Depositional Record最新文献

{"title":"Microbialite cathodoluminescence: A tool for investigating palaeoredox conditions, alteration histories and primary textures across time","authors":"Cedric J. Hagen,&nbsp;Brianna Hibner,&nbsp;Juliana Olsen-Valdez,&nbsp;Haley Brumberger,&nbsp;Catherine G. Fontana,&nbsp;James R. Gutoski,&nbsp;Jessica C. Hankins,&nbsp;Srishti Kashyap,&nbsp;Tyler A. Lincoln,&nbsp;Nicole Mizrahi,&nbsp;Kathryn E. Snell,&nbsp;Elizabeth J. Trower","doi":"10.1002/dep2.70008","DOIUrl":"https://doi.org/10.1002/dep2.70008","url":null,"abstract":"<p>Microbialites have long been utilised by geologists as palaeoenvironmental indicators, despite outstanding questions regarding their formation and preservation in the rock record. Here, we leverage cathodoluminescence (CL) microscopy, a technique commonly used to investigate carbonate formation and diagenetic alteration, to better understand the textural characteristics, formation mechanisms and diagenetic histories of microbialites. We compare CL features to gain insight into palaeoredox conditions and alteration histories for a suite of six microbialite samples spanning from the Proterozoic to modern, finding a strong degree of similarity amongst samples regardless of age or depositional environment. CL reveals that microbialites typically have complex microfabrics that include other accessory minerals and grains, all of which provide insight into their unique formation and palaeoredox histories. We find that the modern microbialite sample showed the greatest difference in CL characteristics compared to the other microbialite samples, most probably because of its aragonitic composition and incomplete lithification. In contrast, the ancient microbialite samples preserve a distinct and most probably primary, mottled luminescence texture despite spanning more than 500 Myr; this mottled texture may typify ancient microbialite fabrics that formed in shallow water settings. We also distinguish a variety of CL characteristics that support previously proposed formation and/or diagenetic histories in these samples. Lastly, we use energy-dispersive X-ray spectroscopy to compositionally identify rare grains observed with CL, highlighting the utility of CL as a possible screening tool for both geological and non-geological components within samples. Our analyses demonstrate the power of using classic CL techniques to answer modern questions in microbialite research.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1010-1028"},"PeriodicalIF":2.0,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135314","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":"Eustatic and tectonic controls on mixed carbonate-siliciclastic ramp deposits in the South Pyrenean foreland basin: The Eocene Alveolina Limestone","authors":"Stefan Schröder,&nbsp;Oliver Neame,&nbsp;Amber Finch,&nbsp;Miquel Poyatos-Moré","doi":"10.1002/dep2.70025","DOIUrl":"https://doi.org/10.1002/dep2.70025","url":null,"abstract":"<p>Palaeogene depositional systems in the South Pyrenean foreland were influenced by eustatic sea level changes, compressive and salt tectonics, as well as biotic and environmental changes during and after the Palaeocene–Eocene Thermal Maximum (PETM). Decoupling these factors requires careful sedimentary and stratigraphic analysis. This study combines outcrop observations and microfacies analysis to derive a depositional model and to evaluate the relative roles of eustasy, tectonics and skeletal biota during deposition of the lower Eocene Alveolina Limestone, which immediately post-dates the PETM. The studied succession is preserved in the footwall of the Montsec thrust. Diagnostic skeletal grains show a systematic upward change from coastal (miliolid foraminifera, charophytes) and inner ramp (miliolid and alveolinid foraminifera), through tidal bars or dunes (alveolinid and nummulitid foraminifera), to middle ramp (bryozoans, echinoderms, encrusters—mainly acervulinid foraminifera and coralline red algae) environments, a deepening succession recording the global early Eocene transgression. A condensation interval rich in red algae, iron and glauconite grains and cement marks the maximum flooding and passage to the overlying tidally-influenced Baronia Formation sandstones. The fossil assemblage is consistent with expansion of foraminifera at the expense of corals in the aftermath of the PETM. Lower