have been limited due to the frequent occurrence of gypsum without any trace of chemical replacement.

This study presents a mineralogical and mechanical analysis of the clay-rich materials and structures identified in the Galera Fault Zone, southern Spain that formed as a consequence of active deformation processes affecting this seismically active region. Significant differences in clay mineral assemblages and chemical composition were identified in rocks from the Galera Fault Zone, through a series of analytical techniques including XRD, SEM, TEM and XRF. Three distinct mineral assemblages were identified: 1) wall-rock assemblages including white marls and dark lutite layers, with the latter also found in injection features. Their assemblage includes dolomite, gypsum, quartz, calcite and phyllosilicates 2) smectite- and palygorskite-rich fault gouges formed on materials from the upper part of the stratigraphic sequence at the NE area of the fault (Galera Village), and 3) sepiolite-rich gouges in areas of the lower part of the stratigraphic sequence at the central SW segment of the fault (Rambla de los Pilares). Fibrous clay-rich gouges were formed by hydrothermal alteration during periods of fluid-rock interaction that was concentrated in fault planes and fractures. Their mineralogy is dominated by authigenic Mg-rich fibrous clay minerals; sepiolite, precipitated directly from an Mg-rich fluid; and palygorskite as the product of the interaction of the fluid with the Al-rich host rock. Experimental data from frictional sliding experiments on these clay-rich fault gouges reveal strong differences in their mechanical properties. Towards the north-eastern areas of the fault, the smectite- and palygorskite-rich gouge has a low friction coefficient (0.17 wet and 0.59 under vacuum) and its values of the friction stability parameter (a–b) are always positive indicating a stable regime that could be related with creeping and stable-sliding processes. In the central-south-western segment, however, the gouge is rich in authigenic sepiolite and presents complete absence of smectite. The higher friction coefficient (0.47 wet and 0.68 under vacuum) and negative values of a–b for this gouge suggest a more neutral to unstable regime that could favour earthquake nucleation.

The Paleozoic flora of the state of Puebla is characterized by the presence of ancient and conservative lineages; we focus this study on the taxonomical Annularia, Bjuvia and the new morphotype. These groups are found in carbonaceous lutite, where paleosoils, small roots and trunks in situ are abundant, and have been associated with swampy environments. In this paper, we discuss the presence of a new architectural form of megaphyll size that has not been registered in other Permian locations. These lutite imprints are the second most abundant in this location and their degree of preservation supports their autochthonous nature. The large size of its funnel-shaped blade and its extremely long petiole support the idea that its size was a response to a competition for biotic resources and to the hydric stress to which communities of this region were exposed, as consequence of the environmental conditions prevailing at the end of the Paleozoic era. It is proposed that they lived in environments with seasonal humidity and this hypothesis is supported by both the abundance of fossil groups and lithology.

The characterisation of sepiolite-bearing samples from five lutite associations occurring in the Cerro de los Batallones deposit has been carried out. Based on both the composition and texture of the sepiolite, two main formation patterns for this clay mineral, transformation from saponite by dissolution–precipitation and direct precipitation from solution, is proposed. From a compositional point of view, sepiolite oscillates between typical Mg-rich sepiolite and near Al-rich sepiolite, all samples showing variable swelling with ethylene glycol (up to 0.25 A). There is a relationship between mechanism of formation and crystallinity of the sepiolite mineral. Both DRX and FTIR analyses led to differentiate between low crystallinity sepiolite (LCS) and high crystallinity sepiolite (HCS). The presence of the triplet 2.61 A, 2.58 A and 2.56 A is especially useful for HCS identification. The two types of sepiolite show slightly a different thermal behaviour. In particular, coordinated water loss at 350 °C in LCS is higher than in HCS. BET surface area is high in all studied samples, reaching up to 360 m 2 /g and 328 m 2 /g in LCS and HCS, respectively. Differences in the microporosity and mesoporosity contribution have also been recognised. The reported dissimilarities account for differences in the technological behaviour of sepiolite clays and therefore these differences must be taken into account as they constrain industrial uses.

The Carboniferous Coal Basin (CCB) in NW Spain has been extensively mined for a long time. At present, abandoned and flooded mines constitute “mining reservoirs” which act as storage facilities containing mine water susceptible to being exploited as a geothermal resource to supply heating and cooling using heat pumps. The development of numerical models capable of predicting the geothermal behaviour of the reservoir after a certain number of years of use can be useful and applicable to this and other sedimentary mining basins. A procedure for predicting in situ thermal conductivity (k) profiles using lithological and mineralogical information for modelling purposes was applied to a mining reservoir in the CCB. First, all the involved geological units were sampled in unaltered outcrops, assuming that weathering have not significantly biased thermal properties. The matrix thermal conductivity of each sample was estimated from the thermal conductivities of the respective mineralogical components, whose proportion were determined by optical microscopy. A final k was acquired considering the effects of porosity, temperature and mineralogical composition of the rock matrix and assuming water as the pore-filling fluid. Finally, the obtained parameters were extended to the deep geological profile, affected by the mining works. Values ranging from 1.42 W m−1 K−1 (lutite) to 4.89 W m−1 K−1 (sublitarenite) were found in the studied reservoir (average of 2.86 W m−1 K−1).

The Kalahari Manganese Deposit (KMD) is the largest land-based manganese deposit, hosting approximately 80% of the world's known, mineable manganese resources. The deposit, located near Kuruman in the Northern Cape Province of South Africa, is one of five erosional relics of the Paleoproterozoic (ca. 2.2 Ga) Hotazel Formation, with sedimentary manganese ores occurring as up to 50 m thick beds interbedded with banded iron-formation (BIF) and hematite lutite. The study focuses on the manganese ores of the Nchwaning–Gloria mining area of the northern KMD. In this area, pronounced mineralogical and major element alteration was imparted on the sedimentary manganese ores by a structurally-controlled hydrothermal fluid flow event. Most notable effects of hydrothermal alteration are the decomposition and leaching of Ca- and Mg-carbonate, and marked residual enrichment of manganese. On the basis of mineral assemblage, grade, texture and geochemical characteristics, three ore types were distinguished in the studied sample set, classified into least altered (LA), partially altered (PA) and advanced altered (AA) types. Advanced altered ores may be further classified into five different types, based on mineral assemblages that contain hausmannite and/or braunite as significant minerals. The rare earth element (REE) geochemistry of these fundamental ore types was studied in detail, to document REE mobility during hydrothermal alteration. Total REE concentrations in LA ores were found to be very low (14–22 ppm) and remarkably uniform, within the range typically observed for BIF. Hydrothermal alteration results in residual enrichment and a much larger scatter in REE contents. A small Ce anomaly observed in the protolith remains similar in magnitude when observed in PAAS-normalised REE plots. The data define, however, a power trend in the (Ce/Ce*) vs (Pr/Pr*) diagram. Such behaviour is interpreted in terms of a conservative system that was predominantly protolith-buffered. Local remobilisation of REE during hydrothermal alteration is attributed to the dissolution of diagenetic apatite and redistribution of hydrothermal trace minerals, including neoformed apatite, monazite and cerianite.

