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Ladislav Slavík - One of the best experts on this subject based on the ideXlab platform.
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Early Devonian (Lochkovian – early Emsian) bioevents and conodont response in the Prague Synform (Czech Republic)
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Ladislav Slavík, Jindřich HladilAbstract:Abstract The Devonian succession of the Prague Synform is characterized by two major lithofacies: shallow-water biodetrital, mostly crinoidal limestones that also include a reefal skeletal accumulation of Pragian age, and a more pelagic facies that is represented mostly by calcisiltites. Among the several Devonian prominent sea-level fluctuations, some can be traced globally, e.g., the Basal Pragian and Kacak events. In recent years, conodont biostratigraphy of the Early Devonian (Lochkovian, Pragian and early Emsian) of the Prague Synform has been refined. The regional subdivision of the Lower Devonian in its type area has been greatly improved by the integration of new biostratigraphic, chemostratigraphic, sedimentological, and petrophysical data that has, in turn, strengthened global correlations for this interval in Earth's history. The complete conodont biozonation of the Early Devonian interval (basal Lochkovian – earliest Emsian) in the Prague Synform includes 17 biozones, which can be applied to sections representing various depositional environments and have more global applicability than previously proposed ‘global’ conodont biozonations. The zonal scale enables a precise biostratigraphic delimitation of the major Early Devonian biotic events (Silurian-Devonian Boundary Event, Lochkovian-Pragian Event and Basal Zlichovian Event). There were major changes in the conodont fauna in response to the Silurian-Devonian Boundary and Lochkovian-Pragian events, however the Basal Zlichovian Event was only characterized by a very gradual transition in the conodont fauna. In parallel to the traditional events defined for the Prague Synform, seven other significant conodont events have been documented. These events represent major turnovers in the conodont fauna that have a direct impact on conodont biostratigraphy, specifically at a global scale. The Icriodus and Irregularis events are congruent with the lower boundaries of the Lochkovian and Pragian stages, respectively. The conodont events established in the Prague Synform largely reflect variations in the seawater depth but are generally independent of lithological changes within sections of the Prague Synform.
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refining the early devonian time scale using milankovitch cyclicity in lochkovian Pragian sediments prague synform czech republic
Earth and Planetary Science Letters, 2016Co-Authors: A C Da Silva, Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Ondřej Bábek, Frederik J Hilgen, Mark J DekkersAbstract:Abstract The Early Devonian geological time scale (base of the Devonian at 418.8 ± 2.9 Myr , Becker et al., 2012 ) suffers from poor age control, with associated large uncertainties between 2.5 and 4.2 Myr on the stage boundaries. Identifying orbital cycles from sedimentary successions can serve as a very powerful chronometer to test and, where appropriate, improve age models. Here, we focus on the Lochkovian and Pragian, the two lowermost Devonian stages. High-resolution magnetic susceptibility ( χ in – 5 to 10 cm sampling interval) and gamma ray spectrometry (GRS – 25 to 50 cm sampling interval) records were gathered from two main limestone sections, Požar-CS (118 m, spanning the Lochkov and Praha Formations) and Pod Barrandovem (174 m; Praha Formation), both in the Czech Republic. An additional section (Branžovy, 65 m, Praha Formation) was sampled for GRS (every 50 cm). The χ in and GRS records are very similar, so χ in variations are driven by variations in the samples' paramagnetic clay mineral content, reflecting changes in detrital input. Therefore, climatic variations are very likely captured in our records. Multiple spectral analysis and statistical techniques such as: Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multi-taper method and Average Spectral Misfit, were used in concert to reach an optimal astronomical interpretation. The Požar-CS section shows distinctly varying sediment accumulation rates. The Lochkovian (essentially equivalent to the Lochkov Formation (Fm.)) is interpreted to include a total of nineteen 405 kyr eccentricity cycles, constraining its duration to 7.7 ± 2.8 Myr . The Praha Fm. includes fourteen 405 kyr eccentricity cycles in the three sampled sections, while the Pragian Stage only includes about four 405 kyr eccentricity cycles, thus exhibiting durations of 5.7 ± 0.6 Myr and 1.7 ± 0.7 Myr respectively. Because the Lochkov Fm. contains an interval with very low sediment accumulation rate and because the Praha Fm. was cross-validated in three different sections, the uncertainty in the duration of the Lochkov Fm. and the Lochkovian is larger than that of the Praha Fm. and Pragian. The new floating time scales for the Lochkovian and Pragian stages have an unprecedented precision, with reduction in the uncertainty by a factor of 1.7 for the Lochkovian and of ∼6 for the Pragian. Furthermore, longer orbital modulation cycles are also identified with periodicities of ∼1000 kyr and 2000–2500 kyr.
