Search Results (110)

The lithological dichotomy in the Hammam Faraun Member (Gulf of Suez, Egypt) reveals a stable western flank with Nullipore carbonate deposits, contrasting with the clastic-prone eastern margin influenced by tectonic activity. This study aims to decipher multifactorial controls on spatial lithological variability and reservoir implications through (1) foraminiferal-based paleoenvironmental reconstruction; (2) integrated sequence stratigraphic–petrophysical analysis for sweet spot identification; and (3) synthesis of lateral facies controls. This study uniquely integrates foraminiferal paleoenvironmental proxies, sequence stratigraphy, and petrophysical analyses to understand the multifactorial controls on spatial variability and its implications for reservoir characterization. Middle Miocene sea surface temperatures, reconstructed between 19.2 and 21.2 °C, align with warm conditions favorable for carbonate production across the basin. Foraminiferal data indicate consistent bathyal depths (611–1238 m) in the eastern region, further inhibited in photic depths by clastic influx from the nearby Nubian Shield, increasing turbidity and limiting carbonate factory growth. Conversely, the western shelf, at depths of less than 100 m, supports thriving carbonate platforms. In the sequence stratigraphy analysis, we identify two primary sequences: LA.SQ1 (15.12–14.99 Ma), characterized by evaporitic Feiran Member deposits, and LA.SQ2 (14.99–14.78 Ma), dominated by clastic deposits. The primary reservoir comprises highstand systems tract (HST) sandstones with effective porosity ranging from 17% to 22% (calculated via shale-corrected neutron density cross-plots) and hydrocarbon saturation of 33%–55% (computed using Archie’s equation). These values, validated in Wells 112-58 (ϕe = 19%, S_hc = 55%) and 113M-81 (ϕe = 17%, S_hc = 33%), demonstrate the primary reservoir potential. Authigenic dolomite cement and clay content reduce permeability in argillaceous intervals, while quartz dissolution in clean sands enhances porosity. This research emphasizes that bathymetry, sediment availability, and syn-sedimentary tectonics, rather than climate, govern carbonate depletion in the eastern region, providing predictive parameters for identifying reservoir sweet spots in clastic-dominated rift basins. Full article

A multidisciplinary study was conducted to reconstruct the paleoenvironmental evolution of Maladroxia Bay, one of the principal bays of the islet of Sant’Antioco in southwestern Sardinia, over the past eight millennia. As part of an archaeological landscape project, this study explores the paleogeography and environment of the bay from a diachronic perspective to gain insights into the Holocene relative sea level history, shoreline displacements, and the environmental conditions during different phases. This study is based on an analysis of four sediment cores in conjunction with a chronological model that is based on radiocarbon dates. Four relative sea level indicators were produced. These are the first such indicators from the early and middle Holocene for the island of Sant’Antioco. The results indicate that in the early Holocene, the area was a terrestrial, fluvial environment without marine influence. In the 6th millennium BCE, the rising sea level and marine transgression resulted in the formation of a shallow inner lagoon. It reached its maximum extent in the middle of the 5th millennium BCE. Afterwards, a gradual transition from lagoon to floodplain, and a seaward shift of the shoreline occurred. The lagoon potentially served as a valuable source of food and resources during the middle Holocene. During the Nuragic period (2nd to 1st millennium BCE), the Bay of Maladroxia was very similar to how it is today. Its location was ideal for use as an anchorage, due to the calm and sheltered conditions that prevailed. Full article

For paleoenvironmental reconstruction, paleontologists prefer large, well-preserved fossils. Yet, such specimens are rare, and countless small fragments, though abundant, often go unused. These fragments lack visible internal structure, thus requiring etching, a procedure not permitted on large, intact specimens. Our research introduces a three-step method to identify the nature of these small fragments. With their structures revealed, we can then analyze the chemical composition of identified tissues. The method was tested using samples of vertebrate fossils collected in Malawi. Even with a limited number of samples, multivariate analyses (Principal Component Analyses—PCA) of these chemical data effectively differentiate fossil and recent samples, as well as bone, dentin, and enamel. This approach successfully reveals the behavior of the mineralized tissues of fossil samples. Ultimately, by leveraging microstructural and chemical data, we can study previously unidentified fragments or rare fossils. This allows for the estimation of preservation state and helps to avoid biases in paleoenvironmental reconstructions. Full article