In this study, we describe the structural diagenesis of diluted turbidite and abyssal lutite deposits of the late Albian Black Flysch (western Pyrenees, northern Spain). We analyze and interpret an association of brittle and ductile soft-sediment deformation structures. To our knowledge, some of them are described for the first time, although they are known in other tectonic settings. We reconstruct a diagenetic history that commenced with a generalized siderite cement precipitation after siliciclastic turbidite deposition. Siderite replaced the finer-grained, diluted uppermost turbidite parts. Siderite precipitation was followed by calcite cementation in turbidites and by soft-sediment brittle (thrust planes, shear veins, and microveins) and ductile (fault-bend folds and culminations developed in relation to thrust-ramp strain) deformation structures. This occurred before hosting lutite lithification by dewatering and compaction.

Gypsum deposits are the currently exploited sulphate rocks with industrial purposes. In addition to the expensive drilling projects, geophysical techniques can be considered to estimate the economical potential of these deposits. An electrical resistivity tomography survey has been carried out in the Pira gypsum formation (SE of the Catalan margin of the Tertiary Ebro Basin, Spain). Additionally, a continuous coring drill was performed in order to support the study. Electrical imaging has been successfully applied to identify the gypsum deposits interlayered in lutite units. Nevertheless, the gypsum-lutite boundaries are diffuse and uncertain in the tomographic lines. Comparison of the cores of the borehole and the electrical response shows a meaningful correlation between electrical resistivity and purity of gypsum. The electrical resistivity tomography profiles display a rather wide range of electrical resistivity value (from 20–1000 Ωm) for the investigated gypsum facies. The highest values are attributed to sulphate layers with >90% of gypsum mineral. Lutite units display higher values than expected due to the presence of evaporite minerals within them (>10 Ωm). Additionally, induced polarization measures have been performed in order to study the chargeability of gypsum deposits. It has been evidenced that impure gypsum rocks (with important presence of lutites within) are slightly chargeable. This property has allowed distinguishing between lutite levels and clay-rich gypsum rocks. Electrical resistivity tomography lines are useful in the prospection of gypsum deposits. However, electrical imaging prospection should be supported by an accurate petrological study of the deposits, in order to properly interpret the resistivity profiles.

A new amber outcrop has been found recently in a bed of lutite within the Escucha Formation near the village of Utrillas (Teruel Province), Spain. This new fossil site, which has been named San Just, contains an exceptional quantity of amber remains associated with fossilized wood and leaves of probable araucarian origin, and is dated as EarlyeMiddle Albian (Early Cretaceous). The amber is physically and chemically similar to other Spanish Early Cretaceous ambers. Values of IRTF are also similar to other Early Cretaceous ambers, except for curve values of 800e400 cm � 1 (in which bands are not visible) and the absence of exocyclic methylenic bands at 880 cm � 1 and 1640 cm � 1 . The latter is also a feature of � Alava amber (Pe~ I and II exposures), and suggests a high degree of maturation. The San Just outcrop is the second in Teruel Province in which biological inclusions (mainly insects and chelicerates) have been found in amber. Insects are represented by hymenopterans (Scelionidae, Evaniidae: Cretevania, Stigmaphronidae), dipterans (Dolichopodidae: Microphorites, Ceratopogonidae), thysanopterans (Stenurothripidae), and coleopterans (Cucujidae). Chelicerates are represented by a mite and two small spiders. There are also plant remains (trichomes and a cluster of gymnosperm pollen grains) and some mycelia, with sporangia and branched hyphae. The relative abundance of highly transparent ‘‘stalactites’’ containing well-preserved arthropod remains, makes this new outcrop an exceptional resource for future research into the palaeoentomofauna and palaeoecology of forest ecosystems on the Iberian Plate during the Early Cretaceous. 2007 Elsevier Ltd. All rights reserved.

The Baza Basin (the eastern part of the Guadix–Baza Basin, in SE Spain) underwent a significant evaporitic sedimentation in non-marine settings during the Plio-Pleistocene. The largest of these settings developed in the central part of the basin as a shallow, saline lake system, where abundant gypsum deposits occur (Benamaurel and Galera Gypsum units). This paper studies these deposits from the cartographic, stratigraphic, sedimentologic, petrographic and isotopic points of view. All the gypsum has been preserved as primary enabling a good characterization of the environmental conditions of the original precipitates. Three interconnected subenvironments or zones –inner, intermediate and marginal– are differentiated in this saline lake system. In the inner zone (shallow to relatively deeper central lake), a regular alternation of gypsum and carbonate laminae accumulated suggesting a seasonal regime. Many of the gypsum laminae display size-gradation (both reverse and symmetrical) indicating free precipitation in a stable brine body. In the intermediate zone (mosaic of shallow lakes), carbonate (dolomitic) beds formed in association with dark lutite levels, gypsum beds, and gypsum nodules and micronodules. Moreover, anoxic conditions developed in this zone, which resulted in the formation of native sulphur occurrences of economic value. In the marginal zone, the evaporitic deposits are developed only locally (the Galera Gypsum unit, in particular). The various gypsum lithofacies in these marginal deposits suggest the presence of a number of shallow to exposed settings (saline mudflat, saline marsh and gypsiferous pond). The isotopic composition ( δ 34 S, δ 18 O) of the gypsum samples is consistent with a Triassic origin of the sulphate as a result of chemical recycling. These data also suggest that a similar recycling mechanism operated in the saline lake system, where the gypsum sediments from the margins were coevally recycled towards the inner part. Both the evaporitic mineralogy and the gypsum and carbonate lithofacies suggest that semiarid conditions prevailed in this basin during the accumulation of the evaporite units.

The Paleoproterozoic Voelwater Subgroup in Griqualand West, South Africa, is an exceptionally well preserved succession of banded iron formation, braunite lutite and shallow marine limestone/dolostone. A detailed chemostratigraphic study was carried out on this succession, resulting in a comprehensive set of whole rock geochemical data, including stable isotope (δ13Ccarb, δ13Corg, δ18Ocarb) and 87Sr/86Sr isotope data. The results are in excellent agreement with previous investigations and reveal trends that correspond closely to mineralogical variations and reflect systematic changes in the depositional environment. Total inorganic carbonate contents (TIC) and δ13Ccarb values increase systematically from manganiferous iron formation at the base of the succession to dolostones that mark the top of the Voelwater Subgroup. These first order trends transgress across all lithologies and mirror the interplay of synsedimentary carbonate formation (utilizing dissolved marine bicarbonate), and Fe-Mn-rich carbonate formation during suboxic early diagenesis. First order trends are modulated by second order variations associated with lithological changes in the lower portion of the Voelwater Subgroup, constituted by three symmetrical cycles of iron formation and braunite lutite deposition. These second order trends, delineated by TIC and δ13Ccarb, as well as δ18Ocarb and major element concentrations (Mn, Fe, SiO2) can be attributed to repeated physicochemical changes in the MnF-BIF depositional environment. Variations in 87Sr/86Sr isotope composition do not relate to lithological changes. Instead, carbonate-rich and/or Sr-rich samples of MnF and BIF with well-preserved early diagenetic carbonate textures define a tight cluster with 87Sr/86Sr signatures of ~0.703 to ~0.706, in good agreement with Paleoproterozoic oceanic crust. Carbonate- and Sr-poor BIF samples with markedly more radiogenic 87Sr/86Sr signatures (~0.711 to ~0.722), in contrast, show evidence of extensive post-depositional recrystallization, apparent effects of dia- or epigenetic fluid flow. Chemostratigraphy and lithostratigraphy of the Voelwater Subgroup are in good agreement with models that predict a layered Paleoproterozoic ocean, with a hydrothermally-dominated Fe-Mn-rich deep water mass, overlain by a mass of oxygenated shallow marine water. A facies distribution model for the Voelwater Subgroup is proposed, taking into consideration not only the presence of these two isotopically distinct water masses, but also abundance and transport of organic carbon and shallow marine carbonate muds, as well as the transformation of primary iron- and manganese oxihydroxide precipitates into carbonate minerals during early suboxic diagenesis.

