Controls on large‐scale patterns of fluvial sandbody distribution in alluvial to coastal plain strata: Upper Cretaceous Blackhawk Formation, Wasatch Plateau, Central Utah, USA

Abstract

Current models of alluvial to coastal plain stratigraphy are concept‐driven and focus on relative sea‐level as an allogenic control. These models are tested herein using data from a large (ca 100 km long and 300 m thick), continuous outcrop belt (Upper Cretaceous Blackhawk Formation, central Utah, USA). Many channelized fluvial sandbodies in the Blackhawk Formation have a multilateral and multistorey internal character, and they generally increase in size and abundance (from ca 10% to ca 30% of the strata) from base to top of the formation. These regional, low‐resolution trends exhibit much local variation, but are interpreted to reflect progressively decreasing tectonic subsidence in the upper Blackhawk Formation and overlying Castlegate Sandstone. The trend may also incorporate progressively more frequent channel avulsion during deposition of the lower Blackhawk Formation. Laterally extensive coal zones formed on the coastal plain during shallow‐marine transgressions, and define the high‐resolution stratigraphic framework of the lower Blackhawk Formation. Large (up to 25 m thick and 1 to 6 km wide), multistorey, multilateral, fluvial channel‐complex sandbodies that overlie composite erosion surfaces occur at distinct stratigraphic levels, and are interpreted as fluvial incised valley fills. Low amplitude (<30 m) relative sea‐level variations are interpreted as the dominant control on stratigraphic architecture in the lower Blackhawk Formation, which was deposited up to 50 km inland from the coeval shoreline. In contrast, the high‐resolution stratigraphy of the upper Blackhawk Formation is poorly defined, and channelized fluvial sandbodies are poorly organized. Vertical and laterally offset stacking of a small proportion (<10%) of sandbodies produced ‘clusters’ that are not confined by ‘master’ erosion surfaces. Avulsion is interpreted to dominate the stratigraphic architecture of the upper Blackhawk Formation. This data‐driven analysis indicates that alluvial to coastal plain stratigraphic architecture reflects a combination of various allogenic controls and autogenic behaviours. The relative sea‐level control emphasized in sequence stratigraphic models is only rarely dominant.

Creating three-dimensional channel bodies in LiDAR-integrated outcrop characterization: A new approach for improved stratigraphic analysis

“…1B), which is an ~300-m-thick coastal-plain, fluvial succession spanning ~4 m.y. of the Late Cretaceous (e.g., Hampson et al, 2012). At the study location, the depositional environment of this formation transitions from a lower marginal-marine section (coal-and mud-prone) to overlying continental-fluvial (e.g., Rittersbacher et al, 2013Rittersbacher et al, , 2014.…”

Sedimentology and reservoir properties of tabular and erosive offshore transition deposits in wave-dominated, shallow-marine strata: Book Cliffs, USA

“…1), which exhibit outcrops of Kenilworth parasequences K3 and K4 (sensu Taylor & Lovell 1995;see also Pattison 1995;Hampson & Storms 2003), Sunnyside parasequences S2 and S3 (Howell & Flint 2003;Davies et al 2006;Sømme et al 2008), and the Grassy G1 and G2 parasequences (O'Byrne & Flint 1995). The palaeo-shoreline trends in these eastward-prograding parasequences are oriented between NNE/SSW and NNW/SSE (Taylor & Lovell 1995;O'Byrne & Flint 1995;Howell & Flint 2003 Hampson et al (2012) …”

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

“…Sediments were supplied from the front of the Sevier Thrust to the shorelines via the fluvial systems of the continental part of the Blackhawk Formation, which transported sediment through up to 150 km of alluvial plain (e.g. Hampson et al, 2012). The shallow-marine deposits of the Star Point Sandstone and Blackhawk Formation can be traced from their most landward extent near the town of Emery, Utah, to the most basinward extent east of the town of Grand Junction, Colorado.…”

“…The shorelines in the Storrs Tongue mainly consists of shorefaces, but, but have abundant distributary channels on top, and contains locally developed deltas (Flores, 1984;Hampson et al, 2012).…”

“…The second virtual outcrop model is of the Ksp010 parasequence of the Storrs Tongue of the Star Point Sandstone (Flores et al, 1984;Hampson et al, 2011;Hampson et al, 2012), in the area west of the town of Castle Dale (Figure 1). The shorelines in the Storrs Tongue mainly consists of shorefaces, but, but have abundant distributary channels on top, and contains locally developed deltas (Flores, 1984;Hampson et al, 2012).…”