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Modeling the early Paleozoic long-term climatic trend

Elise Nardin, Yves Godderis, Yannick Donnadieu, Guillaume Le Hir, Ronald C. Blakey, Emmanuelle Puceat and Markus Aretz
Modeling the early Paleozoic long-term climatic trend
Geological Society of America Bulletin (May 2011) 123 (5-6): 1181-1192


The early Paleozoic climate has been described as warm and equable. However, recent data based on conodont oxygen isotopic composition reveal a large, long, cooling trend through the Ordovician, followed by an abrupt cooling during the Late Ordovician glaciation. This long-term climate change is associated with a major radiation in the Earth life history. Nonetheless, the driving mechanisms for this cooling trend remain unknown. Carbon dioxide consumption by the weathering of fresh rocks from volcanic arcs has recently been suggested as a possible driver for this climate change. However, the impact of the plate motion context has not been explored yet, although it might have a major impact on atmospheric CO (sub 2) levels. Simulations with a climate model coupled to a biogeochemical model (GEOCLIM) show that the atmospheric CO (sub 2) decreased from more than 20 PAL ( approximately 5600 ppmv) in the Furongian down to approximately 10 PAL ( approximately 2800 ppmv) in the Llandovery before rising again in the Early Devonian. We suggest that changes in geography and exposure of fresh volcanic rocks on continents are required to explain the large CO (sub 2) drawdown that led to the onset of cooler to glacial conditions from the Middle Ordovician to the Llandovery. The weathering of fresh volcanic rocks is itself responsible for 33% of the Late Ordovician atmospheric CO (sub 2) decrease; the rest being related to the continent motion through the intertropical convergence zone (ITCZ). Mean annual continental temperature falls by 3 degrees C in the Early Ordovician, reaching 13.5 degrees C during the glacial interval, and rises to 16 degrees C in the Early Devonian.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 123
Serial Issue: 5-6
Title: Modeling the early Paleozoic long-term climatic trend
Affiliation: Observatoire Midi-Pyrenees, Laboratoire des Mecanismes et Transfert en Geologie, Toulouse, France
Pages: 1181-1192
Published: 201105
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 99
Accession Number: 2011-044443
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
Secondary Affiliation: Laboratoire des Sciences du Climat et de l'Environnement, FRA, FranceUniversite Paris Diderot, FRA, FranceNorthern Arizona University, USA, United StatesUniversite de Dijon, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201125
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