In 2006, Mark Papa, CEO of EOG Resources, Inc. directed EOG divisions to focus on identifying and leasing large acreage blocks in shale oil window fairways (Mark Papa, personal communication) in basins throughout the United States while subordinating all exploration for natural gas, and in particular, dry gas. The company’s strategic change to shale oil exploration occurred during what was referred to as a “wall of disbelief” (Birger, 2011) predicated on the premise that oil molecules could not flow through shale-dominated permeability systems. The EOG Garner 1054 C#1, drilled in November 1998, encountered hydrocarbons within the Eagle Ford Formation at a pressure gradient of 0.76 psi/ft, at a subsurface true vertical depth (TVD) of 9300 ft (2834.6 m). Although a wet gas producer, this well was a critical element in the rationale to obtain leases in the oil window of the Eagle Ford Formation. Predicated upon a technical analysis of additional vertical well production within the Eagle Ford Formation indicating the existence of a dual porosity, or matrix-supported flow network, and in conjunction with the generation of fairway criteria mapping, EOG initiated a leasing strategy resulting in the acquisition of 569,000 contiguous acres within the crude oil window fairway.Regional mapping of the Eagle Ford Formation was conducted to model structure, thickness, total organic carbon (TOC), thermal maturity (Ro), oil gravity, and hydrocarbon saturation as well as lithostratigraphic continuity, postulated environments of deposition, and mineralogical variations. An identified fairway situated between the Maverick Basin and the San Marcos arch, a syn-depositional graben system on the margin of a transgressed carbonate platform, was mapped as a relatively thick and laterally continuous stratigraphic section within the targeted Ro, TOC, and favorable hydrocarbon saturation windows. X-ray diffraction (XRD) analysis revealed that while the silica content within the Eagle Ford Shale was low relative to the more topical Barnett Shale and other existing shale resource plays, the mineralogical constituents were that of a brittle carbonate with variable clay content replete with a deceptive gamma log signature as a consequence of elevated levels of uranium and thorium.Distinct structural settings displaying unique structural and stratigraphic attributes were recognized and mapped, all of which had remained within the oil generation window for the last 30 million years. Net rock volume increases associated with prolonged oil generation and expulsion were believed to increase the likelihood of catagenically induced micro-fracturing resulting in enhanced system permeability. Eight strategically located vertical delineation wells were drilled across a 15 by 120 mi (24.1 by 193.1 km) fairway located from Gonzales to LaSalle Counties. Conventional coring coupled with extensive electric logging suites and petrophysical evaluations provided an integrated regional understanding of the Eagle Ford Formation. Nanometer-scale imaging with focused ion beam (FIB) and field emission scanning electron microscopy (FESEM) of Eagle Ford core samples showed interconnected porosity systems and pore sizes capable of transmitting oil molecules. Initial production rates from EOG-operated horizontal delineation drilling confirmed the viability of the Eagle Ford Formation as an overpressured carbonate resource rock with system porosity and permeability capable of long-term economic oil production.The methods defined in this chapter were appropriate for the delineation of the oil window within the Eagle Ford of South Texas; however, hydrocarbon systems are unique and these methods may not be applicable for defining other plays within other basins.

The submerged sill in the Strait of Messina, which is located today at a minimum depth of 81 m below sea level (bsl), represents the only land connection between Sicily and mainland Italy (and thus Europe) during the last lowstand when the sea level locally stood at about 126 m bsl. Today, the sea crossing to Sicily, although it is less than 4 km at the narrowest point, faces hazardous sea conditions, made famous by the myth of Scylla and Charybdis. Through a multidisciplinary research project, we document the timing and mode of emergence of this land connection during the last 40 kyr. The integrated analysis takes into consideration morphobathymetric and lithological data, and relative sea-level change (both isostatic and tectonic), resulting in the hypothesis that a continental land bridge lasted for at least 500 years between 21.5 and 20 cal ka BP. The emergence may have occurred over an even longer time span if one allows for seafloor erosion by marine currents that have lowered the seabed since the Last Glacial Maximum (LGM). Modelling of palaeotidal velocities shows that sea crossings when sea level was lower than present would have faced even stronger and more hazardous sea currents than today, supporting the hypothesis that earliest human entry into Sicily most probably took place on foot during the period when the sill emerged as dry land. This hypothesis is compared with an analysis of Pleistocene vertebrate faunas in Sicily and mainland Italy, including a new radiocarbon date on bone collagen of an Equus hydruntinus specimen from Grotta di San Teodoro (23–21 cal ka BP), the dispersal abilities of the various animal species involved, particularly their swimming abilities, and the Palaeolithic archaeological record, all of which support the hypothesis of a relatively late land-based colonization of Sicily by Homo sapiens.

