Abstract: The ichnogenus Teredolites and the Teredolites Ichnofacies is an accepted proxy for marine influence in paralic to open marine depositional environments. Actualistic approaches and the process-ichnologic framework allow independent analysis of both quantitative and semiquantitative data to interpret the physicochemical conditions when Teredolites are present. Measurements collected in modern environments and Jurassic–Eocene successions produce a spatially and temporally robust dataset of 14,137 borings from 17 tracemaking genera. Life history strategies of extant tracemakers are reflected in Mesozoic borings, which allow reconstruction of paleosalinity. Trends extrapolated indicate four ecotones in modern paralic to nearshore settings, which can be identified into the Late Cretaceous. These zones display variation in boring metrics (length [L], width [W], L:W ratio, size diversity index), densities, and relative composition of Teredolites. Zone 1 represents upper estuary to tidally modified fluvial successions with salinities from 0.5–10 ppt (oligohaline to alpha-mesohaline). Zone 2 represents upper to central estuary successions with salinities from 10–19 ppt (beta-mesohaline to lower polyhaline). Zone 3 represents central to lower estuary successions with salinities from 15–30 ppt (beta-mesohaline to euhaline). Zone 4 represents backshore to open marine successions with salinities from 20–30+ ppt (polyhaline to euhaline). Boring metrics compared against identified fossil genera suggest high species richness in the Western Interior Seaway coincided with physical adaptations to compensate for interspecific competition––differences in reproduction style and media preferences at the time of settlement––in the Late Cretaceous.
{"title":"EVALUATING THE ICHNOFOSSIL TEREDOLITES AS AN INDICATOR OF SALINITY AND PALEOENVIRONMENT","authors":"R. Buntin, S. Hasiotis, P. Flaig","doi":"10.2110/palo.2020.074","DOIUrl":"https://doi.org/10.2110/palo.2020.074","url":null,"abstract":"Abstract: The ichnogenus Teredolites and the Teredolites Ichnofacies is an accepted proxy for marine influence in paralic to open marine depositional environments. Actualistic approaches and the process-ichnologic framework allow independent analysis of both quantitative and semiquantitative data to interpret the physicochemical conditions when Teredolites are present. Measurements collected in modern environments and Jurassic–Eocene successions produce a spatially and temporally robust dataset of 14,137 borings from 17 tracemaking genera. Life history strategies of extant tracemakers are reflected in Mesozoic borings, which allow reconstruction of paleosalinity. Trends extrapolated indicate four ecotones in modern paralic to nearshore settings, which can be identified into the Late Cretaceous. These zones display variation in boring metrics (length [L], width [W], L:W ratio, size diversity index), densities, and relative composition of Teredolites. Zone 1 represents upper estuary to tidally modified fluvial successions with salinities from 0.5–10 ppt (oligohaline to alpha-mesohaline). Zone 2 represents upper to central estuary successions with salinities from 10–19 ppt (beta-mesohaline to lower polyhaline). Zone 3 represents central to lower estuary successions with salinities from 15–30 ppt (beta-mesohaline to euhaline). Zone 4 represents backshore to open marine successions with salinities from 20–30+ ppt (polyhaline to euhaline). Boring metrics compared against identified fossil genera suggest high species richness in the Western Interior Seaway coincided with physical adaptations to compensate for interspecific competition––differences in reproduction style and media preferences at the time of settlement––in the Late Cretaceous.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"53 - 72"},"PeriodicalIF":1.6,"publicationDate":"2022-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46457807","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: This study examines computed tomography (CT) scans of a 15.24-cm diameter and 17.1-cm length core cut from Thalassinoides -bearing strata (Hanifa Formation, central Saudi Arabia) to explore the quantitative variability in burrow percentage when estimated using 2D views. A cropped quadrangular prism of this core allowed 202 2D slices in two vertical orientations and 165 horizontal 2D slices. Thalassinoides volume represents 20.0% (burrow percentage) of the total volume within this cropped quadrangular prism. The estimated burrow percentage by the 2D vertical slices varies from 11.8% to 30.3% with a mean value of 19.9% ± 3.3% and 19.6% ± 3.9%, and coefficients of variation of 17% and 20%, for the two vertical orientations. A wider range and slightly more variability are found when estimated burrow percentage using the horizontal slices (burrow percentage range from 6.1% to 33.1% with a mean value of 19.8% ± 6.5% and coefficient of variation of 33.1%). However, analysis of variance results indicated no statistically significant difference between the distribution of the burrow percentage among vertical and horizontal slices. A test of how randomly selected slices of the CT scan would represent the burrow percentage indicated that even five randomly selected slices could retain a mean comparable to the actual burrow percentage of the CT scan. Based on these results, we suggested a statistical way to quantify the uncertainty associated with estimating the burrow percentage from 2D views, an important step toward a complete understanding of variability in burrow percentage (and bioturbation intensity) when estimated from 2D views.
