Abrasion of detrital grain-coating clays during sediment transport: Implications for diagenetic clay coats

Abstract

Detrital grain-coating clay minerals have been identified as precursors of diagenetic grain-coating clay minerals that inhibit quartz cementation and preserve good reservoir quality properties in deeply buried sandstone reservoirs. Between initial and final deposition, detrital grain coats are likely to be affected by sediment transport processes. To date, it has not been demonstrated that detrital grain-coating clays are able to survive sediment transport. Flume experiments simulating open-channel flow conditions were performed using sediments from the Ravenglass estuary (Cumbria, UK), where the distribution and characteristics of modern detrital grain-coating clays is well established. Scanning electron microscopy and automated mineralogy techniques were employed to study the sediment before and after transport to determine the stability of the detrital grain-coating clays. The experimental results show that detrital grain-coating clays are still present after sediment transport in turbulent flows with velocities up to 0.5 m s−1. The stability of the detrital grain-coating clays was enhanced by (1) high initial clay coat coverage, (2) turbulence characteristics of the flow, and (3) entrapment of the detrital grain-coating clays in bedforms. This work documents the first quantifiable evidence that estuary-derived, detrital clay coats are routinely preserved after sediment transport. Clay coat-rich estuarine sediments can therefore act as the source of clay coated grains found in cleaner estuarine sandstones and may even survive transport out into open marine settings.