The mid-Cretaceous was marked by emplacement of large igneous provinces (LIPs) that formed gigantic oceanic plateaus, affecting ecosystems on a global scale, with biota forced to face excess CO2 resulting in climate and ocean perturbations. Volcanic phases of the Ontong Java Plateau (OJP) and the southern Kerguelen Plateau (SKP) are radiometrically dated and correlate with paleoenvironmental changes, suggesting causal links between LIPs and ecosystem responses. Aptian biocalcification crises and recoveries are broadly coeval with C, Pb, and Os isotopic anomalies, trace metal influxes, global anoxia, and climate changes. Early Aptian greenhouse or super-greenhouse conditions were followed by prolonged cooling during the late Aptian, when OJP and SKP developed, respectively. Massive volcanism occurring at equatorial versus high paleolatitudes and submarine versus subaerial settings triggered very different climate responses but similar disruptions in the marine carbonate system. Excess CO2 arguably induced episodic ocean acidification that was detrimental to marine calcifiers, regardless of hot or cool conditions. Global anoxia was reached only under extreme warming, whereas cold conditions kept the oceans well oxygenated even at times of intensified fertility. The environmental disruptions attributed to the OJP did not trigger a mass extinction: rock-forming nannoconids and benthic communities underwent a significant decline during Oceanic Anoxic Event (OAE) 1a, but recovered when paroxysmal volcanism finished. Extinction of many planktonic foraminiferal and nannoplankton taxa, including most nannoconids, and most aragonitic rudists in latest Aptian time was likely triggered by severe ocean acidification. Upgraded dating of paleoceanographic events, improved radiometric ages of the OJP and SKP, and time-scale revision are needed to substantiate the links between magmatism and paleoenvironmental perturbations.

The Paleocene–Eocene-aged Sele Formation is developed across the basinal region of the Central North Sea. The section comprises a number of deep-marine fan systems that expanded and contracted across the basin floor in response to relative sea-level changes on the basin margin and fluctuating sediment yield off the Scottish landmass modulated by climate and hinterland uplift. Persistent sediment entry points to the basin resulted in the development of discrete axial and transverse fan fairways with a geometry dictated by an irregular bathymetry sculpted by differential compaction across Mesozoic faults, halokinesis and antecedent fan systems. A high-resolution biostratigraphic framework has allowed the evolution of fan-dispersal systems in response to these effects to be tracked across the basin within four genetic sequences. The proximal parts of the fans comprised channel complexes of low sinuosity, high lateral offset, and low aggradation. The development of these systems in a bathymetrically confined corridor of the Central Graben (c. 65 km wide), combined with high sediment supply, resulted in the eventual burial of any underlying relief. The behaviour of sand-rich reservoirs in this region is dominated by the permeability contrast between high-quality channel fairways and more heterolithic overbank regions, with the potential for early water breakthrough and aquifer coning in the channel fairways, and unswept volumes in overbank locations. Compartmentalization of compensationally stacked channel bodies occurs locally, with stratigraphic trapping caused by lateral channel pinch-outs, channel-base debrites, mud-rich drapes and abandonment fines. Towards the southern part of Quadrant 22, approximately 150 km down-palaeoflow, the systems became less confined and in this region are dominated by channel–lobe complexes, which continued to interact with an irregular bathymetry controlled by antecedent fans, mass-transport complexes and halokinesis in the form of rising salt diapirs. Reservoirs in this region are inherently stratigraphically compartmentalized by their heterolithic lithology and compensational stacking of lobes, and further complicated by structuration and instability induced by the diapiric or basement structures needed to generate a trapping structure in these settings.

