Karmen Fio Firi, Katarina Gobo, J. Sremac, Frane Marković
Abstract: The Lower Triassic of the Muć-Ogorje area in Central Dalmatia (southern Croatia) is characterized by clastic and carbonate deposits which are investigated through a 230 m thick succession. The fossil associations identified point to a Dienerian age for the lower, and a Spathian age for the upper part of the studied profile, while trace fossils suggest deposits of Smithian age in the middle part, enabling comparisons with other successions in the region. Changes in sedimentology and associated biota throughout the succession, and environmental conditions are reconstructed for seven facies associations, the distribution of which suggests multiple oscillations in relative sea level. Sedimentary structures point to the influence of high environmental energy, possible storms, with signs of tectonic influence in the studied area. The study deposits lack ooid limestone intervals, which are well represented in other Lower Triassic sections in Croatia, Slovenia, Italy, and Hungary. Moreover, the study section exhibits changes in biota abundance, presence of organic-rich laminae and pyrite, as well as changes in siliciclastic input and transgressive-regressive cycles, especially within the upper, Olenekian, part of the succession studied. The results confirm that environmental stress was persistent throughout the Early Triassic, and contribute to our better understanding of the aftermath of the end Permian extinction and the environmental conditions of the western Tethys epicontinental shelf area.
{"title":"CHANGES IN ENVIRONMENTAL CONDITIONS, BIOTA, AND DEPOSITIONAL PATTERNS WITHIN LOWER TRIASSIC CLASTIC AND CARBONATE DEPOSITS, MUĆ-OGORJE, CENTRAL DALMATIA (CROATIA)","authors":"Karmen Fio Firi, Katarina Gobo, J. Sremac, Frane Marković","doi":"10.2110/palo.2020.082","DOIUrl":"https://doi.org/10.2110/palo.2020.082","url":null,"abstract":"Abstract: The Lower Triassic of the Muć-Ogorje area in Central Dalmatia (southern Croatia) is characterized by clastic and carbonate deposits which are investigated through a 230 m thick succession. The fossil associations identified point to a Dienerian age for the lower, and a Spathian age for the upper part of the studied profile, while trace fossils suggest deposits of Smithian age in the middle part, enabling comparisons with other successions in the region. Changes in sedimentology and associated biota throughout the succession, and environmental conditions are reconstructed for seven facies associations, the distribution of which suggests multiple oscillations in relative sea level. Sedimentary structures point to the influence of high environmental energy, possible storms, with signs of tectonic influence in the studied area. The study deposits lack ooid limestone intervals, which are well represented in other Lower Triassic sections in Croatia, Slovenia, Italy, and Hungary. Moreover, the study section exhibits changes in biota abundance, presence of organic-rich laminae and pyrite, as well as changes in siliciclastic input and transgressive-regressive cycles, especially within the upper, Olenekian, part of the succession studied. The results confirm that environmental stress was persistent throughout the Early Triassic, and contribute to our better understanding of the aftermath of the end Permian extinction and the environmental conditions of the western Tethys epicontinental shelf area.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"16 - 33"},"PeriodicalIF":1.6,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43529378","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}
Abstract: The fossiliferous, argillaceous dolostone of the latest Middle Devonian (Givetian) Milwaukee Formation contains abundant disarticulated fish skeletal elements. This study refines depositional environment reconstruction of the Milwaukee Formation through taphonomic analysis of this fish assemblage. Robust skeletal elements of placoderm grinding teeth, fin spines, and armored plating dominate the assemblage. Specimens display variation in taphonomic attributes including color, luster, corrasion (chemical corrosion and/or physical abrasion), presence of pyrite and phosphate permineralization, and epibionts. Rare occurrences of teeth belonging to osteichthyan fish are also taphonomically variable. Associated invertebrates are diverse and include abundant cephalopod internal molds and pyritized brachiopods often randomly oriented in shell hashes. In sum, these observations suggest deposition on a marine shelf between normal and storm wave base. During low-energy background periods, fish plates exposed on the seafloor would undergo initial disarticulation, epibiont attachment, and color- and luster-altering corrasion and phosphatization. Buried skeletal elements were ‘protected’ from epibiont attachment and corrasion, but occasional low oxygen conditions in the substrate led to early diagenetic pyrite permineralization. Periodic high-energy storm events were responsible for complete disarticulation as well as reworking and reexposure of buried skeletal elements (and burial of others), resulting in a time-averaged assemblage with a wide range of taphonomic attributes. Robust placoderm skeletal elements were best suited to survive fossilization in this setting and therefore the placoderm-dominated fossil assemblage appears to be an artifact of taphonomic processes and energy of the depositional environment.
