IF 1.6 4区地球科学

Palaios Pub Date : 2023-12-20 DOI: 10.2110/palo.2023.002

Vincent Caron, Brice Deschamps, Alexandre ROBERT-DUARTE, J. Bailleul

{"title":"NEW QUANTITATIVE DESCRIPTORS (SHAPE AND MACROBORING) OF BIOGENIC NODULES: EXAMPLES FROM THE LESSER ANTILLES AND NEW ZEALAND","authors":"Vincent Caron, Brice Deschamps, Alexandre ROBERT-DUARTE, J. Bailleul","doi":"10.2110/palo.2023.002","DOIUrl":"https://doi.org/10.2110/palo.2023.002","url":null,"abstract":"Encrusting (Ei), Macroboring (Mi), and Dissymmetry (Di) indices are proposed as quantitative descriptors of biogenic nodules. (Ei) measures the amount of encrustation, (Mi) the contribution of boring traces affecting the internal structure of nodules, and (Di) the regularity of the biogenic accretion around the nucleus. The latter has been used to construct a classification scheme of possible shapes for encrustations. Raw data to calculate the indices were obtained from numerical treatments of digitized photographs of nodule cross-sections. The morphometric (Di) and taphonomic (Ei and Mi) indices have been calculated for carbonate nodules from subtidal temperate and tropical settings in New Zealand (Flat Point Beach) and in the Caribbean (St. Bartholomew Island), respectively. Results for nucleated rhodoliths collected from shallow high-energy settings in these two climatic settings show that their morphometric and taphonomic characters are not species-specific (Lithoporella/Mastophora rhodoliths from St. Barth, and Lithothamnion-Sporolithon rhodoliths from New Zealand), but depend instead on hydrodynamic conditions and on the original shape of nuclei. Acervulinid macroids sampled in deeper waters (28 m) off St. Barth are nucleus-free and have a Macroboring index (Mi) significantly higher than that of rhodoliths from shallower environments, due to discontinuous influence of waves and currents, and low sedimentation rates. The quantitative descriptors proposed here might: (1) complement the characterization of biogenic nodules in specific depositional environments; (2) aid in hydrodynamic and paleoenvironmental reconstructions of biogenic nodule-bearing deposits; and (3) constitute valuable tools in future comparative studies.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139169327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

LOCOMOTION TRACES EMPLACED BY MODERN STALKLESS COMATULID CRINOIDS (FEATHERSTARS) 现代无柄缨壳类动物（羽龙）留下的运动痕迹

IF 1.6 4区地球科学

Palaios Pub Date : 2023-11-29 DOI: 10.2110/palo.2022.007

Reed A. Myers, C. Furlong, M. Gingras, J. Zonneveld

{"title":"LOCOMOTION TRACES EMPLACED BY MODERN STALKLESS COMATULID CRINOIDS (FEATHERSTARS)","authors":"Reed A. Myers, C. Furlong, M. Gingras, J. Zonneveld","doi":"10.2110/palo.2022.007","DOIUrl":"https://doi.org/10.2110/palo.2022.007","url":null,"abstract":"Modern crinoids have the ability to use their arms to crawl along the sea floor and some are capable of swimming short distances. The first and only evidence of crinoid locomotion reported from the rock record was described from the Middle Jurassic of the Cabeço da Ladeira Lagerstätte (Portugal) resulting in description of the ichnotaxon Krinodromos bentou. Although the mechanics of crinoid movement are well documented the morphological ranges of crinoid motility tracks are unknown. This study uses observations of crinoid movement and their effects on sediment using modern comatulid crinoids to propose possible trace fossil morphologies. Using 20 experimental trials supported by photography, video analyses, 3D orthogrammetry and resin casting, the morphological ranges of crinoid motility tracks are included in five distinct morphologies attributed to ambling, crawling, walking, running, and landing/taking-off traces, the latter of which are emplaced before and after swimming. Traces produced by ambling occur as epigenic hook-shaped grooves. Crawling traces comprise closely spaced hook-shaped grooves and ridges preserved in concave and convex epirelief. Walking traces consist of semi-bilaterally symmetrical collections of three or more grooves, and associated ridges, preserved in convex and concave epirelief. Running traces consist of semi-bilaterally symmetrical collections of one to three straight to semi-sinusoidal grooves and associated ridges preserved in concave and convex epirelief. Landing/taking-off traces are mounded features preserved in convex epirelief, with grooves radiating from the center. The five trace types described in this paper provide insight into morphological features that can be associated with modern crinoid activities and used to identify crinoid trace fossils, which are rarely reported, in the rock record.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139214373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A FOSSIL FOREST FROM ITALY REVEALS THAT WETLAND CONIFERS THRIVED IN EARLY PERMIAN PERI-TETHYAN PANGEA 意大利的森林化石揭示了二叠纪早期的近特提斯泛大陆湿地针叶树的繁盛

