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- Bercovici, Antoine, et al.
(författare)
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Palynostratigraphy of John's Nose, a new Cretaceous-Paleogene boundary section in southwestern North Dakota, USA
- 2012
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Ingår i: Palynology. - : Informa UK Limited. - 1558-9188 .- 0191-6122. ; 36, s. 36-47
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Tidskriftsartikel (refereegranskat)abstract
- This study documents the terrestrial palynological record at the John's Nose section, a new Cretaceous-Paleogene (K-Pg) boundary site in North Dakota, USA. In addition to Mud Buttes and Pyramid Butte, John's Nose represents the third K-Pg section in southwestern North Dakota that preserves direct evidence of the Chicxulub asteroid impact, allowing for direct comparison over the timing and trends of the palynological record in respect to this event. The palynological analysis of John's Nose section reveals the presence of 68 pollen and spore taxa. Immediately above the boundary clay, a high abundance of fern spores of the genera Cyathidites and Laevigatosporites is recorded (with 59% of the assemblage being represented by Cyathidites). This very distinctive K-Pg 'fern spike' event is correlated with the devastation of land plants immediately following the asteroid impact and matches the composition generally reported from other sites in southwestern North Dakota. Palynostratigraphy demonstrates that the placement of the K-Pg boundary based upon the identification of the Last Appearance Datum (LAD) of typical Maastrichtian taxa (K-taxa) may be misleading. The presence of occasional K-taxa up to a few meters above the boundary clay at John's Nose represents an important difference when compared to previous reports. In light of this observation, LADs should be used cautiously as the primary criteria to identify the boundary; some K-taxa may have a short-term presence in the earliest Paleogene, or be reworked. In the John's Nose section, major changes and extinction in the palynological record occur at the geochemical K-Pg boundary, indicating that a catastrophic turnover took place over a short time.
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| 2. |
- Bercovici, Antoine, et al.
(författare)
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Palynostratigraphy of the cretaceous-paleogene mass-extinction interval of the Northern Hemisphere
- 2012
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Ingår i: Dìcéngxué zázhì. - 0253-4959. ; 36:2, s. 165-178
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Tidskriftsartikel (refereegranskat)abstract
- For a long time debate has taken place regarding the trends and extinction rates associated with the Cretaceous- Paleogene (K-Pg) mass extinction event on land. While mainly focussed on vertebrates and more especially non-avian dinosaurs, the dynamics of the plant cover remains nonetheless a major component for the understanding the biological response across the K-Pg interval and associated ecosystem destabilization. In this paper, we present a review of the late Cretaceous to Paleogene pollen and spore stratigraphy within the Northern Hemisphere Aquilapollenites paleophytogeographic province. In the United States of America, Late Cretaceous assemblages are marked by the appearance of a series of key-taxa, the Santonian-Campanian transition is characterized by the appearance of Aquilapollenites and associated triprojectate genera, while the base of the Maastrichtian is marked by the appearance of the oculate genus Wodehouseia as well as Kurtzipites sp. The K-Pg extinction event remains easily identifiable in the palynological record with the disappearance of a series of angiospermous taxa part of the Wodehouseia spinata Assemblage Zone, which are characterized by relatively large size and complex wall structure. The recovery palynoflora in the Paleocene is represented by assemblages dominated by porate grains, with key-species from the Momipites and Caryapollenites genera. As current data covers mostly the North American terrestrial record, more research efforts are needed within Chinese,European and Southern Hemisphere localities to provide for a better understanding of the global response of the terrestrialbiosphere to the K-Pg impact event.
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| 3. |
- Bercovici, Antoine, et al.
(författare)
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Permian continental paleoenvironments in Southeastern Asia: New insights from the Luang Prabang Basin (Laos)
- 2012
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Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120. ; 60, s. 197-211
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Tidskriftsartikel (refereegranskat)abstract
- In Laos (Southeastern Asia), Late Paleozoic sediments were identified by early French explorations across Indochina during the late 19th century (Pavie missions), but little work was undertaken to characterize the sedimentological and stratigraphical context until now. From detailed sedimentological and paleontological studies, we propose an interpretation of the depositional environment and of the stratigraphic context of series located on the right bank of the Mekong River in the Luang Prabang Basin where three main formations were described. The silicoclastic Red Claystone Formation, attributed to alluvial plain environment, contains large fragments of unidentified dicynodonts. The Limestones and Sandstones Formation preserves a new macrofloral assemblage displaying affinities with Middle to Late Permian Cathaysian floras of South China. This assemblage occurs as an intercalation within marine calcareous sandstones that have yielded a marine fauna, including the ammonoid Pseudotirolites sp. which indicates a Late Permian (Changhsingian) age. The well-developed Purple Claystones Formation yielded an abundant and well preserved Late Permian fauna composed of a carnivorous amphibian and numerous Dicynodon cranial and postcranial elements. This formation shows a vertical evolution from braided river to alluvial plain with sheet-flood sand bed and bed-load rivers, with a constant supply of volcanic clasts. Results from the analysis of the paleontological associations in the Luang Prabang Basin suggest that a continental communication between Laurussia and the Indochina Block existed during the Permian, allowing for migration of the terrestrial Dicynodon fauna. (C) 2012 Elsevier Ltd. All rights reserved.
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| 4. |
- Miguel Sender, Luis, et al.
