Depositional Record最新文献

This volume examines tidal sedimentary systems through 11 articles, spanning ancient and modern tidalites, technological advances and implications for human management. Highlighting contributions from Tidalites 2022 and beyond, it underscores tidalites' significance in sedimentology, environmental forecasting and energy transition, reflecting decades of research by the Tidalites Scientific Group.

Present wetlands have proven to be delicate, biodiverse ecosystems, that are natural sinks for CO₂ and act as good indicators for climate changes. This means that ancient wetlands found in the fossil record may be very useful for inferring past climate changes. Since the times of early humans, wetlands have played an important role in providing resources for the ecosystems in which hominins and their associated fauna lived. The identification of palaeowetlands in the fossil record and their characterisation is therefore crucial to enable a better understanding of how early humans interacted with the landscape and its resources. Although there are many classification schemes for modern wetlands, developed for multiple purposes, only two have been found for ancient wetlands in the literature, and these cannot be used as a systematic tool to identify ancient wetlands in the geological record. A new classification for inland freshwater palaeowetlands, with a focus on carbonate wetlands, is proposed here, recognising key features that can be preserved in the fossil record. Its application requires templates to be used in the field and/or the core laboratory. To test the applicability of the classification, Pliocene-Pleistocene carbonate-dominated palaeowetlands identified in the Guadix Basin (southern Spain) have been classified using the proposed system. The information extracted from the geological record shows how useful the classification may be to characterise early human settings.

The Bebedero tectonic depression in San Luis province, Argentina, is a closed drainage basin that has formed as a result of block-faulting and rifting processes. The Bebedero lake exhibits notable similarities to the endorheic watersheds of the western United States, particularly those of Death Valley, the Saline Valley and, to a lesser extent, the Great Salt Lake. While it is currently classified as a playa lake, there is evidence of lake levels near the sill that overflowed during the Late Pleistocene. Several lines of evidence suggest that climate is the major controlling factor in the basin's fill. The Salina del Bebedero Basin is an underfilled lake basin type, particularly a discharge lake basin. This assertion is supported by recent findings, including precise topography, stratigraphy, facies associations, radiocarbon ages and palaeontology from one section and two transects. The following presentation comprises stratigraphic correlations, palaeoenvironmental reconstructions and a graphical model of lake stages based on these new results and previously published research. This paper provides a model of lake-level fill from the Late Pleistocene to the present, identifying distinct highstands and lowstands associated with global climate events. The surface and depth of the lake were reconstructed for each stage. The maximum expansion was estimated at 1000 km² during the Pre-Last Glacial Maximum and 782.6 km² during the Last Glacial Maximum, with depths ranging from 60 to 75 m. Lake Bebedero exhibited similar lake-level responses to climate variations as Lake Bonneville, Great Salt Lake, as well as sub-environmental similarities with Death Valley and the Saline Valley. In addition to its palaeoclimate significance, Lake Bebedero has archaeological records of an early settlement dating back ca 10 to 6 cal ka BP. The scarcity of data concerning the early human settlement in southern South America makes archaeological evidence relevant. Therefore, the inferences regarding climate and environment derived from studies of the lake provide important information about the first human groups to populate these regions.

High-resolution sequence analysis of three drill-cores with well-constrained optically simulated luminescence ages reveals a stratigraphic evolution of the Baeksu tidal flat (south-west coast of Korea) that documents the development of tide-dominated estuary infill interacting with minimal fluvial processes since marine isotope stage 6. The stratigraphic architecture and its correlation along an upper mudflat-to-subtidal transect showcase two different hierarchies of sequences and small-scale (fifth-order) subsequences that are nested within larger-scale (fourth-order) sequences. Two fourth-order sequences with a frequency of 100 kyr consist of lower fluvial deposits and overlying tidal deposits, respectively, reflecting a twofold regressive–transgressive sedimentary sequence related to glacial–interglacial cycles. The sequence boundary is marked by an abrupt facies change from oxidised spit gravels (marine isotope stage 3) to tidal muds (marine isotope stage 1). An interesting feature is the presence of two packages of retrograding spit/tidal deposits corresponding to marine isotope stage 5a/b and marine isotope stage 3 interstadials deposited during short-lived sea-level rise, in spite of the long-term phase of glacial sea-level fall spanning from marine isotope stage 5d to marine isotope stage 2. Identification of deeply oxidised tidal deposits dated to marine isotope stage 5a/b confirms that two short-term fluctuations in sea level occurred during the long-lived glacial period. Such nested successions are assigned as fifth-order subsequences with 40 kyr time intervals. The late Quaternary Baeksu tidal flat succession was thus mainly controlled by two different frequencies and magnitudes of sea-level changes, associated with major interglacials (marine isotope stage 5e and 1) and minor interstadials (marine isotope stage 5a and 3). More importantly, transgressive episodes are significantly better preserved than regressive phases. This study provides a good example of how multi-order, multiple transgressive deposition may be preserved in a tide-dominated estuarine setting, particularly where river inputs are negligible.

