Plio-Pleistocene sedimentation in coastal grabens, north-east Rhodes, Greece

Abstract

The stratigraphy of marine Plio-Pleistocene sediments from northeast Rhodes (Dodecanese islands, Greece) is revised in the light of facies mapping and the recognition of three major transgression-regression cycles. Before late Pliocene submergence, metamorphosed Mesozoic limestones formed a high-relief karstic landscape. During subsequent transgressions, subsiding basins with spectacular cliffed and bioeroded margins were infilled by a mosaic of cdrbonatedominated sediments, sourced by high rates of carbonate productivity on narrow shelves rimming the basins and their drowning islands. Periods of relative sea-level fall superimposed a complex series of 'fossil' coastal geomorphological features such as cliffs, abrasion platforms, surf caves, notches, boulder beaches and palaeokarsts. These created the rugged present day topography of the iskdnd's northeast coast.Three main lithostratigraphic units, the Kritika, Rhodes and Lindos Acropolis Formations, are defined. The Rhodes and Lindos Acropolis Formations are subdivided into mappable facies groups rather than members, as the lithofacies are strongly diachronous. The Kritika and Rhodes Formations were each subaerially exposed and partly eroded before re-transgression. Although there is a general pattern of lithological succession, details vary across the study area and some facies groups are restricted in development, indicating differences in tectonic behaviour and palaeogeomorphology between neighbouring basins. A preliminary process-response model is presented for the sedimentation history of the Rhodes and Lindos Acropolis Formations, using sedimentological, palaeontological, palaeoecological and ichnological data.

Tectonic and climatic controls on coastal sedimentation: The Late Pliocene–Middle Pleistocene of northeastern Rhodes, Greece

“…This depth greatly exceeds the magnitude of normal glacioeustatic sea-level changes (Pillans et al, 1998;Zazo, 1999). It attests to the tectonically induced major drowning of northeastern Rhodes, previously suggested (Meulenkamp et al, 1972;Hanken et al, 1996;Kovacs and Spjeldnaes, 1999), although some low amplitude climate-related sea-level changes probably also occurred (Kovacs and Spjeldnaes, 1999;Steinthorsdottir, 2002). Allowing for at least 520 m of accommodation space created during the Olduvai subchron (duration 0.18 Ma), the average rate of tectonic drowning is 2.6 mm/year.…”

“…The classical Vagia section was studied by Løvlie et al (1989), Frydas (1994), Moissette and Spjeldnaes (1995), Hanken et al (1996), Kovacs and Spjeldnaes (1999), and Steinthorsdottir (2002). Løvlie et al (1989) placed the Pliocene-Pleistocene boundary at around 5 m above the base of the Lindos Bay clay.…”

“…This basement was repeatedly faulted in various directions, resulting in the formation of steep horsts and grabens that later controlled the nature and distribution of the Pliocene-Pleistocene deposits (Hanken et al, 1996). In such a sedimentary setting, facies changes are common and correlations between separated graben infills are often difficult to establish.…”

“…A 4 to 20 m thick fossiliferous bioclastic limestone that rests unconformably on the bioeroded Mesozoic basement, on the Kritika Formation, or on the Haraki limestone. The depositional environment varies from shoreface at the base to lower offshore in its uppermost part (Beckman, 1995;Hanken et al, 1996;Spjeldnaes and Moissette, 1997;Steinthorsdottir, 2002). Palaeomagnetic studies by Løvlie et al (1989) indicate a Late Pliocene age.…”

1000 m long gas blow-out pipes

“…11). The lower parts of the pipe-related structures are located in shallow marine limestones termed the Kolymbia Limestone of Pliocene age (Hanken et al, 1996;Løvlie and Hanken, 2002). The pipes extend through the 15 m high coastal sections of the overlying pelagic Lindos Bay clay member of the Rhodes Formation but the original height of the pipes is not known as the upper part is eroded.…”