Sedimentary Sequence Research Articles

Geological and Geomorphological Characterization of the Anthropogenic Landslide of Pie de la Cuesta in the Vitor Valley, Arequipa, Peru

This study presents the geological and geomorphological characterization of the Pie de la Cuesta landslide, a large (>60 ha) slow-moving (up 4.5 m/month) landslide in Southern Peru. The landslide has been active since 1975 and underwent a significant re-activation in 2016; the mass movement has caused the loss of property and agricultural land and it is currently moving, causing further damage to property and land. We use a combination of historical aerial photographs, satellite images and field work to characterize the landslide’s geology and geomorphology. The landslide is affecting the slope of the Vitor Valley, constituted by a coarsening upward sedimentary sequence transitioning from layers of mudstone and gypsum at the base, to sandstone and conglomerate at the top with a significant ignimbrite layer interbedded within conglomerates near the top of the sequence. The landslide is triggered by an irrigation system that provides up to 10 L/s of water infiltrating the landslide mass. This water forms two groundwater levels at lithological transitions between conglomerates and mudstones, defining the main failure planes. The landslide is characterized by three main structural domains defined by extension, translation and compression deformation regimes. The extensional zone, near the top of the slope, is defined by a main horst–graben structure that transitions into the translation zone defined by toppling and disaggregating blocks that eventually become earth flows that characterize the compressional zone at the front of the landslides, defined by thrusting structures covering the agricultural land at the valley floor. The deformation rates range from 8 cm/month at the top of the slope to 4.5 m/month within the earth flows. As of May 2023, 22.7 ha of potential agricultural land has been buried.

Paleomagnetic Data Bearing on the Origin of the Supra‐ Subduction Zone Ophiolites in Southeast Anatolia and the Progressive Closure of the Neotethys Ocean in the Eastern Mediterranean

AbstractThe Late Cretaceous supra‐subduction zone (SSZ) ophiolites in SE Anatolia form two parallel belts: the northern ophiolitic belt, which was emplaced onto the Tauride platform and a second southern belt emplaced on the Arabian platform. There are controversial hypotheses about the geometry and tectonic process of these ophiolites, which are still not well understood. Here, we test three alternative tectonic models for; (a) One single ocean which is defined by the İzmir‐Ankara‐Erzincan Ocean; (b) A southern branch of the Neotethys Ocean; (c) Two separate oceanic basins, which are the Berit Ocean and the South Neotethys Ocean. We present paleomagnetic results from 161 sites focusing on the sheeted dyke complex, cumulate gabbros, extrusive and sedimentary sequences of the Upper Cretaceous ophiolites in the SE Anatolian region. We also sampled the unconformable cover units from Middle Eocene and Miocene sedimentary rocks to distinguish emplacement related tectonic rotations from post‐emplacement tectonic rotations. Our data indicate that the southern ophiolites (Hatay ophiolite, cumulate gabbro + lava) were formed at a paleolatitude of and those of the northern ophiolites (Göksun, İspendere, Guleman ophiolite, cumulate gabbro + lava) were formed at a paleolatitude of . We hypothesize that the northern ophiolites were derived from the Ocean in a NW‐SE directed subduction zone between the Taurides and the Bitlis Pütürge massif, while the southern ophiolites, in contrast, were formed in the South Neotethys Ocean in a NNW‐SSE directed subduction zone farther northeast of the Taurides. Both the ophiolites reached their present position during Late Cretaceous to Middle Miocene, affected by rigid‐block rotations almost in counterclockwise sense.