There are at least a dozen Phanerozoic continental flood basalts and oceanic plateaus (large igneous provinces) that roughly obey a “rule of two times one million” (volume of extruded lava of one million cubic kilometers and duration of volcanic activity ~1 m.y.). The correlation between large igneous province ages and mass extinctions (and oceanic anoxia events) is excellent, but quantitative scenarios are still wanting. We hypothesize that the temporal sequences of extrusions determine the severity of extinction: Volcanic pulses separated by thousands of years allow the ocean-atmosphere system time to recover, whereas large volcanic pulses occurring in a shorter sequence may result in a runaway effect and cause a mass extinction. Detailed flow-by-flow magnetic stratigraphies of thick sections have identified directional groups (sequences of superimposed lava flows with the same paleomagnetic direction that cooled in a time too short to record secular variation). With help of this simple tool, many single eruptive events with a volume larger than 1000 km3, some in excess of 10,000 km3, emplaced in possibly less than a decade, have been identified. We review this evidence, mainly for the following flood basalt provinces: Columbia, Brito-Arctic, Deccan, Karoo-Ferrar, Central Atlantic magmatic province, and Siberian Traps. Large igneous province volcanism occurs in a highly discontinuous way, on embedded time scales, on the order of 10 m.y., 1 m.y., 100 k.y., and 10 yr. This provides constraints for models of plume-lithosphere interaction and magma production. A next step is to model the consequences of massive injection of gases that can be derived from these time and duration estimates. Early attempts are reviewed in a companion paper in this volume.

The investigation of rapid sea-level and climate change is critical to understanding the geologic history of the Black Sea and its effect on ancient civilizations of the region and adjacent areas. The current consensus of western scientists is that only local sea-level curves may be constructed because of local-to-regional changes in sedimentation, tectonics, and other factors. Recently, however, I.P. Balabanov published a synoptic sea-level curve for the entire Black Sea that spans the Pleistocene-Holocene transition and the Holocene based on older radiocarbon dates. This curve has been heavily criticized and is viewed skeptically by western workers for the reasons already mentioned as well as the use of questionable methodologies. Here, we examine Balabanov's curve in light of these criticisms by comparing his sea-level curve to other independently derived sea-level and environmental indices. We find that, despite its drawbacks, many of the fluctuations of the Balabanov curve coincide with repeated ocean-atmosphere reorganizations, which involve shifts from cool to warm phases and corresponding changes in the species composition of foraminiferal assemblage ecozones, precipitation, and runoff. We suggest that following the initial invasion of the Black Sea by marine Mediterranean waters during the Pleistocene-Holocene transition, climatic amelioration (warming) following each cool phase of an ocean-atmosphere reorganization resulted in shifting precipitation patterns that produced repeated, rapid freshwater discharges into the Black Sea from surrounding rivers. In this scenario, runoff following each reorganization temporarily altered the species composition of foraminiferal assemblages, as noted in earlier studies. Freshwater discharges during the Holocene were likely lower than those envisioned by Balabanov but may have affected sea level sufficiently to alter coastal geomorphology and coastal aquifers rapidly, while causing the translocation of settlements from areas where submarine archaeological sites are now situated. Sea-level and climate change during the Pleistocene-Holocene transition may have been similar to that of the Holocene, but greatly amplified.