4区地球科学

Palaios Pub Date : 2023-10-30 DOI: 10.2110/palo.2023.015

STEFFEN TRÜMPER, RONNY RÖßLER, CORRADO MORELLI, KARL KRAINER, SARA KARBACHER, BJÖRN VOGEL, MATTEO ANTONELLI, ENRICO SACCO, EVELYN KUSTATSCHER

{"title":"A FOSSIL FOREST FROM ITALY REVEALS THAT WETLAND CONIFERS THRIVED IN EARLY PERMIAN PERI-TETHYAN PANGEA","authors":"STEFFEN TRÜMPER, RONNY RÖßLER, CORRADO MORELLI, KARL KRAINER, SARA KARBACHER, BJÖRN VOGEL, MATTEO ANTONELLI, ENRICO SACCO, EVELYN KUSTATSCHER","doi":"10.2110/palo.2023.015","DOIUrl":"https://doi.org/10.2110/palo.2023.015","url":null,"abstract":"Abstract In-situ fossil forests are valuable biogenic archives for the structure and setting of paleocommunities and the ecology of their organisms. Here, we present the first trees preserved in growth position in their embedding strata from the Kungurian (lower Permian) Athesian Volcanic Group, Northern Italy—one of the most extensive volcanic successions of post-Variscan Euramerica. We reconstruct the structure, rise and demise, and paleoecology of the forest based on high-resolution documentation of facies architectures and petrography, and the paleontological and taphonomic characters of the fossil content. Generally, the fossiliferous strata record a volcanotectonically controlled base-level rise in a limnic, possibly endorheic wetland basin from a low-relief volcanic landscape. The forest, preserved as calcified stem bases with roots, grew during a short interval of lake-level stasis on a small deltaic sheetflood fan. The forest comprised trees less than 5 m tall with tabular root systems adapted to the waterlogged substrate, and was buried and destroyed by mass flows following rapid submergence. These mass-flow deposits yield parautochthonous woody debris providing anatomical evidence of conifers as the major arborescent plants of the fossil forest. Our results not only elucidate the root architecture of Paleozoic conifers, but also document the ecomorphological plasticity of these plants and substantiate the presence of coniferopsids in wetlands around the Carboniferous/Permian boundary. Further, the evidence of lake perenniality in the studied succession is among the youngest known from the Permian of Europe, pointing to the highly differentiated late-icehouse impacts on continental environments in the Euramerican tropics.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136067457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

PLANT COMMUNITY CHANGE ACROSS THE PALEOCENE–EOCENE BOUNDARY IN THE GULF COASTAL PLAIN, CENTRAL TEXAS 德克萨斯州中部海湾沿岸平原古新世-始新世边界植物群落变化

