Depositional Events Research Articles

Quantifying the Impact of Hurricane Harvey on Beach−Dune Systems of the Central Texas Coast and Monitoring Their Changes Using UAV Photogrammetry

Historically, the Texas Gulf Coast has been affected by many tropical storms and hurricanes. The most recent severe impact was caused by Hurricane Harvey, which made landfall in August 2017 on the central Texas coast. We evaluated the impact of Hurricane Harvey on the barrier islands of the central Texas coast, including San Jose Island, Mustang Island, and North Padre Island. We used public data sets, including 1 m resolution bare-earth digital elevation models (DEMs), derived from airborne lidar acquisitions before (2016) and after (2018) Hurricane Harvey, and sub-meter scale aerial imagery pre- and post-Harvey to evaluate changes at a regional scale. Shoreline proxies were extracted to quantify shoreline retreat and/or advance, and DEM differencing was performed to quantify net sediment erosion and accretion or deposition. Unmanned aerial vehicle surveys were conducted at each island to produce high-resolution (cm scale) imagery and topographic data used for morphological and change analyses of beaches and dunes at the local scale. The results show that Hurricane Harvey caused drastic local shoreline retreat, reaching 59 m, and significant erosion levels of beach−dune elements immediately after its landfall. Erosion and recovery processes and their levels were influenced by the local geomorphology of the beach−foredune complexes. It is also observed that local depositional events contributed to their post-storm rebuilding. This study aims to enhance the understanding of major storm impacts on coastal areas and help in future protection planning of the Texas coast. It also has broader implications for coastlines on Earth affected by major storms.

A machine-learning based approach to predict facies associations and improve local and regional stratigraphic correlations

The geological record has challenged stratigraphers through time. Many depositional, tectonic and paleobiological events require stratigraphic positioning to determine temporal relationships among such events. This task is complicated and challenging, especially in sedimentary succession with scarcity or lack of paleontological content bearing biostratigraphic value and radiometric ages. Therefore, subjective personal criteria adopted during correlations and field mapping activities make stratigraphic correlations more complex and confusing. New methodological approaches are necessary to test human expertise in recognizing stratigraphic units with environmental significance and to contribute to stratigraphic correlations based on quantitative data. We used cores obtained by coal drilling campaigns during the 1970s and 1980s on the southern border of the Paraná Basin, southern Brazil, to generate a quantitative database. Data obtained from gamma spectrometry in the cores of Carboniferous to Permian age measured total count (cps), potassium (K), uranium (U) and thorium (Th). We used machine learning (ML) to predict facies associations and to confront the quantitative database with the three facies associations mapped through time based on qualitative geological mapping criteria. The k-nearest neighbors (KNN) algorithm reached maximum accuracy values of 86.0%% and f1-score of 90.0%, 73.0% and 91.0% for facies associations 1, 2 and 3, respectively, using exponential moving average and normalized data. This KNN-based method using gamma spectrometric data opened new possibilities to perform local and regional stratigraphic correlations using quantified data. New tests must be performed to improve this promising correlation method in other regional settings and related basins.

Cenozoic sedimentary evolution of the Tiereke section on the northern Tarim Basin: implications for the intracontinental mountain building of the Eastern Tian Shan

The Tian Shan is one of the world's largest intracontinental orogens and provides an excellent example for deciphering the intracontinental responses to the tectonics of plate boundaries. Despite its significance, the timing and driving mechanism of the Cenozoic mountain building of the Tian Shan in the context of the India–Eurasia collision remain controversial. In this study, Cenozoic stratigraphy of the Tiereke section along the western Kuqa Depression of the northern Tarim Basin on the south foreland of Eastern Tian Shan (east of 80°E) has been investigated. The results indicate that the Cenozoic deposition of the Tiereke region sequentially experienced a transgression from the Kumugeliemu Group to the Suweiyi Formation and a regression from the Suweiyi to the Kuqa Formations. Based on the contact relationships and conglomerate textures, three stages of high-energy alluvial deposition have been identified in the lower Kumugeliemu Group, upper Jidike and Kangcun–Kuqa Formations, respectively. These sedimentary events were interpreted to represent phases of Eastern Tian Shan mountain building at c. 54 Ma, c. 27 Ma and since c. 9.7 Ma according to previous magnetostratigraphic results, which were possibly related to the initial India–Eurasia collision, the collision between the India and Tarim lithospheric mantles, and the basinward propagation of deformation, respectively. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration

Siliciclastic strata of the Colorado Plateau attract attention for their striking red, green, bleached, and variegated colors that potentially record both early depositional and later diagenetic events. We investigated the proximal-most strata of the Paradox Basin, from their onlap contact with the Precambrian basement of the Uncompahgre Plateau to the younger Cutler strata exposed within 10 km of the Uncompahgre Plateau to attempt to understand the significance of the striking colors that occur here. These strata preserve a complex geology associated with buried paleorelief and sediment-related permeability variations at a major basin-uplift interface. Strata exposed within ∼1.5 km of the onlap contact exhibit a pervasive drab color in contrast to the generally red colors that predominate farther from this front. In-between, strata commonly host variegated red/green/bleached intercalations. Thin-section petrography, SEM, XRD, Raman spectroscopy, Mössbauer spectroscopy, and whole-rock geochemistry of samples representing different color variations from demonstrate that water–rock interactions charged the rocks with Fe(II) that persists primarily in the phyllosilicate fraction. Color variations reflect grain-size differences that allowed the reduction of fluids from regional fault and basement/fill contacts to permeate coarser-grained Cutler sediments. Hematite and chlorite occur in both red and green sediments but are absent in the bleached sediments. Pervasive hematite in both red and green layers suggests that sediments were hematite-rich before later alteration. Chlorite and smectite are elevated in green samples and inversely correlated with biotite content. Green coloration is generally associated with 1) coarser grain sizes, 2) spatial association with basement contacts, 3) elevated smectite and/or chlorite, 4) less total Fe but greater Fe(II)/Fe(III) primarily in the phyllosilicate fraction, and 5) uranium enrichment. The bleached coloration reflects the removal of pigmentary Fe(III) oxide, while the green coloration is due to the removal of pigmentary hematite and the abundance of Fe(II)-bearing phyllosilicates. Abundant mixed-layer and swelling clays such as smectite, illite/smectite, and chlorite/smectite (including tosudite) dominate the mineralogy of the clay fraction. These results are consistent with other studies demonstrating fault-associated fluid alteration in the Paradox Basin region. However, the pervasive greening was not observed in many of these studies and appears to reflect the unique aspects of the paleovalley system and the importance of biotite alteration to Fe(II)-bearing phyllosilicates.

The formation of fan‐deltas in mountain lakes: Findings from Zelené Kežmarské Lake (Slovakia)

AbstractFan‐deltas are formed in mountain lakes, contributing to changes in shorelines' shapes and filling lake basins with sediments. Factors that condition sediment delivery to the lakes and the formation of fan‐deltas are not fully understood. This study aims to identify processes forming fan‐deltas in mountain lakes based on the sedimentary architecture of a fan‐delta filling Zelené Kežmarské Lake (Slovakia). Our study is based on ground‐penetrating radar and seismic refraction surveys conducted over the lake and debris‐flow fans in its vicinity, and grain‐size analyses of the surface deposits. The internal structure of the fan‐delta comprises foreset deposits representing the fan‐delta lobes. Mouth bars were identified in the near‐shore zone. The fan‐delta is built of sands and silty sands whereas an alluvial debris‐flow dominated fan west of the lake contains gravels. A general trend of downslope fining of the fan surface sediments, disturbed by zones of coarse gravels, was identified in the surficial sediments forming the fan. The fan‐delta was formed by depositional events in humid periods, alternating with dry periods featured with a small or no deposition. The lake‐level steadily rose in the humid periods and remained stable in dry periods. The contrast between the coarse sediments forming the alluvial debris‐flow dominated fan, and sands forming the fan‐delta was caused by a selective deposition. Coarse gravels in the fan were mobilized in humid periods but did not reach the lake‐shore. The reason was a basement rock ridge situated parallel to the lake shore. Sands were delivered to the fan‐delta in humid periods owing to frequent high‐energy flows. A deposition of silts took place in dry periods. The studied fan‐delta might preserve the sedimentary record of three humid periods from the last 200 years. However, further studies are needed to establish the timing of the fan‐delta formation.