{"title":"INSIGHTS FROM FOSSIL FISH TAPHONOMY INTO THE DEPOSITIONAL ENVIRONMENT OF THE LOWER MILWAUKEE FORMATION (BERTHELET MEMBER, LATEST MIDDLE DEVONIAN)","authors":"Andrew J. Rich, James J. Zambito","doi":"10.2110/palo.2021.040","DOIUrl":"https://doi.org/10.2110/palo.2021.040","url":null,"abstract":"Abstract: The fossiliferous, argillaceous dolostone of the latest Middle Devonian (Givetian) Milwaukee Formation contains abundant disarticulated fish skeletal elements. This study refines depositional environment reconstruction of the Milwaukee Formation through taphonomic analysis of this fish assemblage. Robust skeletal elements of placoderm grinding teeth, fin spines, and armored plating dominate the assemblage. Specimens display variation in taphonomic attributes including color, luster, corrasion (chemical corrosion and/or physical abrasion), presence of pyrite and phosphate permineralization, and epibionts. Rare occurrences of teeth belonging to osteichthyan fish are also taphonomically variable. Associated invertebrates are diverse and include abundant cephalopod internal molds and pyritized brachiopods often randomly oriented in shell hashes. In sum, these observations suggest deposition on a marine shelf between normal and storm wave base. During low-energy background periods, fish plates exposed on the seafloor would undergo initial disarticulation, epibiont attachment, and color- and luster-altering corrasion and phosphatization. Buried skeletal elements were ‘protected’ from epibiont attachment and corrasion, but occasional low oxygen conditions in the substrate led to early diagenetic pyrite permineralization. Periodic high-energy storm events were responsible for complete disarticulation as well as reworking and reexposure of buried skeletal elements (and burial of others), resulting in a time-averaged assemblage with a wide range of taphonomic attributes. Robust placoderm skeletal elements were best suited to survive fossilization in this setting and therefore the placoderm-dominated fossil assemblage appears to be an artifact of taphonomic processes and energy of the depositional environment.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"1 - 15"},"PeriodicalIF":1.6,"publicationDate":"2022-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45581591","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}
Abstract: The Pennsylvanian–Permian Maroon Formation of northwest Colorado is an up to 4,600 m thick succession of mainly siliciclastic continental red-beds deposited in equatorial intermontane basins of the Ancestral Rocky Mountains. Sedimentary surfaces of fluvio-lacustrine to eolian siltstones and fine-grained sandstones from various stratigraphic levels within the Maroon Formation preserve cm-sized straight to gently curved sediment-filled acicular structures referred to five morphological groups: single, branched, stellate, rosette, and bunched. Depositional environment, shape, and size of the structures are most similar to ice crystal marks that result from freezing of water-saturated fine-grained substrate at the sediment-air interface. They differ from other syngenetically produced crystals and crystal pseudomorphs in sedimentary rocks mainly by crystal shape and environmental conditions. The potential ice crystal marks of the Maroon Formation are notable for the fidelity and morphological diversity of the crystal casts and could be a key for the understanding of similar but hitherto often only called enigmatic structures of the sedimentary rock record. The ice crystal mark occurrences in the Maroon Formation suggest that night frost affected lower elevation equatorial areas during the climax of the Late Paleozoic Ice Age and may stimulate research on evolutionary adaptations of early terrestrial biota to overcome significant air temperature fluctuations.