New data and review of classic sections from the Middle and Upper Ordovician North American Midcontinent in the Upper Mississippi Valley provide a refined picture of the age, stable isotope geochemistry, faunal composition, and—ultimately—origin of this epeiric ramp succession. Sequence stratigraphic analysis reveals a series of unconformity-bounded, genetically related facies packages. Shallowing and deepening trends are sometimes difficult to resolve due to a paucity of hydrodynamic indicators, yet unconformity surfaces are well marked by hardgrounds and confirmed by negative C-isotope spikes. Recent conodont biostratigraphy, new U-Pb radioisotopic ages for K-bentonites, and correlation of C-isotope profiles to global trends suggest that the succession spans the Darriwilian to Hirnantian epochs. Focus on Platteville to lower Galena Group strata (Sandbian to early Katian) provides a temporally high-resolution look at the onset and evolution of a long-term (>2 m.y.) positive carbon-isotope excursion, short-term perturbations in that record, and relationship to the preservation and diversity of the enclosed fauna and strata. Major changes in authigenic mineral suites and organic carbon content throughout the Upper Ordovician Upper Mississippi Valley suggest at least three major redox cycles. The combined evidence for globally recognized, positive carbon-isotope excursions coincident with these redox cycles, as well as high-frequency, sea-level fluctuations and successive faunal turnover events, suggests far-field responses to multiple global oceanic anoxic events.

The tectonics and paleogeography of Ordovician rocks in China record the four major paleoplates—the South China, North China, Tarim, and Xizang (Tibet) Blocks. New paleogeographic maps of South China for the Tremadocian, Darriwilian, Sandbian–early Katian, and late Katian–Hirnatian time intervals display lithofacies and biofacies belts that depict continuous changes from the Yangtze Platform through the Chiangnan (Jiangnan) Slope to the Zhujiang Basin. North China was dominantly a carbonate platform during the Ordovician. Facies belts, particularly the trilobite biofacies belts, change westward from the platform edge to the slope along the west margin of the platform. In Tarim, Ordovician rocks provide the main source and reservoir rocks for oil and gas. The vast expanse of the block was a northward-deepening, shallow-water platform that was fringed by peripheral, deeper water facies belts developed along the northern side of the South Tianshan. Facies analysis indicates that the paleogeographic setting varied in response to eustatic sea level changes. North of the Tibet Block lies a long mobile belt that crosses more than half of China from west to east. The Tibet Block is mainly composed of two units, the north Qiantang region, which remained as a separate, small paleoplate through the late Paleozoic, and the south Gandise-Himalaya region, which persisted as a distinct paleoplate through the late Paleozoic and well into the Mesozoic. Ordovician rocks consisting mainly of carbonates with shelly faunas have been recorded from regions of the Tibet Block.

The Katian Age (early Late Ordovician) was a time of significant decline in marine biodiversity, but whether this decline was a real phenomenon or an artifact of the relatively few studies devoted to this interval requires further research. We examined the pattern of graptolite faunal changes across the boundary between the Climacograptus bicornis and Diplacanthograptus caudatus graptolite zones in North America and on several other continents. A sharp decline in species diversity occurs in the Appalachian Basin. Scores for normalized diversity dropped from 20 in the C. bicornis Zone to 7 in the D. caudatus Zone. Only 11% of the species present in the C. bicornis Zone carry over into the D. caudatus Zone. A similar pattern occurs in central Oklahoma. Regions at higher paleolatitude, such as Wales and Baltoscandia, exhibit low graptolite diversity in lower Katian strata, and then diversity declines further in higher strata. In other regions at low paleolatitude, such as Australasia and Scotland, however, diversity is fairly constant across this interval (although the percentage of carryover taxa remains low). We conclude that seawater temperature change or disruption of the oceanic density structure, which might accompany temperature change, provides explanations for the similarity between Laurentian and higher paleolatitude diversity patterns. Flooding of the Laurentian craton through the Sebree Trough by cool, subpolar Iapetus seawater may have adversely affected graptolite diversity there. Regions at high paleolatitudes likely underwent cooling associated with Katian climate deterioration. Thus seawater cooling, albeit driven by different mechanisms, may have produced similar diversity patterns at different paleolatitudes.