Timing and geometry of the Chemehuevi Formation reveal a late Pleistocene sediment pulse into the Lower Colorado River

The Chemehuevi Formation is a distinctive 50−150-m-thick wedge-shaped Pleistocene sedimentary unit deposited by the Colorado River. It lines the perimeters of the river’s floodplains and bedrock canyons for more than 600 km between the mouth of the Grand Canyon and the delta region in the Gulf of California. The formation is composed of a basal tan to light-yellowish-brown and pale-orange mud-dominated facies overlain and interbedded by a light-yellow-brown sand-dominated facies. The unit is one of two extensively exposed aggradational packages in the Lower Colorado River corridor, in addition to a series of other smaller alluvial terrace deposits. The Chemehuevi Formation appears to represent the response of a fully integrated Colorado River system to a significant perturbation, in contrast to the Bullhead Alluvium, which is likely a unique result of Pliocene river integration. The aggradation of the Chemehuevi Formation in the Lower Colorado River corridor may be similarly due to a unique event in the Colorado River system, or it may instead be a well-preserved sedimentary sequence recording typical behavior of the Colorado River below the Grand Canyon in the late Pleistocene. As such, multiple causal mechanisms have been proposed, but no study to date has conclusively explained the Chemehuevi Formation. To help resolve its timing, duration, and origin, we applied post-infrared infrared stimulated luminescence, carbonate U-Th series, and zircon sensitive high-resolution ion microprobe U-Th series geochronology to determine the ages of key exposures of the unit over a wide spatial area. These new data demonstrate that the Chemehuevi Formation was deposited ca. 110−90 ka. The depositional ages collectively overlap, suggesting that deposition occurred rapidly relative to the resolution of the geochronometers. The new depositional timing coincides with a shift from glacial to interglacial conditions after the marine isotope stage 5-6 transition. This observation is consistent with a climate-induced sediment pulse as a causal mechanism, yet correlations with similar deposits in the Colorado River headwaters or in neighboring catchments appear elusive. Potentially, climate transitions between glacial and interglacial periods induced a sediment pulse from hillslopes of the Colorado River system that resulted in the Chemehuevi Formation. An alternative or additional explanation is that the Chemehuevi Formation represents release of lava dam−impounded sediment in the Grand Canyon. The surface geometry of the Chemehuevi Formation projects upstream to the approximate location of lava dams, and the largest possible lava dam impoundment (the Upper Prospect dam) is comparable in volume to the formation. The lava dam hypothesis appears to be a possible explanation for the Chemehuevi Formation. However, tying deposition to a specific lava dam or series of lava dams remains challenging due to discrepancies in timing and volume. The combined effects of a series of lava dams may have led to the Chemehuevi Formation, as the last Pleistocene lava dam eruption coincides with the onset of deposition. Alternatively, the formation may result from the combined effects of both regional climate transitions and the lava dams that created a transient reservoir to compound a climate transition−driven sediment pulse. The geochronologic data presented here do not allow us to distinguish between the lava dam or climate transition hypotheses but will need to be reconciled with any future proposed depositional model.

A Paleoenvironmental Reconstruction of Lake Vrana on the Island of Cres (Croatia) Based on the Geochemistry and Mineralogy of the Late Pleistocene and Holocene Sediments

A 7.4 m long sediment core has been retrieved from the central part of Lake Vrana on the island of Cres to reconstruct the paleoenvironmental conditions. Lake Vrana is the deepest freshwater lake in Croatia, located in the karst region of the eastern Adriatic coast. A dated sediment sequence in Lake Vrana of 4.4 m has spanned the past 16.4 kyr, and it featured a dynamic sediment deposition until the beginning of the Holocene, including strong sediment input and supply to the lake by runoff sediments of dolomitic origin from the catchment in the period 16.4–14.4 cal kyr BP. High organic carbon content, which originates from mixed terrestrial and aquatic origins in the periods 14.4–13.3 cal kyr BP and 12.7–11.7 cal kyr BP, indicates fluctuating lake levels in shallow water environments during the Late Glacial to Holocene transition. The Holocene sequence indicates the development of more stable conditions and continuous sediment deposition, characterized by an increasing trend of siliciclastic sediments delivered into the lake during the early Holocene (11.7–10 cal kyr BP) and dominantly from 8 to 4.4 cal kyr BP, indicating enhanced input and erosion, which coincides with the humid and pluvial period recorded in the central Mediterranean region. It is followed by sediments with high organic carbon content between 4.4 and 1.6 cal kyr BP, which points to higher lake productivity. Calcite sedimentation prevailed between 1.6 to 0.4 cal kyr BP, indicating stable deeper-lake conditions. Predominantly, siliciclastic sediments from 0.4 to 0.1 cal kyr BP pointed to erosion during the Little Ice Age (LIA), with enhanced precipitation and sediment discharge from the catchment. The re-establishment of calcite sedimentation has been observed over the last 100 years.