{"title":"POTENTIAL ICE CRYSTAL MARKS FROM PENNSYLVANIAN–PERMIAN EQUATORIAL RED-BEDS OF NORTHWEST COLORADO, U.S.A.","authors":"S. Voigt, K. Oliver, B. Small","doi":"10.2110/palo.2021.024","DOIUrl":"https://doi.org/10.2110/palo.2021.024","url":null,"abstract":"Abstract: The Pennsylvanian–Permian Maroon Formation of northwest Colorado is an up to 4,600 m thick succession of mainly siliciclastic continental red-beds deposited in equatorial intermontane basins of the Ancestral Rocky Mountains. Sedimentary surfaces of fluvio-lacustrine to eolian siltstones and fine-grained sandstones from various stratigraphic levels within the Maroon Formation preserve cm-sized straight to gently curved sediment-filled acicular structures referred to five morphological groups: single, branched, stellate, rosette, and bunched. Depositional environment, shape, and size of the structures are most similar to ice crystal marks that result from freezing of water-saturated fine-grained substrate at the sediment-air interface. They differ from other syngenetically produced crystals and crystal pseudomorphs in sedimentary rocks mainly by crystal shape and environmental conditions. The potential ice crystal marks of the Maroon Formation are notable for the fidelity and morphological diversity of the crystal casts and could be a key for the understanding of similar but hitherto often only called enigmatic structures of the sedimentary rock record. The ice crystal mark occurrences in the Maroon Formation suggest that night frost affected lower elevation equatorial areas during the climax of the Late Paleozoic Ice Age and may stimulate research on evolutionary adaptations of early terrestrial biota to overcome significant air temperature fluctuations.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"377 - 392"},"PeriodicalIF":1.6,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45050109","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}
Marcos Antonio Batista dos Santos Filho, G. Fauth, B. Sames, E. Wolfgring, Jorge Villegas‐Martín
Abstract: This paper presents the results of a paleoenvironmental study of two Hauterivian–Aptian adjacent sections (Transnordestina A/B) of the Iguatu Basin using ostracods and aided by X-ray fluorescence (XRF), total organic carbon (TOC), total sulfur (S), and spectral analyses. Cluster analysis divided the 10 genera found into two main groups: one composed of Alicenula-Pattersoncypris?-Brasacypris-Hastacypris-Ilyocypris?, and the second composed of Cypridea-Looneyellopsis-Rhinocypris?. The first group is interpreted as representing paleoenvironments with permanent waterbodies, such as lakes, and the second as being indicative of ephemeral settings, such as temporary pools in an inundation plain. XRF analysis using the positive peaks of Ca/Ti and Ca/RTi, Fe, Al ratios show a few dry periods, particularly in the lower and middle part of Transnordestina A, between 0 to 175 m and 385 to 475 m, which also display a small number of ostracods. Total S shows several high peaks which might be indicative of gypsum deposition during droughts. Spectral analysis of molar Ti/Al ratio shows two intervals with different sedimentation rates, between 0 and 233 m, and 233 to 836 m. For the first interval, six 100 ka eccentricity cycles were identified; the low number of ostracods for the interval and highly variable Ca/Ti and Ca/RTi, Fe, Al values indicate a different sedimentation rate in a drier environment. For the second interval, ten 405 ka cycles were identified; its higher ostracod count and more stable Ca/Ti and Ca/RTi, Fe, Al values could be indicative of increasing humidity.