The interval from the middle Eocene to early Oligocene represents one of the most significant transitions in Earth’s climate, during which greenhouse conditions were supplanted by icehouse conditions of the present day. This global transition was preceded by a long-term cooling phase and short-term uncorrelated variations in several marine proxies, which indicate paleoceanographic instabilities prior to the key climatic transition. We integrate previous multidisciplinary studies with recent data from the Massignano section (Umbria-Marche Basin) and summarize interpretations of studies from the past 20 yr that have been based on the Eocene-Oligocene boundary global stratotype section and point (GSSP). Based on the many data sets from this section, with an emphasis on the rock magnetic data, we propose that the fluctuations and final cessation of a westward subtropical Eocene Neotethys (STENT) current were drivers in the climatic transition from greenhouse to icehouse conditions. Our hypothesis considers that the global variable climatic conditions were synchronous to large changes in circulation in the western Neotethys Ocean, which were primarily due to paleogeographic and sea-level changes. Specifically, the closing of the gateway between the Arabian and Eurasian plates, through coupling of sea-level changes, could represent the threshold or one of the triggers that caused the paleoceanographic variations in the Neotethys and in global ocean circulation patterns during the end of the Eocene.

We present an overview of the Eocene-Oligocene transition from a marine perspective and posit that growth of a continent-scale Antarctic ice sheet (25 × 106 km3) was a primary cause of a dramatic reorganization of ocean circulation and chemistry. The Eocene-Oligocene transition (EOT) was the culmination of long-term (107 yr drawdown and related cooling that triggered a 0.5‰–0.9‰ transient pre-scale) CO2 cursor benthic foraminiferal δ18O increase at 33.80 Ma (EOT-1), a 0.8‰ δ18O increase at 33.63 Ma (EOT-2), and a 1.0‰ δ18O increase at 33.55 Ma (oxygen isotope event Oi-1). We show that a small (~25 m) sea-level lowering was associated with the precursor EOT-1 increase, suggesting that the δ18O increase primarily reflected 1–2 °C of cooling. Global sea level dropped by 80 ± 25 m at Oi-1 time, implying that the deep-sea foraminiferal δ18O increase was due to the growth of a continent-sized Antarctic ice sheet and 1–4 °C of cooling. The Antarctic ice sheet reached the coastline for the first time at ca. 33.6 Ma and became a driver of Antarctic circulation, which in turn affected global climate, causing increased latitudinal thermal gradients and a “spinning up” of the oceans that resulted in: (1) increased thermohaline circulation and erosional pulses of Northern Component Water and Antarctic Bottom Water; (2) increased deep-basin ventilation, which caused a decrease in oceanic residence time, a decrease in deep-ocean acidity, and a deepening of the calcite compensation depth (CCD); and (3) increased diatom diversity due to intensified upwelling.

Three time lines through the neritic stratigraphic record distributed around the northern margin of the Australo-Antarctic Gulf (AAG) mark three fundamental shifts in global environments collectively comprising the Auversian facies shift. The three lines are: (1) the beginning: the Khirthar transgression and the onset of neritic carbonate accumulation in the Bartonian Age (preceding onset of the Middle Eocene climatic optimum [MECO]); (2) the midlife change (Bartonian-Priabonian transition): the shift from carbonate-rich to carbonate-poor, higher-nutrient environments under estuarine circulation, causing widespread dysaerobia culminating in opaline silicas; and (3) the Eocene-Oligocene = Priabonian-Rupelian boundary and glaciation during oxygen isotope event Oi-1, with return of improved ventilation in neritic environments and resumption of carbonate accumulation. Meanwhile, it was warm and very wet at ~60°S. In developing a scenario for the death of the AAG, the birth of the Southern Ocean, and the transition from Paleogene greenhouse Earth to Neogene icehouse Earth, the neritic record of the northern margin is more in accord with the “Dinocyst biogeographic hypothesis” than with the “Tasman gateway hypothesis.”