Lithogeochemistry of upper precambrian terrigenous rocks of Belarus. Communication 1. Bulk chemical composition, general features and anomalies

The first of two publications is devoted to the lithogeochemical features study of the pilot collection of the Upper Precambrian sandstones and siltstones samples, selected from four boreholes: Bogushevskaya 1, Bykhovskaya, Lepel 1 and Korminskaya (Belarus). This article analyzes the general features of their bulk chemical composition and shows the possibilities and limitations for further reconstructions. It has been established that the Riphean and the Vendian rocks included in the pilot collection, visually identified as sandstones, are actually quartz, feldspathic-quartz and arkose varieties with different cement types. The Vendian “siltstones” in their geochemical characteristics correspond to coarse- and fine-grained siltstones and, to a greater extent, mudstones with a predominance of illite, as well as various admixtures of berthierine, kaolinite and smectite. Considering the trace elements enrichment factors of these rocks a number of dissimilarities were identified, caused both by the source rocks composition and sedimentary environments changes. The data point position of the studied samples on the Zr/Sc–Th/Sc diagram suggests that the composition of all the Riphean and the Vendian rocks is dominated by first sedimentation cycle material. This suggests that the lithogeochemical characteristics of the rocks of the pilot collection quite correctly reflect similar features of the source rock complexes and can be used to reconstruct the paleogeodynamic and paleoclimatic factors that controlled the accumulation of the Riphean and the Vendian sedimentary sequences of Belarus.

Untapped Mineral Potential of Somaliland: A review

This comprehensive study explores the untapped mineral potential of Somaliland, a region rich in geological diversity and significant mineral deposits. By examining the intricate geology of Somaliland, including its ancient Precambrian basement and younger sedimentary sequences, the research uncovers valuable insights into the region's mineral wealth. Extensive exploration activities reveal substantial reserves of base metals, precious metals, industrial minerals, and gemstones, highlighting the region's promise for future mining endeavors. The findings underscore the strategic importance of Somaliland's mineral resources, offering a roadmap for sustainable development and economic growth through enhanced geological surveys, infrastructure investment, and robust regulatory frameworks. This article serves as a vital resource for geologists, investors, and policymakers interested in unlocking the mineral wealth of Somaliland and fostering regional development.

Petrogenesis of supracrustal rocks from the Maxianshan and Xinglongshan Groups in the eastern Central Qilian block: Constraints on the construction of Rodinia

