The Oligocene volcano-sedimentary sequence of the Dipotama Basin, N. Greece: temporal relationships between Tertiary granites and volcanics, and implications for the regional tectonic evolution

Abstract

The Oligocene volcano-sedimentary sequence of the Dipotama Basin, Rhodope zone, N. Greece is found unconformably overlying the Tertiary Skaloti granite along an erosional contact. The sequence comprises a thin basal conglomerate with granite and tuff pebbles in a calcitic matrix followed by lignite-bearing tuffs and distal airfall crystal and ash tuffs, with some physical reworking, overlain by an ignimbrite series. Diagenetic alteration in the volcano-sedimentary sequence is evident as calcification, while the lower part of the ignimbrite is clay-altered. The similar ages of the granite and overlying ignimbrite means that rapid uplift and erosion of about 6 km of crust occurred before subsidence allowed the development of a basin to contain the lignite-bearing sequence. The Dipotama Basin is one of a series of continental Tertiary basins covering a large part of the eastern Mediterranean, which became isolated during uplift, followed in Pliocene times by renewed inundation and a subsequent phase of uplift to produce the current mountain chain of N. Greece. Rapid uplift of thickened continental crust exhumed the Skaloti and other granites, while subsequent extensional collapse allowed the deposition of the Tertiary volcano-sedimentary sequences.