{"title":"PALEOENVIRONMENTAL ANALYSIS OF A LOWER CRETACEOUS PALEOLAKE FROM THE IGUATU BASIN BASED ON ITS OSTRACOD FAUNA AND XRF DATA","authors":"Marcos Antonio Batista dos Santos Filho, G. Fauth, B. Sames, E. Wolfgring, Jorge Villegas‐Martín","doi":"10.2110/palo.2021.006","DOIUrl":"https://doi.org/10.2110/palo.2021.006","url":null,"abstract":"Abstract: This paper presents the results of a paleoenvironmental study of two Hauterivian–Aptian adjacent sections (Transnordestina A/B) of the Iguatu Basin using ostracods and aided by X-ray fluorescence (XRF), total organic carbon (TOC), total sulfur (S), and spectral analyses. Cluster analysis divided the 10 genera found into two main groups: one composed of Alicenula-Pattersoncypris?-Brasacypris-Hastacypris-Ilyocypris?, and the second composed of Cypridea-Looneyellopsis-Rhinocypris?. The first group is interpreted as representing paleoenvironments with permanent waterbodies, such as lakes, and the second as being indicative of ephemeral settings, such as temporary pools in an inundation plain. XRF analysis using the positive peaks of Ca/Ti and Ca/RTi, Fe, Al ratios show a few dry periods, particularly in the lower and middle part of Transnordestina A, between 0 to 175 m and 385 to 475 m, which also display a small number of ostracods. Total S shows several high peaks which might be indicative of gypsum deposition during droughts. Spectral analysis of molar Ti/Al ratio shows two intervals with different sedimentation rates, between 0 and 233 m, and 233 to 836 m. For the first interval, six 100 ka eccentricity cycles were identified; the low number of ostracods for the interval and highly variable Ca/Ti and Ca/RTi, Fe, Al values indicate a different sedimentation rate in a drier environment. For the second interval, ten 405 ka cycles were identified; its higher ostracod count and more stable Ca/Ti and Ca/RTi, Fe, Al values could be indicative of increasing humidity.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"356 - 376"},"PeriodicalIF":1.6,"publicationDate":"2021-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47243626","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}
It really is a wonderful opportunity to be able to write a Spotlight piece as past Co-editor of PALAIOS. After all, since my time as a student in the deep, deep South (i.e., south of the Rio Grande), I loved reading the front piece of the freshly arrived-in-the-mail PALAIOS journal—sent by snail mail at that time and patiently awaited! Those lines, typically provocative, revealed their authors in a very different light, sharing personal perspectives, with the fresh flavor of ideas presented in an almost colloquial way, without the necessary rigor and structure of a more formal scientific contribution. These lines try to follow this spirit of a Spotlight article and hopefully will trigger some excitement and out-of-the box thinking in a student somewhere, maybe in a distant corner of our planet, or in a place close to home. Since Dolf Seilacher’s seminal work unravelling the links between environmental factors and benthos response, ichnology has become instrumental for facies analysis and paleoenvironmental reconstructions. The underlying reasoning was straightforward. Trace fossils can be seen as evidence of organisms’ behavior, and that behavior is strongly affected by environmental factors. Therefore, careful reading of the trace-fossil record provides valuable information that can be used in paleoenvironmental interpretations. Seilacher built up this approach with his work in rocks of different ages formed in a wide variety of environments, from strata close to his home town of Tübingen, such as the Jurassic of southern Germany, to localities visited during far away expeditions, most notably the Cambrian of the Salt Range in Pakistan (e.g., Seilacher 1955). According to this view of the ichnologic record, the fact that similar trace-fossil assemblages are present in specific sedimentary facies all through the geologic column reflects behavioral convergence: different types of animals employ similar responses to deal with similar sets of problems. This underlying reasoning is at the core of the ichnofacies model. If we unlock the behavioral signal recorded in trace fossils, we can unravel the role played by the different environmental factors (or at least identify dominant controlling factors). Accurate integration of the ichnologic dataset with sedimentologic and stratigraphic information allows a dynamic reconstruction of the environmental setting and provides an interpretation in terms of animal-substrate interactions, depositional processes, and sedimentary environments. Note that, contrary to a common misconception, trace fossils neither indicate depositional processes, nor sedimentary environments, but are a biological response to environmental factors (e.g., oxygen, energy, salinity). A bivalve living within the sediment produces an escape trace in response to being buried under an episodic sedimentation event. This unhappy bivalve cares not about the nuances of depositional dynamics, and whether their being buried is due to a storm, a t
