Three‐dimensional modelling and sequence stratigraphy of a carbonate ramp‐to‐shelf transition, Permian Upper San Andres Formation

Abstract

This study highlights three‐dimensional variability of stratigraphic geometries in the ramp crest to basin of mixed carbonate–siliciclastic clinoforms in the Permian San Andres Formation. Standard field techniques and mapping using ground‐based lidar reveal a high degree of architectural complexity in channellized, scoured and mounded outer ramp stratigraphy. Development of these features was a function of location along the ramp profile and fluctuations in relative sea‐level. Deposition of coarse‐grained and fine‐grained turbidites in the distal outer ramp occurred through dilute and high‐density turbidity flows and was the result of highstand carbonate shedding within individual cycles. In this setting, high‐frequency cycles of relative sea‐level are interpreted on the basis of turbidite frequency, lateral extent and composition. Submarine siliciclastic sediment bypass during lowstand cycles resulted in variable degrees of siliciclastic preservation. Abundant siliciclastic material is preserved in the basin and distal outer ramp as point‐sourced lowstand wedges and line‐sourced early transgressive blankets. In mounded topography of the outer ramp, siliciclastic preservation is minimal to absent, and rare incised channels offer the best opportunity for recognition of a sequence boundary. Growth of mounded topography in the outer ramp began with scouring, followed by a combination of bioherm construction, fusulinid mound construction and isopachous draping. Intermound areas were then filled with sediment and continued mound growth was prevented by an accommodation limit. Mound growth was independent of high‐frequency cycles in relative sea‐level but was dependent on available accommodation dictated by low‐frequency cyclicity. Low‐angle ramp clinoforms with mounded topography in the outer ramp developed during the transgressive part of a composite sequence. Mound growth terminated as the ramp transformed into a shelf with oblique clinoform geometries during the highstand of the composite sequence. This example represents a ramp‐to‐shelf transition that is the result of forcing by relative sea‐level fluctuations rather than ecologic or tectonic controls.

Facies, stratigraphy, and evolution of a middle Ediacaran carbonate ramp: Khufai Formation, Sultanate of Oman

“…In the Permian Basin of west Texas, bypass of eolian sand into downslope environments is well documented (Phelps et al, 2008). Sequence boundaries sit directly below packages of siliciclastics, suggesting that Khufai sands also may have accumulated during increases in accommodation.…”

“…Previous studies of mixed clastic-carbonate systems have demonstrated the stratigraphic controls on sand-body accumulation (Kerans et al, 1994;McNeill et al, 2004;Barnaby and Ward, 2007;Phelps et al, 2008). In the Permian Basin of west Texas, bypass of eolian sand into downslope environments is well documented (Phelps et al, 2008).…”

“…The arid setting is consistent with active eolian sand dune formation, although all of the sand bodies in the Khufai Formation show evidence of both wave reworking and combination with marine carbonate sediments (ooids, coated sand grains). Phelps et al (2008) suggested that the sands were deposited in the marine realm but were likely introduced by eolian and local fluvial processes and reworked during parasequence-scale flooding events as evidenced in the Permian San Andres Formation. The models presented previously describing the small deposits of sand in the southern Huqf as tidal channels are consistent with our observations (Gorin et al, 1982).…”

Multi-scale three-dimensional distribution of fracture- and igneous intrusion- controlled hydrothermal dolomite from digital outcrop model, Latemar platform, Dolomites, northern Italy

“…Observations can also be done directly on the DOM. This usually implies manual picking of XYZ points on the model in order to derive, for example, layering and platform geometry (Boro, 2012;Gramigna et al, 2013), faults, fractures, and slip vectors (Jones et al, 2009;Kurtzman et al, 2009;Rotevatn et al, 2009;Lapponi et al, 2011;Jacquemyn et al, 2012), vugs and karst cavities (Kurtzman et al, 2009;Labraña, 2011) or the geometry and distribution of sedimentary (Phelps et al, 2008;Fabuel-Perez et al, 2009) and diagenetic geobodies . Several successful attempts are made for automated processing.…”

Applications of digital outcrop models: two fluvial case studies from the Triassic Wolfville Fm., Canada and Oukaimeden Sandstone Fm., Morocco

“…The use of digital field techniques is becoming a more common tool to aid fieldwork and some powerful applications have been demonstrated in recent studies, for example in sedimentological and structural studies (Hodgetts et al 2004;Verwer et al 2004b;Adams et al 2005;Labourdette and Jones 2007;Phelps and Kerans 2007;Olariu et al 2008;Phelps et al 2008;Fabuel-Perez et al 2009a;Hodgetts 2009;Verwer et al 2009a;Verwer et al 2009b;Wilson et al 2009) as well as in earth surface process (Wawrzyniec et al 2007;McCormick et al 2008) and ichnology (Bates et al 2008). Work has further focussed on how the digital data can best be captured and visualized, and in quantifying uncertainties inherent in the datasets (Bond et al 2007;Enge et al 2007;Verwer et al 2007;Buckley et al 2008).…”