Sedimentary strata on the Southern California shelf and slope (Point Conception to Dana Point) display patterns and rates of sediment accumulation that convey information on sea-level inundation, sediment supply, and oceanic transport processes following the Last Glacial Maximum. In Santa Monica Bay and San Pedro Bay, postglacial transgression is recorded in shelf deposits by wave-ravinement surfaces dated at 13–11 ka and an upsection transition from coastal to shallow-marine sediment facies. Depositional conditions analogous to the modern environment were established in the bays by 8–9 ka. On the continental slope, transgression is evidenced in places by an increase in sediment grain size and accumulation rate ca. 15–10 ka, a consequence of coastal ravinement and downslope resedimentation, perhaps in conjunction with climatic increases in fluvial sediment delivery. Grain sizes and accumulation rates then decreased after 12–10 ka when the shelf flooded and backfilled under rising sea level. The Santa Barbara coastal cell contains the largest mass of postglacial sediment at 32–42 × 109 metric tons, most of which occurs between offshore Santa Barbara and Hueneme Canyon. The San Pedro cell contains the second largest quantity of sediment, 8–11 × 109 metric tons, much of which is present on the eastern Palos Verdes and outer San Pedro shelves. By comparison, the mass of sediment sequestered within the Santa Monica cell is smaller at ~6–8 × 109 metric tons. The postglacial sediment mass distribution among coastal cells reflects the size of local fluvial sediment sources, whereas intracell accumulation patterns reflect antecedent bathymetric features conducive for sediment bypass or trapping.

Post-Turonian (Late Cretaceous) rudist-bearing limestones of the Nurra region in northwestern Sardinia (northern Tethyan margin) and in the central-southern Apennines and Apulia (central Tethyan domain) have recorded relevant changes in the characteristics of the carbonate platforms following the “middle” Cretaceous crisis events which affected the peri-Tethyan region as well as other regions worldwide.Rudist bivalves became the dominant lithogenetic taxon owing to their proliferation in shallow-water environments and strong dominance of Late Cretaceous carbonate factories. Their inception, evolution, and demise were seemingly controlled by a complex interplay of environmental processes that, acting on a global scale, profoundly modified the Early Cretaceous hydrosphere-atmosphere system and forced Tethyan depositional systems to change their organization, internal architecture, and facies patterns. As a result, wide, open shelves developed where the almost ubiquitous mode of carbonate fixation was that of foramol factories.In this paper, evidence of the remarkable regional variability in the rudist-bearing carbonate platforms of the Mediterranean Tethys is presented. The analysis of the resulting shallow-water facies has demonstrated that, in spite of several stratigraphic similarities and common sedimentological features, some remarkable differences occurred between the northern Tethyan margin and the central Tethyan banks as regards the areal partitioning of the main paleoecologic controlling factors. This resulted in the deposition of rhodalgal successions in Sardinia (northern Tethyan margin) and rudist-rich foramol facies in the Apennine-Apulia (central Tethys) regions, respectively. Such Late Cretaceous carbonate systems can be viewed as geological products which have closely and coherently recorded the globally changing environmental conditions of the oceanic realm. In spite of this, the difference of the facies partitioning in different Tethyan regions according to a latitudinal gradient is interpreted as derived mainly from local variable paleoceanographic and paleoclimatic conditions.

The Silurian rocks of the Cincinnati Arch in Ohio, Kentucky, and Indiana have been studied for nearly two centuries. Compilation of data from these studies, combined with detailed analysis of nearly 20 continuous drill cores and remeasuring and resampling of more than 60 major outcrops, is the basis for a high-resolution sequence stratigraphic framework. Seven depositional sequences are assigned on the basis of through-going unconformities, which mirror those already recognized in the early Llandovery to early Ludlow of the northern Appalachian Basin. Revision of the conodont biostratigraphy for the Cincinnati Arch has produced results that both agree and disagree with the other lines of data implemented in the sequence stratigraphic depositional model. Biostratigraphic correlations between southern Ohio and the Niagara Falls area are largely in agreement with correlations based on other lines of data, as are correlations between west-central and western Ohio, southeastern Indiana, and northern Kentucky. However, correlations between southern and west-central Ohio show major areas of disagreement. Preliminary whole rock carbonate carbon isotope analyses in western-central Ohio show patterns roughly comparable to those documented in the Niagara region, Gotland, and elsewhere. Chemostratigraphic data that might resolve inconsistencies in the correlations between southern and west-central Ohio were not yet available at the time of publication.