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Refining the Early Devonian time scale using Milankovitch cyclicity in Lochkovian–Pragian sediments (Prague Synform, Czech Republic)
Earth and Planetary Science Letters, 2016Co-Authors: A C Da Silva, Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Ondřej Bábek, Frederik J Hilgen, Mark J DekkersAbstract:Abstract The Early Devonian geological time scale (base of the Devonian at 418.8 ± 2.9 Myr , Becker et al., 2012 ) suffers from poor age control, with associated large uncertainties between 2.5 and 4.2 Myr on the stage boundaries. Identifying orbital cycles from sedimentary successions can serve as a very powerful chronometer to test and, where appropriate, improve age models. Here, we focus on the Lochkovian and Pragian, the two lowermost Devonian stages. High-resolution magnetic susceptibility ( χ in – 5 to 10 cm sampling interval) and gamma ray spectrometry (GRS – 25 to 50 cm sampling interval) records were gathered from two main limestone sections, Požar-CS (118 m, spanning the Lochkov and Praha Formations) and Pod Barrandovem (174 m; Praha Formation), both in the Czech Republic. An additional section (Branžovy, 65 m, Praha Formation) was sampled for GRS (every 50 cm). The χ in and GRS records are very similar, so χ in variations are driven by variations in the samples' paramagnetic clay mineral content, reflecting changes in detrital input. Therefore, climatic variations are very likely captured in our records. Multiple spectral analysis and statistical techniques such as: Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multi-taper method and Average Spectral Misfit, were used in concert to reach an optimal astronomical interpretation. The Požar-CS section shows distinctly varying sediment accumulation rates. The Lochkovian (essentially equivalent to the Lochkov Formation (Fm.)) is interpreted to include a total of nineteen 405 kyr eccentricity cycles, constraining its duration to 7.7 ± 2.8 Myr . The Praha Fm. includes fourteen 405 kyr eccentricity cycles in the three sampled sections, while the Pragian Stage only includes about four 405 kyr eccentricity cycles, thus exhibiting durations of 5.7 ± 0.6 Myr and 1.7 ± 0.7 Myr respectively. Because the Lochkov Fm. contains an interval with very low sediment accumulation rate and because the Praha Fm. was cross-validated in three different sections, the uncertainty in the duration of the Lochkov Fm. and the Lochkovian is larger than that of the Praha Fm. and Pragian. The new floating time scales for the Lochkovian and Pragian stages have an unprecedented precision, with reduction in the uncertainty by a factor of 1.7 for the Lochkovian and of ∼6 for the Pragian. Furthermore, longer orbital modulation cycles are also identified with periodicities of ∼1000 kyr and 2000–2500 kyr.
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warming or cooling in the Pragian sedimentary record and petrophysical logs across the lochkovian Pragian boundary in the spanish central pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Jose Ignacio Valenzuelarios, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
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Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, José Ignacio Valenzuela-ríos, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
Jindřich Hladil - One of the best experts on this subject based on the ideXlab platform.
