Sedimentological and architectural aspects of dryland fluvial systems, modern analogues to the triassic deposits of the Tern Field, northern North Sea
This study examines two Modern outcrop analogues to the Cormorant Formation of the Tern Field are in order to delimit controls on architectural development. Ground-truthing of a whole-rock trace element geochemical correlation technique is also undertaken in order to understand the processes controlling perceived correlations in similar studies on sub-surface data. The Huab River in Namibia is a Modern dryland fluvial system experiencing the development of a channel fan. Detailed sedimentary logging of the fan feature reveals a systematic variation in facies, from high net-to-gross deposits in the upstream portion to low net-to-gross deposits in the downstream portion. The Plio-Pleistocene deposits of the ancestral Rio Grande in New Mexico provide an example of a dryland fluvial system developed in an active rift setting with structural context preserved throughout the area. A systematic facies variation throughout the basins is identified and related to a structural control and reveals confinement of the fluvial system close to the bounding fault in the Palomas Basin. In the Hatch-Rincon Basin facies variations from high net:gross deposits in the basin centre to low net:gross deposits in the basin margin reflect subsidence upon two bounding faults. Sedimentological analysis of three cores from the Triassic Cormorant Formation divides the succession into three facies packages. Data from the two field analogues is utilised in constructing two depositional models and two architectural models. A terminal fan model and a typical through-draining braided fluvial system are envisaged as possible depositional mechanisms. Ground-truthing of a whole-rock trace element correlation technique was carried out in both field analogues. A grainsize control upon whole-rock trace element concentration is identified in both field areas, potentially limiting the ability of the technique to be responsive to provenance. This study shows that research in areas where depositional context is preserved can provide unambiguous data that is not available in ancient studies.