(författare)
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A new uppermost Albian flora from Teruel province, northeastern Spain
- 2012
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Ingår i: Geodiversitas. - : Museum National d'Histoire Naturelle, Paris, France. - 1638-9395 .- 1280-9659. ; 34:2, s. 373-397
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports a new Early Cretaceous flora discovered recently near the village of Estercuel (Teruel province, northeastern Spain). The plant bearing beds belong to the uppermost part of the Early Cretaceous succession, at the top of the fluvial deposits of the Utrillas Formation. The site has yielded a diverse assemblage of plant compressions including lycopods and ferns, various gymnosperms as well as terrestrial and aquatic angiosperms. Leaves of aquatic lycopods (Isoetites sp.) constitute a minor component of the palaeobotanical assemblage. Filicales are not very common, with Dicksoniales (Onychiopsis sp.) and a few specimens of Cladophlebis type fronds. The gymnosperms are represented by fragmented remains of long parallel veined Desmiophyllum leaves as well as a great abundance of conifer axis corresponding to the form-genus Pagiophyllum and female cones. Terrestrial angiosperms include pinnately lobed leaves of the genus Myricompia, simple leaves with spatulate lamina and some petiolate leaves both corresponding to angiosperms of uncertain affinity. Aquatic angiosperms consist of Nelumbo-like floral receptacles (Nelumbonaceae, Proteales) and Aquatifolia cf: fluitans (Nympheales). The palynological assemblage is dominated by pollen of gymnosperms (mainly Taxodiaceaepollenites hiatus, Classopollis major and Araucariacites australis). It also includes many angiosperm grains (Afropollis jardinus, Clavatipollenites spp., Di-chastopollenites spp., Liliacidites doylei, Monosulcites chaloneri, Penetetrapites mollis, Pennipollis spp., Phimopollenites augathellaensis, Retimonocolpites textus, Rousea spp., Senectotetradites varireticulatus, Stellatopollis barghoornii, Striatopollis spp., Transitoripollis sp. cf. T similis, Tricolpites spp., Tricolporoidites sp.) and records the first occurrence of tricolporate forms in the uppermost part of the Utrillas Formation. Both macroflora and microflora assemblages present taxa similar to those of the uppermost Albian Shaftesbury Formation in northwestern Alberta in Canada, the uppermost Albian Denton Shale Member of Bokchito Formation in southern Oklahoma, the lower part of the Upper Albian Dakota Formation from the mid-west of North America, and Subzone II C of the Potomac Group, eastern United States. Both macro- and microflora assemblages display boreal influence with some similar taxa to those of the Upper Albian Kome Formation in western Greenland and some taxa as Afropollis jardinus and Stellatopollis barghoornii more frequently found in the tethyan and gondwanan realms. A gondwanan affinity is also indicated by the presence of Klitzschophyllites leaves.
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| 5. |
- Vajda, Vivi, et al.
(författare)
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Palynostratigraphy of the Cretaceous-Paleogene mass-extinction interval of the Southern Hemisphere
- 2012
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Ingår i: Dìcéngxué zázhì. - 0253-4959. ; 36:2, s. 153-164
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Tidskriftsartikel (refereegranskat)abstract
- The palynofloral changes around the Cretaceous-Paleogene (K-Pg) mass extinction event reveal the fine details of vegetation response to a global environmental crisis-in this case an asteroid impact in Mexico 65.5 million years ago. Due to the extinction of several plant taxa at the K-Pg boundary, palynostratigraphy is a prime tool for localizing the Cretaceous-Paleogene boundary in non-marine successions. The Southern Hemisphere includes the tropical to sub-tropical Palmae Province, the high-latitude Nothofagidites/Proteacidites Province, and a transitional zone of mixed floristic composition. Maastrichtian key-species that go extinct at the Cretaceous-Paleogene boundary within the Palmae Province include Aquilapollenites magnus, Buttinia andreevi, Crassitricolporites brasiliensis, Proteacidites dehaani and Gabonisporis vigourouxii. In the Nothofagidites/Proteacidites Province, taxa such as Tricolporites lilliei, Triporopollenites sectilis, Quadraplanus brossus, Nothofagidites kaitangata, and Grapnelispora evansii have their last appearances at the boundary. It is obvious that more thorough analyses of the palynological signals across the K-Pg boundary in the The palynofloral changes around the Cretaceous-Paleogene (K-Pg) mass extinction event reveal the fine details of vegetation response to a global environmental crisis-in this case an asteroid impact in Mexico 65.5 million years ago. Due to the extinction of several plant taxa at the K-Pg boundary, palynostratigraphy is a prime tool for localizing the Cretaceous-Paleogene boundary in non-marine successions. The Southern Hemisphere includes the tropical to sub-tropical Palmae Province, the high-latitude Nothofagidites/Proteacidites Province, and a transitional zone of mixed floristic composition. Maastrichtian key-species that go extinct at the Cretaceous-Paleogene boundary within the Palmae Province include Aquilapollenites magnus, Buttinia andreevi, Crassitricolporites brasiliensis, Proteacidites dehaani and Gabonisporis vigourouxii. In the Nothofagidites/Proteacidites Province, taxa such as Tricolporites lilliei, Triporopollenites sectilis, Quadraplanus brossus, Nothofagidites kaitangata, and Grapnelispora evansii have their last appearances at the boundary. It is obvious that more thorough analyses of the palynological signals across the K-Pg boundary in the Southern Hemisphere and China are required to elucidate the detailed patterns of vegetation response at different latitudes and at varying distances from the impact site in Yucatan, Mexico.
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