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Early Devonian (Lochkovian – early Emsian) bioevents and conodont response in the Prague Synform (Czech Republic)
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Ladislav Slavík, Jindřich HladilAbstract:Abstract The Devonian succession of the Prague Synform is characterized by two major lithofacies: shallow-water biodetrital, mostly crinoidal limestones that also include a reefal skeletal accumulation of Pragian age, and a more pelagic facies that is represented mostly by calcisiltites. Among the several Devonian prominent sea-level fluctuations, some can be traced globally, e.g., the Basal Pragian and Kacak events. In recent years, conodont biostratigraphy of the Early Devonian (Lochkovian, Pragian and early Emsian) of the Prague Synform has been refined. The regional subdivision of the Lower Devonian in its type area has been greatly improved by the integration of new biostratigraphic, chemostratigraphic, sedimentological, and petrophysical data that has, in turn, strengthened global correlations for this interval in Earth's history. The complete conodont biozonation of the Early Devonian interval (basal Lochkovian – earliest Emsian) in the Prague Synform includes 17 biozones, which can be applied to sections representing various depositional environments and have more global applicability than previously proposed ‘global’ conodont biozonations. The zonal scale enables a precise biostratigraphic delimitation of the major Early Devonian biotic events (Silurian-Devonian Boundary Event, Lochkovian-Pragian Event and Basal Zlichovian Event). There were major changes in the conodont fauna in response to the Silurian-Devonian Boundary and Lochkovian-Pragian events, however the Basal Zlichovian Event was only characterized by a very gradual transition in the conodont fauna. In parallel to the traditional events defined for the Prague Synform, seven other significant conodont events have been documented. These events represent major turnovers in the conodont fauna that have a direct impact on conodont biostratigraphy, specifically at a global scale. The Icriodus and Irregularis events are congruent with the lower boundaries of the Lochkovian and Pragian stages, respectively. The conodont events established in the Prague Synform largely reflect variations in the seawater depth but are generally independent of lithological changes within sections of the Prague Synform.
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refining the early devonian time scale using milankovitch cyclicity in lochkovian Pragian sediments prague synform czech republic
Earth and Planetary Science Letters, 2016Co-Authors: A C Da Silva, Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Ondřej Bábek, Frederik J Hilgen, Mark J DekkersAbstract:Abstract The Early Devonian geological time scale (base of the Devonian at 418.8 ± 2.9 Myr , Becker et al., 2012 ) suffers from poor age control, with associated large uncertainties between 2.5 and 4.2 Myr on the stage boundaries. Identifying orbital cycles from sedimentary successions can serve as a very powerful chronometer to test and, where appropriate, improve age models. Here, we focus on the Lochkovian and Pragian, the two lowermost Devonian stages. High-resolution magnetic susceptibility ( χ in – 5 to 10 cm sampling interval) and gamma ray spectrometry (GRS – 25 to 50 cm sampling interval) records were gathered from two main limestone sections, Požar-CS (118 m, spanning the Lochkov and Praha Formations) and Pod Barrandovem (174 m; Praha Formation), both in the Czech Republic. An additional section (Branžovy, 65 m, Praha Formation) was sampled for GRS (every 50 cm). The χ in and GRS records are very similar, so χ in variations are driven by variations in the samples' paramagnetic clay mineral content, reflecting changes in detrital input. Therefore, climatic variations are very likely captured in our records. Multiple spectral analysis and statistical techniques such as: Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multi-taper method and Average Spectral Misfit, were used in concert to reach an optimal astronomical interpretation. The Požar-CS section shows distinctly varying sediment accumulation rates. The Lochkovian (essentially equivalent to the Lochkov Formation (Fm.)) is interpreted to include a total of nineteen 405 kyr eccentricity cycles, constraining its duration to 7.7 ± 2.8 Myr . The Praha Fm. includes fourteen 405 kyr eccentricity cycles in the three sampled sections, while the Pragian Stage only includes about four 405 kyr eccentricity cycles, thus exhibiting durations of 5.7 ± 0.6 Myr and 1.7 ± 0.7 Myr respectively. Because the Lochkov Fm. contains an interval with very low sediment accumulation rate and because the Praha Fm. was cross-validated in three different sections, the uncertainty in the duration of the Lochkov Fm. and the Lochkovian is larger than that of the Praha Fm. and Pragian. The new floating time scales for the Lochkovian and Pragian stages have an unprecedented precision, with reduction in the uncertainty by a factor of 1.7 for the Lochkovian and of ∼6 for the Pragian. Furthermore, longer orbital modulation cycles are also identified with periodicities of ∼1000 kyr and 2000–2500 kyr.
