Development of an incised valley‐fill at an evolving rift margin: Pleistocene eustasy and tectonics on the southern side of the Gulf of Corinth, Greece

Abstract

This study from the southern margin of the Gulf of Corinth documents a Late Pleistocene incised valley-fill succession that differs from the existing facies models, because it comprises gravelly shoal-water and Gilbert-type deltaic deposits, shows strong wave influence and lacks evidence of tidal activity. The valley-fill is at least 140 m thick, formed in 50 to 100 ka between the interglacials Marine Isotope Stage 9a and Marine Isotope Stage 7c. The relative sea-level rise left its record both inside and outside the incised valley, and the age of the valley-fill is estimated from a U/Th date of coral-bearing deposits directly outside the palaeovalley outlet. Tectonic up-warping due to formation of a valley-parallel structural relay ramp contributed to the valley segmentation and limited the landward extent of marine invasions. The valley segment upstream of the ramp crest was filled with a gravelly alluvium, whereas the downstream segment accumulated fluvio-deltaic deposits. The consecutive deltaic systems nucleated in the ramp-crest zone, forming a bathymetric gradient that promoted the ultimate growth of thick Gilbert-type delta. The case study contributes to the spectrum of conceptual models for incised valley-fill architecture. Four key models are discussed with reference to the rates of sediment supply and accommodation development, and it is pointed out that not only similarity, but also all departures of particular field cases from these endmember models may provide valuable information on the system formative conditions. The Akrata incised valley-fill represents conditions of high sediment supply and a rapid, but stepwise development of accommodation that resulted from the spatiotemporal evolution of normal faulting at the rift margin and overprinted glacioeustatic signals. This study adds to an understanding of valley-fill architecture and provides new insights into the Pleistocene tectonics and palaeogeography of the Corinth Rift margin.

Reciprocal Changes In Foreset To Bottomset Facies In A Gilbert-Type Delta: Response To Short-Term Changes In Base Level

“…Such deltas occur in many lacustrine basins (Gilbert 1885;Dunne and Hempton 1984;Kazancı 1988Kazancı , 1990Johnson et al 1995;Smith and Jol 1997;Milligan and Chan 1998;Ilgar and Nemec 2005;Alçiçek 2007;Ghinassi et al 2009) and are common in marine settings (Colella 1984;Postma and Roep 1985;Colella 1988aColella , 1988bMassari and Parea 1990;Massari 1996;Sohn et al 1997;Lønne and Nemec 2004;Mortimer et al 2005;Longhitano 2008), particularly as the bayhead systems in fjords (Prior et al 1981;Kostaschuk and McCann 1987;Prior and Bornhold 1988;Corner et al 1990;Prior and Bornhold 1990;Nemec et al 1999) and in estuarine incised valleys (Postma 1984b;Li et al 2006;Breda et al 2007;Gobo et al 2014a;Leszczyński and Nemec 2014). Their characteristic tripartite architecture (Fig.…”

“…Long-term large changes result in vertical stacking of successive deltas (Colella 1984(Colella , 1988a(Colella , 1988bGawthorpe and Colella 1990;García-García et al 2006;Breda et al 2009) or cause incision of deep fluvial valleys that are filled by younger bayhead deltas (Dart et al 1994;Ford et al 2007Ford et al , 2013Rohais et al 2008;Backert et al 2010;Gobo et al 2014a). Short-term smaller changes result in alternation of oblique and sigmoidal topset-foreset clinoform architecture in the prograding delta (Massari 1996;García-García 2004;Breda et al 2007;Gobo et al 2014a, in review).…”

Miocene sea-level changes in northernmost Anatolia: Sedimentary record of eustasy and tectonism at the peri-Pontide fringe of Eastern Paratethys

“…The sea-drowned Karaganian incised valleys in the basin are a typical example of "overfilled" estuaries (sensu Simms et al, 2006), with the marine-flooding events quickly countered by the advance of bayhead shoreline. Such incised-valley estuaries signify a high rate of sediment supply and anincremental low-rate rise of relative sea level (see Gobo et al, 2013, their Fig. 13D).…”

“…occasional Gilbert-type deltas in the valley-fill succession reflect the bathymetric magnitude of marine-flooding events (see Breda et al, 2009;Gobo et al, 2013).…”

Ground deformation and associated hazards in NW peloponnese (Greece)

“…Briole et al, 2000;Hatzfeld et al, 2000;Bernard et al, 2006) and the Gulf of Patras (e.g. Beckers et al, 2015;Gobo, Ghinassi, Nemec, Sjursen, & Hampson, 2014) triggering off numerous mass movements and causing subsidences.…”