Geochemical behavior of heavy metals and radionuclides in a pit lake affected by acid mine drainage (AMD) in the Muskau Arch (Poland)

Pit lakes in the ‘anthropogenic lake district’ in the Muskau Arch (western Poland; central Europe) are strongly affected by acid mine drainage (AMD). The studied acidic pit lake, ŁK-61 (pH <3), is also exposed to floods due to its location in the flood hazard area, which may significantly influence the geochemical behavior of elements. The elemental compositions of water and lake sediment samples were measured with ICP–OES and ICP–MS. The sediment profile was also examined for 137Cs and 210Po activity concentrations using gamma and alpha spectrometry, respectively. Grain size distribution, mineralogical composition, diatoms, and organic matter content in the collected core were also determined. The key factors responsible for the distribution of selected heavy metals (e.g., Cu, Ni, Pb, Zn) and radioisotopes (137Cs and 210Po) in the bottom sediments of Lake ŁK-61 are their coprecipitation/precipitation with Fe and Al secondary minerals and their sorption onto authigenic and allogenic phases. These processes are likely driven by the lake tributary, which is an important source of dissolved elements. The data also showed that the physiochemical parameters of Lake ŁK-61 water changed during an episodic depositional event, i.e., the flood of the Nysa Łużycka River in the summer of 2010. The flood caused an increase in the water pH, as interpreted from the subfossil diatom studies. The down-core profiles of the studied heavy metal and radionuclide (HMRs) contents were probably affected by this depositional event, which prevented a detailed age determination of the collected lake sediments with 137Cs and 210Pb dating methods. Geochemical modeling indicates that the flood-related shift in the physicochemical parameters of the lake water could have caused the scavenging of dissolved elements by the precipitation of fresh secondary minerals. Moreover, particles contaminated with HMRs have also possibly been delivered by the river, along with the nutrients (e.g., phosphorus and nitrogen).

Mid-Mesoproterozoic (ca. 1.37 Ga) anorogenic magmatism in the Dabie orogen, northern Yangtze Craton: Response to the breakup of Columbia

It is evident that the Yangtze Craton was involved in the formation and breakup of the Columbia supercontinent. However, due to the scarcity of Mesoproterozoic geological records and reliable paleomagnetic data, little is known about the timing, paleogeographic position, and geological processes of the Yangtze Craton. We conducted detailed geological mapping, petrographic, geochemical, and in situ zircon U-Pb and Lu-Hf isotopic investigations on newly recognized Mesoproterozoic quartz syenite and monzogranite in the Dabie orogen, northern Yangtze Craton. The results show that the quartz syenite and the monzogranite were emplaced at 1369 ± 12 Ma and 1372 ± 5 Ma, respectively. Both rocks are high in total alkali (K2O + Na2O) content and FeOt/(FeOt + MgO), with elevated diagnostic 10,000*Ga/Al ratios and Zr + Nb + Ce + Y concentrations, and enrichment in light rare earth elements. They are also depleted in heavy rare earth elements with significant negative Eu anomalies but remarkably low Sr, Cr, and Ni contents. These compositions define affinity to A1-type granite. In addition, the quartz syenite displays variable zircon Hf and homogeneous whole-rock Nd isotopic compositions with positive εHf(t) values of +0.7 to +5.7 (average +2.4) and εNd(t) values of −0.1 to +2.5 (average +1.0). In contrast, the monzogranite has homogeneous zircon Hf and whole-rock Nd isotopic compositions with negative εHf(t) values of −5.7 to −2.6 (average −4.8) and εNd(t) values of −3.5 to −1.5 (average −2.2). We propose that the quartz syenite was likely generated by the partial melting of juvenile, crust-derived melt with involvement of minor mantle-derived material, while the monzogranite was likely derived from the partial melting of ancient crust in an extensional tectonic regime (e.g., continental rift). Based on the newly recognized ca. 1.37 Ga granitic magmatism and previously reported magmatic events, we argue that the mid-Mesoproterozoic (ca. 1.37 Ga) magmatism in the Yangtze Craton occurred in response to the breakup of Columbia, and represents the separation of the Yangtze Craton from Columbia. Furthermore, according to comparable magmatic and sedimentary events, we propose that the Yangtze Craton, along with central Hainan Island, may have been linked to northwestern Laurentia, southwestern Siberia, and northeastern Australia during 1.6−1.4 Ga.

A natural death assemblage of fishes from an early modern archeological context in Antwerp (Belgium)

AbstractAn unusual concentration of tens of thousands small fish remains discovered during rescue excavations in the town of Antwerp, Belgium, is described. The material was found in a small depression with no associated archeological material but could be dated to the first half of the 16th century based on its stratigraphic position. About 3500 freshwater fish were found in articulating position and it is shown that they died naturally during a single depositional event after an exceptional flood. The species spectrum and the reconstructed fish lengths make it possible to document the season when the catastrophic mortality occurred. This assemblage differs from the few assemblages of natural mortality reported in the literature, which are all of the attritional type.

