Quantification of the Bed-scale Architecture of Submarine Depositional Environments and Application to Lobe Deposits of the Point Loma Formation, California

Abstract

Submarine-fan deposits form the largest sediment accumulations on Earth and host significant reservoirs for hydrocarbons. While many studies of ancient fan deposits qualitatively describe lateral architectural variability (e.g., axis-to-fringe, proximal-to-distal), these relationships are rarely quantified. In order to enable comparison of key relationships that control the lateral architecture of submarine depositional environments, we digitized published bed-scale outcrop correlation panels from five different environments (channel, levee, lobe, channel-lobe-transition-zone, basin plain). Measured architectural parameters (bed thickness, bed thinning rates, lateral correlation distance, net-to-gross) provide a quantitative framework to compare lithology architectures between environments. The results show that sandstone and/or mudstone bed thickness alone or net-to-gross do not reliably differentiate between environments. Lobe sub-environments display the most variability in all parameters, which could be partially caused by subjectivity of qualitative interpretations of environment and demonstrates the need for more quantitative studies of bed-scale heterogeneity. These results can be used to constrain forward stratigraphic models and reservoir models of submarine depositional environments.

Quantifying the lateral heterogeneity of distal submarine lobe deposits, Point Loma Formation, California: Implications for subsurface lateral facies prediction

“…McGlown (2015) studied the continuity and grain‐size characteristics of HEB ( sensu Haughton et al, 2009) in the Point Loma Formation. Fryer (2018) reinterpreted the depositional environment of lobe deposits to the south of the current study area (Figure 2B) focussing on metrics such as bed thickness and thinning rate. The current study area is contained within Unit 2 of Nilsen and Abbot (1981), Lobe Complex 1 of Fleming (2010).…”

Foredeep vs. wedge-top facies trends and hierarchical thickness distributions, Pennsylvanian Atoka Formation, Ouachita Mountains, USA

“…(A) shows the proximal-distal trend of bed thickness distributions in unconfined setting (after Carlson and Grotzinger, 2001;Sinclair et al, 2016;Pantopoulos et al, 2018). (B) shows the contrast of bed thickness distributions in confined and unconfined setting (after Fryer and Jobe, 2018). (C) shows the contrast of the distributions of lobe architecture thickness in confined and unconfined setting (after Pré lat et al, 2010;Pettinga et al, 2018).…”

“…1A) or from axial to marginal locations (Walker, 1978;Bouma et al, 1985;Mutti, 1985;Spychala et al, 2017). This proximaldistal variation corresponds to the relative high bed thinning rate due to flow expansion of unconfined turbidity currents (Fryer and Jobe, 2018;Liu et al, 2018;Tőkés and Patacci, 2018). The distribution of bed thicknesses is expected to display limited dispersion due to the lack of flow thickening mechanism.…”

“…The distribution of bed thicknesses is expected to display limited dispersion due to the lack of flow thickening mechanism. Assuming all other external forces remain the same, the bed thicknesses of confined lobe deposits are expected to show a similar proximal-distal trend but to a lesser extent, because confined turbidity currents have limited flow expansion and are forced to thicken, which will result in lower bed thinning rates over the same distance in the deposits (Sinclair and Cowie, 2003;Marini et al, 2015;Fryer and Jobe, 2018;Liu et al, 2018;Tőkés and Patacci, 2018).…”