Meter-scale peritidal carbonate strata from an isolated platform in the Nanpanjiang Basin of South China were tested for the presence of periodic or quasi-periodic climatic signals. These signals provide information on factors controlling cyclic sedimentation in the equatorial eastern Tethys during the Early Triassic greenhouse period. Parasequences are composed of shallowing-upward successions of subtidal facies, including skeletal packstone and grainstone, calcimicrobial boundstone, and oolitic packstone and grainstone, intertidal laminated lutite and ribbon rock, and rare supratidal microbial laminite. Parasequence stacking patterns display three orders of cyclicity, suggesting hierarchical stratigraphic relationships. Gamma analysis of Kominz and Bond [Earth Planet. Sci. Lett. 48 (1990) 233–244] was used to estimate facies-dependent thickness–time conversion factors (i.e. γ s), and to construct γ -tuned and γ -untuned time series for two stratigraphic sections. Spectra of these time series indicate the presence of quasi-periodic signals, with prominent short-eccentricity (94.9–131.2 kyr), short-obliquity (35.8 kyr), and long-precessional index (21.2 kyr) peaks, and minor long-eccentricity (412.9 kyr), long-obliquity (45.3 kyr), short-precessional index (17.7 kyr), and constructional-tone (9.7 kyr) peaks when calibrated on the γ -tuned spectra. Thus, Milankovitch climatic forcing probably greatly influenced sedimentation. The calibration indicates that the subtidal facies has a sedimentation rate of 24.6–30.7 cm/kyr and the intertidal–supratidal facies has a rate of 2.7–6.0 cm/kyr. The estimated duration of deposition of the two sections is 1139–1423 kyr, and corresponds to a stratigraphic completeness of 32–92%. The completeness is much greater than that of icehouse stratigraphic records. We speculate that variations in carbonate productivity and environmental conditions driven by Milankovitch climatic forcing, combined with low-amplitude sea-level fluctuations, were likely major controls on cyclic sedimentation. Furthermore, evolutional spectra of the two sections show that dominant Milankovitch climatic forcings varied from short-eccentricity, obliquity, to long-precessional index during the course of sedimentation. Some spectral differences between the two sections suggest variations in depositional/recording mechanisms of Milankovitch climatic signals between platform interior and windward platform margin.

Asbestiform manjiroite and todorokite occur as infill of bedding parallel extension veinlets in supergene altered braunite-kutnahorite lutite at the Smartt Mine in the Kalahari manganese field, South Africa. Geological evidence and preliminary geochronological studies suggest that hydraulic extension and formation of the asbestiform Mn oxihydroxides took place during Tertiary uplift and tilting of the South African Subcontinent. Careful chemical studies of both minerals confirm the role of Mg as a minor but essential constituent in the todorokite structure that is located on a distinct – but as yet undetermined – crystallographic site within the tunnels of the todorokite framework structure. This site is distinct from the one occupied by large cations such as Ca, Na and K.

During the 1960's and the 1970's the Liedena Sandstone was a type deposit for “flysch-like facies” (sandstone and lutite alternations) of coastal sedimentary systems. However, the depositional system of these beds was never accurately defined. The sedimentological analysis along 100 km of outcrops in the western part of the South Pyrenean Zone (Navarre) allows these peculiar facies to be assigned to a mixed intertidal flat. Furthermore, sandy beach facies, different types of heterolithic, backbarrier deposits and conglomeratic, fluviatile facies have been recognized associated with these intriguing deposits. Generally, a northwestward-facing barrier-island system or wave-dominated delta was the likely depositional environment.

Sixty-five landslides have been mapped in the Meredal Valley, carved in one of the Asturian Precoastal Ranges on Mesozoic bedrock. From a genetic point of view, two groups of landslides can be distinguished: landslides developed mainly over Triassic lutites (complex movements, flows and rockslides) and landslides developed from calcareous cliffs (rock avalanches). Many of them are relict landslides, although evidence of activity can be recognized, as a result of a partial reactivation of some of the landslides. Four chronological classes have been established according to geomorphological criteria and the degree of preservation of the landslides. A lateral plugging deposit provides a minimum age of 5050±40 B.P. for the oldest class. In the same way, a stalactite gives to the third class of landslides a minimum age of 3392±128 B.P. The origin of landslides can be related to the plastic behavior of lutite and the permeability of the overlying limestone, which allows vertical seepage of water. From a regional point of view, landslides could be connected with Quaternary fluvial incision processes, as well as to Holocene high rainfall events.

The Jimbu Microgranite, a series of high-level microgranite plutons exposed in central Arnhem Land in northern Australia, was emplaced into flat-lying sandstones and lesser mudstones, carbonates and basalts of the Katherine River Group during the latter stages of deposition. New SHRIMP U–Pb zircon results indicate a crystallization and emplacement age for the Jimbu Microgranite of 1720±7 Ma. Intrusion took place in an essentially static tectonic setting, and accommodation space was not created by regional extension or by consumption of the host package by the intrusion. Rather, pluton emplacement was facilitated by three distinct mechanisms: the thick basal sandstone package was updomed; overlying lutite units were laterally shortened by outward gravity slide; the uppermost sandstone unit was raised vertically above the pluton by way of a monoclinal margin and steep reverse detachment faults. Decollement at ductility transitions in the rock package is required for the coexistence of these three structural styles. The three resulting structural elements include: relatively steeply and radially outward dipping domes of lower Katherine River Group sandstones with granite cores; irregular, short-wavelength fold patterns in the overlying incompetent lutites; discrete flat-lying blocks of the uppermost sandstone unit with steeply upturned or downturned margins. Plutonism is also suspected of being the cause of similar domes elsewhere in the McArthur Basin and in the adjacent Mount Isa Inlier. The model presented here may also be partly applicable to other basins with similar geometries and volcano-sedimentary histories, where tectonism is currently invoked to explain deformation.

Studies of the auriferous Witwatersrand placers and associated rocks have revealed that certain palaeo-environments, especially braided fluvial, are particularly well represented in this part of the rock record. However, there is a paucity of lithofacies indicating certain other palaeo-environments. Possible reasons for their scarceness or absence are suggested in this paper. It is generally assumed that pre-vegetational fluvial systems would have been characteristically braided, because of the absence of land plants necessary to stabilise river banks. A question arising is what kind of downstream changes such pre-vegetational braided streams underwent. A recent study of a braided stream placer revealed that the depositing system retained its braided character right down to the palaeo-shoreline. However, gravel did not reach the palaeo-beach. As with many modern examples, beach conglomerates are rare in the Witwatersrand rocks. The paucity of conglomeratic beach placers is ascribed to the low probability of gravel being transported across coastal plains, because of the relatively low slopes or depths of rivers here. The Witwatersrand fluvial channels are generally considered to have had high width-to-depth ratios, because of the absence of land vegetation to stabilise channel banks. However, two examples of deep, relatively narrow scour features, with predominantly fine-grained fills, occur near the base of the Central Rand Group. The low width-to-depth ratios of these scour features, which probably represent palaeo-valleys, are ascribed to severe incision during a rapid sea-level fall. The auriferous fluvial systems of the Witwatersrand are generally considered to have been entirely braided, due to the lack of bank stability. However, the fluvial B placer of the Welkom goldfield is confined to discrete channels. Their banks are thought to have been stable, due to the cohesive nature of the lutite into which the gravelly streams incised. In addition, braiding sensu stricto was probably inhibited by initial incision and a low sediment supply. No deposits of specifically deltaic sub-environments have been found in the Central Rand Group. Their absence is attributed to the following factors: (a) the paucity (absence?) of well-defined palaeo-river mouths; (b) low concentrations of suspended sediment; (c) intermittent sediment supply to the palaeo-coastline; and (d) reworking by tidal and longshore currents. Alluvial-fan deposits are also apparently absent in the Witwatersrand rocks. The absence of fan deposits is attributed to the poor potential for development and preservation of fan deposits in the compressive tectonic setting proposed for the Witwatersrand Basin. Although ventifacts have been found in the Witwatersrand rocks, no aeolianites have been reported. Their apparent absence is probably due to (a) reworking in a predominantly humid climate, and (b) transport of sand by dominant winds to areas unfavourable for the preservation of aeolianites.