Effects of Emeishan Large Igneous Province on organic matter accumulation, Sichuan Basin, China

Volcanic activity is often associated with the formation of organic-rich sedimentary deposits. However, the relationships between volcanism and depositional events of hydrocarbon source rock during geological history remain unclear. To fill the knowledge gap, we investigated the relationships based on a case study of the Emeishan Large Igneous Province (ELIP) during the late Guadalupian. We carried out a detailed petrological and geochemical investigation of the upper Maokou Formation (i.e., the Mao III Member) in the Shangsi section, Sichuan Province, China. The Mao III Member has a relatively high abundance of organic matter (OM), good OM type, and appropriate thermal maturity that is conducive to hydrocarbon generation. Paleoenvironmental reconstructions based on multiple geochemical proxies indicate that the Mao III Member records relatively high primary productivity, enhanced anoxic conditions, intense upwelling but weak water mass restriction, decreased detrital input and sedimentation rate, and fluctuations in volcanic and hydrothermal activity. The marked positive correlations between primary productivity, redox conditions, and OM abundance suggest that the former two factors controlled OM accumulation. In addition, the detrital input has a slight dilution effect on the OM abundance. No direct relationship was observed between hydrothermal activity and OM abundance. In contrast, volcanic activity related to ELIP had a major role in enhancing the primary productivity and more reducing conditions, which is confirmed by the marked correlations between Hg/TOC, Cuauth, and Vauth values. This suggests that ELIP volcanism had a significant positive effect on OM enrichment in the Mao III Member, which may be a common feature associated with large volcanic events at other times in Earth's history.

Zeroing of IRSL signals in cobbles surfaces from a modern river floodplain in the Manas river, Tian Shan

A newly developing method, rock surface luminescence dating, provides a novel means of constraining the burial age of fluvial gravel and unveiling the transport and exposure-burial process of fluvial bed-load. A crucial requirement for successful age determination in luminescence dating of buried rock surfaces is that a sufficiently thick surficial layer was reset to a near-zero level of signal prior to deposition and burial. However, little such effort has been made on modern fluvial gravels from various depositional environments to provide a sound justification for the use of luminescence dating in such settings. In this study, we reported an investigation of daylight bleaching in modern cobbles with different sizes and shapes at a modern river floodplain from the Manas River, Tian Shan, to test the reliability and applicability of fluvial cobble optical dating. Four multi-elevated-temperature post-infrared infrared (MET-pIRIR) stimulated luminescence signals of rock slices were measured using a modified MET-pIRIR protocol to establish residual luminescence-depth profiles. The residual does of pIRIR and MET-pIRIR signals of sub-surface rock slices were also estimated using different modified SAR protocols. The results showed that the high temperature IRSL signal could be reset to ∼2–3 mm depth into cobbles surface and flat cobbles seem easier to bleach than spherical cobbles. The residual doses of sub-surface rock slices of cobbles from modern river floodplain was ∼0.4 Gy and ∼1.1 Gy for the IR50 and the pIRIR170 signal respectively, suggesting a residual age of ∼0.1 ka and ∼0.2 ka. The residual ages of MET-pIRIR signals of sub-surface rock slices of cobble MNS2-5 were ∼0.5–1 ka at higher stimulation temperature. Our results show that the fluvial cobble optical dating techniques have great potential for providing reliable chronologies for river floodplain gravel and other fluvial depositional events.

Mesophotic vs. shallow water reefs: ecosystem connectivity in the Silurian of Gotland

The Lower Silurian Visby Beds (ca. 430 Ma) exposed on the island of Gotland (Sweden) yield the oldest so far described MCE’s (mesophotic coral ecosystems). Several basic questions concerning these ecosystems, including their extent, positioning, and particularly their spatial relation and affinity with the shallow water reefs, remain unanswered. We describe a deeply incised erosional channel infilled by redeposited detrital and biodetrital material including corals and stromatoporoids, which represents a unique example of a fossil depositional structure connecting shallow- and deep-water reef environments of that time. The mesophotic environment is embodied by limestones and marls, in which the channel is incised, while the shallow water habitats are represented by the redeposited material infilling the channel. The erosional channel contains material derived from hypothetical adjacent shallow-water reefal settings, which indicates that it served as an interconnecting zone between shallow- and deep-water benthic communities. The vertical connectivity of the shallow-water reefs and the adjacent mesophotic ecosystems results in a significant taxonomic overlap between these communities. This is especially important when taking into account that the Visby Beds are the oldest example of a fossil mesophotic ecosystem described so far. This indicates that the development of the earliest mesophotic ecosystems should not be attributed solely to gradual expansion of corals and stromatoporoids into greater depths, but probably took place also by means of redistribution of shallow water taxa during high-energy sedimentary events.