4区地球科学

Palaios Pub Date : 2023-10-30 DOI: 10.2110/palo.2022.008

JENNIFER D. WAGNER, DANIEL J. PEPPE, JENNIFER M. K. O’KEEFE, CHRISTOPHER N. DENISON

{"title":"PLANT COMMUNITY CHANGE ACROSS THE PALEOCENE–EOCENE BOUNDARY IN THE GULF COASTAL PLAIN, CENTRAL TEXAS","authors":"JENNIFER D. WAGNER, DANIEL J. PEPPE, JENNIFER M. K. O’KEEFE, CHRISTOPHER N. DENISON","doi":"10.2110/palo.2022.008","DOIUrl":"https://doi.org/10.2110/palo.2022.008","url":null,"abstract":"Abstract Long-term global warming during the early Paleogene was punctuated by several short-term ‘hyperthermal’ events, the most pronounced being the Paleocene–Eocene Thermal Maximum (PETM). During this long-term warming, tropical climates expanded into extra-tropical areas, creating a widespread band of thermophilic flora that reached into the paratropics, possibly as far north as mid-latitude North America in some regions. Relatively little is known about these paratropical floras, despite distribution across the North American Gulf Coastal Plain. We assess floras from the Gulf Coastal Plain in Central Texas before and after the Paleocene–Eocene boundary to define plant ecosystem changes associated with rapid global warming in this region. After the Paleocene–Eocene boundary, these floras suggest uniform plant communities across the Gulf Coastal Plain, but with high turnover rate and changes in community composition. Paleoecology and paleoclimate assessments from Central Texas Paleocene and Eocene floras suggest a warm and wet environment, indicative of tropical seasonal forest to tropical rainforest biomes. Fossil evidence from the Gulf Coastal Plain combined with the Bighorn Basin, Wyoming data suggest that early Paleogene warming helped create a paratropical belt that extended into mid-latitudes. Evaluating the response of fossil plant communities to rapid global warming has important implications for understanding and preparing for current global warming and climate change.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136102355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

TAPHONOMY OF TINY TETRAPOD TRACKS IN AN EXAMPLE FROM THE LOWER PERMIAN (CISURALIAN) SŁUPIEC FORMATION (SW POLAND) 下二叠纪(顺苏拉)sŁupiec组(波兰西南部)一个例子中微小四足动物足迹的分类

4区地球科学

Palaios Pub Date : 2023-10-30 DOI: 10.2110/palo.2022.015

GRZEGORZ SADLOK

{"title":"TAPHONOMY OF TINY TETRAPOD TRACKS IN AN EXAMPLE FROM THE LOWER PERMIAN (CISURALIAN) SŁUPIEC FORMATION (SW POLAND)","authors":"GRZEGORZ SADLOK","doi":"10.2110/palo.2022.015","DOIUrl":"https://doi.org/10.2110/palo.2022.015","url":null,"abstract":"Abstract The continental Lower Permian Słupiec Formation (the Sudetes Mountains, southwestern Poland) is well known for the occurrence of fossilized tracks of Early Permian tetrapods. Previous reports have focused on the taxonomy of tracks and their producers. The track assemblage was apparently missing the footprints of amphibians and thus such tetrapods were thought to be truly absent in the Słupiec Early Permian paleohabitat. The present paper utilizes the results of experiments and field surveys in order to test a possibility that tracks of tiny tetrapods (e.g., with body mass &lt; 9 g), including amphibians, could be missing due to taphonomic filtration. The experimental tests were performed to investigate the following: (1) the interplay between the sizes of the penetrator (representation of trackmaker’s pes and manus) and the particles within the substrate, with emphasis on how the size interplay affects the lamina-modification mechanism, e.g., lamina-piercing by sand versus lamina compaction/displacement by sand or clay; (2) undertrack production in laminated sandy substrates by tiny tetrapods; and (3) the taphonomic impact that biofilm may have on the occurrence of tiny tetrapod tracks in clay. The results of experimental tests and the field survey suggest that tiny tetrapod tracks (e.g., amphibians) may be underrepresented in the Słupiec Formation track assemblage due to negative taphonomic filtration.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136068456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