accommodation space and higher detrital input in the footwall of the Montsec thrust caused stratigraphic thinning and interbedding of carbonate debrites and sandstones. This suggests that the Montsec tectonic structure was at least partially emergent already during the earliest Eocene. Uplift of the Montsec tectonic structure, which was probably related to salt movements and compressive tectonics, and the early Eocene transgression facilitated a detrital provenance shift from a southern provenance in the Palaeocene to north/northeasterly Pyrenean sources. The large tidal bedforms in the Alveolina Limestone, deposited by currents amplified in a narrow strait, may provide evidence for the development of an Atlantic-Mediterranean seaway.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1132-1165"},"PeriodicalIF":2.0,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70025","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135216","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":"Constructing a cave sediment stratigraphy for the Dachstein Massif sheds light on landscape evolution (Eastern Alps)","authors":"Franziska Holzer,&nbsp;Lukas Plan,&nbsp;Susanne Gier","doi":"10.1002/dep2.70028","DOIUrl":"https://doi.org/10.1002/dep2.70028","url":null,"abstract":"<p>The Dachstein in Austria is the second largest karst massif in the Alps. It is dominated by Upper Triassic limestone and 290 km of cave passages have been documented. For this study, five major cave systems on the northern edge of the Dachstein were investigated: Hirlatzhöhle, Mammuthöhle, Rieseneishöhle, Schönberghöhle and Günter-Stummer-Höhle. Thirty-five sediment profiles or exposures between 860 m a.s.l. and 1945 m a.s.l. were analysed with respect to stratigraphy, grain size, mineral composition and carbon content. Our study distinguishes the following main types of non-autochthonous sediments. The stratigraphically deepest sediment in the highest—and therefore oldest—cave (Ruin Level, c. 1900 m a.s.l.) is a dark clay with laterite-derived minerals, suggesting formation before c. 15 Ma, consistent with the previously proposed Eocene–Oligocene age. At intermediate elevations (Giant Cave Level, c. 1350 m a.s.l.), a poorly sorted channel facies forms the initial allochthonous sediment. In Hirlatzhöhle to the west, it is reddish-brown and dominated by para-autochthonous radiolarite components, while in the eastern caves, it is greenish (chlorite) and contains Augensteine sensu lato from metamorphosed rocks of the Niedere Tauern. Previous burial age dating of the quartz suggests an emplacement in the caves 4–6 Ma ago. In caves at this elevation, a dark brown fine-grained sediment of slack-water facies follows, which is probably a palaeosol derived from the allochthonous crystalline sediment cover. Above, rounded limestone gravel is at least partly attributed to glacial meltwater. At the top, and almost ubiquitous, is a bright clayey silt. It is carbonate rich and has a varve-like layering. This sediment is attributed to Pleistocene meltwaters and glacial backflooding. While it is normally a few tens of centimetres thick in the Giant Cave Level, it can reach a few metres in the Berger Level (c. 950 m a.s.l.) below. Only there is it partly overlain by Holocene carbonate sands.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1166-1195"},"PeriodicalIF":2.0,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135214","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":"Trace elements, rare earth elements and isotopes of poorly preserved fossils from lower Cretaceous carbonates (Eastern Black Sea): Implications for early diagenetic alteration","authors":"Merve Özyurt","doi":"10.1002/dep2.70026","DOIUrl":"https://doi.org/10.1002/dep2.70026","url":null,"abstract":"<p>Poorly preserved belemnite samples are often disregarded in palaeoclimatology and palaeoceanography research within the Eastern Pontides (NE Türkiye), which is part of the Alp-Himalayan Belt that experienced extensive orogenic and magmatic activity. Late Jurassic–Early Cretaceous carbonates are widely exposed in the Eastern Pontides, having undergone a complex diagenetic history since deposition. Belemnite rostra samples from the uppermost part of the carbonate sequence (Aptian–Albian strata) exhibit diagenetic overprints. These poorly preserved belemnite samples can serve as excellent