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Refining the Early Devonian time scale using Milankovitch cyclicity in Lochkovian–Pragian sediments (Prague Synform, Czech Republic)
Earth and Planetary Science Letters, 2016Co-Authors: A C Da Silva, Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Ondřej Bábek, Frederik J Hilgen, Mark J DekkersAbstract:Abstract The Early Devonian geological time scale (base of the Devonian at 418.8 ± 2.9 Myr , Becker et al., 2012 ) suffers from poor age control, with associated large uncertainties between 2.5 and 4.2 Myr on the stage boundaries. Identifying orbital cycles from sedimentary successions can serve as a very powerful chronometer to test and, where appropriate, improve age models. Here, we focus on the Lochkovian and Pragian, the two lowermost Devonian stages. High-resolution magnetic susceptibility ( χ in – 5 to 10 cm sampling interval) and gamma ray spectrometry (GRS – 25 to 50 cm sampling interval) records were gathered from two main limestone sections, Požar-CS (118 m, spanning the Lochkov and Praha Formations) and Pod Barrandovem (174 m; Praha Formation), both in the Czech Republic. An additional section (Branžovy, 65 m, Praha Formation) was sampled for GRS (every 50 cm). The χ in and GRS records are very similar, so χ in variations are driven by variations in the samples' paramagnetic clay mineral content, reflecting changes in detrital input. Therefore, climatic variations are very likely captured in our records. Multiple spectral analysis and statistical techniques such as: Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multi-taper method and Average Spectral Misfit, were used in concert to reach an optimal astronomical interpretation. The Požar-CS section shows distinctly varying sediment accumulation rates. The Lochkovian (essentially equivalent to the Lochkov Formation (Fm.)) is interpreted to include a total of nineteen 405 kyr eccentricity cycles, constraining its duration to 7.7 ± 2.8 Myr . The Praha Fm. includes fourteen 405 kyr eccentricity cycles in the three sampled sections, while the Pragian Stage only includes about four 405 kyr eccentricity cycles, thus exhibiting durations of 5.7 ± 0.6 Myr and 1.7 ± 0.7 Myr respectively. Because the Lochkov Fm. contains an interval with very low sediment accumulation rate and because the Praha Fm. was cross-validated in three different sections, the uncertainty in the duration of the Lochkov Fm. and the Lochkovian is larger than that of the Praha Fm. and Pragian. The new floating time scales for the Lochkovian and Pragian stages have an unprecedented precision, with reduction in the uncertainty by a factor of 1.7 for the Lochkovian and of ∼6 for the Pragian. Furthermore, longer orbital modulation cycles are also identified with periodicities of ∼1000 kyr and 2000–2500 kyr.
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warming or cooling in the Pragian sedimentary record and petrophysical logs across the lochkovian Pragian boundary in the spanish central pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Jose Ignacio Valenzuelarios, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
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Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, José Ignacio Valenzuela-ríos, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
Gunnar Schraut - One of the best experts on this subject based on the ideXlab platform.
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Trilobiten aus dem Unter-Devon des südöstlichen Anti-Atlas, Süd-Marokko
Senckenbergiana lethaea, 2000Co-Authors: Gunnar SchrautAbstract:In der vorliegenden Arbeit werden Trilobiten aus dem Unter-Devon (Pragium — Ober-Emsium) des südöstlichen Anti-Atlas (Süd-Marokko) abgebildet und beschrieben. Es handelt sich dabei hauptsächlich um Rheinische Formen, welche dem obersten Pragium und dem Ober-Emsium angehören. Ältere Taxa aus der Herzynisch-böhmischen Fazies liegen ausschließlich aus dem Pragium vor. 19 Arten und Unterarten konnten von insgesamt 8 verschiedenen Lokalitäten (Fundpunkte und Profile) aufgefunden werden. Neu sind die folgenden fünf Taxa: Paralejurus elayounensis n. sp., Phacops (Phacops) saberensis torkozensis n. ssp., Phacops (Phacops) vogeli n. sp., Reedops intermedius chlupaci n. ssp. und Treveropyge marokkensis n. sp. Arduennella maillieuxi ( Asselberghs 1923) und Parahomalonotus planus planus ( Koch 1883) werden erstmals aus dem Unter-Devon (oberstes Pragium) von Marokko beschrieben. Die schon bekannten Formen besitzen Vertreter im Rheinischen Schiefergebirge (Deutschland), in der Bretagne (Frankreich), in Böhmen (Tschechische Republik) und in Spanien. Konsequenterweise bedeutet dies, daß die genannten geographischen Bereiche im mittleren und oberen Unter-Devon durch einen flachen Schelf ohne deutlich ausgeprägte paläobiogeographische Schranken miteinander verbunden waren und/oder geographisch nicht weit auseinander lagen. This paper deals with trilobites from the Lower Devonian (Pragian — Upper Emsian) from the south-eastern part of the Anti-Atlas System (South Morocco). Nineteen species and subspecies were determined from 8 different Lower Devonian localities, and these are described, figured and compared to similar forms. The following species and subspecies are new: Paralejurus elayounensis n. sp., Phacops (Phacops) saberensis torkozensis n. ssp., Phacops (Phacops) vogeli n. sp., Reedops intermedius chlupaci n. ssp. and Treveropyge marokkensis n. sp. Most of them represent rhenish forms from the uppermost Pragian and the Upper Emsian. Hercynian-bohemian forms are only present in the Pragian Stage. Arduennella maillieuxi ( Asselberghs 1923) and Parahomalonotus planus planus ( Koch 1883) are recorded for the first time in the Devonian of Morocco. Since most of the species are well known forms from the Rheinisches Schiefergebirge (Germany), Brittany (France), Bohemia (Czech Republic) and from Spain there must have been very close paleobiogeographic relations. Therefore a shallow marine shelf with no paleobiogeographical boundaries probably existed between this regions and/or they were located very close together.
