The origin of clay-coated sand grains and sediment heterogeneity in tidal flats

Wooldridge, Luke J, Worden, Richard H ORCID: 0000-0002-4686-9428, Griffiths, Joshua, Utley, James EP ORCID: 0000-0003-0397-5607 and Thompson, Anu (2018) The origin of clay-coated sand grains and sediment heterogeneity in tidal flats. Sedimentary Geology, 373. pp. 191-209.

Text Wooldridge-Worden-2018 Sed Geol accepted paper.pdf - Author Accepted Manuscript Download (24MB)

Abstract

The presence and distribution of clay minerals attached to grain surfaces as coats (also known as rims) are of great interest because they affect petroleum reservoir quality via the inhibition of the porosity-occluding quartz cement during prolonged burial and heating. Being able to predict the distribution of clay-coated sand grains in petroleum reservoirs is thus important to help find and exploit anomalously high porosity sandstones deep in sedimentary basins. The few studies focused on the distribution of clay coats in marginal marine sediments derive from surface sediment-based data sets, with limited emphasis placed on the preservation of the surface trends in sediment undergoing eodiagenesis in the near-surface environments. The post-depositional processes of bioturbation (sediment homogenisation) and infiltration of clay into sand-grade sediment have been widely invoked as potential mechanisms that produce clay coats in modern sands and ancient sandstones. However, the potential for such processes to alter surface trends and govern clay-coat distribution in the subsurface remains unconstrained. In this study, we have developed a novel, quantitative model of clay-coat coverage in order to identify the controlling mechanisms that govern clay-coat distributions. This study has focused on surface and near-surface sediments in the Saltcoats tidal flat deposits of the Ravenglass Estuary, UK. This bio-sedimentary study involved geomorphic mapping, core logging, a range of scanning electron microscopy techniques, and quantification of grain-size, clay fraction content, biofilm abundance (total carbohydrate and biomarker analysis), clay-coat coverage, and clay-coat mineralogy. In this study, we show that infiltration and bioturbation have not significantly affected the extent of clay-coat grain coverage in near-surface sediments. Instead, the extent, distribution, and mineralogy of clay coats in near-surface sediment are governed by the surface-based hydrological segregation of the clay mineral assemblage and biological clay-coat formation.

Item Type:	Article
Uncontrolled Keywords:	Clay coated sand grains, Clay mineralogy, Reservoir quality, Modern analogue, Biofilms, Sediment heterogeneity
Depositing User:	Symplectic Admin
Date Deposited:	18 Jun 2018 08:52
Last Modified:	19 Jan 2023 01:32
DOI:	10.1016/j.sedgeo.2018.06.004
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3022726