Deposition and derivation of clastic carbonates on a Mesozoic continental margin, Othris, Greece

Abstract

The Othris Mountains of eastern Greece contain a calcareous continental margin/ocean basin sequence exposed in a stack of Cretaceous thrust sheets. Upper Triassic to Lower Cretaceous shelf, submarine fan and basinal successions overlie shallow marine units of Lower Triassic and Permian age. In off‐shelf sequences the older sediments are separated from the younger by a horizon of alkaline ‘early‐rifting’ basalts. Ophiolites overthrust the marginal sequence. Pre‐rifting sediments are represented by a varied suite of limestones and clastics resting on metamorphic basement and include distinctive, green lithic arenites. In the thrust sheet immediately over the para‐autochthonous shelf sequence, pre‐rifting sediments are separated from the rift basalts by an intermittent horizon of calcareous sandstones and conglomerates reworked from uplifted basement and older sediments. Textural and petrographic immaturity suggests that these are probably deposits derived from fault scarps, produced in an early phase of rifting. Above the basalts in the same sheet is a suite of calciclastic sediment‐gravity‐flow deposits, apparently sedimented on a submarine fan. Progressive downslope modification of calcirudites suggests deposition from evolving, high concentration flows. Massive calcarenite facies (? grain flows) are unusually abundant; a possible reflection of a shallow palaeo‐shelf break since provenance and palaeocurrent evidence proves the clastic carbonates to have been derived from a calcareous shelf. In addition to limestone lithoclasts the calcirudites, but not the massive calcarenites, contain fragments of pre‐rifting lithologies including the distinctive arenites. Since the shelf sequence in Othris is totally nondetrital these clasts imply derivation of coarse sediment from an off‐shelf position; probably the walls of a submarine canyon. This may have occurred either by direct erosion of wall rock, or by reworking of material from an older clastic sequence. In the latter case the inferred fault‐scarp deposits are a likely source.

Depositional environments along a carbonate ramp to slope transition in the Silurian of Washington Land, North Greenland

“…Comparable massive, generally non-graded beds have previously been interpreted as the product of grain flows (e.g., Price 1977;Stauffer 1967), but such beds are normally less than 5 cm thick (Lowe 1976a;cf. Mullins and van Buren 1979).…”

“…The coarse-sand to pebble base of some calcarenites is comparable to the grit facies of Price (1977) and likewise is taken to indicate deposition from dense basal layers of turbidity currents. At the other extreme the muddy graded calcarenites indicate deposition from muddy dilute turbidity currents (cf.…”

Geometry and petrophysical parameters of a calcarenitic turbidite lobe (Barremian-Aptian, Pas-de-la-Cluse, France)

“…The morphologies of carbonate and siliciclastic turbidite systems have been compared by Price (1977), Colacicchi and Baldanza (1986) and Eberli (1991), Colacicchi and Monaco (1994). Submarine carbonate gravity deposits are often composed of breccias, calcarenites, or a combination of the two.…”

Upper Campanian calciclastic turbidite sequences from the Hacımehmet area (eastern Pontides, NE Turkey): integrated biostratigraphy and microfacies analysis

“…Such deposits may be referred to as the calciclastics (Braunstein 1961): allochthonous, detrital carbonate sediments, transported and redeposited as calciturbidites or limestone turbidites (Meischner 1964). Calciclastics were initially considered to be submarine fan deposits with a point source and channelized sedimentation, similar to their siliciclastic counterparts (Price 1977;Bosellini et al 1981). Alternatively, many calciclastic deposits were generally line sourced rather than point sourced (Colacicchi and Baldanze 1986), and were interpreted according to carbonate apron models with a line source and sheetflow sedimentation (Mullins and Cook 1986;Eberli 1987).…”