Depositional Record最新文献

{"title":"Diverse morphologies found in living microbial mats and associated microbialites—A field report from the alkaline and hypersaline Nuoertu Lake, Badain Jaran Desert, N-China","authors":"S. V. Hohl,&nbsp;M. Steiner,&nbsp;X.-Y. Hu,&nbsp;H.-Y. Liu","doi":"10.1002/dep2.70062","DOIUrl":"https://doi.org/10.1002/dep2.70062","url":null,"abstract":"<p>During recent sampling of the alkaline and hypersaline Lake Nuoertu in the Badain Jaran Desert, Inner Mongolia, PR China, various living microbial mat morphologies, along with associated lithified microbialites and stromatolitic tufa were discovered. Our fieldwork confirmed preliminary findings from the late 1990s that linked carbonate formations to subterranean freshwater discharge into the alkaline lakes of the Badain Jaran desert. This field report provides an overview of the microbialite morphologies, including phyto-microbialites, columnar and domical-linked as well as hemispherical roll-up structures, their redox stratification and water quality measurements at several lake sites and one groundwater spring. Environmental DNA data of differently pigmented mat layers reveal a well-defined vertical microbial zonation with cyanobacteria and aerobic heterotrophs dominating the top layer and deeper anaerobic layers characterised by anoxygenic purple sulphur bacteria and sulphate reducing bacteria, as well as sulphur bacteria and fermenters in strictly anoxic zones. This work serves as a preliminary report, highlighting the newly documented alkaline environment that hosts a key living microbialite community in China.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70062","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146002161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Domed-rim microbial polygons and their preservation potential","authors":"Franziska R. Blattmann,&nbsp;Timothy I. Eglinton,&nbsp;Negar Haghipour,&nbsp;Simon E. Rouwendaal,&nbsp;Stefano M. Bernasconi,&nbsp;John M. Rivers,&nbsp;Maria Dittrich,&nbsp;Zulfa Al Disi,&nbsp;Kenneth H. Williford,&nbsp;Fadhil Sadooni,&nbsp;Hamad A. Al-Saad Al-Kuwari,&nbsp;Tomaso R. R. Bontognali","doi":"10.1002/dep2.70061","DOIUrl":"https://doi.org/10.1002/dep2.70061","url":null,"abstract":"<p>Microbially induced sedimentary structures (MISS) derive from the interaction between sediments and unicellular microorganisms and are of interest to the search for the earliest signs of life in ancient rocks, on Earth and on Mars. Here, we describe a type of MISS in the form of a polygonal structure characterised by a domed rim. Despite earlier suggestions of a biological origin, several aspects regarding their formation mechanism, the criteria to distinguish these structures from abiotic mud cracks, and their preservation potential in the geological record remain insufficiently constrained. To identify and define the distinctive features characterising this MISS, we have investigated the morphology and formation mechanism of polygonal microbial mats in two modern sabkha locations in Qatar. The sedimentological, mineralogical and geochemical analyses suggest that the studied polygons result from microbe-mineral interactions causing the stabilisation of detrital minerals (e.g. quartz, feldspar) and precipitation of micrite comprised of calcite and high-Mg calcite. The polygonal morphology is mainly the result of two co-occurring mechanisms: shrinkage, as a result of desiccation and microbial growth. A ∼1.5 cm-sized domed-rim has been identified as the key morphological feature that is exclusively present in and that allows for the recognition of, the polygons that form in association with a growing microbial mat. In cross-section, a domed-rim is comprised of millimetre-thick laminae showing angular relationships (e.g. overgrowth of older lamina sets) that, we argue, cannot be formed in the absence of growing biomass. Finally, through the study of a radiocarbon-dated ancient sabkha outcrop, it is shown that domed-rim microbial polygons can survive degradation and diagenesis, producing a mineral fossil structure that can potentially be preserved for billions of years.