HELMINTHOPSIS AND CYLINDRICHNUS ICHNOGUILDS FROM MIOCENE THIN-BEDDED TURBIDITES, TIERRA DEL FUEGO, ARGENTINA 阿根廷火地岛中新世薄层浊积岩中的线虫和圆柱线虫

4区地球科学

Palaios Pub Date : 2023-09-30 DOI: 10.2110/palo.2022.058

E.B. OLIVERO, M.I. LÓPEZ CABRERA

{"title":"<i>HELMINTHOPSIS</i> AND <i>CYLINDRICHNUS</i> ICHNOGUILDS FROM MIOCENE THIN-BEDDED TURBIDITES, TIERRA DEL FUEGO, ARGENTINA","authors":"E.B. OLIVERO, M.I. LÓPEZ CABRERA","doi":"10.2110/palo.2022.058","DOIUrl":"https://doi.org/10.2110/palo.2022.058","url":null,"abstract":"Abstract Miocene thin-bedded turbidites from Tierra del Fuego record scarce graphoglyptids and two unusual ichnoguilds composed of diminutive elite trace fossils. The first, a monoichnospecific Cylindrichnus ichnoguild, consists of crowded, post-depositional burrows formed in surface sediments during the final phase of turbidite deposition. The second, a pre-depositional Helminthopsis ichnoguild, consists of dense aggregates of simple trails, mainly Helminthopsis and Helminthoidichnites, occupying a very shallow tier in organic-rich mud covering the sea floor prior to turbidite deposition. The trace makers of Cylindrichnus were opportunistic suspension/detritus feeding organisms, probably polychaetes, which bloomed during high flux of labile organic matter brought to internal and external levees by turbidity currents. The trace makers of Helminthopsis and Helminthoidichnites were probably nematodes that grazed on organic-rich muddy sediments with abundant disseminated pyrite associated with Kinneyia-like and other problematic wrinkle structures, suggesting sulfur-cycling chemosynthetic microbial communities originated during interturbidite phases. The rhythmical alternation of the Cylindrichnus and Helminthopsis ichnoguilds clearly differentiate the thin-bedded turbidites of the Viamonte Formation from channel-levee complexes elsewhere, stressing the point that ichnoassemblages reflect sets of environmental parameters and not necessarily particular depositional settings.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135038393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

FRESHWATER STROMATOLITES FROM AN EARLY PERMIAN WETLAND (MANEBACH, THURINGIAN-FOREST BASIN, GERMANY): STRUCTURE, DEVELOPMENT, AND PALEOENVIRONMENTAL CONTEXT 德国图林根森林盆地manebach早二叠纪湿地淡水叠层石:结构、发育和古环境背景

4区地球科学

Palaios Pub Date : 2023-09-30 DOI: 10.2110/palo.2022.049

ALEXANDRA HELLWIG, STEFFEN TRÜMPER, RONNY RÖßLER, MICHAEL KRINGS

{"title":"FRESHWATER STROMATOLITES FROM AN EARLY PERMIAN WETLAND (MANEBACH, THURINGIAN-FOREST BASIN, GERMANY): STRUCTURE, DEVELOPMENT, AND PALEOENVIRONMENTAL CONTEXT","authors":"ALEXANDRA HELLWIG, STEFFEN TRÜMPER, RONNY RÖßLER, MICHAEL KRINGS","doi":"10.2110/palo.2022.049","DOIUrl":"https://doi.org/10.2110/palo.2022.049","url":null,"abstract":"Abstract Fossil stromatolites enclosing structurally preserved land plant remains have rarely been documented and studied in detail. Permineralized woody Tylodendron sp. conifer axes (slender stems, branches) from a lacustrine sedimentary sequence in the lower Permian fossil Lagerstätte of Manebach (Thuringian-Forest Basin, central Germany) are frequently surrounded by stromatolites that consist of successive, usually asymmetrical microbial layers. The stromatolites show various growth forms ranging from laminar to palisadic. They developed in stagnant water from microbial overgrowth dominated by slender, unbranched sessile cyanobacterial filaments aligned vertically into tufts or turf-like stands. Interspersed among the filaments were other filamentous and coccoid microorganisms. Preservation of the Tylodendron axes can be exquisite and sometimes even includes extraxylary tissues containing remains of fungi, suggesting that stromatolite formation began soon after the axes had entered the water and were perhaps even conducive to their preservation. Structurally similar fossil microbialitic structures from elsewhere likewise demonstrate that they were effective in preserving plant morphology. The Manebach stromatolites and the plant remains they contain contribute to a more accurate understanding of the complex biological processes in late Paleozoic lake ecosystems.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135038396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

