Architecture and sedimentology of the Kerinitis Gilbert-type fan delta, Corinth Rift, Greece

Abstract

The Kerinitis Delta in the Corinth Rift, Greece, is a footwall derived, coarsegrained, Gilbert-type fan delta deposited in the hangingwall of a linked normal fault system. This giant Gilbert-type delta (radius 3AE8 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).

Patterns of Quaternary uplift of the Corinth rift southern border (N Peloponnese, Greece) revealed by fluvial landscape morphometry

“…In a similar way, from a corrected S R age estimate of 350-400 ka and GR ne twork values of 410-420 m in the central sector, we derive a minimum uplift rate of 1.05-1.2 mm year -1 for the penultimate uplift phase. (Backert et al, 2010;Briole et al, 2000).…”

Depositional evolution of a progradational to aggradational, mixed-influenced deltaic succession: Jurassic Tofte and Ile formations, southern Halten Terrace, offshore Norway

“…By implication, mass balance consideration for progradational-to aggradational systems implies that the coarsest grain sizes in lower delta plain and delta front deposits will be encountered during initial progradation, when pebbly, coarse sand was transported to the coastline where it was deposited in mouths bars (FA2) and distributary channels (FA3,FA4). During this period, fine-grained sand may have been bypassed to the basin floor, as is common in coarse-grained deltas (Walker, 1966;Hampson, 1997;Rohais et al, 2008;Backert et al, 2010), transported alongshore out of the study area or the input sediment supply may have lacked this grain size fraction (Michael et al, 2013). During subsequent delta plain aggradation, pebbly, coarse sand could have been stored in fluvial channels (FA3) on the upper delta plain, with only very fine-to-medium sand reaching the lower delta plain, where it was deposited in tidal flats and channels (FA5, FA6; Fig.…”

“Bottomsets” of the lava−fed delta of James Ross Island Volcanic Group, Ulu Peninsula, James Ross Island, Antarctica

“…Bottomsets were defined by Gilbert (1885) as gently inclined (# 10°) fine grained sediments and represent the down−dip terminations of foresets, where the lithofacies association is transitional, deposited by both gravitational flow and suspension fall− out processes (Colella 1988;Massari and Parea 1990;Nemec 1990b;Chough and Hwang 1997;Ford et al 2007;Backert et al 2010). Significant variations in the lithofacies development, especially in the role of glacigenic vs. volcaniclastic depos− its in the studied outcrops, point to different depositional processes and paleo− geography before the onset of the lava−fed (hydroclastic) foresets of the same delta.…”