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70061","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146002162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Precipitation mechanism of anhydrite cement in lacustrine tight sandstone: Implications for fluid activity, mass transfer and pore origin of open diagenetic system in tight sandstone","authors":"Long Luo,&nbsp;Meng Li,&nbsp;Shanzheng Tan,&nbsp;Xianfeng Tan,&nbsp;Xin Yu,&nbsp;Jon Gluyas,&nbsp;Jia Wang,&nbsp;Wei Jiang,&nbsp;Xuejiao Qu,&nbsp;Kangjun Wu,&nbsp;Yiting Gu","doi":"10.1002/dep2.70059","DOIUrl":"https://doi.org/10.1002/dep2.70059","url":null,"abstract":"<p>Anhydrite is a common type of cement occurring in the tight (low permeability) sandstone reservoirs in continental lake basins. The precipitation of anhydrite cement is governed by fluid activity during diagenesis and its precipitation controls the pore evolution in tight sandstones. It is important to understand the formation mechanism of anhydrite cement in order to forecast the quality of tight sandstone reservoirs ahead of drilling. Jurassic Shishugou Group lacustrine sandstones of the Fukang Sag of Junggar Basin, NW China, are important low-permeability oil reservoirs. In the Shishugou Group sandstones, abundant anhydrite cement occurring mainly along a deep fault zone is associated with significant oil and gas shows. The electronic probe and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) were applied to investigate the formation time, precipitation conditions, material sources and precipitation process of anhydrite cement and provide new insights for fluid activity, diagenetic system and the formation of pores in the tight sandstone. Anhydrite cement is mainly formed by the dissolution and reprecipitation of early diagenetic calcite cements, feldspars and volcanic rock fragments at the mesodiagenetic stage. The dissolution of calcites and detrital grains (feldspars and volcanic rock fragments) provided sufficient Ca²⁺ for both pore-filling and grain-replacive anhydrite. Organic acids can provide abundant SO₄²⁻ from the Permian petroleum source rock and transport it to the Shishugou Group sandstone through the deep-penetrating faults. The sufficient SO₄²⁻ in an acidic environment is favourable for the precipitation of anhydrite at the mesodiagenetic stage. The precipitating process of the anhydrite cement in the Shishugou Group sandstone involved obvious mass transfer and dissolution in an open diagenetic system due to the hydrocarbon charging through deep faults.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70059","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial mediation and climatic control on dolomite precipitation in a hypersaline lake: Insights from Salinas Lake, southern Iberia","authors":"Guolai Li,&nbsp;Zeina Naim,&nbsp;Luis Gibert,&nbsp;Jan-Berend Stuut,&nbsp;Annemiek C. Waajen,&nbsp;Gonzalo Jimenez-Moreno,&nbsp;Mónica Sánchez-Román","doi":"10.1002/dep2.70058","DOIUrl":"https://doi.org/10.1002/dep2.70058","url":null,"abstract":"<p>This study examines the climatic controls on dolomite precipitation through a multiproxy investigation of a carbonate-rich sediment core from Salinas Lake, a hypersaline playa in Alicante, south-eastern Iberia. The ~120,000 year record captures depositional cycles and palaeoenvironmental changes driven by late Pleistocene to Holocene climate variability. Integrated analyses of sedimentology, lithology, geochemistry (elemental concentrations, total organic carbon, stable carbon and oxygen isotopes), scanning electron microscopy, microbial community characterisation and palynology reconstruct lake hydrology and its influence on carbonate mineralogy. The sediment succession is marked by alternating calcite- and dolomite-rich intervals, with dolomite crystals displaying morphological evolution from spherical to rhombohedral forms with depth. Stable isotope signatures (δ¹³C: −6.5‰ to −2.4‰ VPDB; δ¹⁸O: −2.3‰ to +4.9‰ VPDB), alongside microbial structures such as extracellular polymeric substances (EPS) and internal crystal voids, suggest a biologically mediated precipitation mechanism. These mineralogical shifts closely correspond to rapid hydrological changes driven by Dansgaard–Oeschger climate oscillations, with dolomite formation favoured under arid, evaporative conditions that concentrate Mg and Ca ions and promote microbial mat development. Halophilic microbial communities, capable of catalysing carbonate precipitation, probably enhance dolomite nucleation and growth through EPS production and geochemical modulation. This work underscores the complex interplay between climate, hydrology, microbial activity and sedimentary mineral formation, providing new insights into the longstanding ‘dolomite problem’ within sedimentary environments.