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The article focuses on intact stalked crinoids from the late Aptian of North East Spain, offering insights into the Mesozoic Marine Revolution in the Tethys. It provides a detailed description of the deposit and paleoenvironmental interpretation, including crinoid predation and preservation. It explores the fossilized remains preserved in a series of strata, analyzing the orientation and preservation states of crinoids to infer their behavior before death and burial.

The Chinese loess-paleosol sequences provide important archives for studying paleoenvironmental changes. However, the lack of independent and accurate time scales hinders the study between loess and other records. Asian stalagmite d18O records indicate synchronous patterns of paleoprecipitation d18O over large geographic regions. The record of hydrogen isotopic composition of plant wax (dDwax) in Chinese loess is also controlled by rainwater dD. Both share a common origin. The linear relationship between rainfall d18O and dD variance provides the basis to tie together chronologies of the same climate event in different records. Here, we show a new loess chronology by correlating chronologies of marker boundaries of the prominent climate chronozones in stalagmite d18O and summer insolation to the equivalent climate stratigraphy in the loess dDwax sequence. We first developed and tested this novel methodology with data since the last interglacial on a millennial scale, and then applied this approach to the loess dDwax sequence for the past 800 k.y. to improve the traditional chronology based on magnetic susceptibility and grain size. The new dDwax time series provides not only an improved chronology for studying paleoclimate changes during interglacial intervals, it also represents a unique database with which to better understand the links between the Asian monsoon changes in the Chinese loess and other global climate events, especially for the periods prior to 640 ka, for which stalagmite records are not available. [ABSTRACT FROM AUTHOR]

Trace metal elements (TMEs) are commonly used to reconstruct the environmental conditions present during the deposition of organic-rich sediments. For example, TME concentrations controlled by changes in primary productivity and redox conditions are widely used in paleoenvironmental studies. Recently, these proxies have undergone a resurgence of interest and are commonly used in large-scale (10-1000 km) studies. However, applying these geochemical proxies at basin scale while ignoring variations in sedimentation rates (SR) may lead to misinterpretation of paleoenvironmental conditions. Here, we show how SR can affect the geochemical records and may lead to incorrect interpretations of TME evolution. Accounting for SR, we computed the authigenic fraction accumulation rates of key TMEs in the Upper Montney Formation and Doig Phosphate (Triassic, western Canada), and we correct the concentration of these elements in the Vaca-Muerta Formation (Jurassic-Cretaceous, Argentina). Our SR-corrected TME proxies require a different interpretation of paleoenvironmental conditions (e.g., primary productivity, basin restriction) compared to conventional TME results and highlight that elementary enrichments commonly interpreted as indicative of anoxic depositional environments may reflect low SR and the formation of condensed intervals. This work also introduces a new workflow to account for SR in paleoenvironmental studies at basin scale and over long time periods. [ABSTRACT FROM AUTHOR]

Studies of paleocommunities and trophic webs assume that multispecies assemblages consist of species that coexisted in the same habitat over the duration of time averaging. However, even species with similar durability can differ in age within a single fossil assemblage. Here, we tested whether skeletal remains of different phyla and trophic guilds, the most abundant infaunal bivalve shells and nektobenthic fish otoliths, differed in radiocarbon age in surficial sediments along a depth gradient from 10 to 40 m on the warm-temperate Israeli shelf, and we modeled their dynamics of taphonomic loss. We found that, in spite of the higher potential of fishes for out-of-habitat transport after death, differences in age structure within depths were smaller by almost an order of magnitude than differences between depths. Shell and otolith assemblages underwent depth-specific burial pathways independent of taxon identity, generating death assemblages with comparable time averaging, and supporting the assumption of temporal and spatial co-occurrence of mollusks and fishes. [ABSTRACT FROM AUTHOR]

