Sediment Ponding in the Deep Sea

Unifites: structureless muds of gravity-flow origin in Mediterranean basins

“…Turbulence modification associated with hydraulic jump beyond the base-of-slope would likely alter grain support and flocculation conditions over the basin plain. Possibly some textural-compositional fluctuations in structureless muds are induced by rebound of gravity flows from basin pond walls [1,20].…”

“…Records commonly show a remarkable continuity of acoustic reflectors across flat basin plains, and a thinning or wedging out of reflectors at the basin margins. The process of preferential entrapment in terminal catchment basins fed from adjacent slopes has been termed ponding [1]. Hersey ([1], p. 1257) speculated, largely on the basis of seismic records, that "... when a turbidity current has entered a basin and has been dammed by its borders, it is then turned back and circulates within the basin, distributing suspended matter more or less evenly over it.…”

The Origin of the Mediterranean Evaporite

“…The presence of a salt deposit under the Balearic Basin had been suspected since 1961 when diapiric structures resembling salt domes were identified on the seismic reflection profiles of Chain cruise 21 (see Hersey, 1965). Similar diapiric structures were known from the eastern Mediterranean, but there had been doubts whether these are indeed salt domes, or whether they are mud diapirs instead (H. Closs and D. Neev, personal communication).…”

“…The so-called M-Reflector has not only been observed under the abyssal plains (e.g., Hersey, 1965;Leenhardt, et al, 1970;Mauffret, 1970;Montadert et al, 1970), but is also present under submarine ridges and slopes (see Wong and Zarudzki, 1969;Ryan, et al, 1971;Selli and Fabbri, 1971;Finetti, et al, 1970). The reflecting surface is regionally flat under the abyssal plain, but rises and falls more or less conformably with the submarine topography, under the slopes and ridges (Figure 1).…”

“…Mediterranean abyssal plains today are traps for turbidites (Norin, 1958;Hersey, 1965;Ryan et al, 1965;Stanley et al, 1970). There could be no good explanation why a deep-water Upper Miocene basin, surrounded by steep slopes and lands of high relief on all sides, would not receive turbidity currents.…”