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Trilobiten aus dem Unter-Devon des südlichen Antiatlas (Marokko) — ihre Bedeutung für die zeitliche Korrelation zwischen Rheinischer und Herzynischer Fazies
Senckenbergiana lethaea, 1998Co-Authors: Gunnar SchrautAbstract:Von sieben Fundpunkten im Unter-Devon des südlichen Antiatlas (Marokko) werden Trilobitenfaunen bearbeitet und auf ihre stratigraphische Wertigkeit hin untersucht. Insgesamt können bisher drei verschiedene zeitliche Bereiche ausgeschieden werden, welche dem Pragium, dem obersten Pragium sowie dem oberen Ober-Emsium angehören. Cheirurus (Crotalocephalina) gibbus ( Beyrich 1845) kennzeichnet das mittlere Unter-Devon (Pragium; Nowakia (Turkestanella) acuaria -Zone). Treveropyge prorotundifrons ( Richter & Richter 1943), Arduennella maillieuxi ( Asselberghs 1923) und Parahomalonotus planus planus ( Koch 1883) gehören ungefähr in das oberste Pragium. Greenops (Greenops) struvei Morzadec 1969 ist aus dem oberen Ober-Emsium ( Polygnathus patulus -Zone) bekannt. Die dargestellten Trilobiten-Zonen besitzen zum Teil ein zeitliches Auflösungsvermögen, welches mit denen der Conodonten, Tentaculiten oder Ammonoideen verglichen werden kann. Über den Zeitraum des mittleren bis oberen Unter-Devon (Pragium bis Ober-Emsium) wechseln sich Rheinische Formen mit Herzynischen bzw. Mischfaunen ab, was für eine zeitliche Korrelation zwischen beiden Faziesbereichen von großer Bedeutung ist. Seven localities from the Lower Devonian of the southern part of the Antiatlas (Morocco) yielded trilobites which were examined in detail about their stratigraphical value. Three levels could be differentiated which represent the Pragian, the uppermost Pragian and the upper part of the Upper Emsian. Cheirurus (Crotalocephalina) gibbus ( Beyrich 1845) is due to the middle part of the Lower Devonian (Pragian; Nowakia (Turkestanella) acuaria -Zone). Treveropyge prorotundifrons ( Richter & Richter 1943), Arduennella maillieuxi ( Asselberghs 1923) and Parahomalonotus planus planus ( Koch 1883) are representing approximately the uppermost part of the Pragian and Greenops (Greenops) struvei Morzadec 1969 is only known from the upper part of the Upper Emsian ( Polygnathus patulus -Zone). To compare with other index fossils trilobites could partly be as high resoluting stratigraphical markers as conodonts, tentaculites or ammonoids. During the Pragian and Emsian Hercynian to Rhenish or Rhenish-Hercynian mixed facies are observable, which are very important for time correlation between these two very different types of facies.
