Sedimentary patterns on the western East Pacific Rise flank in the Central South Pacific

Michael.Horn [ at ]


Depositional patterns near mid ocean ridges (MOR) have scarcely been the focus of seismic and geological studies although they provide valuable information about sedimentation processes and oceanic circulation without the influence of upwelling or terrigenous material input. New high-resolution seismic reflection data at the western flank of the East Pacific Rise (EPR) provide insights in sedimentation distribution at a flank of a MOR. Observations reveal two different zones of sedimentation with a constant sediment thickness inside Zone 1 (age between 4 and 9 Ma) and a decreasing sedimentary cover inside Zone 2 (age between 9 and 18.5 Ma). The results are not in agreement with existing models for deposition at MORs. An empirical model developed in 1967 predicts increasing sediment thickness in Zone 1 and a constant cover inside Zone 2. The assumptions of a numerical model developed for the Atlantic Ocean could only explain the decrease in sediment thickness. Variations of the carbonate compensation depth (CCD) exist in the Pacific but the palaeo-CCD is not as shallow as in the Atlantic. It is not certain whether it really has affected the sediments during the Middle Miocene. To explain the observed pattern we consider another approach attributing the differences to bottom current activity. Bottom current flow and a decreased sedimentation rate since the Miocene-Pliocene boundary can explain the low sediment accumulation and the constant sedimentary cover inside Zone 1 as well as the decreasing cover thickness inside Zone 2. The onset of the proposed bottom current activity fits modifications in global oceanic circulation due to renewed cooling following the Mid Miocene Climatic Optimum. This signal is documented our data via the formation of the two zones of sedimentary thickness.

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Conference (Talk)
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Treffen der Deutschen Geophysikalischen Gemeinschaft Leipzig, 04 Mar 2013 - 07 Mar 2013.
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Horn, M. and Uenzelmann-Neben, G. (2013): Sedimentary patterns on the western East Pacific Rise flank in the Central South Pacific , Treffen der Deutschen Geophysikalischen Gemeinschaft Leipzig, 4 March 2013 - 7 March 2013 .

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