archives for basin early diagenetic evolution. However, the diagenetic evolution of these poorly preserved belemnite samples has not been fully studied within the context of the diagenetic evolution of the basin. Thus, this study presents a comprehensive dataset including isotope analyses (Sr/C/O) and trace element, including REE chemistry of these belemnite samples to elucidate the basin's early diagenetic history. The studied samples are commonly dark grey and show visible signs of diagenetic processes, including dissolution, silicification and pyrite mineralisation. These samples show high Fe (1259–5176 ppm; ave. 2859 ppm) and Mn (77–387 ppm; ave. 232 ppm), low Sr/Mn (0.63–12.33; ave. 3.47) and low Sr/Rb (42–568, ave. 200) values, consistent with a diagenetic alteration. Interestingly, carbon and strontium isotopes of belemnite samples correlate well with those from well-preserved belemnite rostra from the Aptian–Albian strata. They exhibit a diagnostic sea water REE_N signature, including mildly enriched Gd/Gd* ratios of 1.04–1.48 (ave. 1.24) and high La/La* of 1.54–5.50 (ave. 2.51) and Ce/Ce* of 0.46–0.60 (ave. 0.51). However, slight LREE enrichment is observed, with La/LuN ratios ranging from 0.81 to 1.74 (average: 1.21) and La/YbN ratios from 0.9 to 1.79 (average: 1.22). A slight positive Eu anomaly is also present, with Eu/Eu* ratios between 1.15 and 1.55 (average 1.36). Y/Ho ratios range from 35.00 to 45.00 (average 39.84), and Sm/Yb ratios from 1.70 to 4.05 (average 2.42). These geochemical characteristics, along with δ¹⁸O values that deviate from typical marine carbonate signatures, suggest a subsequent low-temperature hydrothermal alteration, potentially triggered by hydrothermal activity associated with an Early Cretaceous magmatic event. This finding underscores the significance of analysing REEs in poorly preserved belemnite rostra, offering valuable insights into early diagenetic pathways, dissolution/precipitation processes and water–rock interaction.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1107-1131"},"PeriodicalIF":2.0,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70026","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135215","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":"Carbonate microfacies and transgressive-regressive sequences of Oxfordian shallow-water limestones (Korallenoolith, Lower Saxony Basin)","authors":"Deyan Zhang,&nbsp;François-Nicolas Krencker,&nbsp;Stefan Huck,&nbsp;Ulrich Heimhofer","doi":"10.1002/dep2.70022","DOIUrl":"https://doi.org/10.1002/dep2.70022","url":null,"abstract":"<p>This study represents a detailed analysis of a stratigraphic section of Oxfordian (Late Jurassic) age with the aim to reconstruct the facies pattern and sequence-stratigraphic evolution, followed by a discussion of the dominant controls on shallow marine carbonate platform sedimentation in the Lower Saxony Basin (LSB). During the Oxfordian, the LSB was covered by a shallow epicontinental sea, in which a thick succession of marine limestones and marls was deposited. The stratiform Oxfordian carbonate bodies hold significant economic potential due to their ability to form hydrocarbon reservoirs or targets for future geothermal exploration. The scarcity of open-marine biostratigraphic marker fossils and the presence of numerous sedimentary gaps pose significant challenges for establishing reliable correlations with Oxfordian deposits globally. This study focuses on the Oxfordian Korallenoolith Formation, which is well exposed in the Bisperode section located ~40 km SW of Hannover. The ~126 m thick section was described bed-by-bed during fieldwork and complemented by 73 petrographic thin sections that were analysed for carbonate microfacies. Based on differences in grain and mud composition and primary sedimentary fabrics, an integrated log of the Bisperode quarry was constructed. Seven facies types (FTs) and 13 microfacies types (MFs) are characterised upon which a reef-bearing carbonate ramp model was built. Following the magnitude of the transgressive/regressive trends concept, three low-order sequences are recognised, which are composed of eight higher order sequences. The low-order sequences correlate well to the established sequence-stratigraphic model and the higher order sequences point to a possible control of their stacking pattern by Milankovitch long eccentricity cycles. This study is important because it helps to better understand the link between the stacking pattern of Oxfordian strata in the LSB and allocyclic processes. It thus provides a foundation for basinwide and inter-basin sequence-stratigraphic correlation, allowing future global chemostratigraphic comparisons and providing valuable insights into the synchronicity of geological events.