Controversy has long surrounded the reconstruction of the East Asian blocks in the Rodinia supercontinent, which was a coherent large landmass during 900–750 Ma and is now dispersed over all current major continents. The Central Qilian block is a Precambrian microcontinent in the early Paleozoic Qilian orogenic belt, which marks the junction of the North China, South China and Tarim cratons. In this paper, we present a systematic study of the petrology, whole-rock geochemistry, and geochronology of supracrustal rocks from the Maxianshan Group and the Xinglongshan Group in the easternmost part of the block. The metasedimentary rocks from both groups overlie a gneissic granite, which has a zircon U-Pb age of 970 ± 6 Ma with εHf(t) values of −3.5 to + 2.5 and is an I-type granite formed in a back-arc setting. Paragneisses from the Maxianshan Group and micaschists from the lower formation of the Xinglongshan Group have detrital zircon U-Pb ages of 2465–876 Ma that peak at ca. 950 Ma. They show strongly decreasing zircon εHf(t) values of + 0.8 to −11.3 and ages from 1174 Ma to 876 Ma. Their protoliths constituted a sedimentary sequence with a long history of deposition during 1174–911 Ma in a continental arc-related basin. Metabasaltic tuffs from the middle formation of the Xinglongshan Group are tholeiitic with a zircon U-Pb age of 958 ± 9 Ma and indicate a back-arc setting. Metasandstones from the upper formation of the Xinglongshan Group have detrital zircon ages of 2668–732 Ma that peak at 810 Ma and 984 Ma and indicate a passive margin setting. Combining our results with existing data, we propose that the Maxianshan Group and the Xinglongshan Group make up an early Neoproterozoic trench-arc-basin system at a continental margin of Rodinia. Oceanic crust subduction underneath the continent at 1174–896 Ma with formation of a mature continental arc, and continuous subduction from 824 to 735 Ma with opening of the Proto-Tethys Ocean as a back-arc basin are suggested for the formation of the Central Qilian block.

Paleoenvironmental reconstruction of coal deposition during the Cretaceous-Paleogene transition in the Eastern Cordillera Basin, Colombian Andes

Stratal stacking patterns and factors influencing peat accumulation in coastal and continental settings represent a significant problem in studying coal-bearing sequences. To address this issue, this work focused on the Cretaceous-Paleogene Guaduas Formation on the Checua-Lenguazaque Syncline (CLS) coalfield in the Eastern Cordillera Basin (Colombian Andes). This study relies on geological survey, facies analysis, sequence stratigraphy, organic geochemistry, and coal petrography. Through these methods, depositional systems and sequences were characterized, and their relationship with coal composition was established. Sedimentary facies were categorized into four Facies Associations (FAs): lagoon, tidal flat, delta plain, and mixed fluvial system. Five T-R sequences (S1 to S5, in ascending order) were identified. S1 consists of lagoon and tidal sandstone, mudstone, and coal. S2-S4 comprise tidal, deltaic, and fluvial deposits. S5 is composed mainly of deltaic and fluvial facies. Thick coal seams (> 0.7 m) were concentrated in the regressive system tracts of S1 and S3, while the transgressive coals were deposited in S2-S3 and are associated with tidal environments. The organic petrography showed enrichment in vitrinite (30.00–85.20 %), while liptinite (0.00–16.60 %) and inertinite (4.60–34.40 %) varied according to depth and paleoenvironments. CLS coalfield displays an environmental evolution from shallow marine and lagoon deposits to deltaic and fluvial environments. Minor sea-level fluctuations, changes in accommodation, siliciclastic influx, and plant community distinguish this sedimentary succession. The deposition of the Guaduas Formation is characterized by a prograding pattern with dominant shallowing-upward cycles in a high accommodation setting. The organic matter accumulated under limno-telmatic to telmatic conditions in mesotrophic to ombrotrophic environments with nutrients derived mainly from rainfall. The paleoclimate for the Guaduas Formation indicates wet and hot conditions for flora expansion. This investigation determined paleoenvironments of the Maastrichtian-Paleocene coastal to fluvial successions within the tropical latitudes, indicating a strong relationship between depositional systems, sequence stratigraphy, paleoclimate, and coal composition.

West Siberian sedimentary basin. Crustal subsidence caused by rock contraction in its lower part due to prograde metamorphism

