Along-Strike Variations In Stratigraphic Architecture of Shallow-Marine Reservoir Analogues: Upper Cretaceous Panther Tongue Delta and Coeval Shoreface, Star Point Sandstone, Wasatch Plateau, Central Utah, U.S.A.

Abstract

Along-strike variations in sediment supply and process regime may result in different facies distributions, preservational biases, and stratigraphic architectures in shallow-marine strata. Data from a large (c. 100 km), nearly continuous outcrop belt aligned oblique to depositional strike was integrated with nearby subsurface well data and petrological analysis of distal fine-grained deposits, to analyze along-strike variations in stratigraphic architecture in a single parasequence in the upper Cretaceous Star Point Sandstone, Wasatch Plateau, central Utah, USA.The parasequence comprises wave-dominated shoreface deposits in the southern part of the study area and represents a single episode of shoreline regression and transgression. Four progradationally stacked bedsets (BS1-BS4) in the distal deposits of the parasequence are the expression of minor variations in relative sea level, sediment supply, and/or wave climate. The four bedsets can be traced to river-dominated deltaic deposits (Panther Tongue) in the northern part of the study area. We interpret the parasequence on the scale of the Wasatch Plateau outcrop belt as the record of deposition in a regressive river-and waveinfluenced delta deflected asymmetrically towards the SSW, subparallel to the regional paleo-shoreline trend, and a coeval wave-dominated strandplain. The lateral transition from river-to wave-dominated facies is attributed to the localization of a major river acting as a sediment point source in the north, with wave-induced longshore transport to the south. Our results imply that characterizing lateral facies distributions and the expression of bedsets is vital for interpreting along-strike variability in controlling mechanisms of stratigraphic architecture, and that external forcing may be recorded differently along depositional strike. ALONG-STRIKE VARIATIONS IN THE UPPER CRETACEOUS PANTHER TONGUE DELTA, UTAH 969 J S R 970 A. FORZONI ET AL. J S R ALONG-STRIKE VARIATIONS IN THE UPPER CRETACEOUS PANTHER TONGUE DELTA, UTAH 971 J S R 972 A. FORZONI ET AL. J S R ALONG-STRIKE VARIATIONS IN THE UPPER CRETACEOUS PANTHER TONGUE DELTA, UTAH 973 J S R FIG. 4.-Stratigraphic logs and accompanying photos of wave-dominated shoreface facies successions. A) Upward-shallowing wave-dominated shoreface succession truncated by a wave ravinement surface overlain by fining-upward transgressive deposits at Deer Creek. B) Three upward-coarsening bedsets of variably amalgamated storm-event beds in a wave-dominated lower shoreface succession at Muddy Creek. C) Upward-coarsening wave-dominated shoreface succession truncated by a wave ravinement surface at Des Bee Dove Mine. A cemented bed separates bedsets N3 and N4. Localities are shown in Figure 2. 974A. FORZONI ET AL.

Sedimentary architecture and depositional controls of a Pliocene river-dominated delta in the semi-isolated Dacian Basin, Black Sea

“…In line with previous studies of similar facies (Fielding, 2010;Hampson, 2010;Forzoni et al, 2015), we interpreted these organic-rich layers to be deposited on coastal-plain mires during fluvial flooding.…”

“…In comparison to similar studies on comparable facies (Forzoni et al, 2015), we interpreted these deposits as being formed by the lateral and longitudinal accretion of distributary mouth bars. This bi-directional accretion supposedly created the wide range of palaeocurrent directions.…”

Grain size fractionation by process‐driven sorting in sandy to muddy deltas

“…Mouth bar complexes, which are defining features in delta architecture and description in the field (Forzoni et al, 2015), show a bias for preserving the sand fractions of the supplied sediment. Simulations reported here show that the preferential preservation and/or description of mouth bars would lead to a biased interpretation of ancient deltaic systems as having a sand-dominated supply.…”

“…One of the most important identifying features of ancient deltaic deposits are the sandy clinoforms of their delta front mouth bar complexes (Forzoni et al, 2015) and mouth bar complexes are therefore of particular interest in the analysis. Mouth bars form in the highly complex transitional region influenced by both fluvial and marine forces.…”

Accommodation and sediment‐supply controls on clastic parasequences: A meta‐analysis

“…Similarly, strike‐oriented spatial variations in A/S associated with along‐shore gradients in the rate of sediment supply can determine lateral changes in type and timing of development of parasequence stacking patterns (Fig. D; Van Wagoner et al ., ; Schlager, ; Martinsen & Helland‐Hansen, ; Forzoni et al ., ).…”