Recent updates to the reconstructions of Cenozoic environmental changes (global sea level, temperature, and atmospheric carbon dioxide content) have made it intriguing to compare them to paleontological records for original interpretations. Paleogene brachiopods have remained in the shadow of their Paleozoic–Mesozoic predecessors, and the reactions of their diversity to the Earth’s dramatic changes are poorly understood. The present work aims to fill this gap via a comparison of several diversity and paleoenvironmental curves. The generic diversity was established by stages with two essentially different paleontological datasets, and several fresh paleoenvironmental reconstructions were adopted. It was observed that neither Paleogene eustatic fluctuations nor changes in the atmospheric carbon dioxide content correspond well to the generic diversity dynamics of brachiopods. The changes in the total number of genera and the global temperatures demonstrate similarity at the Danian–Ypresian interval, but not later. The fluctuations in the brachiopod diversity are near the same level during the Eocene–Oligocene, despite strong paleoenvironmental changes, implying the intrinsic resistivity of these organisms to external influences. Additionally, the Cretaceous/Paleogene mass extinction, the Paleocene–Eocene thermal maximum, and the Early Eocene optimum could enhance the diversity dynamics together with the long-term temperature changes. In contrast, the influences of the Late Danian warming event and the Oi-1 glaciation were not observed. Full article

The eastern Junggar Basin in Xinjiang, China is a key coal-bearing region dominated by the Middle Jurassic Xishanyao Formation. Despite its significance as a major coal resource base, detailed paleoenvironmental reconstructions of its coal seams remain limited. This study investigates the B₁, B₂, B₃, and B₅ coal seams of the Xishanyao Formation using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) to assess geochemical indicators of the depositional environment during coal formation. The results show that the coal samples are characterized by high inertinite content and low vitrinite reflectance, indicative of low-rank coal. Slight enrichment of strontium (Sr) was observed in the B₁, B₂, and B₅ seams, while cobalt (Co) showed minor enrichment in B₃. Redox-sensitive elemental ratios (Ni/Co, V/Cr, and Mo) suggest that the peat-forming environment ranged from oxidizing to dysoxic conditions, with relatively high oxygen availability and strong hydrodynamic activity. A vertical trend of increasing paleosalinity and a shift from warm–humid to dry–hot paleoclimatic conditions was identified from the lower (B₁) to upper (B₅) coal seams. Additionally, the estimated atmospheric oxygen concentration during the Middle Jurassic was approximately 28.4%, well above the threshold for wildfire combustion. These findings provide new insights into the paleoenvironmental evolution of the Xishanyao Formation and offer a valuable geochemical framework for coal exploration and the assessment of coal-associated mineral resources in the eastern Junggar Basin. Full article

The South China Block hosts extensive sedimentary phosphorites that offer valuable insights into both paleoenvironmental reconstruction and rare earth element (REE) resource potential. However, the mechanisms governing REE enrichment in these deposits remain poorly understood. This study investigates two distinct phosphorite layers from the Lower Cambrian Zhujiaqing (ZJQ) Formation in the Bailongtan (BLT) area of the Yangtze Platform using integrated analyses including petrology, XRD, major and trace elements, δ¹³C and δ¹⁸O isotopes, and LA-ICP-MS. The lower thin-bedded phosphorite, composed of finer phosphatic grains (<300 μm), exhibits significantly higher REE concentrations (883.6 ± 160.9 ppm; n = 48) compared to the upper thick-bedded phosphorite (303.2 ± 82.7 ppm; n = 64), which is dominated by larger, reworked grains (300–600 μm). Intervening strata consist of laminated phosphate-bearing carbonates interbedded with quartz, dolomite, and pyrite. PAAS-normalized REE patterns display MREE–HREE enrichment, negative Ce anomalies (avg. 0.60 ± 0.18; n = 18), and positive Y anomalies—indicative of oxic depositional conditions. The elevated REE content in the lower layer, coupled with the lowest δ¹³C values (−4.59‰), suggests enrichment linked to organic matter degradation. A proposed two-stage depositional model links REE enrichment to proximity with REE-rich deep-shelf waters, underscoring the critical role of redox and depositional dynamics in phosphorite-hosted REE accumulation. Full article

