Mineral Assemblages at IODP Sites U1387 and U1389, Gulf of Cadiz: Definition by Principal Component Analysis and Interpretation of Their Geologic Significance
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Date
2015-08
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Publisher
The Ohio State University
Abstract
The Gulf of Cadiz and the West Iberian margin were the location where
Expedition 339 of the Integrated Ocean Drilling Program (IODP) collected sediment
cores to better understand the Mediterranean Outflow Water (MOW) and its history.
Sediment from Sites U1387 and U1389 was analyzed by X‐ray diffraction (XRD) method
aboard the JOIDES Resolution to determine the bulk mineralogy at the two sites. In this
study, shipboard data were processed using Paleontological Statistics (PAST) software
to identify mineral assemblages using principal components analysis. The mineral
assemblages were defined by covarying minerals, and were used to determine sediment
provenance. At Site U1387, the three most important principal components defined five
mineral assemblages that consisted of plagioclase, dolomite, kaolinite, K‐feldspar,
augite, aragonite and chlorite. At Site U1389, the three most important principal
components defined six mineral assemblages made up of plagioclase, dolomite,
chlorite, and aragonite. Principal Component 2 at Site U1387 and Principal Component
1 and 3 at Site U1389 are indicative of a relationship between marine biogenic vs.
terrigenous detrital sediment supply, and the other principal components identify
various assemblages of detrital terrigenous minerals. The results generally identified a
local provenance from the Guadiana and Guadalquivir Rivers, with erosion of exposed
beaches and cliffs as other possible sources of sediment supply. This supports the
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conclusion that Gulf of Cadiz sediments have been supplied from a variety of nearby
areas, with transport and deposition influenced by many environmental and geological
influences.
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Keywords
Mineral Assemblages, Gulf of Cádiz, Principal Component Analysis, Sedimentology