{"title":"SPOTLIGHTTHE ARROWS IN ORGANISM-SUBSTRATE INTERACTIONS","authors":"M. Mángano","doi":"10.2110/palo.2021.054","DOIUrl":"https://doi.org/10.2110/palo.2021.054","url":null,"abstract":"It really is a wonderful opportunity to be able to write a Spotlight piece as past Co-editor of PALAIOS. After all, since my time as a student in the deep, deep South (i.e., south of the Rio Grande), I loved reading the front piece of the freshly arrived-in-the-mail PALAIOS journal—sent by snail mail at that time and patiently awaited! Those lines, typically provocative, revealed their authors in a very different light, sharing personal perspectives, with the fresh flavor of ideas presented in an almost colloquial way, without the necessary rigor and structure of a more formal scientific contribution. These lines try to follow this spirit of a Spotlight article and hopefully will trigger some excitement and out-of-the box thinking in a student somewhere, maybe in a distant corner of our planet, or in a place close to home. Since Dolf Seilacher’s seminal work unravelling the links between environmental factors and benthos response, ichnology has become instrumental for facies analysis and paleoenvironmental reconstructions. The underlying reasoning was straightforward. Trace fossils can be seen as evidence of organisms’ behavior, and that behavior is strongly affected by environmental factors. Therefore, careful reading of the trace-fossil record provides valuable information that can be used in paleoenvironmental interpretations. Seilacher built up this approach with his work in rocks of different ages formed in a wide variety of environments, from strata close to his home town of Tübingen, such as the Jurassic of southern Germany, to localities visited during far away expeditions, most notably the Cambrian of the Salt Range in Pakistan (e.g., Seilacher 1955). According to this view of the ichnologic record, the fact that similar trace-fossil assemblages are present in specific sedimentary facies all through the geologic column reflects behavioral convergence: different types of animals employ similar responses to deal with similar sets of problems. This underlying reasoning is at the core of the ichnofacies model. If we unlock the behavioral signal recorded in trace fossils, we can unravel the role played by the different environmental factors (or at least identify dominant controlling factors). Accurate integration of the ichnologic dataset with sedimentologic and stratigraphic information allows a dynamic reconstruction of the environmental setting and provides an interpretation in terms of animal-substrate interactions, depositional processes, and sedimentary environments. Note that, contrary to a common misconception, trace fossils neither indicate depositional processes, nor sedimentary environments, but are a biological response to environmental factors (e.g., oxygen, energy, salinity). A bivalve living within the sediment produces an escape trace in response to being buried under an episodic sedimentation event. This unhappy bivalve cares not about the nuances of depositional dynamics, and whether their being buried is due to a storm, a t","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"353 - 355"},"PeriodicalIF":1.6,"publicationDate":"2021-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43415011","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}
B. Breithaupt, M. Chan, Winston M. Seiler, Neffra Matthews
Abstract: Within the eolian Lower Jurassic Navajo Sandstone, exposed in the Coyote Buttes area of Vermilion Cliffs National Monument in Arizona, a site (informally known as the “Dinosaur Dance Floor”) is reinterpreted as an enigmatic, modified (possibly pedogenic) eolian surface that was exposed and further modified and accentuated by modern weathering and erosion. The resultant surface is covered with small, shallow potholes or weathering pits, with no direct evidence of dinosaur activity.
