Genesis, Architecture, and Numerical Modeling of Intra-Parasequence Discontinuity Surfaces In Wave-Dominated Deltaic Deposits: Upper Cretaceous Sunnyside Member, Blackhawk Formation, Book Cliffs, Utah, U.S.A.

Towards a sequence stratigraphic solution set for autogenic processes and allogenic controls: Upper Cretaceous strata, Book Cliffs, Utah, USA

“…First, a localized (10 0 -10 2 km 2 ) autogenic variation in sediment flux or transport capacity through a distributary river channel may have caused an internal threshold in differential floodplain topography to be exceeded, thus triggering delta-lobe switching and shoreline reorganization, which in turn modified local wave climate (e.g. within parasequences in Aberdeen and Sunnyside members of the Blackhawk Formation; Sømme et al 2008;Charvin et al 2010). Second, the distribution of channelized fluvial sandbodies in alluvial-to-coastal-plain strata of the Blackhawk Formation reflects river avulsion across a wide range of boundary conditions , but variations in avulsion-generated patterns of sandbody distribution are modified or overprinted by temporal variations in tectonic subsidence rate and the location of valleys cut during relative sea-level falls (Hampson et al 2012).…”

“…Such delta-lobe switching may also have driven temporal variations in wave-generated, alongshore sediment supply and in localized shoreline palaeogeography, which are subtly expressed in wave-dominated shoreface successions within parasequences (e.g. Sømme et al 2008). Thus, shallow-marine strata of the Blackhawk Formation contain a subtle but pervasive architectural motif that probably records autogenic processes over time scales significantly shorter than parasequence duration (i.e.…”

Distribution of discontinuous mudstone beds within wave-dominated shallow-marine deposits: Star Point Sandstone and Blackhawk Formation, Eastern Utah, USA

“…The subaerial expression of the shoreface deposits are believed to have been strandplains with linear beach ridges, while the coastal plain behind the DF are believed to have consisted of a distributary channel and arcutate beach ridges (e.g. Sømme et al, 2008) …”

“…Bedsets (sensu van Wagoner et al, 1990) are thin (1-10 m) intra-parasequence cycles of upward-shallowing, progradational packages of sediment which show an apparent upwardshoaling succession of facies, commonly from offshore transition to lower-shoreface, and are abruptly overlain by more distal facies (Storms and Hampson, 2005;Sømme et al, 2008). The upper bounding surfaces dip gently paleo-seawards, and can be traced for many kilometers in that direction, but lose their character as they are truncated by upper shoreface deposits updip.…”

“…Minor rises in relative sea-level, which cause shoreline trajectories to climb more steeply, will lead to a change in facies stacking in the lower shoreface and offshore transition zone, without dislocating the shoreline landward (Hampson and Storms, 2003;Storms and Hampson, 2005). Local changes in wave regime or changes in sediment supply, often caused by avulsion of rivers feeding sediment to the shoreline, will also result in local disconformities that are not associated with a landward migration of the shoreline (Hampson and Storms, 2003;Storms and Hampson, 2005;Sømme et al, 2008;). These discontinuities happen at a sub-regional scale and can potentially be correlated between wells within a single oilfield at standard well spacing .…”