The history of the crustal subsidence in the Mesozoic and Cenozoic in the West Siberian Basin – the largest sedimentary basin in the world – is considered. Most researchers associate its formation with post-rift subsidence of the crust, which followed an episode of strong lithospheric stretching about 250 million years ago near to the Permian to the Triassic transition. A characteristic feature of post-rift subsidence is a decrease in its rate in time. During the Mesozoic-Cenozoic history, in Western Siberia the rate of crustal subsidence should have slow down by an order of magnitude. However, the analysis of long (700–900 km) seismic profiles in the north of Western Siberia and in the Southern Kara Sea shows that since the beginning of the Mesozoic in these regions, on average, there has been an acceleration of the crustal subsidence. Under such circumstances, lithospheric stretching in them could be responsible for only a small part of the total subsidence of the crust of 6–7 km. In Western Siberia, the Earth’s crust is close to the isostatic equilibrium. Then, in the absence of strong stretching, the accumulation of thick sedimentary sequences in the basin could only have been caused by rock contraction in the lower crust due to prograde metamorphic reactions. To obtain the above results, we used, for the first time, some simple methods to analyze the structure of the sedimentary cover in the West Siberian Basin. Detailed seismic profiles have been published for many other deep basins on all the continents. The methods of their interpretation implemented in this paper can be easily applied to determine the role of lithospheric stretching in the formation of deep sedimentary basins on the global scale.

Heterogeneous interfaces of aluminum bronze/Inconel 718 dissimilar alloys under different wire arc directed energy deposition sequences

Heterogeneous interfaces of aluminum bronze/Inconel 718 dissimilar alloys under different wire arc directed energy deposition sequences

Study of the influence of nitrogen doping on magnetic anisotropy in CoFe/MgO thin films with different deposition sequences

Abstract The ferromagnetic (FM)/MgO structure multilayers with perpendicular magnetic anisotropy (PMA) play a crucial role in magnetic random-access memory. It is essential to explore the methods for modulating magnetic anisotropy and to clarify the underlying mechanisms. We study the regulation of the magnetic anisotropy with nitrogen (N) doping concentration (CN) in two samples: Ta/CoFe(N)/MgO/Ta (S1) and Ta/MgO/CoFe(N)/Ta (S2) with different deposition sequences. The S1 sample exhibits in-plane magnetic anisotropy (IMA) without N doping. And the sample presents PMA when CN = 15%. The S2 sample shows weak PMA without N doping, and the sample converts to IMA when CN = 15%. X-ray photoelectron spectroscopy is performed to evaluate the oxidation level of Fe at the CoFe/MgO interface by the peak area ratio of Fe oxide to Fe (ϵ). It is believed that excessively high and low ϵ values correspond to over-oxidation and under-oxidation of Fe, respectively. For films deposited in different sequences, both over-oxidation and under-oxidation lead to IMA, while moderate oxidation facilitates the formation of PMA. The microstructure analysis reveals that the N doping does not affect the crystallization of the films, indicating that magnetocrystalline anisotropy has a minor influence on the changes of K eff.

Palaeoecological Conditions in the South-Eastern and Western Baltic Sea during the Last Millennium

We present the reconstruction of palaeoenvironmental conditions in the Gdansk, Bornholm, and Arkona Basins of the Baltic Sea over the last millennium. A multiproxy study (including geochemical, XRF, grain size, AMS, and micropalaeontological analyses) of five short sediment cores was performed. The relative age of the sediments was determined based on the Pb distribution along the sediment sequences, as radiocarbon dating has resulted in an excessively old age. The retrieved cores cover two comparable warm periods, the Medieval Climate Anomaly and the Modern Warm Period, for which the increase in surface water productivity was reconstructed. Notably, the production of diatoms was higher during the colder periods (the Dark Ages and Little Ice Age), but this was also the case within the Modern Warm Period. In the Gdansk Basin, the initial salinity increase during the Littorina transgression started after 7.7 cal. a BP. The increased inflow activity was reconstructed during the Medieval Climate Anomaly, even in the Gdansk Basin, despite, in general, very low foraminiferal amounts and diversity. The strongly positive North Atlantic Oscillation Index during this period led to the prevalence of westerly winds over the Baltic region and stronger saltwater intrusions. In the recent sediments, the reconstructed inflow frequency demonstrates a variability against the reduction trend, and a general decline compared to the Medieval Climate Anomaly is seen.