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1084-1106"},"PeriodicalIF":2.0,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135550","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":"Insights into the genesis of thick halite in the Kuqa Depression (Tarim Basin, China): New mineralogical, lithological and geochemical evidence","authors":"Peng Qin,&nbsp;Dakang Zhong,&nbsp;Zhonggui Hu","doi":"10.1002/dep2.70019","DOIUrl":"https://doi.org/10.1002/dep2.70019","url":null,"abstract":"<p>The Palaeogene Kumugeliemu Group in the Kuqa Depression of the Tarim Basin of western China is characterised by a thick and massive sequence of evaporites, with a maximum thickness of up to 1000 m. The formation mechanism of such thick evaporite deposits remains unclear. In this study, sedimentological and geochemical research methods were employed to investigate the sedimentary characteristics and sources of halite. Sedimentary fabrics in halite, mudstone, sandstone, gypsum and carbonate indicate that halite was formed in a shallow water environment. Results of X-ray diffraction of halite and mudstone show that there is no tachyhydrite in halite and there is no pyrite in mudstone, which differs in the characteristics of deep-water salt and hydrothermal salt, respectively, indicating that halite was not formed in a deep-water environment. Rare earth elements indicate that sea water was the main source material for salt deposition. The colour of mudstone, Sr/Cu ratio and Rb/Sr ratio indicate that palaeoclimate was characterised by dry and hot conditions. The distribution characteristics of lithologic succession and the thickness of halite in Mbr 2 of the Kumugleiemu Group indicate that the halite was formed in restricted environments. According to above evidence, a ‘multistage marine transgression’ salt formation model was established, which suggests that, in a restricted paleogeographic environment, multiple transgressions brought sea water that, under dry and hot climate conditions, underwent repeated evaporation and concentration to form thick evaporite deposits.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1063-1083"},"PeriodicalIF":2.0,"publicationDate":"2025-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135551","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":"Contributions of arid climate and hydrothermal fluid flow on sedimentation in saline-alkaline lakes: Insight from the Ibar intramontane basin (Southern Serbia)","authors":"Nevena Andrić-Tomašević,&nbsp;Benjamin F. Walter,&nbsp;Vladimir Simić,&nbsp;Mohsin Raza,&nbsp;Dragana Životić,&nbsp;Željana Novković,&nbsp;Jochen Kolb,&nbsp;Axel Gerdes,&nbsp;Aratz Beranoaguirre","doi":"10.1002/dep2.70017","DOIUrl":"https://doi.org/10.1002/dep2.70017","url":null,"abstract":"<p>Saline-alkaline lakes are common in tectonically active, semi-arid regions, resulting from the interplay between tectonic, hydrothermal, surface processes and climate. This study investigates their contribution to the evolution of the saline-alkaline succession in the intramontane Ibar Basin (Southern Serbia). The succession is investigated using detailed sedimentological analysis, in situ U–Pb geochronology of carbonates acquired by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), major and trace element geochemistry and fluid inclusion analysis. Dominantly clastic sedimentation is represented by alluvial fan, flood plain, delta and marginal and profundal lake facies associations. Microbialite and littoral to sublittoral oil shales formed in the areas protected from clastic input. The stratigraphic succession shows a transition from alluvia to a hydrologically open and closed lacustrine environment. U–Pb geochronology of microbialite of a close lake phase (~17 Ma) suggests basin evolution during the Early to Middle Miocene age. The hydrologically closed lake phase is marked by borate-rich facies, which comprise mainly colemanite overgrown by secondary ulexite within profundal lake facies associations. The