The mineralogy of the managanese ores of the giant Paleoproterozoic Kalahari manganese deposit of the Transvaal Supergroup has been subject of many studies and up to now 135 different ore and gangue minerals have been described, of which eight represent new mineral species. Through correlation of different mineral assemblages with specific geological events and by determining relative ages of minerals in outcrop, hand specimen and under the microscope an attempt is made in this publication to construct a paragenetic sequence for this complex mineral assemblage. Sedimentation and early diagenesis of the Hotazel Formation, composed of interbedded iron formation and braunite lutite, was followed by low-grade metamorphism and associated stratabound metasomatism. Braunite lutite of sedimentary origin, comprising 97% of the total ore reserve, is composed of braunite, hematite and kutnahorite, and abundant early diagenetic kutnahorite and manganoan calcite forming laminae and ovoids. Fluid flow during late diagenesis or lower greenschist facies metamorphism led to stratabound metasomatic oxidation of Mn-bearing carbonates to hausmannite and Mn-poor calcite. Three structurally controlled hydrothermal alteration events succeed metamorphism. These events are referred to as Wessels, Mamatwan and Smartt events. The Wessels alteration event is the oldest of the three events and it is of great economic importance because virtually all of the high-grade ore (> 42% Mn), 3% of the total ore reserve, formed during this event through alteration of carbonate-rich low-grade Mamatwan-type ore (braunite lutite) to high-grade, carbonate-poor Wessels-type manganese ore. This Wessels hydrothermal alteration event took place in the northwestern part of the Kalahari deposit, associated with a system of major north-south- and minor east-west-striking normal faults. The Mamatwan alteration event is observed throughout the Kalahari manganese deposit but alteration is very localized. Reduction halos and discolouration of braunite lutite around fracture or joint-hosted sulphide-carbonate mineralization are typical of the Mamatwan alteration event. In contrast, the Smartt alteration event is characterized by oxidation of braunite lutite and the formation of todorokite and manganomelane. Syn- and Post-Kalahari supergene alteration has taken place below the suboutcrop of the Hotazel Formation against the calcretized sediments of the Cenozoic Kalahari Formation. Cryptomelane and pyrolusite are the predominant products of surficial weathering.

The Tertiary sediments of the southern part of Almazán basin (Province of Soria) exhibit two different facies with a sharp transition between them: (1) a coarse detrital facies; and (2) a lutite and carbonate facies. The vertical evolution of these facies in the different sections and boreholes is made up of several retrograde depositional sequences which evolve from proximal alluvial fans to carbonate lacustrine systems associated with the most distal fan sediments.The variation of the mineralogical association (carbonates, quartz, detrital clay minerals, palygorskite and, occasionally, sepiolite and smectites) allows four ‘mineralogical facies’ to be established. Each facies has a distinctive mineralogy related to the main genetic processes: (1) detrital facies; (2) transitional facies; (3) ‘chemical dolomite-palygorskite’ facies and (4) ‘chemical calcite’ facies. Although the carbonates (calcite and dolomite) are always the most abundant minerals, fibrous clay minerals are also important. The main mechanism of mineral authigenesis in this basin is chemical precipitation; the presence and distribution of carbonates and fibrous clay minerals is controlled by the relative concentrations of [Mg2+], [Ca2+], pCO2, pH and [SiO4H4]. Palygorskite occurrences, in these conditions, are related to dissolution-precipitation mechanisms of pre-existing detrital material.

Eolian dust derived from the desert regions of North Africa is blown far into the tropical Atlantic Ocean by persistent easterly and northeasterly winds. In this paper, we demonstrate that the iron oxides, hematite and goethite, are a worthwhile addition to proxy monitors of eolian sedimentation in the tropical Atlantic. Iron oxides are identified by diffuse reflectance spectrophotometry, a technique capable of identifying these minerals in concentrations as low as 0.01% by weight. We analyze samples from both the modern and last glacial maximum (LGM) synoptic levels from 178 sample locations yielding a total of 356 samples distributed throughout the Atlantic Ocean. To determine the relative contribution of the iron oxides, we factor analyzed the modern and LGM levels as a single data set. The iron oxide factor explains about 25% of the variance in the combined core top and LGM data set. Mapped factor scores for the LGM and modern ocean indicate high iron oxide values are present in just two regions, one off eastern North America and the other off northwest Africa. In the region off eastern North America, iron oxide occurs primarily during the LGM as the previously noted “brick red lutite,” a unique sediment type derived from the erosion of Permo-Carboniferous red beds in Atlantic Canada. A larger, lobe-shaped area of iron oxide rich sediment is present off northwest Africa in both the modern and LGM levels. The modern iron oxide lobe is coincident with the distribution of eolian dust as determined by observations from ships, satellites, and analysis of air samples. During the LGM, iron oxides exhibit a similar distribution except the southern margin of the region shifts equatorward and iron oxide concentration increases.