Inferring drivers of nitrate and sediment event dynamics from hysteresis metrics for two large agricultural watersheds

AbstractExcess nitrate and sediment, mobilized by precipitation events and transported into surface waters, is a global water quality challenge. Recent advances in high‐frequency in situ water quality monitoring sensors have created opportunities to investigate constituent concentration dynamics during short‐term hydrological changes. In this study, we characterized the event‐scale variability of nitrate () and turbidity (a surrogate for sediment transport) in two large agricultural watersheds of the Upper Mississippi River Basin using hysteresis loop characteristics to determine sources and dominant transport mechanisms. We then applied factor analysis to detect variable groupings and thus determine controls on nitrate and sediment dynamics. We observed consistent counterclockwise hysteresis patterns between the two watersheds. This was indicative of distal contributions and/or late‐event mobilization and flushing, which was controlled by the characteristics of the event hydrology (such as, event duration and magnitude of event discharge). However, turbidity hysteresis loops indicated different sediment delivery behaviours between the two watersheds. The smaller watershed with more diverse land use demonstrated consistent clockwise hysteresis patterns indicating early event flushing or rapidly responding pathways. The time lag between turbidity and discharge peaks was identified as a driver of hysteresis magnitude for the smaller site. In contrast, the larger and more agricultural watershed showed variability between dilution versus flushing as well as delivery pathways between events. The hysteresis magnitude was driven by the event peak discharge and discharge range demonstrating an increase in stream power with scale influenced sediment dynamics at the larger site that switched behaviour. This result is critical for watershed water quality management, especially in the context of a changing climate and further underscores the utility of high‐frequency sensors monitoring data to offer deep insights into hydrological processes controls on contaminant transport and delivery.

Marine inundation history during the last 3000 years at Lake Kogare-ike, a coastal lake on the Pacific coast of central Japan

Sediment cores collected at Lake Kogare-ike, a coastal lake on the Pacific coast of central Japan, record the marine inundation history during the last 3000 years. The sediments consist mainly of organic mud, sand, gravel, inorganic mud, and volcanic ash, and inundation events were recognized as 19 event deposits (E1–E19, from top to bottom) interbedded with the organic mud. Visual observation by naked eyes and X-ray computed tomography (CT) images identified 16 event deposits based on quantitative and qualitative changes in sand contents and changes in the textures and colors of the sediment samples (E1–E3, E5, E6, E8, E9, and E11–E19). The other three event deposits (E4, E7, and E10) were identified only on the CT images as layers with higher radiodensity than the underlying and overlying organic mud layers. The sedimentary features, the spatial bias of the event deposits toward seaward areas, the diatom assemblages, and the frequency of inundation events suggest that 13 (E1–E10 and E12–E14) of the 19 event deposits were formed by tsunamis or extraordinary storms. To constrain the depositional ages of the event deposits, Bayesian age–depth models were constructed based on radiocarbon dating of plant macrofossils and concentrated fossil pollen and the 137Cs profile. The depositional ages of the event deposits indicate that five or possibly six event deposits can be correlated with historical tsunamis along the Nankai Trough: E2, either of E3 or E4, E5, E7, and E9 correspond to the 1707 CE Hoei, the 1605 CE Keicho, the 1498 CE Meio, the 1096 CE Eicho, and the 684 CE Hakuho tsunamis, respectively. E1 was possibly formed by the 1944 CE Showa-Tonankai tsunami, the 1854 Ansei–Tokai tsunami, the 1959 Isewan typhoon, or a combination of two or all three events.