textural features suggest that colemanite initially precipitated at or below the sediment/water interface. The subsequent growth, as observed from the primary fluid inclusions in colemanite and calcite, indicates precipitation from the evolving bittern brine under evaporitic, redox conditions, which during diagenesis reached temperatures of 200–220°C. High Ca²⁺/Na⁺ ratios in the brine favour colemanite precipitation. Gradual Ca²⁺ depletion and clay breakdown (dewatering) lead to ulexite and borax precipitates. The results imply that B, Ca and Na were mobilised and transported into the basin by hydrothermal fluids that previously leached bedrock and/or by streams carrying products of the volcanic rocks' weathering. However, brine saturation and syndepositional precipitation were initiated by an arid climate through evaporation, while further growth was driven by reflux of fluids during diagenesis. This study highlights the importance of the tectonics of the collisional orogens and associated processes, arid climate and basin hydrological regime on the deposition of B, Ca-rich deposits in saline-alkaline lakes.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 4","pages":"1029-1062"},"PeriodicalIF":2.0,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135541","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":"Geochemical evaluation of black limestones in the Early Cretaceous platform carbonates of Gümüşhane (NE Turkey): An insight into petroleum source rock potential and palaeoenvironment conditions","authors":"Çiğdem Saydam Eker,&nbsp;Uğur Volkan Arı,&nbsp;Selçuk Alemdağ","doi":"10.1002/dep2.70012","DOIUrl":"https://doi.org/10.1002/dep2.70012","url":null,"abstract":"<p>This study assesses the organic matter (OM) content, kerogen type, maturity, depositional environment conditions and sedimentation model of Early Cretaceous (Berriasian–Aptian) black limestones in NE Turkey using geochemical analyses, including Rock-Eval/total organic carbon (TOC), gas chromatography–mass spectrometry, gas chromatography, major and trace elements and stable carbon isotope of OM measurements. The investigated black limestones' TOC, hydrogen index and potential yield values range from 0.07 to 2.91 wt%, 76 to 636 mg HC/g TOC and 0.15 to 11.17 mg HC/g rock, respectively. These results indicate that the examined limestones have variable source rock potential, ranging from low to high. <i>T</i>_max values, calculated saturated biomarkers and aromatic components suggest that the OM contained in the black limestones varies between thermally immature and mature, consistent with the potential index values. The OM found in the black limestone contained kerogen varying between type I and III. It is a composition of marine and terrigenous OM, as shown by the δ¹³C isotope values, biomarker components and <i>n</i>-alkane distributions and their parameters. This OM was deposited in a salinity water environment with marine–terrigenous (transitional) surroundings under oxic, suboxic to anoxic and arid–hot climate conditions. These findings provide critical insights for assessing the hydrocarbon potential of carbonate platforms in similar geological settings.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 3","pages":"917-953"},"PeriodicalIF":1.9,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144292788","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":"Shifting baselines of coral-reef species composition from the Late Pleistocene to the present in the Florida Keys","authors":"Lauren T. Toth,&nbsp;Anastasios Stathakopoulos,&nbsp;Scarlette Hsia,&nbsp;David Weinstein","doi":"10.1002/dep2.70009","DOIUrl":"https://doi.org/10.1002/dep2.70009","url":null,"abstract":"<p>The ongoing global-scale reassembly of modern coral reefs is unprecedented compared with the observed stability of most late Quaternary reef assemblages. One notable exception is the marine isotope stage (MIS) 5e (<i>ca</i> 130–116 thousand years ago [ka]) reefs in the Florida Keys, where the ubiquitous shallow-water coral, <i>Acropora palmata</i>, was near absent. Little is known, however, about reefs that grew during MIS5d–a (<i>ca</i> 116–74 ka), between MIS5e and the Holocene. It is therefore unclear whether Florida's unique MIS5e coral assemblages represent a geologically brief anomaly or a more persistent departure from the western Atlantic coral-reef archetype. We