{"title":"WEATHERING PITS VERSUS TRAMPLE MARKS: A REINTERPRETATION OF THE “DINOSAUR DANCE FLOOR”: A JURASSIC NAVAJO SandSTONE SURFACE IN THE VERMILION CLIFFS NATIONAL MONUMENT, ARIZONA","authors":"B. Breithaupt, M. Chan, Winston M. Seiler, Neffra Matthews","doi":"10.2110/palo.2020.077","DOIUrl":"https://doi.org/10.2110/palo.2020.077","url":null,"abstract":"Abstract: Within the eolian Lower Jurassic Navajo Sandstone, exposed in the Coyote Buttes area of Vermilion Cliffs National Monument in Arizona, a site (informally known as the “Dinosaur Dance Floor”) is reinterpreted as an enigmatic, modified (possibly pedogenic) eolian surface that was exposed and further modified and accentuated by modern weathering and erosion. The resultant surface is covered with small, shallow potholes or weathering pits, with no direct evidence of dinosaur activity.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"331 - 338"},"PeriodicalIF":1.6,"publicationDate":"2021-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42044760","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}
Abstract: A bonebed of multiple skeletons of the Triassic horned reptile Shringasaurus indicus was discovered in the upper Denwa Formation, Satpura Gondwana Basin, India. The monotaxic bonebed contains multiple individuals of different ontogenic stages indicating herding behavior by Shringasaurus indicus. The herd was a mixed-sex herd. The adult and sub-adult bones in the bonebed exceed the number of juvenile bones. The distribution of the bones was slightly patchy, bones of different individuals were admixed, and several bones were piled up implying mass mortality. The bonebed occurs in a fine-grained mudrock that is hydraulically incompatible with long-distance transport and concentration by currents. Sedimentary facies analysis indicates that the bonebed accumulated and was buried in a crevasse splay deposit between two ENE-WSW trending channel-fill complexes. The northern channel-fill complex was formed by unidirectional flow with lateral channel migration towards the south and with minor contemporaneous tectonic subsidence. Repeated breaching of the levee by this channel flow led to the incremental development of the crevasse splay deposit. The herd of Shringasaurus indicus, which lived near to the perennial channel, was drowned en masse and the carcasses were trapped within the muddy sediments of the crevasse splay deposit. Apart from a partially articulated skeleton, the rest of the bones were disarticulated but remained associated. The bones show little evidence of post-mortem modifications. With a continuous supply of the sediments through the spillover channels, the bones were buried before complete disarticulation and dispersal had taken place.
{"title":"TAPHONOMY AND DEPOSITIONAL SETTING OF THE SHRINGASAURUS INDICUS (ARCHOSAUROMORPHA: ALLOKOTOSAURIA) BONEBED FROM THE MIDDLE TRIASSIC DENWA FORMATION, SATPURA GONDWANA BASIN, INDIA","authors":"S. Sengupta, D. Sengupta","doi":"10.2110/palo.2021.013","DOIUrl":"https://doi.org/10.2110/palo.2021.013","url":null,"abstract":"Abstract: A bonebed of multiple skeletons of the Triassic horned reptile Shringasaurus indicus was discovered in the upper Denwa Formation, Satpura Gondwana Basin, India. The monotaxic bonebed contains multiple individuals of different ontogenic stages indicating herding behavior by Shringasaurus indicus. The herd was a mixed-sex herd. The adult and sub-adult bones in the bonebed exceed the number of juvenile bones. The distribution of the bones was slightly patchy, bones of different individuals were admixed, and several bones were piled up implying mass mortality. The bonebed occurs in a fine-grained mudrock that is hydraulically incompatible with long-distance transport and concentration by currents. Sedimentary facies analysis indicates that the bonebed accumulated and was buried in a crevasse splay deposit between two ENE-WSW trending channel-fill complexes. The northern channel-fill complex was formed by unidirectional flow with lateral channel migration towards the south and with minor contemporaneous tectonic subsidence. Repeated breaching of the levee by this channel flow led to the incremental development of the crevasse splay deposit. The herd of Shringasaurus indicus, which lived near to the perennial channel, was drowned en masse and the carcasses were trapped within the muddy sediments of the crevasse splay deposit. Apart from a partially articulated skeleton, the rest of the bones were disarticulated but remained associated. The bones show little evidence of post-mortem modifications. With a continuous supply of the sediments through the spillover channels, the bones were buried before complete disarticulation and dispersal had taken place.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"339 - 351"},"PeriodicalIF":1.6,"publicationDate":"2021-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44867555","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}
Abstract: Ooimmuration is here defined as a taphonomic process by which fossils are preserved within ooids. It is a form of lithoimmuration, although depending on the role of microbes in the formation of the ooid cortex, ooimmuration can also be considered a type of bioimmuration. Fossils enclosed within ooids are protected from bioerosion as well as the abrasion common in energetic depositional environments such as ooid shoals. Many taxa in some fossil assemblages may be known only because they were ooimmured. We describe as examples of ooimmuration fossils preserved in an oolite from the Middle Jurassic (Bajocian) Carmel Formation in southwestern Utah.