Although Quaternary deposits within the Ganyanchi (Salt Lake) pull-apart basin along the eastern Haiyuan fault preserve a record of both the paleoenvironmental and tectonic evolution of the northeastern Tibetan Plateau, this sedimentary archive has yet to be dated. Here we report a paleomagnetic study of a 328-m-long sediment core drilled near the modern depocenter of the basin, and use this record to both date the onset of sedimentation and reconstruct the depositional history of the basin. The observed magnetic polarity sequence comprises 13 normal and 12 reversed polarity zones, and we explore two possible correlations to the geomagnetic polarity time scale. Our preferred correlation minimizes changes in sedimentation rate and extends from the Brunhes normal polarity chron to the Gauss normal polarity chron. This correlation indicates that the Ganyanchi Basin began to develop by at least ca. 2.76 ± 0.03 Ma. Sediment accumulation rates (SAR) were elevated in two intervals, from ca. 1.92 to 1.78 Ma, when they were ~130.3 m/m.y., and from ca. 0.77 Ma to present, when they were ~234.6 m/m.y. We attribute these enhanced depositional episodes to both Northern Hemisphere cooling and local tectonic effects, with SAR values increasing as the regional climate has shifted toward overall drier and cooler conditions. [ABSTRACT FROM AUTHOR]

Symmetric sand ripples formed by water waves are common features on modern coasts and in sedimentary rocks. The size and spacing of wave ripples generally scale with water depth and wave conditions, and are widely used to reconstruct coastal environments of the geologic past. Interpretations based on average ripple dimensions and assumed constant wave conditions are informative, but many rippled beds contain striking patterns involving defects--deviations from straight, evenly spaced ripple crests--that suggest more dynamic flow regimes. We report a set of laboratory experiments that reveal how these patterns form in rippled beds adjusting to a change in wave conditions. As the ripples in our experiments evolved toward a new spacing, they developed defects that are widely observed in modern environments and in the rock record. The dominant defect type depends on the sign and magnitude of the adjustment in ripple spacing and the number of wave periods since the change in wave conditions. A regime diagram summarizing these associations quantitatively links ripple defects to transient flow conditions. Our experiments reveal the origin of previously unexplained ripple patterns and add a new dimension to paleoenvironmental interpretations. [ABSTRACT FROM AUTHOR]

In order to understand the onset of Snowball Earth events, precise geochronology and chemostratigraphy are needed on complete sections leading into the glaciations. While deposits associated with the Neoproterozoic Sturtian glaciation have been found on nearly every continent, time-calibrated stratigraphic sections that record paleoenvironmental conditions leading into the glaciation are exceedingly rare. Instead, the transition to glaciation is normally expressed as erosive contacts with overlying diamictites, and the best existing geochronological constraints come from volcanic successions with little paleoenvironmental information. We report new stratigraphic and geochronological data from the upper Tambien Group in northern Ethiopia, which indicates that the glacigenic diamictite at the top of the succession is Sturtian in age. U-Pb zircon dates obtained from two tuffaceous siltstones that are 74 and 84 m below the diamictite are 719.68 ± 0.46 Ma and 719.68 ± 0.56 Ma (2s), respectively. We also report a U-Pb date of 735.25 ± 0.25 Ma from a crystal-rich tuff located 2 m above the nadir of a high-amplitude, basin-wide, negative d13C excursion previously correlated with the Islay anomaly. This age for the anomaly agrees with Re-Os age constraints from Laurentia, suggesting that the d13C signal is globally synchronous and preceded the Sturtian glaciation by ~18 m.y. The interval between the Islay anomaly and Sturtian glaciation is recorded in the Tambien Group as an ~600 m succession of predominantly shallow-water carbonates and siliciclastics with d13C values recording a prolonged period at +5‰, followed by an interval of lower, but still positive, values leading up to the glaciation. Our data are consistent with synchronous global onset of the Sturtian glaciation at ca. 717 Ma. Shallow-water carbonates in strata directly below the first diamictite suggest that glacial onset was rapid in terranes of the Arabian-Nubian Shield. [ABSTRACT FROM AUTHOR]

Mars Science Laboratory (MSL) Curiosity rover data are used to describe the morphology of desiccation cracks observed in ancient lacustrine strata at Gale crater, Mars, and to interpret their paleoenvironmental setting. The desiccation cracks indicate subaerial exposure of lacustrine facies in the Sutton Island member of the Murray formation. In association with ripple cross-stratification and possible eolian cross-bedding, these facies indicate a transition from longer-lived perennial lakes recorded by older strata to younger lakes characterized by intermittent exposure. The transition from perennial to episodically exposed lacustrine environments provides evidence for local to regional climate change that can help constrain Mars climate models. [ABSTRACT FROM AUTHOR]