Impacts of groundwater flow on borehole heat exchangers: Lessons learned from Estonia

The production of geothermal energy relies on subsurface properties. In low-enthalpy geothermal regimes, thermal energy extracted with a borehole heat exchanger (BHE) is the subsurface heat conducted from the rock and grout to the BHE fluid. Estonian geology provides a good opportunity to investigate how groundwater flow impacts BHE heat production. The hundreds of metres thick sedimentary rock sequence holds four main aquifers. We modelled single BHEs with lengths of 400 m, 500 m and 1000 m and a BHE field of ten 400-m wells at three sites across Estonia. Then, we parametrized different hydraulic conditions to compare how the groundwater flow velocity impacts the thermal energy yield of the systems.Our results indicate that if groundwater flow increases above 0.03 m/day, it increases the total energy yield from 3 % to 20 %. Thermogeological parameters, such as subsurface temperature and thermal conductivity, affect the thermal energy yield of the wells more than the modelled groundwater flow. Our study provides an estimate of the thermal energy yield from different BHE types and the detailed sensitivity analysis. We conclude that geothermal energy is a significant renewable energy resource for Estonia and areas with similar geology and climate.

Modern Pollen Signatures and Vegetation Dynamics in Northwestern Himalaya, India

ABSTRACT Palynological studies have been conducted for the first time in the Renukaji Wildlife Sanctuary (RWS), a Sal-dominated region within the foothills of Northwestern (NW) Himalaya in Himachal Pradesh, India. This research enhances our understanding of the relationship between modern pollen rain and vegetation, as well as pollen representation in sediments. Furthermore, it contributes to palaeovegetation reconstruction based on paleoclimatic trends by improving our interpretation of pollen deposition patterns. The study area was delineated into three distinct zones based on biological niche characteristics: Zone 1 (Recreation Zone), Zone 2 (Buffer Zone), and Zone 3 (Core Zone). Pollen analysis conducted on 30 surface soil samples and moss cushions, collected from all three zones, reveals the dominance of dry deciduous taxa, followed by extra-terrestrial taxa and wet deciduous taxa. Land Use Land Cover (LULC) analysis performed using satellite data reveals that Shorea robusta (Sal) mixed forest covers 32% of land, followed by Pinus spp. (8%) and their associates (25%). Shorea robusta, a mixed wet deciduous taxon and high pollen producer, exhibits low pollen counts, possibly due to chemical and microbial decomposition or low pollen dispersal efficiency. This study utilises a comparative database correlating pollen data with contemporary vegetation patterns to establish a robust framework for assessing sedimentary pollen sequences. Through this approach, we aim to elucidate past vegetation dynamics and infer climate fluctuations within the NW Himalaya.

Provenance of the Mesoproterozoic Shennongjia Group in the north Yangtze Block, South China, and implications for reconstructions of the Nuna and Rodinia supercontinents

Magmatic activity in the range ca. 1.6−1.5 Ga is spatially restricted globally, and its distribution has been an important tool for constraining the reconstruction of the Nuna supercontinent. Abundant ca. 1.6 Ga detrital zircons have recently been discovered in the Luanshigou and Taizi formations of the middle Mesoproterozoic Shennongjia Group in the north Yangtze Block, South China. Detrital zircon age spectra and multi-dimensional scaling results indicate the Shennongjia Group was derived from variable sources. The ca. 1.6 Ga detrital zircons in the middle Mesoproterozoic units were probably sourced from Laurentia and Australia-Mawson, whereas detrital zircons of other age groups were provided by the local rock units in the north Yangtze Block. Similarities in sedimentary sequences, detrital zircon age spectra, and corresponding Hf isotopic patterns of the Shennongjia Group with other Mesoproterozoic successions in Yangtze Block (e.g., Baoban-Shilu, Huili, and Kunyang groups) suggest that the block contained a number of micro-blocks during the Mesoproterozoic. Furthermore, the compiled new and published detrital zircon data from the north Yangtze Block along with those from other continents containing ca. 1.6 Ga zircons reveal that the Yangtze Block was most likely situated within a rift zone between southeast Australia-Mawson and southwest Laurentia. The ca. 1.6 Ga zircons in the Shennongjia Group were derived from these bounding source regions during the middle Mesoproterozoic. By the late Mesoproterozoic, based on a comprehensive provenance analyses and comparison of detrital zircon data, the Yangtze Block was probably located on the margins of the Rodinia supercontinent, close to north-central India, Australia, and East Antarctica.