Nchwaningite, Mn~+Si03(OH)2' H20, is an orthorhombic chain silicate [space group Pea2" Z = 4, a = 12.672(9), b = 7.217(3), e = 5.341(2) A], occurring as aggregates shaped like pin cushions, together with calcite, bultfonteinite, and chlorite at N'chwaning mine, located in the Kalahari manganese field, northern Cape Province, South Africa. The aggregates consist of light brown, transparent needles, which average 1.0 x 0.1 x 0.05 mm in size. Nchwaningite is named after the mine N'chwaning II, where it was found first. Nchwaningite is biaxially negative with the refractive indices ex= 1.681(2), fJ = 1.688(2), 'Y= 1.690(2), 2 ~ = 54.4(4)°. The optical orientation is X = b, Y = a, Z = c. Nchwaningite has two perfect cleavages parallel to (010) and (100). The calculated density is 3.202 glcm3. The chemical composition, as determined by electron microprobe analyses, indicates minor substitutions of Mg for Mn. The crystal structure, including H positions, was solved and refined from X-ray singlecrystal data to R = 2.14%, Rw = 2.91%. The nchwaningite structure consists of double layers of laterally linked so-called truncated pyroxene-building units formed by a double chain of octahedra, topped with a Zweier single chain of Si tetrahedra. Symmetry-equivalent units are linked laterally but turned upside down. This yields a double-layer structure with H bridges linking the layers. A striking feature of the structure is that one Mn06 comer is formed by a H20 molecule. The tetrahedral chain and octahedral distortion of the new mineral is compared with pyroxenes having MnH in Ml [synthetic MnSi03 (P2/e clinopyroxene) andjohannsenite CaMn(Si03)2]' To test a complete Ca and Mg substitution for Mn in the new nchwaningite structure type, distance least-square refinements were performed. It was found that Ca and Mg analogues would also yield reasonable interatomic distances and polyhedra. OCCURRENCEAND ORIGIN sedimentation of the distinct Fe and Mn formations resulted from the different conditions of solubility and preThe Kalahari manganese field is the largest continental cipitation of Fe and Mn, related to cyclic sea-level changes. Mn deposit on the Earth, located in the northern Cape Furthermore, Beukes and Gutzmer (personal communiProvince, South Africa. Three Mn layers are interbedded cation) assumed a primary precipitation of braunite towith Fe formations of the Hotazel Formation of the gether with calcium manganese carbonates, whereas Bau Transvaal Sequence. These layers cover an area of about (personal communication), using REE-data, postulated a 35 x 15 km, and the ore varies in thickness from 6 to primary MnH precipitate with braunite as a secondary 45 m, with reserves of about 1.3 billion tons (Taljaardt, product. Using trace-element profiles in the Ongeluk la1982). vas, Schuette and Cornell (1992) postulated an early alSeveral controversial theories about the primary sedi- teration of fresh andesites caused by heated sea water, mentary origin of the Mn ores exist: Beukes (1983) and leading to the precipitation of Fe and Mn. Nel et al. (1986) postulated a volcanogenic or volcano- The majority of the ore, the so-called Mamatwan type, exhalative source for Fe and Mn, related with submarine is a fine crystalline sedimentary laminated braunite and volcanism in a basin west of the Kapvaal craton. The kutnohorite lutite of relatively low grade, containing a precipitation of Fe and Mn resulted from an upwellingof maximum of -38 wt% Mn. A small portion of the ore 02-undersaturated, Fe- and Mn-rich bottom waters on is developed as coarse crystalline massive Wessels-type the shelf in a photic zone with the first O2 producers. The ore of relatively high grade with Mn contents between 42

Aridisols with smectite B horizons are usually classified as Argids although the argillic characters may not always be present. In the Chihuahuan Desert of northern Mexico, some Aridisols have clayey horizons that do not seem to result from clay illuviation. Our purpose was to determine the origin of the clay enrichment and the mineralogical relationships between the parent materials and the B horizons. The study area is the Mapimi Playa, derived from a lutite lagoonal sediment parent material. A soil sequence from Orthids to Argids was identified. Four profiles were analyzed. The particle-size distribution was determined by the sedimentation and centrifugation methods. The clay fractions were studied by x-ray diffraction and peak decomposition, infrared spectroscopy, and chemical analyses. Soil water extracts were analyzed with an absorption spectrometer. From the Orthids to the Argids, clay enrichment in B horizons is controlled by the

Symposium on Marine Benthic Ecology and Biodiversity - A Compilation of Recent Advances held in Honor of J Frederick Grassle, Rutgers Univ, Inst Marine Coastal Sci, New Brunswick, NJ, NOV 20-21, 2008; International audience; We report new in situ observations and laboratory studies of specimens of a small (diameter 2.4-7.5 cm) strikingly hexagonal form originally described from sedimented steps in a wall of the axial valley of the Mid-Atlantic Ridge (water depth 3430-3575 m) near 26 degrees N, 45 degrees W that appears to be identical to the iconic form Paleodictyon nodosum described as a trace fossil from Eocene flysch deposits at sites in Europe and Wales. Our findings follow: The form is apparently agglutinated in sea floor sediment (a veneer of calcareous lutite over red metalliferous sediment) and consists of three equidistant rows of tiny holes (diameter similar to 1 mm) that intersect at an angle of 120 degrees and continuously connect through vertical shafts (length 2-3 mm) with an underlying horizontal network of tubes or tunnels identical with the fossil form. The number of rows of holes and spacing of rows increase with overall diameter of the form indicative of organic growth. The form is shaped like a shield surrounded by a lip and moat with surface relief (similar to 0.5 cm) that is absent in the fossil form. The surface relief exposes the underlying red sediment and may have been produced either by excavation (constructional origin) or by infaunal growth (body form). Protoplasm is absent in recovered specimens, as indicated by negative results of staining techniques, explained by either initial absence or loss. Genetic sequencing of material from the form identified different foraminifera that had settled on the pattern of holes which acts as a baffle to trap organic matter. Models in flume tanks show that the shield-like form deflects flow of ocean currents into a self-ventilating structure capable of aerating and of circulating organic particles through the tubes or tunnels. Microbial counting techniques indicated background abundances within and outside the form. We come to two alternative interpretations of the findings resolvable with further studies: The modern P. nodosum is a burrow consistent with interpretation of the ancient form as a trace fossil. The modern P. nodosum is a compressed form of a hexactinellid sponge adapted to a sedimentary substrate, which means that the ancient form is a body fossil with possible affinity to the Ediacara fauna. (C) 2009 Elsevier Ltd. All rights reserved.

11 pages, 8 figures, 4 tables., Some urban solid waste landfill sites in Spain are located on geological substrates of gypsiferous lithology. Although this type of substrate is assumed to be of low permeability, it can develop secondary pores by dissolution and, under favourable environmental conditions, form a karstic system that may pose serious geotechnical problems in the medium and long term. The purpose of this work was to study alterations caused by selective tests in various sections of a gypsum lithological column obtained from the Colmenar de Oreja landfill site (Spain). The tests were used to assess the influence of individual environmental factors and involved the addition of milli-RO water, solutions containing a 1%, 5% or 10% concentration of landfill leachate, and 2, 5, 10 and 15 mg l 1 solutions of NaCl in successive immersion–drying cycles at 15, 20 or 60 C. Differences in alterability between the six studied segments of the lithological column were found to be due to differences in lutite content, specific crystal habit and type of cement. Segments with specular gypsum were the strongest in the tests, while the segment with the highest amount of detrital materials was the most responsive to temperature and moisture changes. The treatments that produce greater alterations are those that contain only milli-RO water., This work was supported by Comunidad Autónoma de Madrid (CAM) under Project COR0062/94.

9 pages,figures and tables statistics., The role of municipal solid waste (MSW) landfill leachate on the genesis of minor amounts of pyrite associated with gypsum in an otherwise predominantly evaporitic sequence was studied in geological and geochemical terms. The potential association between landfill leachate and the conditions required for bacterial reduction of sulfate and fixation of H2S as pyrite were examined. The lithological column was generally found to contain little or no Fe. The d34S values for sulfates were consistent with previously reported data; however, the measured d18O values were slightly higher. Sulfides disseminated in the marl/lutite exhibited higher d34S values ( –8&) than gypsum-coating pyrite crystals (d34S < –30&). Dissolution of gypsum to sulfate and the supply of metabolizable organic matter and Fe required for H2S fixation as sulfides may have originated from landfill leachate. Intermittent availability of leachate, a result of the precipitation regime, can facilitate sulfur disproportionation and lead to fractionations as high as SO2/4-S2 -50º%

