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158 results on '"Weissert, H"'

3. Timing of early angiosperm radiation: recalibrating the classical succession

Author

Hochuli, P.A., Heimhofer, U., and Weissert, H.

Subjects
Geology -- Research, Earth sciences
Abstract

New stratigraphically controlled pollen data from the late Early Cretaceous of Portugal allow a recalibration of the classical continental succession of the Potomac Group (USA), which has long been used to demonstrate the gradual morphological changes of angiosperm leaves and pollen. The Portuguese record represents the best dated succession of angiosperm pollen assemblages of the interval between the late Barremian and the mid-Albian. Comparison of the angiosperm pollen record of the Potomac Group with the pollen assemblages from Portugal and with other independently dated records indicates that the distinct differences in the angiosperm pollen assemblages between the three formations of this group (the Patuxent Formation, Arundel Clay Formation and Patapsco Formation) are related to discontinuities. Our revised age model for the Potomac Group implies a major discontinuity between the Arundel Clay (of early Albian age), and the Patapsco Formation (of mid-Albian--early Cenomanian age). The Portuguese record reveals a so far undocumented radiation phase of angiosperms within the early Aptian to mid-Albian in which monocolpate angiosperm pollen of monocot and/or maguoliid affinity appear as a highly diversified group. These new findings imply that the onset of the radiation of monocots--magnoliids preceded the radiation of eudicots by at least 10 Ma.

Published
2006

4. Timing of Early Cretaceous angiosperm diversification and possible links to major paleoenvironmental change

Author

Heimhofer, U., Hochuli, P.A., Burla, S., Dinis, J.M.L., and Weissert, H.

Subjects
Portugal -- Environmental aspects, Palynology -- Observations, Angiosperms -- Environmental aspects, Earth sciences
Abstract

Palynological records from the Western Portuguese and Algarve basins (Portugal) provide new insights on the timing and pattern of the early diversification of angiosperms (flowering plants) and its relationship to global environmental perturbations during the late Early Cretaceous. Angiosperm pollen displays a stepwise increase in both diversity and relative abundance during the late Barremian to middle Albian interval (ca. 124-104 Ma), reflecting the incipient radiation of flowering plants in lower midlatitude floras. Our results provide new evidence for the age interpretation of the previously described angiosperm mesofossil floras and associated in situ pollen assemblages from the Western Portuguese basin, until now interpreted as Barremian or possibly Aptian in age. Biostratigraphic and sedimentologic evidence indicates a post-Aptian age for these assemblages, hence demonstrating a major radiation phase of angiosperms during the early Albian. Correlation of the angiosperm pollen record with data on global paleoenvironmental changes suggests a link between the rapid adaptive radiation of flowering plants and major climatic and oceanographic perturbations during the late Early Cretaceous. Keywords: Early Cretaceous, angiosperms, diversification, palynology, Portugal.

Published
2005

6. The Valanginian Weissert Oceanic Anoxic Event Recorded in Central-Eastern Sardinia (Italy)

Author

Bottini, C., Dieni, I., Erba, E., Francesco Massari, and Weissert, H.

Subjects
010506 paleontology, lithostratigraphy, lcsh:QE1-996.5, Carbon isotopes, 010502 geochemistry & geophysics, Sardinia, 01 natural sciences, Valanginian, Weissert Oceanic Anoxic Event, biostratigraphy, lcsh:Geology, lcsh:Paleontology, lcsh:QE701-760, 0105 earth and related environmental sciences
Abstract

Investigations on the S’Ozzastru section from the northern part of the Mt Albo area (central-eastern Sardinia, Italy) for integrated litho- bio- and chemostratigraphy allowed the identification of the Valanginian Weissert Oceanic Anoxic Event (OAE), testified by a positive carbon isotope excursion (CIE). The section, which represents the deepest-water succession of the Valanginian in Sardinia, is composed of the Schiriddè Limestone followed by the Siniscola Marl, both proposed as new lithostratigraphic units. The presence among the ammonites of Busnardoites campylotoxus allows the attribution of the Schiriddè Limestone to the upper Lower Valanginian Campylotoxus Zone auctt. (= Karakaschiceras inostranzewi Zone of Reboulet et al. 2014). Further characterization of this unit was not possible since it is barren/almost barren of nannofossils. The Siniscola Marl can be ascribed to the lower Upper Valanginian on the basis of the ammonite fauna indicating the Verrucosum Zone, and of the nannofossil content suggesting the Zone NK3. The carbon isotope record in the Siniscola Marl is characterized by a positive excursion with values up to 2.98 ‰. In the nannofossil assemblages, nannoconids are not particularly abundant and are found, among others, together with C. oblongata, D. lehmanii, and pentaliths. The scarcity of nannoconids is regarded as a biostratigraphic support for the identification of the Weissert OAE, as it possibly reflects the “nannoconid decline” interval which characterizes this event. The end of the Weissert OAE CIE is not recorded probably because of tectonic causes., Rivista italiana di paleontologia e di stratigrafia, 124 (3), ISSN:0035-6883