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70058","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146007354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Taking machine learning with a grain of sand: Sediment Analysis Neural-network Data-engine (SAND-e) reveals sedimentological differences between turbid and clear-water reefs","authors":"G. William M. Harrison,&nbsp;Teigan G. Collins,&nbsp;Allia Rosedy,&nbsp;Nadia Santodomingo,&nbsp;Willem Renema,&nbsp;Kenneth G. Johnson","doi":"10.1002/dep2.70051","DOIUrl":"https://doi.org/10.1002/dep2.70051","url":null,"abstract":"<p>Sediment is an important facet of sand cay reefs as it is responsible for reef accretion and island formation, with shifts in the proportions of sediment producers being proxies for ecological shifts. However, manual sediment analyses require experts to identify thousands of sand grains by hand before beginning data analysis. To accelerate the process, we developed the Sediment Analysis Neural-network Data-engine (SAND-e) to estimate the proportions of sediment producers, based on segmentation and classification of carbonate sand grains from microscope camera imagery. Sediment from Darvel Bay was used for training due to the variability of sand cay reefs available in that area. SAND-e segmented 1686 images into 32 883 grains within 3.5 h. The grains were then fed through SAND-e's classifier ensemble, containing four classifiers that voted to classify the grains into one of five classes (calcareous algae, coral, foraminifera, molluscs and ‘other’) in 1 hour. Both SAND-e and 11 humans annotated grains from the same dataset to ensure that SAND-e's accuracy was within the already accepted error rate deriving from multiple human annotators.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146007353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupled authigenic Mg silicate and carbonate precipitation in saline lakes of the Salar de Atacama, Northern Chile","authors":"Erica P. Suosaari,&nbsp;Christophe Dupraz,&nbsp;Amanda M. Oehlert,&nbsp;Ioan Lascu,&nbsp;Brooke E. Vitek,&nbsp;Alan M. Piggot,&nbsp;Alvaro T. Palma,&nbsp;R. Pamela Reid","doi":"10.1002/dep2.70055","DOIUrl":"https://doi.org/10.1002/dep2.70055","url":null,"abstract":"<p>The interplay between microbial activity and mineral precipitation in extreme environments plays a critical role in shaping sedimentary textures and influencing biosignature preservation. This study explores coupled Mg silicate and carbonate precipitation in the marginal lakes of the Salar de Atacama, Northern Chile, expanding previous findings from the Salar de Llamara. Using field samples from the Aguas de Quelana and Soncor sectors, sedimentary deposits classified as sediments, unlithified microbial mats and lithified microbial buildups are each characterised by distinct microbial architectures and mineralisation processes. Detailed analyses conducted via scanning electron microscopy, energy dispersive spectroscopy (EDS) and X-ray diffraction identified minerals and mineral associations and revealed pathways of coupled Mg silicate–carbonate precipitation. Results indicate that organic matter production is followed by precipitation of amorphous to nanocrystalline Mg silicate. Aragonite then templates on and replaces Mg silicate and infills voids. Dense microbial colonies within high-viscosity extracellular polymeric substances (EPS) promote precipitation of welded Mg silicate (W-MS), conferring structural stability, while loosely organised EPS networks result in porous deposits of granular sediments. W-MS serves as a scaffolding that enhances preservation of morphological biosignatures. Overall, sedimentary product diversity reflects variations in microbial density and EPS organisation, suggesting that variations in initial microbial colony distribution and EPS determine the eventual sedimentary product. Our results also highlight the role of Mg silicate–carbonate precipitation in the formation of grainy sediments, expanding prior work on Mg silicate–carbonate coupling forming microbialites and unlithified microbial mats in the Atacama Desert. The data set presented here provides a robust analogue for interpreting ancient sedimentary systems and emphasises the significance of microbe–mineral interactions forming Mg silicate–carbonate deposits in extreme environments.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70055","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146002173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laguna Fuente de Piedra: An example of a dolomite factory recording ~50,000 years of depositional and paleoclimatic evolution","authors":"Zeina Naim,&nbsp;Guolai Li,&nbsp;Luis Gibert,&nbsp;Jan-Berend Stuut,&nbsp;Gonzalo Jiménez-Moreno,&nbsp;Mónica Sánchez-Román","doi":"10.1002/dep2.70052","DOIUrl":"https://doi.org/10.1002/dep2.70052","url":null,"abstract":"<p>We examine the depositional dynamics and paleoclimatic significance of the evaporite–dolomite association in Laguna Fuente de Piedra (LFP), a modern saline, endorheic playa lake system in southern Spain. This study presents results from a multidisciplinary approach, examining the two longest continuous