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Die GattungScabrella (Trilobita) im Unterdevon von Nord-Afrika, West- und Süd-Europa
Senckenbergiana lethaea, 1998Co-Authors: Gunnar SchrautAbstract:Neues und gut erhaltenes Material von Scabrella pradoana ( de Verneuil 1850) aus dem Unterdevon (oberstes Pragium) des südlichen Antiatlas (Marokko) hilft die bisherigen Kenntnisse über die Morphologie und geographische Verbreitung der Gattung zu erweitern. Darauf aufbauend werden alle Arten von Scabrella Wenndorf 1990 zusammenfassend dargestellt, abgebildet und beschrieben. Das Taxon besteht aus drei Arten [ Scabrella asselberghsi ( Maillieux 1936), Scabrella pradoana ( de Verneuil 1850) und Scabrella spinoissima ( Schlüter 1900)] und zwei Formen ungenauer Zuordnung [ Scabrella n. sp. B sensu Wenndorf 1990, Scabrella sp. sensu Wenndorf 1990]. Scabrella ist im Unterdevon (oberstes Pragium bis Unter-Emsium) von Nord-Afrika, West- und Süd-Europa verbreitet, leicht bestimmbar aber selten. Von Scabrella pradoana ( de Verneuil 1850) wird das Cephalon und das Pygidium rekonstruiert und die mögliche Bedeutung dieser Art für die Stratigraphie und Korrelation zwischen Rheinischer und Herzynischer Fazies diskutiert. New and good preserved material of Scabrella pradoana ( de Verneuil 1850) from the Lower Devonian (uppermost Pragian) of the southern part of the Antiatlas (Morocco) is presented so that we now have more informations about morphology and geographical distribution of the genus. Scabrella Wenndorf 1990 includes three different species [ Scabrella asselberghsi ( Maillieux 1936), Scabrella pradoana ( de Verneuil 1850), Scabrella spinoissima ( Schlüter 1900)] and two species with uncertain taxonomic rank [ Scabrella n. sp. B sensu Wenndorf 1990 and Scabrella sp. sensu Wenndorf 1990]. They are described, figured and discussed. Scabrella is an uncommon genus in the Lower Devonian (uppermost Pragian to Lower Emsian) from North Africa, Western and Southern Europe and is easy to identify. From Scabrella pradoana ( de Verneuil 1850) the Cephalon and Pygidium are reconstructed. Its value for stratigraphy and correlation between Rhenish and Hercynian facies is discussed.
Tomas Hrstka - One of the best experts on this subject based on the ideXlab platform.
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warming or cooling in the Pragian sedimentary record and petrophysical logs across the lochkovian Pragian boundary in the spanish central pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Jose Ignacio Valenzuelarios, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
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Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, José Ignacio Valenzuela-ríos, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
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refining the early devonian time scale using milankovitch cyclicity in lochkovian Pragian sediments prague synform czech republic
Earth and Planetary Science Letters, 2016Co-Authors: A C Da Silva, Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Ondřej Bábek, Frederik J Hilgen, Mark J DekkersAbstract:Abstract The Early Devonian geological time scale (base of the Devonian at 418.8 ± 2.9 Myr , Becker et al., 2012 ) suffers from poor age control, with associated large uncertainties between 2.5 and 4.2 Myr on the stage boundaries. Identifying orbital cycles from sedimentary successions can serve as a very powerful chronometer to test and, where appropriate, improve age models. Here, we focus on the Lochkovian and Pragian, the two lowermost Devonian stages. High-resolution magnetic susceptibility ( χ in – 5 to 10 cm sampling interval) and gamma ray spectrometry (GRS – 25 to 50 cm sampling interval) records were gathered from two main limestone sections, Požar-CS (118 m, spanning the Lochkov and Praha Formations) and Pod Barrandovem (174 m; Praha Formation), both in the Czech Republic. An additional section (Branžovy, 65 m, Praha Formation) was sampled for GRS (every 50 cm). The χ in and GRS records are very similar, so χ in variations are driven by variations in the samples' paramagnetic clay mineral content, reflecting changes in detrital input. Therefore, climatic variations are very likely captured in our records. Multiple spectral analysis and statistical techniques such as: Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multi-taper method and Average Spectral Misfit, were used in concert to reach an optimal astronomical interpretation. The Požar-CS section shows distinctly varying sediment accumulation rates. The Lochkovian (essentially equivalent to the Lochkov Formation (Fm.)) is interpreted to include a total of nineteen 405 kyr eccentricity cycles, constraining its duration to 7.7 ± 2.8 Myr . The Praha Fm. includes fourteen 405 kyr eccentricity cycles in the three sampled sections, while the Pragian Stage only includes about four 405 kyr eccentricity cycles, thus exhibiting durations of 5.7 ± 0.6 Myr and 1.7 ± 0.7 Myr respectively. Because the Lochkov Fm. contains an interval with very low sediment accumulation rate and because the Praha Fm. was cross-validated in three different sections, the uncertainty in the duration of the Lochkov Fm. and the Lochkovian is larger than that of the Praha Fm. and Pragian. The new floating time scales for the Lochkovian and Pragian stages have an unprecedented precision, with reduction in the uncertainty by a factor of 1.7 for the Lochkovian and of ∼6 for the Pragian. Furthermore, longer orbital modulation cycles are also identified with periodicities of ∼1000 kyr and 2000–2500 kyr.