Lacustrine palaeotemperature reconstructions are important for characterising past temperature and hydroclimate change, validating multi-proxy reconstructions and evaluating global climate models. In particular, lake water temperature is often derived from geochemical proxies—including clumped isotopes (Δ₄₇), oxygen isotopes (δ¹⁸O), alkenone lipids (U^k’₃₇) and GDGT compounds (TEX₈₆). However, global climate models, constrained by resolution, computational demand and cost, are designed to simulate large-scale processes, often at the expense of resolving lakes and simulating lake temperature. Consequently, this limitation complicates the comparison of climate model-simulated variables such as air temperature, with lake water temperature or with other proxy variables (e.g. pollen-derived air temperature), and requires the use of a transfer function to relate lake temperature to air temperature. Previous work developed transfer functions to translate proxy-derived seasonal lake water temperature to mean annual air temperature using ground-based measurements from 88 lakes. This study reports new lake-to-air temperature transfer functions (for annual, spring through summer, spring, summer and warmest month) that incorporate lake surface water temperature, and new variables including latitude and elevation, by analysing climate reanalysis data and long-term satellite observations of surface temperatures for 1395 modern lakes via regression-based inverse modelling. With the use of multiple regression models and a dataset roughly 10 times larger, the error in predictions of mean annual air temperature is reduced by up to 48% compared to previous work. To demonstrate the potential of the new transfer functions for integrating and comparing proxy data with model output, Pliocene and Pleistocene mean annual air temperature was reconstructed from Δ₄₇-derived lake temperatures and compared with model simulations for the Last Glacial Maximum and mid-Piacenzian warm period. The new transfer functions, with reduced error, should enable more accurate palaeotemperature reconstructions from proxy-derived lake water temperature and allow for more comprehensive assessments of climate model skill.

In this study, sandstones of the Lower Jurassic Datta Formation in the Salt and Trans-Indus ranges are investigated regarding composition, diagenesis, provenance and reservoir properties using petrography, scanning electron microscopy and petrophysical analysis. The detrital mineral composition of the Datta Formation indicated that the sandstones are quartzose, lithic-quartzose, lithic-feldspatho-quartzose, lithic-quartzo-feldspathic, quartzo-lithic and feldspatho-quartzose, primarily from the recycled orogen setting, including the Malani Igneous Suite, the Aravali Range and Nagar Parkar. The Datta Formation has sub-angular to well-rounded, fine to coarse and moderate to well-sorted grains. Numerous diagnostic processes that occurred in the early to late stages of diagenesis, such as compaction, pressure solution, cementation, alteration, dolomitisation and dissolution, are supported by evidence in the Datta Formation. Dissolution, physical compaction, dolomitisation and alteration enhanced the reservoir quality, while pressure solution and cementation reduced the reservoir quality of the Datta Formation. The porosity types detected in the Datta Formation under scanning electron microscopy are vuggy, intracrystalline/intraparticle, dissolution and intercrystalline, with an average petrographic visual porosity of 11%. The petrophysical aspects of the Datta Formation in the Chonai-01 well and the correlation between four wells indicated that the hydrocarbons had shifted up-dip towards the Isa-Khail-01 well, so it is recommended for drilling because of the greater depositional thickness. The comparison of the Datta Formation with age-equivalent units in other regions of eastern Tethys provided a better understanding of reservoir heterogeneities that can be applicable in areas with similar geological conditions for future petroleum exploration.

Lake margin deposits are the subject of increased study, but this is often focussed on either clastic or carbonate/microbial dominated end members. This study examines the interaction of clastic and carbonate systems. The Upper Triassic Edderfugledal Formation in East Greenland provides superb exposures through a carbonate dominated lacustrine succession. Fluctuations in lake level, interpreted as a response to cyclic, orbitally forced, climatic variance resulted in a highly mobile lake shore zone. The response of the shore zone environment to these fluctuations in lake level, and the interaction of both clastic and carbonate components, are documented in this study. A general trend from more arid to more humid conditions is recognised through the Edderfugledal Formation. This trend is reflected in a transition from more ephemeral lacustrine conditions with low sediment input to conditions where lacustrine episodes were more prolonged and clastic input was increased. Deposits reflecting more ephemeral conditions are dominated by extensive post-depositional disruption including desiccation, pedogenic processes and evaporite precipitation. These effects increase towards the lake margins where exposure was most common and most prolonged. Increasingly humid conditions and the associated longer-lived lacustrine developments and increased clastic sediment input resulted in a very different form of lake margin. During transgressive phases sediment input was pushed back to the lake margin allowing extensive microbialite development. Ooidal shoals developed in shallow water beyond the extent of clastic input. The lakeward migration of the ooidal shoals and the progradation of clastic systems eventually stifled the microbialites prior to the next transgressive event. In a mixed clastic-carbonate lacustrine setting the interaction of sediment supply and production are key factors in governing facies development and these are in turn predominantly controlled by lake-level change and lake margin bathymetry.

