Building up or out? Disparate sequence architectures along an active rift margin—Corinth rift, Greece

Abstract

Early Pleistocene synrift deltas developed along the southern Corinth rift margin were deposited in a single, dominantly lacustrine depocenter and were subject to the same climate-related base-level and sediment supply cyclicity. Two synrift deltas, just 50 km apart, show markedly different sequence geometry and evolution related to their location along the evolving border fault. In the west, strongly aggradational fan deltas (>600 m thick; 2–4 km radius) deposited in the immediate hanging wall of the active border fault comprise stacked 30–100 m thick stratal units bounded by flooding surfaces. Each unit evolves from aggradational to progradational with no evidence for abrupt subaerial exposure or fluvial incision. In contrast, in the central rift, the border fault propagated upward into an already deep lacustrine environment, locating rift-margin deltas 15 km into the footwall. The deltas here have a radius of >9 km and comprise northward downstepping and offlapping units, 50–200 m thick, that unconformably overlie older synrift sediments and are themselves incised. The key factors driving the marked variation in sequence stratigraphic architecture are: (1) differential uplift and subsidence related to position with respect to the border fault system, and (2) inherited topography that influenced shoreline position and offshore bathymetry. Our work illustrates that stratal units and their bounding surfaces may have only local (<10 km) extent, highlighting the uncertainty involved in assigning chronostratigraphic significance to systems tracts and in calculating base-level changes from stratigraphy where marked spatial variations in uplift and subsidence occur

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

“…Solid lines show observable trajectories in the transition zone and dashed lines show our interpretation of retrogradation back to the fault and/or correlative surfaces to down‐dip maximum flooding surfaces. Kerinitis cross‐section from Gawthorpe, Andrews, et al () after Backert et al ()…”

“…Complementary field studies have shown that sequence boundary development is best expressed at fault tip regions (Dorsey & Umhoefer, —Loreto Basin) and the observed stratigraphic cyclicity has been attributed to fault‐related subsidence events (Dorsey et al, —Loreto Basin) and climatic forcing (Dart et al, ; Backert et al, —Gulf of Corinth). Marked differences occur in the sequence stratigraphy of two coeval fan deltas 50 km apart, due to contrasting tectonic controls between footwall (Kryoneri) and hangingwall (Kerinitis) sites (Gawthorpe, Andrews, et al, ). However, along‐strike and down‐dip variation on smaller length‐scales (<10 km) within the same hangingwall basin has not yet been attempted.…”

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

“…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).…”

“…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). 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).…”

“…The southern shore of the Gulf of Corinth (Figure 2) offers an ideal field laboratory for exploring interfan architectures, as there are a series of modern fan deltas along the coast, Late Pleistocene lowstand fan deltas that are submerged and imaged in bathymetry data, and a number of exhumed syn-rift fan deltas that formed along normal faults since ~1.8 Ma (Ford et al, 2016;Gawthorpe et al, 2017a). A number of studies focus upon the stratigraphic architecture of the Early-Middle Pleistocene Gilbert-type fan deltas in the Gulf of Corinth: Evrostini/Ilias (Zelilidis and Kontopoulos, 1996;Zelilidis, 2003;Rohais et al, 2007aRohais et al, , 2008Gobo et al, 2014Gobo et al, , 2015, Kryoneri (Gawthorpe et al, 2017b), Vouraikos (Ford et al, 2007), Kerinitis (Ori et al, 1991;Poulimenos et al, 1993;Dart et al, 1994;Gawthorpe et al, 1994;Backert et al, 2010;Gawthorpe et al, 2017b) and Selinous fan deltas (Poulimenos et al, 1993;Barrett et al, 2019). These studies highlight the F I G U R E 1 Source-to-sink block model with interfan areas highlighted in alluvial, deltaic and deepwater settings.…”