sediment cores retrieved from the basin. One core was drilled in the Salina area, located in the eastern part of the basin, which represents the zone that dries last and is referred to as the Salina core (14.4 m). The second core, Las Latas (46.2 m), was retrieved from the southwestern part of the basin, which is the zone that dries first. This study characterises carbonate minerals and their precipitation mechanism in the sediments from these two cores over the past ~50,000 years. Six major lithofacies were identified based on variations in mineralogy (carbonates, sulphates and siliciclastic minerals) and sedimentary patterns. Observed shifts in the depositional environment are hypothesised to result from changes in the hydrological balance, which in turn is controlled by paleoclimatic evolution. During dry and cold periods, the basin experienced higher evaporation rates, leading to the deposition of evaporites along with dolomite in a continental sabkha environment with ephemeral floods. These arid conditions favoured large production of endogenic sulphates and carbonates (dolomite) and reduced clastic input. In contrast, wetter periods were characterised by increased clastic influx and the precipitation of calcite–aragonite facies, in a shallow ephemeral to permanent lake, mostly during the Pleistocene–Holocene transition, continuing into the Holocene. These findings show the high sensitivity of shallow continental sedimentary systems to climate variations and provide information on significant short-lived climatic events, tentatively correlated with Heinrich events, in the western Mediterranean region.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70052","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146007878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of formation mechanism of tufa deposits by chemical breakdown of legacy paper mill sludge","authors":"Md Jahangir Alam,&nbsp;John M. MacDonald","doi":"10.1002/dep2.70054","DOIUrl":"https://doi.org/10.1002/dep2.70054","url":null,"abstract":"<p>This study investigates the formation mechanisms of anthropogenic tufa deposits resulting from the chemical breakdown of legacy paper mill sludge (PMS) at the former Dalmore Paper Mill site in Auchendinny, Scotland. Tufa, a form of calcium carbonate (CaCO₃), typically forms in natural freshwater environments; however, this research explores its precipitation through interactions between alkaline industrial waste (PMS) and atmospheric CO₂. Field and laboratory analyses were carried out to assess the geochemical characteristics of the stream water, as well as the mineralogical and isotopic composition of the associated tufa deposits. X-ray diffraction (XRD) analysis revealed that PMS is composed predominantly of calcite, while tufa samples also contain minor amounts of quartz and kaolinite. Stream water measurements indicated alkaline conditions (pH 8.27–8.98) and elevated calcium concentrations, with calcite saturation indices suggesting conditions favourable for carbonate precipitation. Stable isotope analysis of tufa deposits (δ¹³C −24.62‰ to −13.74‰; δ¹⁸O −17.50‰ to −7.66‰) revealed a dominant contribution from atmospheric CO₂, confirming a precipitation mechanism driven by CO₂ ingassing and hydroxylation reactions. The results support a model where rainwater infiltrates PMS heaps, leaching calcium into stream waters. As these calcium-rich waters mix with atmospheric CO₂, supersaturation occurs, leading to rapid calcite precipitation. The resulting tufa deposits exhibit laminated structures and high porosity, indicating episodic deposition under variable geochemical conditions. This study provides the first detailed evidence of tufa formation from PMS and suggests that such industrial waste materials can act as carbon sinks, capturing and mineralising atmospheric CO₂. These findings expand the understanding of anthropogenic carbonate systems and highlight the potential of PMS as a low-cost material for environmental remediation and carbon sequestration, supporting sustainable waste management strategies and contributing to climate mitigation goals.