Feedback processes that drove Earth's second major increase in ocean–atmosphere oxygen levels during the Neoproterozoic are poorly constrained. Variability in seawater redox over geological timescales is commonly linked to changes in the biogeochemical cycling of P and thus the rate of primary production and generation of photosynthetic oxygen. In the modern surface ocean, an important source of bioessential P and micronutrients (Fe, Cu, Co, Zn, Mo, Cr and Ni) is aeolian dust derived from deserts and arid, post-glacial landscapes. It is interpreted herein that glacial retreat following the Sturtian (ca 717 to 660 Ma) and Marinoan (ca 650 to 635 Ma) snowball glaciations provided copious dust to the global ocean. Correlation of interglacial siltstone successions in palaeogeographical context suggests that such dust accumulation was diachronous and concentrated in the palaeo-horse latitudes (30° N and 30° S). Delivery of this dust from continents is likely reflected in the steep increase in global radiogenic Sr isotope values (⁸⁷Sr/⁸⁶Sr) in post-Sturtian carbonates, and changes in the δ¹⁸O signatures of Cryogenian zircons derived from subducted marine sediments. Accumulation of sedimentary organic matter also peaked during interglacial periods, suggesting a causal link between glaciation, aeolian dust and primary production. This relationship implies windblown dust was an important source of P and micronutrients for an evolving biological pump that stimulated primary production, enhanced burial of organic carbon and increased ocean–atmosphere oxygen concentrations. Thus, delivery of aeolian dust to the global ocean was likely critical for sustaining Earth's second major increase in oxygen. Sequestration of atmospheric CO₂ in organic-rich siltstones and shales is also interpreted to have been an important negative feedback process, which together with silicate weathering, prevented runaway greenhouse conditions during interglacial periods. The oxygen produced by this aeolian marine biological pump may have helped pave the way for the evolution of multicellular animals in the Ediacaran.

The Smithian–Spathian boundary interval is characterised by a positive carbon isotopic excursion in both δ¹³C_carb and δ¹³C_org, concurrent with a major marine ecosystem reorganisation and the resurgence of microbialite facies. While these δ¹³C records have been traditionally interpreted as capturing global carbon cycle behaviour, recent studies have suggested that at least some excursions in early Triassic δ¹³C values may incorporate influences from authigenic or early diagenetic processes. To examine the mechanistic drivers of Smithian–Spathian boundary geochemistry, the carbonate geochemistry of a core from Georgetown, Idaho (USA), was analysed using a coupled δ^44/40Ca, δ²⁶Mg and trace-metal framework. While the δ¹³C record in the Georgetown core is broadly similar to other Smithian–Spathian boundary sections, portions of the record coincide with substantial shifts in δ^44/40Ca, δ²⁶Mg and trace-metal compositions that cannot feasibly be interpreted as primary. Furthermore, these geochemical variations correspond with lithology: The δ¹³C record is modulated by variations in the extent of dolomitisation, and the diagenetic styles recognised here coincide with individual lithostratigraphic units. A primary shift in local sea water δ¹³C values is inferred from the most geochemically unaltered strata, from ca 3‰ in the middle Smithian to ca 5‰ in the early Spathian, although the timing and pathway through which this occurs cannot be readily identified nor extrapolated globally. Therefore, the Georgetown core may not directly record exogenic carbon cycle evolution, showing that there is a need for the careful reconsideration of the Smithian–Spathian boundary—and more broadly, Early Triassic—geochemical records to examine potential local and diagenetic influences on sedimentary geochemistry.

The Stockton Formation of the Newark Basin represents an exciting time in Earth history during the early stages of rifting of the North Atlantic, with rapid subsidence and sediment deposition. Much of the previous work on this formation has been done using drill cores, with development limiting surface exposure. While this allows us to build a full stratigraphic sequence of deposition, it has the potential to miss smaller-scale variability and sedimentary structures. It is also difficult to understand the three-dimensional geometries, architecture and relationships between the depositional elements from drill core alone. An outcrop in North Bergen, NJ that was recently exposed during construction provided an opportunity to study the primary and secondary sedimentary structures of a previously hidden part of the Stockton Formation. These sediments and structures were investigated in the field and laboratory, with geochemical data assisting in the interpretation of their origin and history. Despite its small size, this outcrop provides strong evidence for varying rates of basin subsidence, with rocks deposited during more rapid subsidence also showing secondary structures associated with major earthquakes. Rapid subsidence during fluvial deposition resulted in the preservation of more fine-grained, lower-porosity sediments. Recently the Newark Basin has been identified as having characteristics that are favourable for CO₂ storage, however, a detailed understanding of sedimentary lithologies is essential to assessing that potential. If these periods of rapid subsidence have similar lithological consequences basin-wide, this could potentially impact the capacity for carbon sequestration, by reducing porosity and permeability in many areas, and potentially creating barriers to flow.