The present article reports the textures, whole-rock and mineral chemistry, and mineral reactions under greenschist- to amphibolite-facies conditions of Proterozoic aluminum phosphate–bearing metaquartzites from central Madagascar and from the Espinhaço fold belt in Brazil. Based on this information, the mechanism of aluminum phosphate genesis in the protolith of the metaquartzites and the behavior of phosphates (lazulite, augelite, trolleite, svanbergite, goyazite-crandallite, berlinite, and xenotime) during low-grade amphibolite-facies metamorphism is discussed. In Precambrian marine sandstones, aluminum phosphate was a potentially important phosphorus sink before the beginning of abundant organic and large-scale calcium phosphate deposition in the Neoproterozoic. A compilation of alternative calcium phosphate (apatite) deposits in the Precambrian confirms their insignificance for phosphorus fixation before the Neoproterozoic. Efficient phosphorus burial in aluminum phosphates inhibited the rapid buildup of phosphorus nutrient levels in the early Precambrian oceans.

Iskenderun Bay is a major shallow embayment in the eastern part of the Mediterranean Sea, where the African and Anatolian Plates converge. This tectonically active basin was investigated for oceanographic, sedimentological, geochemical, and foraminiferal parameters. On the basis of the data acquired, the distribution of living and fossil foraminifera in 284 grab and 54 gravity core samples was determined, the basin floor bathymetry of the bay constructed, radiocarbon ages of sediments and fossils ascertained, and depositional environments reconstructed. It has been discovered that for the last 13.5 k.y., water masses were stratified and sedimentation was discontinuous within the basin, which is characterized by irregular sea bottom morphology. The sedimentation rate was very slow, varying in time and space from 0 to 0.012 cm yr−1. The foraminiferal distributions were spatially varied and discontinuous and indicate a reversal from deep to shallow marine conditions in the cores. These irregularities were attributed to active tectonics in the bay and a major tectonic uplift of the bay since the late Pleistocene.

Black shales and Mn carbonates interbedded with glacial deposits from the Neoproterozoic of southern China exhibit extremely heavy values of pyrite S isotopes that may reflect the peculiar environment of Earth at this time. δ34S averages +30‰ at Tanganshan and +44‰ at Xiangtan, compared with typical values of 0‰ to +5‰ found in younger deposits. Furthermore there is no distinction between the shales and the Mn carbonate ores in the Neoproterozoic, unlike the younger deposits, which show much lighter δ34S in the shales than in the Mn ores (the spread is 25‰). Most other chemical parameters are very similar to both the younger Mn deposits and those from the Paleoproterozoic. The exception is the rare earth elements (REE). All Neoproterozoic Fe ores and most Neoproterozoic Mn ores lack the positive Eu anomaly that characterizes Archean and Paleoproterozoic Fe-Mn accumulations. On the other hand, Neoproterozoic Mn deposits have positive Ce anomalies on North American Shale Composite (NASC) normalized plots, in contrast to other MnCO3 ores. The ΣREE is also higher than in other Mn deposits, but lower than in modern deep-sea crusts. Sulfide S values in all Neoproterozoic shales tend to be exceptionally variable and to often show much heavier values than can be found in marine strata from the Phanerozoic. Therefore the anomalous δ34S values we observed reflect peculiar conditions in the world oceans at this time rather than purely local effects. Times of enrichment of seawater sulfate in 34S do not correspond to periods of glaciation, so the likely cause of the S isotope patterns is not worldwide glaciation, but a generally low level of dissolved sulfate S in the Neoproterozoic oceans that allowed modest increases in the amounts of S removed as pyrite to drive down the oceanic S reservoir enough to produce strong Rayleigh reservoir effects. The abundance worldwide of Sturtian-age Mn and Fe deposits indicates an increase in Fe flux to the oceans that would have been sufficient to depress SO4 2- levels severely and to result in residual dissolved S extremely enriched in 34S. REE evidence indicates that most of this enhanced Fe and Mn flux came from diagenetic remobilization of detrital oxides rather than from ridge-crest hydrothermal systems, in contrast to the Paleoproterozoic banded iron formations. Rapid introduction of lateritic soil residues to restricted basins by low-latitude glaciation could have provided the needed excess Fe and Mn to drive this system.