Integrated organic, inorganic geochemical and palynofacies analyses to characterize the paleoenvironment of the Tortonian (Late Miocene) Wakar Formation, offshore Nile Delta, Egypt

The subsurface Wakar Formation (Fm) has been identified in all wells of the offshore concessions in the eastern Mediterranean in Egypt. This formation is important because it represents the end member of the Late Miocene (Tortonian) siliciclastic sedimentary rock of a vertical thickness between 500 and 900 m in these fields and is a promising formation for gas production in Egypt. There are no comprehensive studies on the geochemistry and palynofacies of this Wakar Fm in literature. Therefore, sixteen collected ditch samples of the entire thickness of the Wakar Fm from a PFM-SE -1 well were investigated. The main objective is to reveal the history of depositional events that prevailed in North Africa at this time. TOC content (average = 0.81 wt%) and generative potential of the Wakar Fm are of poor and fair quantity. The organic matter (OM) belongs to types IIIC and III of coastal and delta settings as revealed by the palynofacies and geochemical data. The Tmax of the samples does not exceed 435 °C (419–432 °C) of the immature stage, which corresponds to the carbon preference index (CPI >1) (1.15–1.4). The thermal alteration index range between 2 and 2+, indicating immature to marginally mature OM. GC of the two extracted samples shows a predominance of short-chain and mid-chain n-alkanes derived mainly from algae and seagrass; the Pr/Ph ratio (3.24–3.02; suboxic) and low terrigenous/aquatic ratio (TAR; 0.23–0.47) indicate that the OM bearing sediments were accumulated in a transitional setting of the suboxic aqueous medium. The dominance of terrestrial OM and low amorphous organic matter also suggests deposition in a marginal basin under dysoxic-anoxic to suboxic-anoxic conditions. Pr/n-C17 versus Ph/n-C18 diagrams confirm that preservation occurred in weakly oxidized environments from a source of kerogen type III gathered from a swamp and transitional marine zones. The inorganic geochemical analyses (XRD and XRF) and the calculated paleoenvironmental indices (i.e; log (Fe2O3/K2O) versus log (SiO2/Al2O3)) indicate that the main composition of the Wakar Fm is a combination of iron shale and sandstone facies. The Fe-sandstone facies occupies the middle part of the formation with a thickness of 170 m, which is the pay zone in the present concession. The parent protolith of Wakar Fm is a combination of intermediate and mafic igneous rocks. The prevailing paleoclimate is arid and semi-arid conditions synchronize the base, and top of the Wakar Fm, which is responsible for weak to moderate chemical weathering as revealed from chemical index of alteration values (CIA average = 67.99). Discriminant functions exhibit a depositional setting belonging to an active continental margin and oceanic island arc between marine and terrestrial zones under oxic-dysoxic environments.

Short-term response of benthic foraminifera to fine-sediment depositional events simulated in microcosm

Abstract. A microcosm experiment was designed to describe how benthic foraminifera react to fine-sediment deposits varying in frequency and intensity as they may occur regularly or occasionally in coastal benthic environments, caused by discharges from (e.g.) river flooding, tidewater glacier melting in polar regions, or diverse anthropic activities linked to harbour or watershed management. The influence of seabed burial resulting from these events on the ecology of benthic ecosystems is often overlooked, and the resilience of benthic communities is poorly known. During a 51 d long experiment, a typical northeastern Atlantic intertidal foraminiferal community, mainly represented by Ammonia confertitesta and Haynesina germanica species, was subjected to two kinds of sedimentary disturbance: (1) a one-time high-volume (OHV) deposit, i.e. sediment about 3 cm thick was added at one time at the beginning of the experiment; and (2) frequent low-volume (FLV) deposits, i.e. sediment about 0.5 cm thick was added each week for 4 weeks. The geochemical environment (e.g. dissolved oxygen penetration in the sediment, salinity, temperature, and nutrient content in the supernatant water) was monitored to follow the microcosm steady state before and during the experiment. In both disturbed microcosms, H. germanica showed a significant linear decrease in abundance during the experiment, while the total abundance of foraminifera was significantly affected only by the OHV treatment, suggesting a stronger effect of a single thick deposit on standing stocks and biodiversity compared to frequent low-volume sediment supplies. Concerning the vertical migration of foraminifera after sedimentary disturbances, the two dominant species moved upwards to the water–sediment interface with migration speeds estimated to be 0.41 and 0.47 mm h−1 respectively for A. confertitesta and H. germanica. In the FLV treatment, the resilient state was already reached within 1 d following a low-thickness burial, while in the OHV, it was achieved between 1 and 7 d after the 3 cm thick deposit. These results suggest that foraminifera can migrate rapidly after a sedimentary burial to recover their preferential life position under the new sediment–water interface, but in the case of an abrupt thick burial, several days are needed to reach a resilient state.