Paleoenvironmental knowledge holds significant scientific value for elucidating the evolutionary history of Earth’s crust and for guiding the exploration of oil and gas resources. This study presents a comprehensive analysis of sporopollen–algae fossils from Well DW-2, located in the Zhu II Depression of the eastern South China Sea. The sampled strata of the well were from 0 to 3230 m in depth, with a substantial number of sporopollen–algae fossils identified within the Enping and Zhuhai Formations spanning from 2501 to 3227 m. Two distinct sporopollen–algae assemblages were delineated from bottom to top. The sporopollen characteristics reveal a transition from tropical and subtropical to subtropical and temperate plant communities, reflecting the warm and humid climate during the formation of the Enping Formation and the relatively cool and dry climate during the formation of the Zhuhai Formation. A significant number of marine dinoflagellate fossils were identified, and the observed changes in algal characteristics suggest that the Enping Formation was accumulated in a shallow marine environment, while the Zhuhai Formation was predominantly formed in a transitional setting between marine and terrestrial conditions at the shelf margin. These findings not only enhance our understanding of the paleoenvironmental conditions in the South China Sea region but also have broader implications for reconstructing global paleoclimates and identifying potential hydrocarbon reservoirs in similar sedimentary basins. Full article

This study presents the first detailed investigation of the petrography, mineralogy, and depositional environment of Messinian gypsum lithofacies outcropping on the western side of the Crati Basin (Calabria, Southern Italy), focusing on three sections: Castelluccio, Striscioli, and Piretto. The different localities preserve in situ gypsum accumulation (laminar gypsum and gypsiferous mudstone) and clastic gypsum deposits (nodular, gypsarenite and gypsrudite) formed during the second stage (5.60–5.55 Ma) of the Messinian Salinity Crisis (MSC). Observation and analyses of macro-, meso- and nanoscale reveal a complex climatic variability and depositional history that reflect different environmental conditions, from shallow-water evaporitic environments to deep basin settings affected by slope failures. The data highlights the influence of tectonic activity on facies distribution within the basin. Overall, this study emphasizes the importance of climatic and geological controls on gypsum deposition, offering a detailed interpretation of the Crati Basin’s evaporitic history and contributing to the broader understanding of Mediterranean Messinian evaporites. Full article

Fossilized body parts of two cold-adapted ground beetle species, Elaphrus lapponicus and Diacheila polita, were identified from a deposit dated to the Late Glacial period in Hokkaido, Japan. The paleoenvironmental reconstruction presented here has been based on modern temperature ranges and environmental conditions, along with paleobotanical evidence from the site. Late Glacial temperatures were at least 6 degrees °C lower than modern temperatures in summer, and the area around the site was mostly covered with forest tundra, which exists only in areas further north than Hokkaido. Full article

