Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions

POYATOS-MORÉ, M.; SCHWARZ, E.; BOYA, S.; GOMIS-CARTESIO, L.; MIDTKANDAL, I.

Congreso; 35th International Meeting of Sedimentology; 2021

Thick shallow-marine successions associated with long-term transgressions are less well known than their thin, well-sorted counterparts, widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary char acteristics, making stacking patterns and sequences difficult to define, and challenging our understanding of the main controls in their resulting depositional architecture. This study presents an example from the Jurassic of the Neuquén Basin (Argentina), with the aim to: a) refine the depositional model of a thick, shallow-marine succession associated with a long-term, early post-rift transgression, b) constrain multi scale controls on stratigraphic architecture and lateral facies variability, and c) discuss their preservation and response to post-depositional processes. To do this, a 10 km continuous exposure, with mapping, sedimentary logging and correlation of stratigraphic units, integrated with subsurface, biostratigraphic and ichnological data. The succession shows an overall retrogradational-aggradational-retrogradational stacking pattern, with several higher frequency regressive units (parasequences and parasequence sets, PSS). The lower part (PSS I) comprises laterally-discontinuous (10´s of m) mouth-bars and distributary channel fills, dominated by several m-thick coarsening- and fining-up sandstone packages and m-scale erosive conglomeratic lenses. Above these, the succession (PSS II-IV) is composed by laterally-continuous (>100´s of m) storm-dominated lower-shoreface to upper-offshore de posits, dominated by