{"title":"OOIMMURATION: ENHANCED FOSSIL PRESERVATION BY OOIDS, WITH EXAMPLES FROM THE MIDDLE JURASSIC OF SOUTHWESTERN UTAH, USA","authors":"Mark A. Wilson, A. Cooke, S. Judge, T. Palmer","doi":"10.2110/palo.2021.036","DOIUrl":"https://doi.org/10.2110/palo.2021.036","url":null,"abstract":"Abstract: Ooimmuration is here defined as a taphonomic process by which fossils are preserved within ooids. It is a form of lithoimmuration, although depending on the role of microbes in the formation of the ooid cortex, ooimmuration can also be considered a type of bioimmuration. Fossils enclosed within ooids are protected from bioerosion as well as the abrasion common in energetic depositional environments such as ooid shoals. Many taxa in some fossil assemblages may be known only because they were ooimmured. We describe as examples of ooimmuration fossils preserved in an oolite from the Middle Jurassic (Bajocian) Carmel Formation in southwestern Utah.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"326 - 329"},"PeriodicalIF":1.6,"publicationDate":"2021-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42114910","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}
Abstract: A category of wrinkle structures, often termed Kinneyia structure or Runzel marks, comprises bedding plane features consisting typically of anastomosing, low-relief, flat-topped ridges with intervening depressions. Topographic relief is usually less than a millimeter. They are locally common on the upper surfaces of fine- to medium-grained sandstone beds interbedded with mudstone deposited in offshore settings, especially in Precambrian and lower Paleozoic strata but as young as Cretaceous. For more than the last two decades these wrinkle structures have been widely regarded as due to microbial mats, and have been taken as evidence for dominance in the Proterozoic of microbially stabilized sediment and, in the Phanerozoic, a matground marine benthic ecology which gradually gave way to a mixground ecology. The detailed morphology and cross-cutting relationships demonstrated by a range of specimens of Proterozoic, Cambrian, and Silurian age, however, cast this interpretation into doubt. The relationship between the wrinkled surface and bioclasts such as shells and both prior- and later-formed scour surfaces, and horizontal and vertical burrows show that these wrinkles did not develop due to the surface topography of microbial mats or compaction of microbial mats during burial, but instead formed at the top of a sand bed at the interface with an overlying layer of mud. Deformation is ascribed to vibration from low-magnitude earthquakes. The presence in some units of small-scale sedimentary dikelets and crack arrays that formed later after some stiffening, along with locally associated seismites and other evidence for nearby faulting, show that syndepositional tectonic activity was not unexpected and support the interpretation that this category of wrinkle structures is a type of seismite.