A transition from microbanded Kuruman to granular Griquatown iron-formation is described in terms of sedimentological, petrographic, and geochemical characteristics (major, minor, trace and rare earth elements) as well as whole rock carbon and oxygen isotopic compositions. Transitions between microbanded and granular iron-formation are uncommon in the global stratigraphic record with microbanding absent from most known granular iron-formations. The Kuruman-Griquatown transition zone differs from other granular iron-formation sequences in being non-oolitic i.e., peloidal and magnetite-rich instead of hematite-rich. It is concluded that the coarsening upward microbanded-granular iron-formation units in the Kuruman-Griquatown sequence represent upward-shallowing storm-dominated deposits; that is, primary microbanded, relatively deep water, fair weather deposits having been intermittently reworked by storm wave action form wavy, sharp-based, graded and poorly sorted, irregular interbeds of granular iron-formation. This is in contrast to typical hematitic oolitic iron-formation units which represent true shoal deposits. Geochemical results strongly support the storm-reworking hypothesis. Microbanded and granular iron-formation beds have similar REE patterns, with negative Ce anomalies and depletion in light REE, reflecting deposits in a marine setting below the zone of shallow surface water. Positive Eu anomalies in the REE patterns suggest admixture of a hydrothermal component of the ocean water. Carbonates in the iron-formation are depleted in 13C indicating involvement of organic matter during diagenetic alteration of the iron-formations. There are also indications that total dissolved carbon dioxide in deeper water was more depleted in 13C than in shallower water. Deposition of the iron-formations was sporadically interrupted by influx of tuffaceous material, now represented by centimeter-thick, shard- and lapilli-bearing stilpnomelane lutite beds. These beds differ chemically from the iron-formations in being enriched in elements such as Al, Sc, Y, Zr, Nb, Hf, Ta, Th, U and the lanthanides, and displaying REE patterns with strong negative Eu and slight positive Ce anomalies. The composition of the parent magma of the volcanics remains uncertain because of probable post-depositional alteration of the volcanic glass; however, it was most probably of intermediate to acidic composition as concluded from the widespread distribution of the ash beds; typical of Plinian-type deposits. Chemical variations in the minor, trace and REE compositions of the iron-formations are closely correlated with the amounts of admixed volcanic ash material. Most of the iron-formations appear chemically very “uncontaminated” being highly depleted in all minor, trace and REE, and organic carbon contents. The iron-formations were therefore most probably deposited as a chemical precipitate on a submerged shallow cratonic platform with volcanic ash as the only exogenic material sporadically reaching the depository.

In addition to its well-known banded iron formations, the late Archean to Paleoproterozoic Hamersley Group of Western Australia contains substantial volumes of thinly laminated carbonaceous shale and carbonate lutite. Locally, some of the laminae in these carbonates are deformed into highly distinctive folds in pockets whose cross-sections range up to about 2 cm in height and 10 cm in length. Individual folds consistently have circular hinge zones and vary in shape from simple buckles to recumbent, elastica, and even spiral geometries. Based on the strength and flexibility with which they responded to soft-sediment deformation, we infer the deformed carbonaceous laminae were bound by cohesive microbial mats. We propose the name roll-up structures for these features as they differ in subtle but important ways from most previously described soft-sediment deformation structures. Roll-up structures only occur in lutites deposited below wave base and are absent from peritidal deposits, suggesting that the microbial mats involved may not have been based on photosynthesis. Large portions of the deep sea floor could presumably have been stabilized by mats built by heterotrophic or chemoautotrophic microbes prior to the Neoproterozoic, given the lack of both predators and competing algae. Roll-up structures are potentially useful as indicators of deposition below wave base, but very few candidates have been reported anywhere else save for the coeval carbonates of the Transvaal basin of South Africa. The paucity of other examples, particularly in younger strata, means that either roll-up structures have simply not been distinguished from other types of soft-sediment deformation structures, or the microbes and/or environmental conditions required to make them are a rarity in Earth history.

Two relict hydrothermal zones were delineated between water depths of 3400 and 3500 m at the lower part of the east wall of the rift valley of the Mid-Atlantic Ridge in the TAG hydrothermal field using a deep-towed side scan sonar tow and a camera-temperature tow along the northern 3 km of the wall, and a submersible transect. Named the North and MIR relict zones, they are located about 4 km and 2 km northeast, respectively, of the known active high-temperature sulfide mound between water depths of 3625 and 3670 m on the rift valley floor near the base of the east wall. The North zone extends about 2 km along the northern end of the lower east wall. The zone includes two moundlike features up to 30 m high by 200 m in diameter imaged by side scan sonar within a 2-km-long line of discontinuous hydrothermal deposits comprising inactive toppled and standing chimneys, layered material, and patchy dark stains on sediment photographed by the camera-temperature tow. Several other moundlike features were imaged with the side scan sonar outside of the photographic coverage. The MIR relict hydrothermal zone 2 km south of the North zone, named after the MIR submersible used to investigate it, consists of three subzones: (1) a 200-m-wide area of diverse types of hydrothermal materials exposed by normal faulting at its western margin; (2) a 400-m-wide by 700-m-long central area of discrete groups of toppled and standing inactive sulfide chimneys up to 25 m high on a substrate of red metalliferous sediment and carbonate lutite; spires sampled on the highest chimneys are composed of coarse-grained, recrystallized sulfides dominated by pyrite and chalcopyrite which contain the first primary, free gold grains (2–3 μm diameter) found at a hydrothermal site on a mid-ocean ridge; and (3) a 150-m-wide hummocky area of layered hydrothermal material with the appearance of low temperature precipitates and carbonate lutite with patchy dark stains at its eastern margin. The active sulfide mound, the North zone, and the MIR zone are each located on the fractured western margins of gentle, dome-shaped areas of pillow flows typically 500 m in diameter interpreted as summits of volcanic centers that may have supplied heat to drive adjacent hydrothermal activity. The distribution and size of the active and inactive hydrothermal zones of the TAG field, the chronology, and the characteristics of relict samples recovered indicate a history of at least 100 ×103 years of high-temperature hydrothermal episodes with multiple overprinting stages of mineralization accompanied by alteration.

The oldest known fossiliferous strata in New Caledonia are the Permian to Jurassic basement rocks of the west coast. Approximately 3,000 m of primary volcanic lithologies of basaltic to rhyolitic composition and volcaniclastic sediments of lutite to rudite grade are represented in the Moindou — Teremba area. They have been subdivided into two groups: Teremba Group and Baie de St.-Vincent Group. They show similarities in lithology and chemical composition with the Takitimu Group and Murihiku Group respectively of Southland, New Zealand. However the New Caledonian sedimentary rocks are devoid of plutonic and metamorphic components, and volcanic composition through the sequence is different. Both Teremba and Baie de St.-Vincent Group lithologies have developed metamorphic mineral assemblages characteristic of prehnite — pumpellyite facies.

Fine-silt to medium-sand grain-size spectra of the carbonate-free fractions of 115 sea bed samples from the northern North Atlantic, the Labrador Sea and Baffin Bay can be explained as mixtures of five distinct end-members. The five end-members resemble combinations of grain-size modes which are characteristic of till-matrix (Dreimanis and Vagners, 1972). Therefore the ultimate source of most of the terrigenous deep-sea sediments in the study area is probably the veneer of glacial comminution products on the surrounding continents. Three sand-rich end-members exhibit patterns of distribution that are largely compatible with the modern transport of ice-rafted debris as inferred from iceberg drift observations. The best sorted of those sandy end-members however also appears to be concentrated in regions characterized by high-energy turbidity and contour currents and so may also represent hydraulically winnowed sediment. The distribution of two lutite end-members appears in general to reflect the transport of fines by moderate to low energy thermohaline currents; although, in Baffin Bay and the northeastern North Atlantic the lutite could have accumulated primarily in turbidites. Ice-rafting by icebergs calved from Greenland glaciers, the reworking of glacigenic sediments on the Iceland—Faeroes Ridge and injection of turbid glacial meltwater into deep Baffin Bay from West Greenland fiords are suggested as the principal means of introduction of clastic particles into the sediment distribution (redistribution) budget of the deep North Atlantic.