Understanding the climate–weathering coupling mechanisms remains pivotal for interpreting global glacial–interglacial cycles, yet advancements have been constrained by the limited high-resolution sedimentary archives. The newly acquired BXZK2017-2 borehole (30.5 m core) from Bohai Bay provides an exceptional sedimentary sequence to investigate the Late Quaternary climate–weathering interactions. Through an integrated high-resolution chronostratigraphic framework (AMS ¹⁴C and OSL dating) coupled with multi-proxy sedimentological analyses (major element geochemistry and granulometric parameters), we reconstructed the chemical–weathering dynamics in the Bohai coastal region since the Late Pleistocene. Our findings revealed four distinct climate-weathering phases that correlate with the regional paleoenvironmental evolution and global climate perturbations: (1) enhanced weathering during mid-MIS3 to ~37.5 cal kyr BP (Chemical Index of Alteration (CIA): 55.9–62.2), corresponding to regional warming and strengthened summer monsoon circulation; (2) weathering minimum in late MIS3 through early–mid-MIS2 (37.5–14.8 cal kyr BP, CIA < 55), marking the peak aridity before the Last Glacial Maximum; (3) maximum weathering intensity from mid-MIS2 to early MIS1 (14.8–3.34 cal kyr BP, CIA: 65–68), documenting the postglacial humidification driven by the intensified East Asian Summer Monsoon; (4) renewed weathering decline during the Neoglacial (3.34 cal kyr BP-present, CIA: 59–63), coinciding with the late Holocene cooling events. Remarkably, this study identifies a striking synchronicity between the CIA in marine drill cores and δ¹⁸O records derived from Greenland ice cores. Our results indicate that chemical weathering proxies from marginal sea sediments can serve as robust recorders of post-Late Pleistocene climate variability, establishing a new proxy framework for global paleoclimate comparative research. Full article

cangas are iron-rich outcrops where rupestrian fields develop in the Carajás Mountain Range (CMR). canga formations are ancient ecosystems characterized by high levels of endemic and threatened plant species that thrive on iron-rich substrates in the southeastern Amazon uplands. The recent taxonomic validation of these species enables more accurate distribution modeling across past, present, and future time scales. This work presents a comprehensive palynological database for the Amazon canga vegetation, resulting from extensive field and herbarium surveys, as well as the compilation and taxonomic validation of species in the Carajás Mountain Range (CMR). This atlas includes 204 plant species: 10 ferns and lycophytes, 62 monocots, and 132 eudicots and magnoliids (mainly herbs, lianas, and trees). Most flowering plants are pollinated by bees, with secondary pollination by other insects and wind. The taxa co-occur in two geoenvironments: (1) forested slopes and caves over plinthosols and ferralsols and (2) slopes with canga vegetation over plinthosols. Seventeen species are potential domesticates used by Indigenous peoples. This highlights canga vegetation as a unique and diverse ecosystem with various survival strategies, emphasizing the need for precise habitat definitions in paleoenvironmental and paleoclimate reconstructions. This atlas provides a valuable reference for palynological studies, enhancing the vegetation reconstruction, climate history analysis, pre-Columbian influences on vegetation patterns, and ecological monitoring. Full article

This study employs a multidisciplinary approach, integrating geoarchaeology, geomorphology, archaeometry, and palynology to analyze settlement patterns and land use in the surroundings of Capua (southern Italy) during the medieval transition. Borehole sampling and stratigraphic studies indicate significant landscape transformations due to human activity, particularly deforestation and agricultural expansion. Radiocarbon dating confirms settlement activity from antiquity through the early medieval period. Results suggest that Capua’s elevated position provided natural flood protection, influencing its continuous habitation. Pollen analysis reveals a shift from forested landscapes to open pastures, indicating intensive land use. Future research will focus on refining the chronology and archeological context of this transition, further clarifying Capua’s historical and environmental development. Full article

This study examines four shallow-water, reef-coral-bearing carbonate successions belonging to the Jhill Limestone Unit of the Gaj Formation, exposed in the area near Karachi (southern Pakistan). Sixty-two samples were collected for the quantitative analysis of the skeletal and foraminiferal assemblages. The analysis of large benthic foraminifera suggests a placement within the late Oligocene, characterized by the setup of the Late Oligocene Warming Event. Thanks to quantitative analyses and multivariate statistics, three biofacies were identified: (1) the reef coral biofacies (BFA), indicative of a sheltered, shallow-water environment above fair-weather wave base; (2) the coralline algal biofacies (BFB), deposited within a mesophotic setting and representing the deepest biofacies among the three recognized ones; and (3) the large benthic foraminiferal and coralline algal biofacies (BFC), subdivided into two sub-biofacies, namely (a) the miogypsinid, thin and flat large benthic foraminiferal and coralline algal sub-biofacies (BFC1), indicative of deeper setting, comprised between BFA and BFB, and (b) the miogypsinid and coralline algal sub-biofacies (BFC2), indicative of shallower settings than BFC1, and bearing evidence of paleo-seagrass meadows. All these biofacies were developed within the photic zone, in a relatively flat seafloor punctuated by patch reefs and seagrass meadows and characterized by a notable nutrient influx. Foraminiferal-based experimental paleobathymetric parameters, including the lepidocyclinids/miogypsinids, the flat nummulitids/lepidocyclinids, and the hyaline/porcelaneous foraminifera ratios, were tested and confirmed as reliable tools for paleodepth and paleoenvironmental reconstructions. Full article