addressed that question by reconstructing the composition of MIS5d–a reefs within 29 coral-reef cores collected throughout the Florida Keys. We then compared the relative composition of corals during MIS5d–a to existing datasets from MIS5e, Holocene and modern (1996 and 2022) reefs to evaluate how far today's reef assemblages have diverged from geological baselines. We show that although the proportion of reef frameworks built by corals was remarkably consistent (<i>ca</i> 38%), species composition changed significantly through time. <i>Acropora palmata</i> was rare throughout MIS5, which we hypothesise was due to greater cold-temperature stress in Florida's subtropical reefs compared with the more climatically stable tropics. In contrast, the massive reef-building coral, <i>Orbicella</i> spp., was regionally dominant throughout the late Quaternary, but has become increasingly rare on modern reefs. By 2022, reefs in the Florida Keys were characterised by a truly novel coral assemblage dominated by <i>Porites astreoides</i> and <i>Siderastrea siderea</i>. In many ways, Florida's reefs defy the concept of a natural baseline; instead, their most persistent characteristic since the Late Pleistocene is their uniqueness. Yet, as reefs are increasingly subjected to unprecedented levels of environmental change, the exceptions to what was normal in the past could, paradoxically, provide the best geological analogues for the future.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 3","pages":"893-916"},"PeriodicalIF":1.9,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144292210","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":"Discovery of Late Holocene-aged Acropora palmata reefs in Dry Tortugas National Park, Florida, USA: The past as a key to the future?","authors":"Anastasios Stathakopoulos,&nbsp;Lauren T. Toth,&nbsp;Alexander B. Modys,&nbsp;Selena A. Johnson,&nbsp;Ilsa B. Kuffner","doi":"10.1002/dep2.70005","DOIUrl":"https://doi.org/10.1002/dep2.70005","url":null,"abstract":"<p>Emblematic of global coral-reef ecosystem decline, the coral ecosystem-engineer <i>Acropora palmata</i> is now rare throughout much of the western Atlantic. Understanding when and where this foundation species occurred during the past can provide information about the environmental limits defining its distribution through space and time. In this paper, the present, historical and newly dated geological records of <i>A. palmata</i> are compared to reveal novel insights into the environmental constraints on its occurrence in Dry Tortugas National Park, a subtropical reef system at the south-western terminus of the Florida reef tract. Although past geological investigation found little evidence of the species in the park, a single, moderately sized <i>A. palmata</i> reef existed throughout historical times (1881 Common Era [CE] to present day; ‘historical population’, termed herein). Over the last 140 years, repeated population declines occurred with little to no recovery, culminating in the extirpation of <i>A. palmata</i> from the area during the 2023–2024 CE global coral bleaching event. Reported here for the first time is a significant record of Late Holocene <i>A. palmata</i> populations that existed from <i>ca</i> 4500 to 375 years before present (‘Late Holocene population,’ termed herein) in three broadly distributed areas of the shallow Dry Tortugas platform. This discovery challenges previous assumptions regarding the species' limited contribution to reef development in the area by providing data that extend the known spatial and stratigraphic extent of Holocene populations in this location. It is posited that, although the Late Holocene climate largely suppressed regional reef development, the new records provide evidence for centennial-scale periods of more favourable and stable climate that allowed for short-term expansions of <i>A. palmata</i> populations in the Dry Tortugas. In conclusion, the species' prospects for future success in this and other subtropical locations is discussed given the observed global trends of increasing sea-surface temperatures.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":"11 3","pages":"808-828"},"PeriodicalIF":1.9,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.70005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144292646","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}