Rapid spatiotemporal variations in rift structure during development of the Corinth Rift, central Greece

Abstract

The Corinth Rift, central Greece, enables analysis of early rift development as it is young (<5 Ma) and highly active and its full history is recorded at high resolution by sedimentary systems. A complete compilation of marine geophysical data, complemented by onshore data, is used to develop a high-resolution chronostratigraphy and detailed fault history for the offshore Corinth Rift, integrating interpretations and reconciling previous discrepancies. Rift migration and localization of deformation have been significant within the rift since inception. Over the last circa 2 Myr the rift transitioned from a spatially complex rift to a uniform asymmetric rift, but this transition did not occur synchronously along strike. Isochore maps at circa 100 kyr intervals illustrate a change in fault polarity within the short interval circa 620-340 ka, characterized by progressive transfer of activity from major south dipping faults to north dipping faults and southward migration of discrete depocenters at~30 m/kyr. Since circa 340 ka there has been localization and linkage of the dominant north dipping border fault system along the southern rift margin, demonstrated by lateral growth of discrete depocenters at~40 m/kyr. A single central depocenter formed by circa 130 ka, indicating full fault linkage. These results indicate that rift localization is progressive (not instantaneous) and can be synchronous once a rift border fault system is established. This study illustrates that development processes within young rifts occur at 100 kyr timescales, including rapid changes in rift symmetry and growth and linkage of major rift faults.

High-angle, not low-angle, normal faults dominate early rift extension in the Corinth Rift, central Greece

“…Seismic reflection interpretations from different authors agree that the dip angle of offshore faults down to ~3 km ranges from 35° to 60° (e.g., Nixon et al, 2016;Taylor et al, 2011). However, controversy remains as to the geometry of faults deeper than 3 km as these have never been directly imaged.…”

“…They also observed seismicity beneath the clustered microseismicity cloud, which they suggested is the continuation of high-angle faults imaged at shallower depth and supports a high-angle fault model rather than an active detachment. Nixon et al (2016) reinterpreted the deep seismic reflection data and suggested that north-dipping south margin faults remain moderately to steeply dipping (35°-60°) below depths of 3 km ( Fig. 1B; Fig.…”

“…Sorel, 2000;Taylor et al, 2011). Model 2 involves planar faults that dip at 45° (model 2a) or 60° (model 2b) to the brittle-ductile transition at a depth of 10 km (after Nixon et al, 2016).…”

Expedition 381 Scientific Prospectus: Corinth Active Rift Development

“…Corinth rifting began at ~5 Ma with three main phases identified by integrating onshore deposits and offshore seismic stratigraphy ( Figure F3) (e.g., Armijo et al, 1996;Sachpazi et al, 2003;Ford et al, 2007;Bell et al, 2009;Taylor et al, 2011;Nixon et al, 2016). Initial Pliocene basinal deposition (preserved onshore) was continental, varying from alluvial fans in the west to lakes in the east ("Lower Group"; Ford et al, 2007Ford et al, , 2013Rohais et al, 2007;Backert et al, 2010).…”

“…This transition is thought to represent increased subsidence and sediment supply into the rift at the location of the modern Gulf of Corinth (Middle Group onshore; probable seismic Unit 1 offshore). During this phase, the rift was controlled by both south-and north-dipping bounding faults (Bell et al, 2009;Ford et al, 2013;Nixon et al, 2016).…”