Holocene mammals (Insectivora, Rodentia, Chiroptera) of Dollsteinhola Cave, Western Norway

The Dolisteinhola cave comprises a sequence of Holocene deposits dating from the late Atlanticum to the first half of the Subboreal period. Climate-sensitive species were found in layers V (Sciurus vulgaris) and layers II - III, IV, IV - V (Apodemus flavicollis). Two humerus of Barbastella barbastellus were also recognised. The faunal assemblage were grouped in three climatic complexes: species which lived both in cold and warm climates; species connected with warmer phases of the climate and species typical for a cold climate.

Sediment supply variation control on Lower Eocene delta sequences (Tremp Basin, Spain)

Sediment supply variations are often overlooked when interpreting depositional sequences, with most studies instead emphasizing changes in accommodation space. Here, we investigated a temporally well-constrained shallow-marine succession in the Tremp Basin to test the control of sediment supply variations on the development of deltaic sequences during the early Eocene. We analyzed the paleoenvironmental record (sedimentary facies and δ13Corg values) of the Morillo Limestone and the Castigaleu Formation (52.2−50.6 Ma). The first progradation of the deltaic system is marked by the abrupt appearance of thick delta-front sandstones and associated with the first negative carbon isotopic excursions (CIEs) in the measured δ13Corg record. Subsequent phases of progradation align with subsequent negative CIEs. Conversely, positive CIEs correspond to finer-grained, more-distal prodelta deposits. A series of hyperthermal events occurred during the deposition, globally identified as negative CIEs on δ13Ccarb reference curves, which we tentatively correlate with our δ13Corg data. We therefore suggest that during deposition of this Lower Eocene shallow-marine succession, the primary trigger behind sequence generation was the high-frequency climate-induced variation in sediment supply, specifically the hyperthermal events, rather than changes in accommodation. This linkage underscores the complex interactions between climate dynamics and sedimentary responses that shape the stratigraphic architecture of shallow-marine settings.

Holocene benthic foraminifera ecological succession in the Panamanian Caribbean

Benthic foraminifera assemblages from a 452 cm long sediment core (GAL18) were collected from a mangrove forest on the Caribbean coast of Panama. The core spans the last ∼5200 cal yrs. B.P. Ninety-six benthic species were recorded in the sedimentary sequence. The most frequent and abundant were the calcite hyaline species Ammonia batava, Ammonia tepida, Ammonia ariakensis, Elphidium articulatum, Elphidium cristobalense, and Cribroelphidium galeroense. The second most abundant were four porcelaneous species: Quinqueloculina cf. araucana, Quinqueloculina cf. poeyana, Quinqueloculina neocostata and Quinqueloculina seminulum. There were also scattered species of agglutinant taxa along the core and in modern sediments. Micropaleontological, sedimentological, and geochemical analyses allowed the recognition of four lithologic units that were consistent with four paleoenvironmental scenarios of ecological succession. (I) The Estuarine Zone deposited at ∼5200–3600 cal yrs. B.P. suggests the development of a mangrove ecosystem along a channeled tidal area with estuarine water exchange and dominant species from brackish waters such as Ammonia and Cribroelphidium. Isotopic (δ13Corg, δ15N), geochemical (C/N, Ca/Ti, K/Rd, Fe/Ca), and pollen data also show a polyhaline environment with bio-calcite production and active coastal weathering. (II) The Seaward Zone deposited between ∼3600–1250 cal yrs. B.P., closest to marine waters, with an overall increase in benthic species, like the euhaline Quinqueloculina spp., and other calcareous organisms. (III) The Transition Zone was deposited amid 1250–650 cal yrs. B.P. when the area experienced less frequent flooding by tidal waters, dominated by polyhaline Elphidium and Ammonia spp., and the establishment of a mangrove ecosystem influenced by changing salinity, as the sea level almost reached its modern position. Finally, (IV) the Landward Zone deposited over the last 650 cal yrs. B.P., where the lack of benthic foraminifera and bio-calcite deposits contrast with high amounts of organic carbon and vegetal debris, which supports that the core site was located further inland than in previous intervals. This multiproxy study features subtle but irreversible changes that a fringe mangrove community can experience over time, highlighting the complex relationship between the coastal region and the sea.

