Inclined heterolithic stratification—Terminology, description, interpretation and significance

Abstract: In northern and central Ethiopia, continental to shallow-marine siliciclastic sediments of up to 430 m thick are exposed. These sediments are referred to as the ‘Adigrat Sandstone’. This study provides a detailed investigation of the stratigraphy, sedimentary facies, depositional environments and palynology of the ‘Adigrat Sandstone’ succession in the Mekelle and Blue Nile basins in order to obtain a complete picture of the large-scale spatial/temporal stacking patterns of depositional systems, whereby a new knowledge of the mode of evolution of the basins and the mechanisms controlling their formation can be obtained. The study also provides a more reliable stratigraphic position for the sandstone succession based on palynological data. Three unconformity bounded stratigraphic units have been identified within the Late Triassic to Middle Jurassic ‘Adigrat Sandstone’ succession. Unit I that represents the lower stratigraphic unit in both basins is Late Triassic (Late Carnian–Early Rhaetian) in age. It is composed of transgressive tide-dominated estuarine and prograding storm-dominated shoreface deposits. The overall northeastward-thickening wedge-shaped geometry of the depositional body and the palaeocurrent patterns in both basins suggest that the sediments accumulated on a vast slowly subsiding passive continental margin in a shallow gulf, which extended northeast into the Neotethys. This indicates that the Late Triassic shallow gulf, which encroached into the Arabian platform from the northeast, had most probably reached the northern and central parts of Ethiopia. A Neotethyan seaway through Saudi Arabia into

TL;DR: In this article, the authors proposed a new method of analysis for fluvial facies, which subdivides fluvic deposits into local suites consisting of one or more of a set of eight basic three-dimensional architectural elements.