Effect of marine incursion on the formation of lacustrine source rocks: A case study of mudstones from the third member of the Shahejie Formation in the southwestern Bozhong Sag, Bohai Bay Basin, China

Bozhong Sag, the largest hydrocarbon generation sag in the Bohai Bay Basin, is characterized by presence of the third member of the Shahejie Formation (E2s3), which serves as a significant source rock. While previous studies have provided insights into the source material, sedimentary environment, and thermal maturity of the E2s3 source rocks, further investigation is required to deepen our understanding of sedimentary events and biological sources. In this research, nine mudstone core samples from the southwestern Bozhong Sag were thoroughly analyzed using organic-inorganic geochemistry and organic petrology. The results reveal the following key findings: (1) The middle and lower sections of the third member of the Shahejie Formation are characterized by high-quality source rocks, with the lower section exhibiting superior quality. The increase in water salinity during warm and humid climates, and the detection of 24-n-propylcholestane compounds reflected the occurrence of transgression events in the E2s3. These transgressions gradually increased from the lower sections to the middle sections of the E2s3. (2) The studied samples exhibit abundant presence of 4α-methyl-24-ethylcholestanes, 24-n-propylcholestanes, 2α-methylhopanes, oleananeabundant algainite, and a small amount of vitrinite. This diversity of hydrocarbon-forming organisms in the E2s3 source rocks is evident. (3) The moderate marine incursion in the lower part of the E2s3 results in nutrient elements that promote the flourishing of bacteria and algae, providing an abundant material basis for the formation of high-quality source rocks. However, the large-scale marine incursion in the middle of the E2s3 weakens water eutrophication, resulting in a decrease in the quality of source rocks compared to the lower part of the E2s3.

Neoichnology of vertebrate traces along the western barrier coast of Ukraine: preservation potential and subsurface visualization

A diverse quite of vertebrate traces covers beach, aeolian, and bay-side (deflation flats) surfaces along the NW Black Sea coast of Ukraine. These include avian, ungulate, and canid footprints, as well as mammal burrows (length &gt;5 cm; depth ~2 cm). The preservation of biogenic structures is enhanced by rapid burial (low-energy sedimentation or event deposition), algal mat formation, and salt encrustation. Continuous high-frequency (800 MHz) ground-penetrating radar (GPR) imaging aided in visualizing subsurface sections of an active burrow complex within a beach-dune ridge. Images near an active fox burrow captured distinct subsurface anomalies (point-source hyperbolic diffractions) in the upper aeolian section above the water table. Unfilled tunnel sections are easily distinguished from buried roots and other targets based on signal velocity and polarity reversals relative to air-to-sediment response at the ground surface. The diffraction geometry (angle) is related to signal velocity, providing valuable information about relative saturation of the overlying substrate. Decimeter-scale deformation of shallow reflections may be attributed to tracking surfaces, with similar examples found immediately below modern surfaces affected by anthropogenic trampling. It is likely that muddy lagoonal tracking surfaces may be preserved under layers of sand (overwash or aeolian deposition) and, following saltwater expulsion, may be recognized in geophysical images as clear deformed paleo-surfaces. Heavy-mineral concentrations (e.g. magnetite-rich sand) are common for beach and dune horizons that have undergone reworking and such anomalies often accentuate physical and biogenic deformation structures. Due to moderate-to-high fraction of ferri- and paramagnetic minerals, these anomalies are also well-expressed in GPR images due to its electromagnetic signal response. A conceptual framework of trace preservation potential (taphonomy) and geophysical recognition (GPR) suitability is proposed for this coastal region, with implications to paleo-environmental reconstruction.

Differentiation of vaginal cells from epidermal cells using morphological and autofluorescence properties: Implications for sexual assault casework involving digital penetration

Analysis of DNA mixtures from sexual assault evidence is an ongoing challenge for DNA casework laboratories. To assist the forensic scientist address source and activity level propositions there is a significant need for new techniques that can provide information as to the source of DNA, particularly for sexual assault samples that do not involve semen. The goal of this study was to develop a new biological signature system that provides additional probative value to samples comprised of mixtures of epidermal and vaginal cells, as may be observed in cases involving digital penetration. Signatures were based on morphological and autofluorescence properties of individual cells collected through Imaging Flow Cytometry (IFC). Comparisons to reference cell populations from vaginal tissue and epidermal cells collected from hands showed strong multivariate differences across > 80 cellular measurements. These differences were used to build a predictive framework for classifying unknown cell populations as originating from epithelial cells associated with digital penetration or epidermal tissue. As part of the classification scheme, posterior probabilities of specific tissue group membership were calculated for each cell, along with multivariate similarity to that tissue type. We tested this approach on cell populations from reference tissue as well as mock casework samples involving hand swabbings following digital vaginal penetration. Many more cells classifying as non-epidermal tissue were detected in digital penetration hand swab samples than control hand swabbings. Minimum interpretation thresholds were developed to minimize false positives; these thresholds were also effective when screening licked hands, indicating the potential utility of this method for a variety of biological mixture types and depositional events relevant to forensic casework. Results showed that samples collected subsequent to digital penetration possessed markedly higher numbers of cells classifying as vaginal tissue as well as higher posterior probabilities for vaginal tissue (≥ 0.90) compared to cell populations collected from hands without prior contact with vaginal tissue. Additionally, digital penetration cell populations may be resolved from saliva cell populations and other non-target tissue types.