THE ROLE OF DRILLING PREDATION IN ISOLATED, NUTRIENT-POOR ECOSYSTEMS: FIRST INSIGHTS FROM RAPA NUI, POLYNESIA 在孤立的、营养贫乏的生态系统中钻食的作用:来自波利尼西亚拉帕努伊岛的第一次见解

IF 1.6 4区地球科学

Palaios Pub Date : 2023-08-31 DOI: 10.2110/palo.2022.044

J. Martinelli, Sandra Gordillo, M. Carla, DE Aranzamendi, Marcelo M. Rivadeneira

{"title":"THE ROLE OF DRILLING PREDATION IN ISOLATED, NUTRIENT-POOR ECOSYSTEMS: FIRST INSIGHTS FROM RAPA NUI, POLYNESIA","authors":"J. Martinelli, Sandra Gordillo, M. Carla, DE Aranzamendi, Marcelo M. Rivadeneira","doi":"10.2110/palo.2022.044","DOIUrl":"https://doi.org/10.2110/palo.2022.044","url":null,"abstract":"Abstract: As a biotic interaction, drilling predation is affected by the evolutionary histories of the predator and prey, as well as the environment. A unique location with distinctive evolutionary histories and environmental conditions is the remote island of Rapa Nui. For mollusks, an evolutionary history in relative isolation has led to high rates of endemism (35–40%), in an area that has some of the most nutrient-poor waters of the global ocean. Here, we use death assemblages collected in Rapa Nui to answer two main questions: (1) How does a pervasive interaction like drilling predation play out in an isolated, oligotrophic marine system? and (2) What role do the environment (exposed vs. sheltered sites) and species traits (feeding, mobility, life habit) play in ‘protecting’ the prey? We predicted that predation would be low relative to other tropical and subtropical islands given the oligotrophic conditions and found that the average drilling frequency (DF) was 5.67% (n = 6122). We observed no significant differences in DF between feeding guilds, mobility types, or life habits. Sheltered sites dominated by the infaunal bivalve Ctena bella had higher predation. In terms of passive defenses for C. bella, larger body size was not an effective defense against drilling predators. We show that drilling predation in Rapa Nui is lower than in high-latitude regions, and it is dependent on how sheltered or exposed sites are. Historically and currently, Rapa Nui has been subject to multiple anthropogenic stressors, including over-extraction and tourism, making efforts to understand its endemic species and their interactions fundamental.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46450775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

NOT ENTIRELY ICHTHYOSAUR: A MYSTERIOUS LAMNIFORM AND ICHTHYOPTERYGIAN-FALL ASSOCIATION FROM THE ABYSSAL UPPER CRETACEOUS OF THE NORTHERN APENNINES (ITALY) 不完全是鱼龙:来自亚平宁北部(意大利)上白垩纪深海的一种神秘的板形和鱼翼龙-瀑布组合

IF 1.6 4区地球科学

Palaios Pub Date : 2023-08-31 DOI: 10.2110/palo.2022.054

Giovanni Serafini, J. Amalfitano, Silvia Danise, E. Maxwell, Riccardo Rondelli, C. A. Papazzoni