Published
2018

12. Evidence for atmospheric carbon injection during the end-Permian extinction

Author

Schneebeli-Hermann, E, Kurschner, W M, Hochuli, P A, Ware, D, Weissert, H, Bernasconi, S M, Roohi, G, Ur-Rehman, Khalil, Goudemand, N, Bucher, H, University of Zurich, and Schneebeli-Hermann, E

Subjects
560 Fossils & prehistoric life, 10125 Paleontological Institute and Museum, 1907 Geology
Published
2013

14. Orbital control on carbon cycle and oceanography in the mid-Cretaceous greenhouse

Author

Giorgioni, M., Weissert, H., Bernasconi, S. M., Hochuli, P. A., Coccioni, Rodolfo, Keller, C. E., University of Zurich, and Giorgioni, M

Subjects
1911 Paleontology, Cretaceous climatic/oceanographic mechanisms similar to those of the Cenozoic, 560 Fossils & prehistoric life, 1910 Oceanography, cycle and orbital variations existed in the mid, Cretaceous oceans were sensitive to global monsoonal variations, 10125 Paleontological Institute and Museum, Mid, A link between C, Cretaceous
Published
2012

19. A close-up view of the Permian–Triassic boundary based on expanded organic carbon isotope records from Norway (Trøndelag and Finnmark Platform)

Author

Hermann, E, Hochuli, P A, Bucher, H, Vigran, J O, Weissert, H, Bernasconi, S M, University of Zurich, and Hermann, E

Subjects
Permian–Triassic, 560 Fossils & prehistoric life, Norway, 1910 Oceanography, organic carbon isotopes, 2306 Global and Planetary Change, 10125 Paleontological Institute and Museum, particulate organic matter
Published
2010

20. Rapid demise and recovery of plant ecosystems across the end-Permian extinction event

Author

Hochuli, P A, Hermann, E, Vigran, J O, Bucher, H, Weissert, H, University of Zurich, and Hochuli, P A

Subjects
global correlation, 560 Fossils & prehistoric life, 1910 Oceanography, paleoclimate, 2306 Global and Planetary Change, chemostratigraphy, 10125 Paleontological Institute and Museum, Early Triassic, Late Permian, palynology
Published
2010

50. An oxygen-minimum palaeoceanographic signal from Early Toarcian cavity fills

Author

Mettraux, M., Weissert, H., and Homewood, P.

Abstract

Moderately deep-marine Toarcian sedimentary rocks of the Médianes Nappe (Alpine Front Ranges, Switzerland) comprise calcarenites and lime-mudstones. They were deposited under storm and fairweather conditions, in the dysaerobic zone, near the storm wave base. These remnants of the northern margin of the Tethyan Ocean show facies where primary sediment ('deep water' stromatolitic micrite) was reworked during early diagenesis. Stromatactis-like cavities were formed by carbonate dissolution near the sediment-water interface. Suboxic early diagenetic conditions are indicated by corroded pyrite and newly formed glauconitic oncoids. Carbon and oxygen stable isotope data indicate cavity stabilization and cementation above the sulphate-reducing zone. Oceanographic conditions during the time of cavity development are reconstructed from the carbon and oxygen isotope composition of cavity cements, of bulk sediment and of associated ammonites. δ 13C values of up to +4‰ are related to the Oceanic Anoxic Event of the Early Toarcian and oxygen-isotope values from cements and ammonites define a shallow Toarcian thermocline (<100 m) and surface-water temperatures up to 25°C.

Published
1989

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