Emerging geochemical proxies have improved our understanding of the broad-scale history of Earth's oxygenation. However, paleoredox work does not always include extensive consideration of sample preservation and paleoenvironmental setting. This is particularly an issue with marine carbonates, which although being potentially ideal ocean redox archives, are commonly altered during diagenesis. Here we provide new insight into the robustness of uranium isotopes (238U/235U ratios: δ238U values) as paleoredox tracers by determining texture-specific δ238U values from a well-described Cryogenian (Balcanoona) reef complex in South Australia. We found high variability in δ238U values between different carbonate components, even within a single sample. Petrographically, the best-preserved components from the Balcanoona reef are marine cements, which have a mean δ238U value of −0.23‰, essentially unfractionated from riverine inputs. These values are interpreted as reflecting a marine system with widespread anoxic and iron-rich settings. Less-well-preserved phases have δ238U values spanning almost the entire extent of the documented isotopic range. This integrated petrographic-geochemical work demonstrates the need for petrographic analysis and careful sample selection on a case-by-case basis in future carbonate metal isotope geochemistry. [ABSTRACT FROM AUTHOR]

The spatial variability of Holocene relative sea-level (RSL) change influences the capacities of coastal environments to accommodate a sedimentary record of paleoenvironmental change. In this study we couch a specific investigation in more general terms in order to demonstrate the applicability of the relative sea-level history approach to paleoseismic investigations. Using subsidence stratigraphy, we trace the different modes of coastal sedimentation over the course of time in the eastern Indian Ocean where RSL change evolved from rapidly rising to static from 8000 yr ago to present. Initially, the coastal sites from the Aceh, Sumatra, coastal plain, which are subject to repeated great earthquakes and tsunamis, built up a sedimentary sequence in response to a RSL rise of 1.4 mm/yr. The sequence found at 2 sites 8 km apart contained 3 soils of a mangrove origin (Rhizophora, Bruguiera/Ceriops, Avicennia pollen, and/or intertidal foraminifera) buried by sudden submergence related to coseismic subsidence and 6 tsunami sands that contain pristine subtidal and planktic foraminifera. After 3800 cal yr B.P. (years before A.D. 1950), sea level stabilized and remained such to the present. The stable relative sea level reduced accommodation space in the late Holocene, suggesting that the continued aggradation of the coastal plain was a consequence of periodic coastal inundation by tsunamis. [ABSTRACT FROM AUTHOR]

Fluviolacustrine sediments filling Gale Crater on Mars show two levels of former exposure and weathering that provide new insights into late Noachian (3.7 ± 0.3 Ga) paleoenvironments of Mars. Diagnostic features of the two successive paleosols in the Sheepbed member include complex cracking patterns of surface dilation (peds and cutans), a clayey surface (A horizon), deep sand-filled cracks with vertical lamination (sand wedges), and replacive sulfate nodules aggregated into distinct bands (gypsic By horizon) above bedded sandy layers (sedimentary C horizon). Shallow gypsic horizon, periglacial sand wedges, and limited chemical weathering are evidence of a hyperarid frigid paleoclimate, and this alternated with wetter conditions for the lacustrine parent materials in Gale Crater during the late Noachian. Depletion of phosphorus, vesicular structure, and replacive gypsic horizons of these Martian paleosols are features of habitable microbial earth soils on Earth, and encourage further search for definitive evidence of early life on Mars. [ABSTRACT FROM AUTHOR]

Lava-fed deltas are extraordinarily useful indicators of fossil water (and ice) levels in glacial, marine, and lacustrine environments. Deltas fed by 'a'a lava should be at least as common as those sourced in pahoehoe, yet they have been rarely described. Although facies models for pahoehoe lava-fed deltas are well established, the architecture and lithofacies of 'a'a-fed equivalents are substantially different and have thus far largely been unrecognized. This can have profound consequences for paleoenvironmental investigations, particularly those attempting to reconstruct past ice sheets. Essential features of 'a'a lava-fed deltas include (1) a subaerial 'a'a lava capping unit comprising massive internal sheet lava overlain by clinkers; (2) a crudely developed subaerial to subaqueous transition (passage zone); (3) a chaotic subaqueous association of abundant lava lobes and hyaloclastite with admixed vesicular, often reddened (oxidized) lava clinkers; and (4) rare subaqueous stratification with predominantly lower dips (~10°-20°) than in deltas fed by pahoehoe lava (~25°-40°). We develop a generic facies model and investigate the emplacement conditions of 'a'a lava-fed deltas in order to facilitate the recognition and environmental interpretation of these important sequence types in ancient successions. [ABSTRACT FROM AUTHOR]