Hawaiian legends of coastal devastation and paleotsunami reconstruction, Nu'u, Kaupō, Maui, Hawai'i

In Hawaiʻi, tsunamis are often described in orally transmitted legends (moʻolelo). This study examines sedimentary evidence of a possible local submarine landslide-generated tsunami, described in a legend from the south east coast of Maui which originated between the 15th Century CE and the first arrival of Europeans in 1778 CE. Physical evidence for a tsunami, found at the Nu'u Refuge, Maui, is primarily comprised of an extensive coral clast deposit (found 8.5 m above msl and 251 m inland from the shoreline) together with waterworn cobbles which form fracture-embedded wedge clasts in a local basalt escarpment (at up to 8 m above msl). U/Th dating of the coral clasts gives a maximum tsunami deposit age of 1671 CE for the event that may have inspired the local moʻolelo. This depositional sequence is used to characterize the nature of the assumed tsunami in terms of inundation distance, maximum wave runup and minimum flow velocities. A numerical model developed using GeoClaw matches well with the physical evidence. The data and modeling presented here suggest that locally-generated tsunamis from submarine landslides warrant further research attention as sources of destructive high energy marine inundation events.

Lithium isotopes track changes in continental weathering regimes across the end-Permian mass extinction in Southwest China

It has been assumed there was a massive amount of volcanic CO2 injection into the Permian-Triassic atmosphere and ocean systems, leading to rapid climatic warming and expansion of marine anoxia. However, it remains intriguing how Earth recovered from such a CO2-driven hyperthermal condition. One potential mechanism involves the negative feedback between continental silicate weathering and atmospheric CO2, which could have helped maintain habitability across the end-Permian mass extinction (EPME) interval. This process can be examined using lithium isotopes (δ7Li), which reflect the balance of physical erosion and chemical weathering, and chemical weathering indices such as the Chemical Index of Alteration (CIA), which indicates the chemical alteration of parent materials during weathering. In this study, we analyze siliciclastic sedimentary rocks from the Lopingian to Lower Triassic depositional sequences in the HK-1 drill core at the Lengqinggou section, a terrestrial coastal depositional environment in Southwest China, to reconstruct changes in continental chemical weathering intensity across the EPME. We observed a significant ∼4 ‰ positive shift in δ7Li, accompanied by a marked decrease in Li content from 26 ppm to 6 ppm. Our corrected CIA data (CIAcorr) also exhibits a considerable decrease from 94 to 59 across the EPME. The new δ7Li and CIAcorr data from the terrestrial section indicate a decrease in overall chemical weathering intensity in Southwest China, alongside an increase in physical erosion rates, suggesting a shift from a transport-limited to a kinetically limited weathering regime across the EPME. These changes in the continental weathering regime appear to be linked to active volcanic activity near the South China Block, which led to massive deforestation and the collapse of soil systems. Dramatic reductions in chemical weathering intensity may result in inefficient atmospheric CO2 consumption through silicate weathering if other climatic and tectonic conditions remain constant, potentially contribute to maintaining high global surface temperatures and prolonged marine anoxia into the Early Triassic.