Architecture and sedimentology of the Kerinitis Gilbert-type fan delta, Corinth Rift, Greece
Résumé
The Kerinitis Delta in the Corinth Rift, Greece, is a footwall derived, coarse-grained, Gilbert-type fan delta deposited in the hangingwall of a linked normal fault system. This giant Gilbert-type delta (radius 3-8 km, thickness > 600 m) was supplied by an antecedent river and built into a brackish to marine basin. Although as yet poorly dated, correlation with neighbouring deltas suggests that the Kerinitis Delta was deposited during a period of 500 to 800 ka in the Early to early Middle Pleistocene. Facies characterizing a range of depositional processes are assigned to four facies associations (topset, foreset, bottomset and prodelta). The dominantly fluvial topset facies association has locally developed shallow marine (limestone) and fluvial-shoreface sub-associations. This delta represents a subsidence-dominated system in which high fault displacement overwhelmed base-level falls (creation of accommodation predominantly > 0). Stratal geometries and facies stacking patterns were used to identify 11 key stratal surfaces separating 11 stratal units. Each key stratal surface records a landward shift in the topset breakpoint path, indicating a rapid increase in accommodation/sediment supply. Each stratal unit records a gradual decrease in accommodation/sediment supply during deposition. The cyclic stratal units and key stratal surfaces are interpreted as recording eustatic falls and rises, respectively. A 30 m thick package of foresets below the main delta records the nucleation of a small Proto-delta probably on an early relay ramp. Based on changes in stratal unit geometries, the main delta is divided
into three packages, interpreted as recording the initiation, growth and death of the controlling fault system. The Lower delta comprises stacked, relatively thin, progradational stratal units recording low displacement on the young fault system (relay ramp). The Middle delta comprises vertically stacked stratal units each recording initial aggradation–progradation followed by progradation; their aggradational component increases up through the Middle delta, which records the main phase of increasing rate of fault displacement. The Upper delta records pure progradation, recording abrupt cessation of movement on the fault. A major erosion surface incising basinward 120 m through the Lower and Middle delta records an exceptional submarine erosion process (canyon or delta collapse).
Mots clés
Pleistocene
middle Pleistocene
planar bedding structures
Cenozoic
clastic rocks
cross-bedding
cross-stratification
deltaic environment
deltas
depositional environment
Europe
fluvial environment
Gilbert-type deltas
Kerinitis Delta
lithofacies
Quaternary
sedimentary rocks
sedimentary structures
Corinth Rift
Greece
Southern Europe