{"title":"NOT ENTIRELY ICHTHYOSAUR: A MYSTERIOUS LAMNIFORM AND ICHTHYOPTERYGIAN-FALL ASSOCIATION FROM THE ABYSSAL UPPER CRETACEOUS OF THE NORTHERN APENNINES (ITALY)","authors":"Giovanni Serafini, J. Amalfitano, Silvia Danise, E. Maxwell, Riccardo Rondelli, C. A. Papazzoni","doi":"10.2110/palo.2022.054","DOIUrl":"https://doi.org/10.2110/palo.2022.054","url":null,"abstract":"Abstract: Axial remains of a large ichthyosaur and a medium-sized anacoracid shark from the deep-water sediments of the Cenomanian of the Northern Apennines (Northern Italy) are described in detail. The specimens were found closely associated (less than 0.3 m apart), and offer an invaluable window into the taphonomy and dead-fall stages of pelagic vertebrates in a Mesozoic abyssal plain. The anacoracid shark remains, initially misinterpreted as an ichthyosaur, consist of eight articulated vertebrae embedded in a block of dark arenaceous matrix, and represent the first occurrence of an articulated shark from the Northern Apennines. The ichthyosaur remains consist of seven discoidal vertebrae and several unidentified fragments. Due to the absence of diagnostic skeletal elements, both specimens are assigned only at higher taxonomic levels. The two fossils, which come from the same outcrop and possibly from the same stratigraphic horizon, share a common taphonomic history, in terms of both their preservation and diagenesis. Mineralogy of the matrices of both is dominated by manganese micro-nodules, consistent with the deposition of polymetallic nodules in bathyal-abyssal settings. Biostratinomic processes that impacted the two specimens also provide insight on the development of Mesozoic marine vertebrate-falls in the deep-sea. Localized pyrite framboids inside the bone spongiosa are possible evidence of the sulfophilic stage (microbially mediated sulfur mobilization during lipid decay) in the ichthyosaur fall. Burrows assigned to Taenidium on the surface of the shark block, interpreted as worm-like feeding burrows or arthropod locomotion and feeding trails, might represent evidence of the enrichment opportunistic stage. Although intriguing, we have no evidence to support the hypothesis that this peculiar association of two pelagic predators is due to ecological interaction between the two animals.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67708918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

MILLENIAL-SCALE TIME AVERAGING INFERRED BY DISCOLORED SHELLS IN BEACH DEATH ASSEMBLAGES 由海滩死亡组合中的变色贝壳推断的千年尺度的时间平均

IF 1.6 4区地球科学

Palaios Pub Date : 2023-07-31 DOI: 10.2110/palo.2022.043

S. Martínez, A. Rojas

{"title":"MILLENIAL-SCALE TIME AVERAGING INFERRED BY DISCOLORED SHELLS IN BEACH DEATH ASSEMBLAGES","authors":"S. Martínez, A. Rojas","doi":"10.2110/palo.2022.043","DOIUrl":"https://doi.org/10.2110/palo.2022.043","url":null,"abstract":"Abstract: Molluscan death assemblages occurring on present-day beaches frequently consist of secondary-colored shells, with yellow to brown and gray to black colors. It is hypothesized that this secondary coloration can be related to postmortem age and to conditions in the taphonomically active zone, altering shells to black and gray tones in reducing conditions, and then becoming yellowish or brownish in oxidizing settings. In this study, we assessed whether the variability in the degree of shell discoloration of two species of the infaunal bivalve Mactra collected in beach death assemblages from a temperate siliciclastic beach in Uruguay is a function of postmortem age, and whether this variability in discoloration can be linked to differences in their elemental composition, microstructure, and provenance. Although we did not detect any differences in mineralogy or elemental composition among shells differing in discoloration, we show that modern (younger than a century) beach shells are not secondary-colored, but have remained white, but some white shells are also old (millennial). In contrast, yellow and gray shells are consistently older than 1,000 years, indicating that this degree of discoloration requires millennial residence times in the taphonomically active zone and suggesting that discoloration can be used as an indicator of time averaging. Discolored shells are derived from subtidal death assemblages.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43076553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

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