Influence of hydrothermal and upwelling events on organic matter accumulation in the gas-bearing lower Cambrian shales of the middle Yangtze Block, South China

With onoing studies on the diversification of animals during the early Cambrian in the Yangtze Block, resource effects associated with environmental changes have started to be elucidated, in which regional sedimentary events might have played an important role. The gas-rich Yichang area in the southern Huangling anticline is a potential area for shale gas development and provides a more suitable target for unravelling the debates on organic matter (OM) accumulation in the Low Cambrian marine black shales. This study integrated elemental geochemical and mineralogy time-series analyses based on core samples drilled in Yichang area on the shallow-water platform to constrain the evolution of the depositional environments and consider the forcing function behind OM enrichment in the Shuijinguo Formation. Distinctive TOC and Cu/Al peaks within the black shale deposited in the Shuijingtuo Member I suggest intensification of bioproductivity level. The chemical index of alteration (CIA), regarded as an indicator of paleoclimatic variation, increased in the upsection, and together with increasing Sr/Cu and quartz/feldspar ratio values, suggest a trend toward warming conditions and a moderate degree of chemical weathering. The geochemical proxies for the degree of water mass restriction (Mo/TOC and Co × Mn) and paleoredox (MoEF, UEF, U/Th and Corg/P) indicate that the shallow-water shelf experienced weakly-to moderately-restricted water conditions under an anoxic/euxinic environment in the Shuijingtuo Member I and transited to a moderately-restricted water mass with suboxic conditions during the late Shuijingtuo and Shipai periods. A positive Eu anomaly within the Shuijingtuo Member I provided robust evidence of hydrothermal activity. We propose here for an opening of deposition conditions on the shallow-water platform which results in enhanced upwelling and hydrothermal activity (Si, Ba, et.), thereby ultimately disrupting the original nutrient cycling for the metabolism and prompting the OM accumulation in the epicontinental sea during the early Cambrian.

Suspended sediment deposition and sediment yields at Lake Peters, northeast Brooks Range, Alaska: Fluvial‐ and lake‐based approaches

AbstractLake‐based studies can provide seasonal‐ to millennial‐scale records of sediment yield to improve our understanding of catchment‐scale sediment transfer and complement shorter fluvial‐based sediment transport studies. In this study, sediment accumulation rates at 40 coring locations in Lake Peters, Brooks Range, Alaska, over ca. 42 years, calculated using fallout radionuclides and sediment density patterns, were spatially modelled based on distance from the primary inflow and lake water depth. We estimated mean interdecadal specific sediment yield (Mg km−2 year−1) using the spatially modelled sediment accumulation rates and compared that result to fluvial‐based sediment delivery for 2015–2016 open‐channel seasons, as well as to yields reported for other Arctic catchments. Using the lake‐based method, mean yield to Lake Peters between ca. 1973 and 2015 was 52 ± 12 Mg km−2 year−1, which is comparable with fluvial‐based modelling results of 33 (20–60) Mg km−2 year−1 in 2015 and 79 (50–140) Mg km−2 year−1 in 2016 (95% confidence intervals), respectively. Although 2016 was a year of above average sedimentation, the last extreme depositional event probably occurred between ca. 1970 and 1976 when a basal layer of fine sand was deposited in a broadly distributed, relatively thick and coarse bed, which we used for lake‐wide correlation. The dual lacustrine–fluvial method approach permits study of within‐lake and catchment‐scale processes. Within Lake Peters, sedimentation patterns show decreasing fluxes down‐lake, sediment bypassing near the primary inflow, the influence of secondary inflows and littoral redistribution, and a focusing effect in the deep proximal basin. At the watershed scale, sediment yield is largely driven by intense summer rainfall and strong seasonal hydroclimatic variability. This research informs paleo‐environmental reconstruction and environmental system modelling in Arctic lake catchments.