{"title":"KINNEYIA-TYPE WRINKLE STRUCTURES ON SANDSTONE BEDS: NOT MICROBIALLY INDUCED BUT DEFORMATION FEATURES CAUSED BY SYNSEDIMENTARY EARTHQUAKES","authors":"B. Pratt","doi":"10.2110/palo.2021.015","DOIUrl":"https://doi.org/10.2110/palo.2021.015","url":null,"abstract":"Abstract: A category of wrinkle structures, often termed Kinneyia structure or Runzel marks, comprises bedding plane features consisting typically of anastomosing, low-relief, flat-topped ridges with intervening depressions. Topographic relief is usually less than a millimeter. They are locally common on the upper surfaces of fine- to medium-grained sandstone beds interbedded with mudstone deposited in offshore settings, especially in Precambrian and lower Paleozoic strata but as young as Cretaceous. For more than the last two decades these wrinkle structures have been widely regarded as due to microbial mats, and have been taken as evidence for dominance in the Proterozoic of microbially stabilized sediment and, in the Phanerozoic, a matground marine benthic ecology which gradually gave way to a mixground ecology. The detailed morphology and cross-cutting relationships demonstrated by a range of specimens of Proterozoic, Cambrian, and Silurian age, however, cast this interpretation into doubt. The relationship between the wrinkled surface and bioclasts such as shells and both prior- and later-formed scour surfaces, and horizontal and vertical burrows show that these wrinkles did not develop due to the surface topography of microbial mats or compaction of microbial mats during burial, but instead formed at the top of a sand bed at the interface with an overlying layer of mud. Deformation is ascribed to vibration from low-magnitude earthquakes. The presence in some units of small-scale sedimentary dikelets and crack arrays that formed later after some stiffening, along with locally associated seismites and other evidence for nearby faulting, show that syndepositional tectonic activity was not unexpected and support the interpretation that this category of wrinkle structures is a type of seismite.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"313 - 325"},"PeriodicalIF":1.6,"publicationDate":"2021-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48594952","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}
Ranita Saha, Shubhabrata Paul, Subhronil Mondal, S. Bardhan, Shiladri S. Das, Sandip Saha, Debattam Sarkar
Abstract: Gastropod drillholes on prey shells provide an opportunity to test the importance of predation in an evolutionary context. Although records of drilling predation are widespread across the Phanerozoic, the temporal distribution and relative importance of this mode of predation is still controversial. Further, some studies indicate a decline of drilling predation in the Mesozoic but other studies do not. In this study, we present a new dataset of gastropod drilling predation on Kimmeridgian and Tithonian bivalves of Kutch, India. Our study suggests that drilling was one of the prevailing modes of predation in the Upper Jurassic of Kutch with strongly variable intensities, ranging from 2% in the Kimmeridgian Seebachia to 26% in the Tithonian Pinna. A significant, albeit small, increase in drilling intensity from the Kimmeridgian to the Tithonian assemblages is associated with a change in relative sea-level and depositional environment. The morphology of drillholes and recent discovery of body fossils from the same stratigraphic units suggest naticid gastropods as the most likely drillers. A literature survey, along with previously collected specimen from the Jurassic of Kutch, reveals a more complex history of drilling predation than previously assumed.
{"title":"GASTROPOD DRILLING PREDATION IN THE UPPER JURASSIC OF KUTCH, INDIA","authors":"Ranita Saha, Shubhabrata Paul, Subhronil Mondal, S. Bardhan, Shiladri S. Das, Sandip Saha, Debattam Sarkar","doi":"10.2110/palo.2020.072","DOIUrl":"https://doi.org/10.2110/palo.2020.072","url":null,"abstract":"Abstract: Gastropod drillholes on prey shells provide an opportunity to test the importance of predation in an evolutionary context. Although records of drilling predation are widespread across the Phanerozoic, the temporal distribution and relative importance of this mode of predation is still controversial. Further, some studies indicate a decline of drilling predation in the Mesozoic but other studies do not. In this study, we present a new dataset of gastropod drilling predation on Kimmeridgian and Tithonian bivalves of Kutch, India. Our study suggests that drilling was one of the prevailing modes of predation in the Upper Jurassic of Kutch with strongly variable intensities, ranging from 2% in the Kimmeridgian Seebachia to 26% in the Tithonian Pinna. A significant, albeit small, increase in drilling intensity from the Kimmeridgian to the Tithonian assemblages is associated with a change in relative sea-level and depositional environment. The morphology of drillholes and recent discovery of body fossils from the same stratigraphic units suggest naticid gastropods as the most likely drillers. A literature survey, along with previously collected specimen from the Jurassic of Kutch, reveals a more complex history of drilling predation than previously assumed.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"301 - 312"},"PeriodicalIF":1.6,"publicationDate":"2021-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41608992","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}
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