The Ethelton conglomerate (lower Cretaceous) is a distinctive unit of the Torlesse terrane outcropping in the banks of the Hurunui River near Ethelton, north Canterbury. It is about 150 m thick, underlain and overlain by north-east striking, vertically dipping thick-bedded sandstone and mudstone containing detrital plant material. Bedding in the conglomerate is at angles of up to 35° to the enclosing strata. Three hundred pebbles were collected on a grid pattern to establish their physical properties and lithological proportions. Pebbles of lithic feldsarenite similar to, but not identical with, the enclosing sediments are dominant, and are of two types—one dominated by granitic K-feldspar, and the other by plagioclase. Pebbles of quartzarenite and quartz-lutite, rhyolite, and lutite are common. Calcareous concretions, granite, jasper, and quartz-pumpellyite-chlorite-epidote pebbles are prominent, but minor. Size distribution and pebble shapes suggest that sorting and shaping took place in a fluv...

Iron-formation was deposited as a distal facies of ferruginous carbonate turbidites in an open shelf environment in front of a shallow-water carbonate platform at the time of deposition of the Campbellrand carbonate sequence. A subsequent transgression resulted in the deposition of open shelf iron-formation on top of the Campbellrand carbonate platform. Progradational sedimentation coupled with shoaling followed, and an iron-formation sequence represented by the Kuruman and Griquatown Iron-formations was deposited. This sequence consists from the base upwards of stacked open-shelf cycles of altered volcanic ash stilpnomelane lutite beds and autochthonous banded ferhythmite units; toe-of-slope greenalite—siderite rhythmites; platform slope greenalite—siderite rhythmites with grainflow bands; platform edge sideritic orthochemical and allochemical iron-formations; epeiric sea orthochemical and allochemical sideritic, hematitic and greenalitic iron-formations; supratidal disclutites and lacustrine banded greenalite lutite. Landwards, the lacustrine felutites were followed by deltaic chloritic claystone, siltstone and quartz wacke of the Koegas Subgroup. Autochthonous ferhythmites of the Kuruman Iron-formation reach a maximum development in a basin near Prieska, whereas orthochemical and allochemical units are more abundant on the Kaapvaal craton. Iron mineral and chert microbanding in the ferhythmites is attributed to seasonal changes in Eh and pH in the depository and may be related to biological activity. Chert mesobanding in the iron-formations is essentially of an early diagenetic origin.

To present a model for flysch deposition involves the simultaneous representation of many parameters. The most significant of these are arenite-lutite bed thickness ratio, mean and variance of arenite-bed thickness, mean palaeocurrent direction and the primary directional structures yielding them. Field and flume data suggest that arenite-bed thickness decreases exponentially away from source, with a complementary increase in siltstone bed thickness in a turbidite fan. If HA, HL. are arenite and lutite bed thicknesses in a couplet (the unit of bedding at a flysch outcrop), then where m and R are constants of the outcrop in the turbidite wedge. Field evidence suggests m= 1, so that R-values allow for a classification of couplets at an outcrop or within a zone. Maximum HA, HL. values are indicative of proximal deposition from turbidites, and usually provide transverse directional structures, as does (HA) max. Arenite bed thickness can be considered as thick beds or thin beds according to whether they exceed a chosen thickness, say t cm. If 15 cm be chosen, the percentage thick arenite-bed thickness HA1 and thin arenite bed thickness percentage, HA2 can be represented with HL. (siltstone bed thickness percentage) over twenty-five couplets, as one point on a triangular diagram. The mean palaeocurrent direction Nφ° E is represented as an arrow through the point, a colour (point or arrow) being used to distinguish the directional structure (flute, ripple, groove, foreset, etc.) producing it. Flysch examples from Ordovician, Silurian and Devonian in Central Victoria are thus interpreted in terms of proximal and distal emplacement. In cases where bedding detail is clear, A + B, C and D + E divisions substitute for HA1HA2 and HL. respectively, for a unit of 1 m thickness of outcrop on the triangular diagram. If thick arenite bed thickness percentage be plotted against total arenite bed thickness percentage, the linear plot of points for outcrop samples results on log-log paper. Limiting lines of the form log HA1= m log HA+ log C (m, C constants) demarcate the field. Parallel and equally spaced lines with values C1, C2, C3,…Cn subdivide this into sub-fields. If the determinations for HA1 in any one sub-field be plotted on a locality map considering only MAXIMUM HA1 values, and the HA1H values conveniently contoured, trends emerge which closely agree with the modal palaeocurrent directions in the case of the Llandovery Deep Creek Flysch 25 km NNW of Melbourne, Australia.

The Haymana Basin is a constituent trough of the Central Anatolian Basin, which was the site of rapid subsidence and accompanying flysch sedimentation during the late Cretaceous and early Tertiary, following closure of the Vardar Ocean and collapse of the carbonate platform forming its southern border. The Eocene Yamak Formation (maximum thickness, 1210 m) abruptly succeeds fine-grained sediments of the Bahcecik Formation, interpreted as a basin-plain facies. Lutite interbeds from the Yamak yield a bathyal marine microfauna and the Formation is characterised by a high proportion of thick medium to coarse sandstones and pebble-to cobble-rudites of turbidite and mass-flow origin, arranged in thick packets of moderate lateral extent. Many of these sand bodies are channelised, with thinning- and fining-upward sequences in which thick amalgamated sandstones and rudites are prominent. Most of the subordinate thickening- and coarsening-upward sequences are erosively succeeded by channelised bodies. These features indicate that the coarse Yamak sediments were deposited in a sand-rich submarine-fan complex in which the channelised mid-fan was the dominant depositional regime. The lateral and vertical relationships of Yamak facies associations indicate that the individual fans were relatively small, elongate and strongly channelised. They show little evidence of lateral migration or coalescence, but apparently result from superposition of successive low-sinuosity channels with only occasional development of channel-mouth “lobes” (in the sense of Mutti and Ricci-Lucchi, 1972, 1975). Facies distributions and palaeocurrent evidence show that sediment was generally conveyed to south and southeast through the Yamak fan system. However, following a prolonged phase of quiescence on the fan and formation of an extensive blanket of purple muds, the uppermost Yamak is marked by northwards progradation of a new channelised fan system.

Unusual late deglacial/early interglacial sedimentation rates following the last two glaciations have been detected from three cores on the eastern Reykjanes Ridge. Morphologic, textural, and mineralogic evidence pinpoint bottom currents as the process responsible for these unusual depositional rates, which rise at first to 10–40 times the regional mean, and then subside slightly to values still 2–5 times the norm. A portion of the lutite excesses in the interglacial sediment of these cores is accounted for by input of fine detritus eroded from subaerially exposed and isostatically uplifted Icelandic basalts. For the most part, however, the extraordinary depositional rates late in the deglacial periods are caused by erosion and redistribution of previously deposited glacialage sediments. We infer that reinitiation of overflow of deep water into the Atlantic due to deglacial removal of the Norwegian Sea ice cover triggered a strong bottom-current flow that dislodged sediment from exposed sites. The deglacial intensification of the deep circulation thus left a major sedimentological imprint on the sediments of the eastern Reykjanes Ridge.

