The relative dominance of allo-controls and local-scale sedimentary processes upon preserved successions of aeolian-marine margins

Abstract

The sedimentology, controls and efficiency of central erg environments are wellconstrained, however marginal relationships are less understood and often underrepresented. The Moab Member of the Curtis Formation is a well-exposed, laterally continuous example of the preserved sediments of an aeolian erg system deposited along a marine margin. It comprises the Upper Jurassic deposits found on the Colorado Plateau, a 380,000km2 area in the Four Corners region of the Western United States. The Moab Member provides an excellent opportunity to study the controls upon aeolian dune fields with increasing proximity to the coastal marine margin. Lateral relationships within the Curtis Formation preserve spatial interactions between systems, temporal interactions are represented by the vertical transition from the Moab Member into the overlying Summerville Formation. This work provides an understanding and analysis of both the sequence-stratigraphical scale and the element scale interactions between dune and contemporaneous sedimentary deposition.
Results from fieldwork carried out in the Canyonlands Section of the Colorado Plateau provided extensive data in the form of sedimentary logs, Spectral Gamma Ray (SGR) data and drone photogrammetry. The collation of these individual data sets enabled a basin wide analysis and the construction of sedimentary models providing a context for the deposition of the Moab Member and its contemporaneous environments.
The results identify a significant change in the sedimentology and geometry of the erg system towards the marine margin. Establishing the morphologies of this system and its interactions with the surrounding environments enabled the identification of ‘pulses’ linked to small scale sea-level fluctuations. When considered within the wider framework of basin sea-level fluctuations identified from shallow marine deposits, which preserved allocyclic signals, these smaller scale events provide a more in-depth characterisation of sequence stratigraphy in the area and hence document the behaviour of the aeolian-marine margin through a transgressive-regressive cycle.