Patterns of origination, evolution, and extinction of early animal life on this planet are largely interpreted from the fossils of the Precam-brian soft-bodied Ediacara Biota, spanning nearly 40 m.y. of the terminal Ediacaran period. Localities containing these fossils are loosely considered as part of either the Avalon, White Sea, or Nama Associations. These associations have been interpreted to have temporal, paleobiogeographic, preservational, and/or paleoenvironmental significance. Surprisingly, elements of all three associations occur within the Ediacara Member of the Rawnsley Quartzite of South Australia. An analysis of over 5000 specimens demonstrates that fossil distribution is strongly controlled by facies and taphonomy rather than time or bio-geography and that individual taxa vary considerably in their environmental tolerance and taphonomic integrity. The recognition that these taxa represent organisms living in various distinct environments, both juxtaposed and shared, holds strong implications for our interpretation of the record of early animal life on this planet and questions the bio-stratigraphic utility of the three associations. Furthermore, although in situ soft-bodied preservation provides a unique perspective on composition of benthic fossil assemblages, the record should not be interpreted as a simple "snapshot". Fossil beds represent a range of preservational modifications varying from current winnowed census samples of benthic communities at different depths and ecological maturity, to entirely transported assemblages. Unless the appropriate environments and taphonomic conditions are present for certain taxa, the absence of a particular taxon may or may not indicate its extinction in space or time. [ABSTRACT FROM AUTHOR]

The paleoenvironmental evolution of the Black Sea is closely linked to the ingression of Mediterranean seawater over the Bosporus sill after the Last Glacial Maximum. We have reconstructed the temporal and spatial development of the Black Sea suboxic chemocline, which divides oxic surface water from anoxic, sulfidic (euxinic) deep water. By combining high-resolution geochemical records of bulk parameters (carbonate, total organic carbon, sulfur), trace metals (Cu, Mo, V), and an isotopic proxy (δ56Fe) from seven sediment cores in the Black Sea, we generated a single composite geochemical core log that serves as a reference archive for the entire basin. Our proxy records reflect the changing depositional and redox conditions of the Black Sea and permit us to estimate the inflow budget of Mediterranean seawater throughout the Holocene. Our data indicate a gradual rise of the chemocline until ca. 5.3 ka, when suboxic waters flooded the shelf for the first time. Trace metal and isotopic inventories document one major descent of the chemocline since the onset of brackish/ marine conditions before the present stable situation was established. [ABSTRACT FROM AUTHOR]

The ANtarctic geological DRILLing Program (ANDRILL) successfully recovered 1138.54 m of core from drill hole AND-2A in the Ross Sea sediments (Antarctica). The core is composed of terrigenous claystones, siltstones, sandstones, conglomerates, breccias, and diamictites with abundant volcanic material. We present sedimentological, morphoscopic, petrographic, and geochemical data on pyroclasts recovered from core AND-2A that provide insights on eruption styles, volcanic sources, and environments of deposition. One pyroclastic fall deposit, 12 resedimented volcaniclastic deposits and 14 volcanogenic sedimentary deposits record a history of intense explosive volcanic activity in southern Victoria Land during the Early Miocene. Tephra were ejected during Subplinian and Plinian eruptions fed by trachytic to rhyolitic magmas and during Strombolian to Hawaiian eruptions fed by basaltic to mugearitic magmas in submarine and/or subglacial to subaerial environments. The long-lived Mount Morning eruptive center, located ~80 km south of the drill site, was recognized as the probable volcanic source for these products on the basis of volcanological, geochemical, and age constraints. The study of tephra in the AND-2A core provides important paleoenvironment information by revealing that the deposition of primary and moderately reworked tephra occurred in a proglacial setting under generally open-water marine conditions. [ABSTRACT FROM AUTHOR]