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70054","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organoclay interaction response to sedimentary environment and sources in Paleogene shales from the Nanpu Sag: Insights for organic matter accumulation mechanism","authors":"Rusi Zuo,&nbsp;Jingong Cai,&nbsp;Wei Duan,&nbsp;Xiang Zeng,&nbsp;Jinyi He,&nbsp;Chuan Cai,&nbsp;Qianyou Wang","doi":"10.1002/dep2.70056","DOIUrl":"https://doi.org/10.1002/dep2.70056","url":null,"abstract":"<p>Shales play a crucial role in the global carbon cycle through organic matter accumulation and hydrocarbon generation. However, the influence of organoclay interaction on organic matter enrichment and hydrocarbon generation remains unclear. To address this, PY-GC/MS, along with a series of experiments, was employed to investigate the Ed₃-Es₁ Formation in the Nanpu Sag. Organic matter in the shales occurs in two forms: mineral-bound organic matter and free organic matter. Mineral-bound organic matter, chemically bound to clay minerals, is primarily derived from aquatic organic matter. Free organic matter, physically associated with minerals, mainly originates from terrestrial plants. The organic matter in the source rocks from the Nanpu Sag varies in occurrence between units. In Es₁, it is primarily composed of mineral-bound organic matter, whereas in Ed₃, it consists of both mineral-bound organic matter and free organic matter. The diversity was the result of the combined influences of sedimentary environment, mineral input, and organic matter source. The deep palaeo-lake during Es₁ deposition, characterised by moderately high salinity and low-energy hydrodynamic conditions, promoted the development of aquatic organic matter and the input of fine-grained minerals, thereby facilitating the formation of mineral-bound organic matter. The shallow palaeo-lake during Ed₃ deposition, characterised by relatively low salinity and strong hydrodynamic conditions, experienced a substantial input of terrestrial detrital minerals and plant fragments, resulting in the abundant presence of free organic matter in the shales. Furthermore, the hydrocarbons produced from the different units exhibit significant variation in yield and composition. Above all, source rock assessment should take organoclay interactions into account. This research can also enhance the understanding of the influence of lacustrine sediment on the global carbon cycle.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70056","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146002182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polygonal tepee structures of Arabia","authors":"Pauline Falkenberg,&nbsp;Sarima Vahrenkamp,&nbsp;Elisa Garuglieri,&nbsp;Alexander Petrovic,&nbsp;Kai Hachmann,&nbsp;Viswasanthi Chandra,&nbsp;Volker C. Vahrenkamp","doi":"10.1002/dep2.70043","DOIUrl":"https://doi.org/10.1002/dep2.70043","url":null,"abstract":"<p>Tepee structures are upward-buckling fracture rims that form a reticulated network of polygonal boundaries when viewed from an aerial perspective. These structures are thought to result from crystallisation forces of cement, causing lateral expansion of consolidating sedimentary materials. Tepee structures are indicative of subaerial exposure and can serve as stratigraphic markers in ancient carbonate sequences. While tepee structures are common in ancient carbonate sequences, in modern settings, they have only been described in the Arabian Gulf. The discovery of fields of polygonal structures, on satellite images of the Red Sea Island of Sheybarah, Saudi Arabia, motivated the authors to assess their genesis and distribution in Arabia. The objectives are to describe in detail tepees and their arrangement in polygonal patterns, investigate the timing of their formation and constrain the relative timing of tepee generation. Furthermore, this study investigates, based on a detailed satellite image survey, whether similar polygonal features can be identified around the Arabian Peninsula. The polygonal crusts on Sheybarah Island are found in intertidal to supratidal settings overlying a well-lithified ravinement surface. They are composed of locally derived poorly sorted sand-to-pebble-sized coral, mollusc and foraminifera debris of predominantly aragonite and high Mg-calcite mineralogy with minor admixtures of siliciclastics. Based on petrographic analysis, microbial-induced cement precipitation is the major lithification agent. Lithification occurs in the upper intertidal zone based on the ubiquitous presence of keystone vugs. Radiocarbon (¹⁴C) dates reveal elevation-aligned ages between approximately 1.5 and 3.0 ka BP, allowing the reconstruction of late Holocene minor sea-level changes aligned with major global climate variations. Hence, polygonal tepee structures may serve as proxies for sea-level changes. Of 126 occurrences of polygonal fields identified from satellite images, 89 in the Red Sea are probably composed of polygonal reefs. The authors hypothesise that polygonal coral reefs originated on tepee crust.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"12 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70043","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145970201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}