Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions: from Argentinean outcrops to the Norwegian shelf subsurface

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

Trondheim

Congreso; 35th Norsk Geologisk Forening Vinterkonferanse; 2021

Geological Society of Norway

Thick shallow-marine successions associated with longterm transgressions are less well known than their thin, well-sorted counterparts, more widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary characteristics, 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, shallowmarine 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 geological 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 deposits, dominated by