The Antarctic Geological Drilling (ANDRILL) program recovered a 1,138- m-long core, AND-2A, during the austral spring 2007-2008 from the Victoria Land Basin for the Southern McMurdo Sound (SMS) Project. The main objective of the SMS Project was to establish a Neogene (ca. 24-2.5 Ma) history recording ice volume changes from an ice-proximal site, in particular the environmental response of the Antarctic margin during the middle Miocene climate transition. This study focuses on the foraminifera taxa recovered from AND-2A, providing a paleoenvironmental analysis including paleobathymetry and ice-proximity estimates. Three assemblages, Cibicides-Cassidulinoides, Ammoelphidiella, and Ehrenbergina, as well as two subassemblages within the Ammoelphidiella assemblage, Globocassidulina and Nonionella, were identified in this study using cluster analysis. Calcareous eurytopic taxa dominate every assemblage and display similarities between Fresh Shelf Water assemblages and Ice Edge Biofacies that were previously defined in other studies focused in the Southern Ocean, as well as assemblages recovered from previous drilling projects in the Ross Sea region. Paleoenvironmental interpretations include an early Miocene record of fluctuating periods of glacial influence from ice-distal, abrupt cooling followed by a continued warming and transition into a more ice-proximal setting in the uppermost middle Miocene. The wellpreserved middle Miocene record reflects more-productive stable environmental conditions with significant freshwater input from outlet glaciers and rivers at the East Antarctic margin, and coincides with previously published palynomorph data indicating a short abrupt warming. Furthermore, the persistent appearance of the planktonic species Neogloboquadrina pachyderma and glacial/sea ice assemblages can be related to the onset of progressive cooling at the Antarctic margin, including periods of fluctuating sea ice extent or glacial proximity. Finally, the Pliocene record contains taxa similar to that of Fresh Shelf Water assemblages and Ice Edge Biofacies recovered in the Southern Ocean today. Paleobathymetric estimates range from inner shelf depths (~50-150 m) in the early Miocene reaching periods of outer-shelf depths (~400 m) in the uppermost early-middle Miocene and Pliocene. [ABSTRACT FROM AUTHOR]

In their seminal paper in 1979, Bull and Schick proposed a conceptual model for the geomorphic response to Pleistocene to Holocene climate change, based on the hyperarid Nahal Yael watershed in the southern Negev Desert. In this model, the change from semiarid late Pleistocene to hyperarid early Holocene climates reduced vegetation cover, increased the yield of sediment from slopes, and accelerated aggradation of terraces and alluvial fans. The model is now over 30 yr old, and during this time, chronologic, paleo-environmental, and hydrogeomorphic research has advanced. Here, we reevaluate the model using data acquired in Nahal Yael over the 30 yr since the original model was proposed. Recent studies indicate that the late Pleistocene climate was hyperarid, and a transition from semiarid to hyperarid climates did not occur. The revised chronology reveals a major 35-20 ka episode of accelerated late Pleistocene sediment production on slopes (with lower rates probably already at ca. 50 ka) due to increased frequency of wetting-drying cycles caused by frequent extreme storms and floods between 35 and 27 ka. Without lag time, these sediments were transported and aggraded in depositional landscape components (fluvial terraces and alluvial fans). This intensified sediment production and delivery phase is unrelated to the Pleistocene-Holocene transition. The depositional landforms were rapidly incised between 20 and 18 ka. Since and/or soon after this Last Glacial Maximum (LGM) incision, most material leaving the basin originated from sediments stored in depositional landforms and was not produced from bedrock. Using these new data, we propose a revision to the Bull and Schick model in this hyperarid environment. Our revision suggests that the model should include the frequent storms and floods responsible for a late Pleistocene pulse of intense weathering due to numerous cycles of wetting and drying on slopes and coeval sediment transport to fluvial terraces and alluvial fans. We also discuss the common use and pitfalls of using the Bull and Schick conceptual model to explain observations in diverse arid environments, usually without sufficient data on basin-specific stratigraphic, chronologic, paleoenvironmental, and paleoclimatic information. [ABSTRACT FROM AUTHOR]

