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| Titel |
Warm Middle Jurassic–Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean |
| VerfasserIn |
Hugh C. Jenkyns, L. Schouten-Huibers, S. Schouten, J. S. Sinninghe Damsté |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 1 ; Nr. 8, no. 1 (2012-02-02), S.215-226 |
| Datensatznummer |
250005370
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| Publikation (Nr.) |
 copernicus.org/cp-8-215-2012.pdf |
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| Zusammenfassung |
| Although a division of the Phanerozoic climatic modes of
the Earth into "greenhouse" and "icehouse" phases is widely accepted,
whether or not polar ice developed during the relatively warm Jurassic and
Cretaceous Periods is still under debate. In particular, there is a range of
isotopic and biotic evidence that favours the concept of discrete "cold
snaps", marked particularly by migration of certain biota towards lower
latitudes. Extension of the use of the palaeotemperature proxy TEX86
back to the Middle Jurassic indicates that relatively warm sea-surface
conditions (26–30 °C) existed from this interval (∼160 Ma) to the
Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general
warming trend through the Late Jurassic followed by a general cooling trend
through the Early Cretaceous. The lowest sea-surface temperatures are
recorded from around the Callovian–Oxfordian boundary, an interval
identified in Europe as relatively cool, but do not fall below 25 °C. The
early Aptian Oceanic Anoxic Event, identified on the basis of published
biostratigraphy, total organic carbon and carbon-isotope stratigraphy,
records an interval with the lowest, albeit fluctuating Early Cretaceous
palaeotemperatures (∼26 °C), recalling similar phenomena recorded
from Europe and the tropical Pacific Ocean. Extant belemnite δ18O
data, assuming an isotopic composition of waters inhabited by
these fossils of −1‰ SMOW, give palaeotemperatures throughout the
Upper Jurassic–Lower Cretaceous interval that are consistently lower by
∼14 °C than does TEX86 and the molluscs likely record
conditions below the thermocline. The long-term, warm climatic conditions
indicated by the TEX86 data would only be compatible with the existence
of continental ice if appreciable areas of high altitude existed on
Antarctica, and/or in other polar regions, during the Mesozoic Era. |
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