Textural and geochemical characteristics of late Pleistocene to Holocene fine-grained deep-sea sediment cores (GM6 and GM7), recovered from southwestern Gulf of Mexico

Abigail Anaya-Gregorio,María Luisa Machain-Castillo,John S Armstrong-Altrin,Mayla A Ramos-Vázquez,Patricia C Montiel-García

doi:10.1186/s42501-018-0005-3

Abstract

Texture, mineralogy, geochemistry, and 14C ages of two deep-sea sediment cores (GM6 and GM7) recovered in the southwestern Gulf of Mexico were investigated to infer their provenance and depositional condition. The sediments are enriched in fine-grained silt and clay and poor in sand content. Mineralogically, the sediments consist of quartz, calcite, smectite, and kaolinite. Based on the 14C data, the age of the GM6 and GM7 sediment cores were calculated as 23,615 cal yrs. BP and 19,007 cal yrs. BP, respectively. The weathering indices such as chemical index of alteration (CIA), chemical index of weathering (CIW), and plagioclase index of alteration (PIA) in GM6 (56–69, 60–74, and 61–73, respectively) and GM7 (54–69, 57–76, and 55–74, respectively) cores revealed a moderate-to-high intensity of weathering. The rare earth element (REE) patterns suggested that the sediments were derived mostly by the weathering of intermediate rocks, exposed along the coastal regions of the Gulf of Mexico. The trace elemental ratios like V/Cr (<2), Ni/Co (<2), and Cu/Zn (<1), authigenic uranium content (<1), and Ce anomaly (Ce/Ce* ≤ 1) suggested that the sediments were deposited under an oxic condition, which was also revealed by the benthic foraminiferal assemblages throughout the GM6 and GM7 sediment cores.

Highlights

The composition of terrigenous sediments is largely influenced by the nature of parent rocks and sedimentary processes during transportation and within the depositional basin (Armstrong-Altrin 2015; Basu 2017)
Immobile elements like rare earth element (REE), Co, Cr, Th, and Sc in sediments are considered as good provenance indicators, because they are not fractionated during sedimentary processes like diagenesis and weathering (Fedo et al 1995)
5.1 Time framework The time framework was elaborated based on seven 14C dates, which was followed by the biostratigraphical scheme of Kennett and Huddlestun (1972) and Kennett et al (1985)

Summary

Introduction

The composition of terrigenous sediments is largely influenced by the nature of parent rocks and sedimentary processes during transportation and within the depositional basin (Armstrong-Altrin 2015; Basu 2017). Unstable minerals and mobile elements can be affected by weathering and erosional processes during transportation. Immobile elements like REE, Co, Cr, Th, and Sc in sediments are considered as good provenance indicators, because they are not fractionated during sedimentary processes like diagenesis and weathering (Fedo et al 1995). Previous studies by Carranza-Edwards et al (2001) reported the composition of coastal sediments from the northwestern part of the Gulf of Mexico and inferred their provenance.

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Discussion

Conclusion