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Mid-Cretaceous greenhouse climate - in search for feedbacks between climate and oceanography

English title Mid-Cretaceous greenhouse climate - in search for feedbacks between climate and oceanography
Applicant Weissert Helmut
Number 126563
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.11.2009 - 31.10.2010
Approved amount 61'528.00
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Keywords (12)

C-cycle; Cretaceous; Greenhouse climate; Black shales; Paleoceanography; Paleoclimatology; Black shale; carbon cycle; carbon isotopes; paleoclimate; sedimentology; palynology

Lay Summary (English)

Lead
Lay summary
The late Early Cretaceous sedimentary climate archives contain a record of repeated greenhouse pulses interrupted by episodes of cool climate sometimes culminating in ice age interludes. Carbon isotope records, used as proxies of global carbon cycling provide evidence for multiple perturbation of the carbon cycle during the late Early and early Late Cretaceous. Positive carbon isotope excursions coincide with formation of Large Igneous Provinces and, therefore, volcanism is considered as the trigger of C-cycle perturbations and greenhouse climate. The positive carbon isotope anomaly in the Aptian is correlated with the formation of the Ontong-Java Igenous Province. A prominent negative carbon isotope spike, which precedes this positive carbon isotope pulse, records an episode of extreme volcanic activity, possibly amplified by release of methane from clathrates. A positive carbon isotope excursion of Barremian age and a negative spike near the Barremian - Aptian boundary indicate that climate and carbon cycling was unstable already in Barremian times. In this project, we are tracing climate trends during Barremian and early Aptian with palynology and isotope geochemistry. We will test the hypothesis that a cool and dry climate phase near the Barremian - Aptian boundary coincided with carbonate sedimentation We will compare data from a Southern Tethyan locality and from a coastal locality in the Lusitanian Basin (Portugal). These data will be combined with sedimentological information and with paleoclimatological data from the literature. In this project we will investigate, if carbon isotope excursions can be related to observed black shale episodes and if "pre-OAE 1 black shales" are comparable in sedimentology and isotope geochemistry to the black shales occurring during OAE 1a. Selected black shale levels of Barremian and early Aptian age will be chosen for detailed palynological, geochemical and sedimentological investigations. These data will be used for comparison of these pre-OAE black shales with major organic-rich deposits formed during OAE1 and OAE2.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

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Associated projects

Number Title Start Funding scheme
132775 Mid - Cretaceous climate and oceanography -towards extreme Greenhouse conditions 01.11.2010 Project funding
68061 Evolution of late Early Triassic ammonoid faunas and climatic/oceanographic constraints 01.10.2002 Project funding
113687 Mid-Cretaceous greenhouse climate and opening oceanic gateways: in search for feedbacks between tectonics, climate and oceanography 01.11.2006 Project funding
113687 Mid-Cretaceous greenhouse climate and opening oceanic gateways: in search for feedbacks between tectonics, climate and oceanography 01.11.2006 Project funding
149168 Cretaceous climate and oceanography 01.11.2013 Project funding

Abstract

« Mid-Cretaceous greenhouse climate in search for feedbacks between climate and oceanography »This proposal forms the continuation of a running PhD thesis at ETH Zürich. The PhD student Christina Keller has been working on this project since November 2006. The late Early Cretaceous sedimentary climate archives contain a record of repeated greenhouse pulses interrupted by episodes of cool/dry climate. Carbon isotope records, used as proxies of global carbon cycling provide evidence for multiple perturbations of the carbon cycle during the late Early Cretaceous.The largest E. Cretaceous positive carbon isotope excursion is dated as Early Aptian in age. This excursion is preceded by a negative carbon isotope spike and a change in fractionation between carbonate carbon and organic carbon. New data acquired in part I of this project (2006-2009) indicate that this spike records an episode of extreme volcanic activity, possibly amplified by release of methane from clathrates. Goal of the prolongation part of this project is to test if the climate before the Aptian greenhouse pulse was already affected by repeated changes in carbon cycling causing the establishment of episodic greenhouse climate conditions. A positive carbon isotope excursion of Barremian and earliest Aptian age interrupted by a negative anomaly near the Barremian - Aptian boundary as well as repeated black shale deposits indicate that climate and carbon cycling was unstable already in Barremian and earliest Aptian times.We will compare sedimentological and geochemical records from a pelagic environment (S. Tethys) with new palynological data, which will provide information on the low latitude climate patterns during a time of episodic black shale formation. In addition, we will compare the new data from Southern Tethyan localities with results from a coastal locality in the Lusitanian Basin (Portugal) in order to trace the differences between the distal, pelagic carbonate environment and the shallow, coastal mixed carbonate-siliciclastic environment and identify which are the global signals and which express local factors.
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