Paleoenvironmental and paleoclimate changes that occurred during the late post-evaporitic stage of the Mediterranean Basin in the Messinian foreland domain of the Adriatic region offer a new perspective on the relationship between orbital forcing and climate response. The magnetic susceptibility record of the Fonte dei Pulcini A section (Maiella Mountains, Italy) allows us to orbitally tune the record between 5.394 and 5.336 Ma and to temporally constrain the paleoenvironmental and paleoclimate changes evidenced by quantitative paleontological (palynomorphs, ostracods, and calcareous nannofossils), stable isotope (δ18O and δ13C), and X-ray diffraction (XRD) analyses. The base of the Fonte dei Pulcini A section is characterized by Paratethyan ostracods and dinocysts, which point to the late Messinian Lago-Mare biofacies (Loxocorniculina djafarovi zone) of the Mediterranean Messinian stratigraphy. From paleontological and geochemical (δ18O) analyses, there is no evidence of a marine incursion in the Fonte dei Pulcini A section. The major changes in terms of paleodepth, paleosalinity, evaporation versus precipitation, aridity versus humidity, and reworking processes occurred in the upper part of the Fonte dei Pulcini A section, during the last Messinian insolation cycle (i-cycle 511/512), which is characterized by high-amplitude oscillations. In contrast, the lower part of the Fonte dei Pulcini A section, which was deposited during relatively low-amplitude insolation cycles, is characterized by more stable environmental conditions. Comparing summer insolation with the paleoenvironmental changes at the Fonte dei Pulcini A section, we identify delays of several thousands of years between orbital forcing and climate response. [ABSTRACT FROM AUTHOR]

Jurassic-aged strata of Asturias, Spain, contain trace fossils including sauropod, theropod, and ornithopod dinosaur footprints, but their paleoenvironmental context has been relatively unstudied. A coastally exposed continuous section at Playa de Vega shows a clear transition from the marine Middle Jurassic Rodiles Formation to the terrestrial Upper Jurassic Vega Formation. Within the >100 m of Vega Formation stratigraphy that was logged there, four distinct types of paleosols were identified: (1) Entisols, (2) Inceptisols, (3) Vertisols, and (4) composite or cumulative paleosols. The paleosol types and their features indicate a floodplain depositional setting with short stature, shrubby vegetation. Theropod and ornithopod tracks have been identified at the base of the section, indicating that a dinosaurian fauna was present at Playa de Vega during the Jurassic. Results from well-characterized climofunctions based on modern soils and paleosol B horizon chemical composition of the Inceptisols and Vertisols yield mean annual precipitation estimates of 400-980 mm yr-1 and mean annual temperature estimates of 8-15 °C. The presence of Vertisols, with both evidence for shrink-and-swell behavior and dispersed pedogenic carbonate, is consistent with a strongly seasonal precipitation regime. The δ13C analyses of pedogenic carbonates yield values that range from -7.09‰ to -8.88‰ (relative to Vienna Peedee belemnite [VPDB]) and indicate carbon dioxide levels about six times pre-industrial levels, consistent with previous results. The Asturian vertebrate track assemblage is remarkably similar to that of the Morrison Formation (western United States), but it has greater overall richness. The pattern is reversed for body fossils. The reconstructed paleoenvironmental and paleoclimatic conditions indicate similar depositional settings in both places, but with a cooler, wetter, more seasonal environment in Asturias. The greater seasonality indicated by the Vega Formation relative to the Morrison Formation may explain the observed differences in richness. [ABSTRACT FROM AUTHOR]

The article discusses a study which describes the giant stromatolites that occur in the Green River Formation deposited in alkaline lakes that covered much of Wyoming, Colorado and Utah for several million years in the Eocene. Topics covered include a description of stromatolites and other microbialites from a paleontologic and astrobiologic perspective, the different properties of stromatolites that are critical to oil recovery, and stromatolites as paleoenvironmental records.

The article presents the author's views on the results of the study by M. A. Gehling and M. L. Droser on the use of Ediacaran fossils in biostratigraphy. He states that Gehling and Droser found that Ediacaran fossils are not useful for biostatigraphy which he considers as a proof of their consolidation of frond fossils to one category. He argues that Gehling and Droser's paleoenvironmental model is undermined by the paleocological control of Ediacaran fossils.