Sedimentation in the 9500 km 2 , 4100 m deep Hispaniola—Caicos Basin is dominated by turbidity currents. Carbonate turbidites originate from the Bahama Islands, Great Inagua and Caicos at the north end of the basin. Mixed carbonate—non-carbonate flows come from Hispaniola and perhaps Cuba. Most flows originate on insular slopes rather than in shallow water. The relatively low CaCO 3 content of hemipelagic sequences throughout the entire basin reveals that the influence of non-carbonate Hispaniola—Cuba sources is widespread. The basin was sampled with closely spaced piston cores. Sand-layer isopach and frequency maps reveal four or five major basin entry points for turbidity currents. Flow size is proportional to the size of source areas. Average volumes of flows originating from Hispaniola—Cuba, the largest source, are 10 9 m 3 . This compares to an average flow volume of 10 6 m 3 for flows derived from the smallest source area, the Southeastern Caicos Bank. Measures of turbidity-current activity, such as thickness and frequency, change in a regular fashion away from each entry point. Average lutite thickness (combining hemipelagic and turbiditic lutite) are greatest near the basin entry points. On the abyssal plain occupying the south half of the basin, Bouma turbidite sedimentary structure sequences tend to be complete. However, on the Caicos Fan, the sedimentary structure sequences in turbidites are characterized by missing or repeated units. Six radiocarbon dates of two widespread presumed pelagic units in the basin yielded younger dates in stratigraphically older positions. The reversed dates are assumed to reflect storm erosion of older sediment on adjacent insular shelves. Consideration of a north—south reflection seismic profile over the basin indicates that the present sediment regimen has pertained through much of the Neogene. The coherence, convergence and termination of reflections in the seismic section are consistent with and tend to confirm conclusions based on the core study regarding the greater extent and volume of sediment deposits derived from the Hispaniola source area.

Thalassinidean crustacean remains (Callianassa) are recorded from lower Miocene burrow networks belonging to the ichnogenus Thalassinoides. They were produced at mid bathyal depths of 1000–3000 m. Mid to lower bathyal basinal sediments and inferred outer neritic to upper bathyal submarine canyon sediments contain sparse ichnocoenoses composed entirely of feeding and dwelling structures, produced by burrowing polychaetes, echinoids and possibly sipunculoids and also by bivalves escaping burial during rapid sedimentation. These two ichnocoenoses are similar to those of proximal turbidite sequences, and this is considered a response to similar rates of sedimentation, water agitation and coarseness of sediment rather than a similarity in depth. An outer neritic to upper bathyal canyon wall ichnocoenosis was developed in semi-consolidated lutites and arenites by burrowing polychaetes, decapod Crustacea (shrimps and crabs) and possibly amphipods and other organisms. Inclined, but randomly oriented Rhizocorallium occur in the canyon wall, and their presence at these depths is explained by inferred abnormally high water turbulence and abundant suspended food matter as well as a favourable semi-consolidated lutite substrate.

Eight types of reflections are interpreted from 3,800 km of 3.5 kHz profiles taken over a 25,000 km2 area of the upper continental slope and shelf in the northeastern Gulf of Mexico off Panama City, Florida. The corresponding sediments in five of the reflection types were sampled in 77 piston cores from which data were obtained on in situ acoustic velocities (V), bulk densities (gr), sediment texture (mean grain size = Mz), CaCO3 content (C), sedimentary structures, and gross sediment composition. A distinct bottom echo with numerous subbottom reflectors (Type I) is observed in deeper areas where terrigenous clay or lutite (Mgi = 9.9 to, gr = 1.4 g/cc, porosity (P) = 74 percent, C = 28 percent, and V (upper 2 m) = 1,435 m/s) predominates. Type I reflection grades upslope into Type IV, which shows a distinct bottom echo with fewer subbottom reflectors, and the corresponding sediment is a foraminiferal silty clay (mz = 9.4 to, gr = 1.43 g/cc, P = 73 percent, V = 1,447 m/s, and C = 37 percent). The ...

A nepheloid layer has been observed by optical means in the lower part of the water column on the continental slope and rise. By sampling it has been found to be a suspension of lutite, apparently in sufficient quantity to induce downslope flow. Sediment transported in the nepheloid layer may be a major component of deep-sea sediment bodies.

Quantitative studies of the variation of the arenite‐lutite ratio, and of bedding thickness for outcrops across the Siluro‐Devonian sediments in the Seymour East Syncline, indicate these significant features: (i) Bunches of massive, thick‐ and thin‐bedded arenites (referred to as members), many containing cobble conglomerate strata, suddenly come in over massively bedded, graded and ungraded lutite. (ii) The arenite members show graded bedding features which are mostly rhythmic, being especially aperiodically interrupted at their bases, and becoming more regular and pulsating in their upper cycles. (iii) Parallel cumulative frequency curves for the bedding of coarse and fine lithologies in these cycles suggest a common origin, viz. their introduction by turbidity currents induced by slumping of coarse sediment into probably deep, standing water. (iv) The siltstones into which the arenite members are emplaced are themselves often graded. Elsewhere, massive, ungraded siltstone resembles the matrice...

Grain-size distribution and mineralogical composition are independent variables in most detrital sediments. Separate classifications are necessary to describe these sediment attributes. Essential characteristics are given when the following format is used: (sorting term) (size term): (cement) (prominent nondetrital) (detrital composition). This polynomial evokes a clear mental image of the sediment. Descriptive nomenclature and procedure are modified from earlier Folk publications. The resultant classification system is objective and practical. Gravel, sand, silt, and clay are end members of triangular diagrams that are divided into named textural categories in accord with apparent natural groupings. Modal size and sorting terms supplement the names of some categories. Rudite, arenite, and lutite are used in a compositional sense for detrital sediments whose texture is respectively indicated by the terms gravel (conglomerate or breccia), sand (sandstone), and mud (mudstone, siltstone, or clayston...

A distinct boundary between sediment types usually occurs at a depth of about 10 cm in bottom cores raised from the Alpha Rise in the Arctic Ocean. The sediment between the tops of the cores and the 10 cm boundary is a dark brown, foraminiferal lutite mixed with ice-rafted sand and pebbles. The sediment between the 10 cm boundary and a depth of about 40 cm is a light brown sand with ice-rafted material but few Foraminifera. The 10 cm boundary apparently represents the most recent change in pelagic deposition in this region and must be connected with climatic changes. Foraminifera from a zone between 7 and 10 cm have been dated by the C14 method as 25,000 ± 3000 and as 30,000 years BP in two different samples. The 10 cm boundary itself has been dated as 70, 000 years BP by a uranium series method. If these dates are accepted, a low sedimentation rate of 1 1 2 to 3 mm/1000 years is indicated for the Alpha Rise and for the Arctic Ocean as a whole if pelagic sedimentation has been uniform over the entire ocean. Cores from the Canada Abyssal Plain differ in character from the Alpha Rise cores consisting primarily of olive-gray lutite without Foraminifera or ice-rafted material. This sediment was probably deposited by turbidity currents. A 3 mm layer of dark brown, foraminiferal lutite occurs at the top of the Canada Abyssal Plain cores. This layer is similar to the upper layer in Alpha Rise cores and apparently represents continued pelagic deposition since the last turbidity current. Foraminifera from this upper 3 mm layer have been dated as 700 ± 100 years BP by the C14 method. The conclusion is that pelagic sedimentation has continued unchanged in the Arctic Ocean from about 70,000 years ago to the present. This implies that the present ice cover has existed for that length of time.