Quantifying faulting and base level controls on syn‐rift sedimentation using stratigraphic architectures of coeval, adjacent Early‐Middle Pleistocene fan deltas in Lake Corinth, Greece

Abstract

Quantification of allogenic controls in rift basin‐fills requires analysis of multiple depositional systems because of marked along‐strike changes in depositional architecture. Here, we compare two coeval Early‐Middle Pleistocene syn‐rift fan deltas that sit 6 km apart in the hangingwall of the Pirgaki‐Mamoussia Fault, along the southern margin of the Gulf of Corinth, Greece. The Selinous fan delta is located near the fault tip and the Kerinitis fan delta towards the fault centre. Selinous and Kerinitis have comparable overall aggradational stacking patterns. Selinous comprises 15 cyclic stratal units (ca. 25 m thick), whereas at Kerinitis 11 (ca. 60 m thick) are present. Eight facies associations are identified. Fluvial and shallow water facies dominate the major stratal units in the topset region, with shelfal fine‐grained facies constituting ca. 2 m thick intervals between major topset units and thick conglomeratic foresets building down‐dip. It is possible to quantify delta build times (Selinous: 615 kyr; Kerinitis: >450 kyr) and average subsidence and equivalent sedimentation rates (Selinous: 0.65 m/kyr; Kerinitis: >1.77 m/kyr). The presence of sequence boundaries at Selinous, but their absence at Kerinitis, enables sensitivity analysis of the most uncertain variables using a numerical model, ‘Syn‐Strat’, supported by an independent unit thickness extrapolation method. Our study has three broad outcomes: (a) the first estimate of lake level change amplitude in Lake Corinth for the Early‐Middle Pleistocene (10–15 m), which can aid regional palaeoclimate studies and inform broader climate‐system models; (b) demonstration of two complementary methods to quantify faulting and base level signals in the stratigraphic record—forward modelling with Syn‐Strat and a unit thickness extrapolation—which can be applied to other rift basin‐fills; and (c) a quantitative approach to the analysis of stacking patterns and key surfaces that could be applied to stratigraphic pinch‐out assessment and cross‐hole correlations in reservoir analysis.

Syn‐rift delta interfan successions: Archives of sedimentation and basin evolution

“…The Kerinitis fan delta is positioned slightly to the west of the P-M fault centre and the Selinous fan delta is positioned ~4 km from the western fault tip. Numerical modelling was used to quantify the amplitude of climate-induced lake-level changes in Lake Corinth during the Early-Middle Pleistocene at 10-15 m (Barrett et al, 2019). Numerical modelling was used to quantify the amplitude of climate-induced lake-level changes in Lake Corinth during the Early-Middle Pleistocene at 10-15 m (Barrett et al, 2019).…”

“…Barrett et al (2019) quantify the minimum period of deposition, average subsidence and sedimentation rates at the Kerinitis and Selinous fan deltas as >451 and 615 kyr, and 0.65 and >1.77 m/ kyr, respectively, based upon stratigraphic observations. Previous studies focus on the facies and stratigraphic architecture of the axial sections of the Kerinitis and Selinous fan deltas (Dart et al, 1994;Gawthorpe et al, 1994;Backert et al, 2010;Gawthorpe et al, 2017b;Barrett et al, 2019). Previous studies focus on the facies and stratigraphic architecture of the axial sections of the Kerinitis and Selinous fan deltas (Dart et al, 1994;Gawthorpe et al, 1994;Backert et al, 2010;Gawthorpe et al, 2017b;Barrett et al, 2019).…”

“…An additional facies association to the scheme of Barrett et al (2019) is FA 2c (upper shoreface, which occurs in the shallow water topset; Locality I; Figure2; Table 1). Four facies (Supporting information) have been added to the bottomset facies association of Barrett et al (2019).…”

“…Red palaeosols (centimetre-thick) are found between gravelly coarse sandstone beds (Barrett et al, 2019). Channel-fill (FA 1a) is the most common and comprises poorly-sorted, sub-angular to subrounded, sandy gravel-cobble conglomerate with clast imbrication and erosive bed bases.…”

“…The lower shoreface FA 2c comprises metre-scale, bi-directional, asymptotic cross-beds resembling hummocky-cross stratification (Barrett et al, 2019). Only the upper shoreface (FA 2b) is observed in the interfan area, during the latest stage.…”