This study examines speleothems, sediments, rock, and water to assess geochemical and mineralogical processes in deep karst systems. Focusing on Slovačka jama cave (−1320 m deep) and the Velebita cave system (−1026 m deep), we identify elemental and mineralogical anomalies that provide valuable records of element transport, mineral formation, and paleoenvironmental changes. Heavy metal anomalies (Al, B, Co, Mn, Na, Tl, Ba, Be, Cr, Cu, Fe, K, Pb, Rb, Ti, U, Zn) at 300–400 m of depth in Slovačka jama indicate a complex interplay of geological conditions, geomorphological processes, atmospheric deposition, and potential anthropogenic influences. Factor analysis reveals two elemental associations: (1) Fe, Pb, Cu, and Zn, linked to terrigenous aluminosilicates, and (2) Cd, Cr, Mo, and Ni, suggesting airborne or geological sources. Mineralogical analysis confirms the dominance of calcite, with quartz, clay minerals, feldspars, magnetite, and goethite also detected. High magnetic susceptibility values in sediment-rich samples suggest Fe-rich mineral inputs from weathering, biogenic activity, or industrial sources. Ba anomalies in feldspar-rich samples and Sr accumulation at depth indicate distinct geochemical processes. These findings enhance our understanding of deep karst geochemistry, crucial for paleoenvironmental reconstructions and groundwater protection. Full article

The middle–upper Eocene successions of northwest Fayum, Egypt, provide a crucial archive for reconstructing paleoenvironmental conditions and paleobiogeographical patterns of the southern Tethys realm. Stratigraphically, the investigated section is subdivided into three rock units: the Gehannam Formation (Bartonian-Priabonian), the Birket Qarun Formation, and the Qasr El Sagha Formation (Priabonian). A total of 101 benthic foraminiferal taxa, representing 31 genera, 23 families, 13 superfamilies, and four suborders, were identified. The middle–late Eocene age is primarily determined by the co-occurrence of index spinose planktonic foraminifera (Acarinina spp., Morozovelloides spp., and Globigerinatheka semiinvoluta) and benthic foraminiferal assemblages, further supported by the presence of the nannofossil marker Chiasmolithus oamaruensis. Four local benthic biozones are identified and correlated with coeval zones in nearby areas. Quantitative analyses of benthic foraminiferal individuals, diversity indices, ecological parameters, and the benthic foraminiferal oxygen index (BFOI) reveal distinct environmental shifts. The rock unit occupied by the late middle Eocene assemblages is diversified and dominated by calcareous infaunal taxa (e.g., Bolivina spp., Fursenkoina spp., and Nonionella spp.), indicative of low-oxygen outer neritic conditions associated with elevated organic influx. In contrast, the late Eocene Birket Qarun and Qasr El Sagha showed an increase in epifaunal forms and reduced diversity, suggesting a transition to dysoxic-oxic conditions. Paleobiogeographical analysis indicates a strong affinity with the Tethyan realm, with potential faunal exchange through the Trans-Saharan Seaway. These findings enhance our understanding of Paleogene marine connections between the Tethyan and Indo-Pacific realms, contributing to broader discussions on Eocene paleobiogeography and depositional dynamics in North Africa. Full article