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Refining the Early Devonian time scale using Milankovitch cyclicity in Lochkovian–Pragian sediments (Prague Synform, Czech Republic)
Earth and Planetary Science Letters, 2016Co-Authors: A C Da Silva, Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Ondřej Bábek, Frederik J Hilgen, Mark J DekkersAbstract:Abstract The Early Devonian geological time scale (base of the Devonian at 418.8 ± 2.9 Myr , Becker et al., 2012 ) suffers from poor age control, with associated large uncertainties between 2.5 and 4.2 Myr on the stage boundaries. Identifying orbital cycles from sedimentary successions can serve as a very powerful chronometer to test and, where appropriate, improve age models. Here, we focus on the Lochkovian and Pragian, the two lowermost Devonian stages. High-resolution magnetic susceptibility ( χ in – 5 to 10 cm sampling interval) and gamma ray spectrometry (GRS – 25 to 50 cm sampling interval) records were gathered from two main limestone sections, Požar-CS (118 m, spanning the Lochkov and Praha Formations) and Pod Barrandovem (174 m; Praha Formation), both in the Czech Republic. An additional section (Branžovy, 65 m, Praha Formation) was sampled for GRS (every 50 cm). The χ in and GRS records are very similar, so χ in variations are driven by variations in the samples' paramagnetic clay mineral content, reflecting changes in detrital input. Therefore, climatic variations are very likely captured in our records. Multiple spectral analysis and statistical techniques such as: Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multi-taper method and Average Spectral Misfit, were used in concert to reach an optimal astronomical interpretation. The Požar-CS section shows distinctly varying sediment accumulation rates. The Lochkovian (essentially equivalent to the Lochkov Formation (Fm.)) is interpreted to include a total of nineteen 405 kyr eccentricity cycles, constraining its duration to 7.7 ± 2.8 Myr . The Praha Fm. includes fourteen 405 kyr eccentricity cycles in the three sampled sections, while the Pragian Stage only includes about four 405 kyr eccentricity cycles, thus exhibiting durations of 5.7 ± 0.6 Myr and 1.7 ± 0.7 Myr respectively. Because the Lochkov Fm. contains an interval with very low sediment accumulation rate and because the Praha Fm. was cross-validated in three different sections, the uncertainty in the duration of the Lochkov Fm. and the Lochkovian is larger than that of the Praha Fm. and Pragian. The new floating time scales for the Lochkovian and Pragian stages have an unprecedented precision, with reduction in the uncertainty by a factor of 1.7 for the Lochkovian and of ∼6 for the Pragian. Furthermore, longer orbital modulation cycles are also identified with periodicities of ∼1000 kyr and 2000–2500 kyr.
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warming or cooling in the Pragian sedimentary record and petrophysical logs across the lochkovian Pragian boundary in the spanish central pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Jose Ignacio Valenzuelarios, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.
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Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ladislav Slavík, Jindřich Hladil, Leona Chadimova, Jauchyn Liao, Aneta Huskova, Helena Calvo, José Ignacio Valenzuela-ríos, Tomas HrstkaAbstract:Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings, where evidence for any polar ice sheets is still absent. In addition to the extant evidence of a major Lochkovian–Pragian offlap, combined with sea level lowering known from the North America, evidence about a major sea level fall and drastic reconstruction of the climatic system in the Pragian is now expanding over significant parts of the peri-Gondwanan belt. The data from Spain provide many new details about this change, including the phenomenon of a stratigraphically condensed upper Lochkovian, a dramatically different type of sedimentation in the Pragian, and a GRS-Th-and-MS anomalous stratigraphic interval in the middle Pragian. The multifaceted evidence allows us to determine the essential parts of the Pragian as a still “hot and humid” period, even with the strong differences from the possibly “extremely hot” Lochkovian.