{"title":"QUANTITATIVE VARIABILITY OF BURROW PERCENTAGE ESTIMATED FROM 2D VIEWS: EXAMPLE FROM THALASSINOIDES-BEARING STRATA, CENTRAL SAUDI ARABIA","authors":"Hassan Abdalla Eltom, A. Alqubalee","doi":"10.2110/palo.2021.012","DOIUrl":"https://doi.org/10.2110/palo.2021.012","url":null,"abstract":"Abstract: This study examines computed tomography (CT) scans of a 15.24-cm diameter and 17.1-cm length core cut from Thalassinoides -bearing strata (Hanifa Formation, central Saudi Arabia) to explore the quantitative variability in burrow percentage when estimated using 2D views. A cropped quadrangular prism of this core allowed 202 2D slices in two vertical orientations and 165 horizontal 2D slices. Thalassinoides volume represents 20.0% (burrow percentage) of the total volume within this cropped quadrangular prism. The estimated burrow percentage by the 2D vertical slices varies from 11.8% to 30.3% with a mean value of 19.9% ± 3.3% and 19.6% ± 3.9%, and coefficients of variation of 17% and 20%, for the two vertical orientations. A wider range and slightly more variability are found when estimated burrow percentage using the horizontal slices (burrow percentage range from 6.1% to 33.1% with a mean value of 19.8% ± 6.5% and coefficient of variation of 33.1%). However, analysis of variance results indicated no statistically significant difference between the distribution of the burrow percentage among vertical and horizontal slices. A test of how randomly selected slices of the CT scan would represent the burrow percentage indicated that even five randomly selected slices could retain a mean comparable to the actual burrow percentage of the CT scan. Based on these results, we suggested a statistical way to quantify the uncertainty associated with estimating the burrow percentage from 2D views, an important step toward a complete understanding of variability in burrow percentage (and bioturbation intensity) when estimated from 2D views.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"35 - 43"},"PeriodicalIF":1.6,"publicationDate":"2022-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49443198","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: Heteropody Index (HI) is a tool used to calculate area differences between the manus and pes of fossil trackways. HI uses a simple length × width calculation to estimate area. However, since most foot impressions are rarely close to square in shape, HI using a different area calculation could potentially more accurately reflect differences in manus and pes foot area. In this study, accuracy of length × width (L×W) as an area estimate for basic shapes and animal footprints, was tested against two other area calculations, the area of a circle: πr2, and length × carpal width (L×CW) (the width at the most proximal point of the foot in contact with the ground). In addition, accuracy of HI calculations using these methods was tested against HI calculations using actual area of the corresponding shape or underfoot area. It was discovered that in general L×W is a better estimate for area than πr2, in most animals except ungulates. However, for those animals where L×W was a better estimate than πr2, L×CW was more accurate. This paper additionally proposes that by combining the findings of these tests with those of Strickson et al. (2019), foot area estimates for dinosaurs can be estimated more accurately using L×CW, to return an area close to estimates for soft tissue. Previous HI measurements may have overestimated extreme heteropody in sauropod dinosaurs.
{"title":"HETEROPODY INDEX: A SQUARE PEG IN A ROUND HOLE?","authors":"E. Strickson","doi":"10.2110/palo.2021.032","DOIUrl":"https://doi.org/10.2110/palo.2021.032","url":null,"abstract":"Abstract: Heteropody Index (HI) is a tool used to calculate area differences between the manus and pes of fossil trackways. HI uses a simple length × width calculation to estimate area. However, since most foot impressions are rarely close to square in shape, HI using a different area calculation could potentially more accurately reflect differences in manus and pes foot area. In this study, accuracy of length × width (L×W) as an area estimate for basic shapes and animal footprints, was tested against two other area calculations, the area of a circle: πr2, and length × carpal width (L×CW) (the width at the most proximal point of the foot in contact with the ground). In addition, accuracy of HI calculations using these methods was tested against HI calculations using actual area of the corresponding shape or underfoot area. It was discovered that in general L×W is a better estimate for area than πr2, in most animals except ungulates. However, for those animals where L×W was a better estimate than πr2, L×CW was more accurate. This paper additionally proposes that by combining the findings of these tests with those of Strickson et al. (2019), foot area estimates for dinosaurs can be estimated more accurately using L×CW, to return an area close to estimates for soft tissue. Previous HI measurements may have overestimated extreme heteropody in sauropod dinosaurs.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"44 - 51"},"PeriodicalIF":1.6,"publicationDate":"2022-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43210203","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}
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}
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: 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}
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