A coarse grained turbidite system with morphotectonic control (Middle Albian, Ondarroa, northern Iberia)

• DOI: 10.1111/j.1365-3091.1994.tb02002.x
• Publication Date: 2006-06-14T18:08:30Z
• Authors: L. M. AGIRREZABALA; J GARCIA‐MONDÉJAR
• Keywords: Siltstone; Outcrop; Conglomerate; Overbank

ABSTRACT The Middle Albian Ondarroa turbidite system is a coarse grained, deep water unit which outcrops in the north‐eastern part of Basque‐Cantabrian region, west Pyrenees. It about 18 km long and 7 wide, shows an unusual ‘L’shape resulting from both direct morphotectonic confinement presence nearby shallow carbonate buildups. Eight main facies have been distinguished within this system: (1) clast‐supported conglomerates; (2) mud‐supported (3) slump deposits; (4) normally graded pebbly sandstones; (5) cross stratified (6) interbedded sandstones mudstones; (7) non‐graded mudstones: (8) mudstones. Inner system, middle outer basin plain divisions distinguished. inner characterized by stacked channel fill conglomerates lesser sandy turbidites consists conglomeratic fining upwards sequences, several metres thick. has alternating non‐channellized mudstones, without any predictable vertical arrangement. mudstone‐siltstone laminations lesser, randomly occurring thin bedded turbidites. Three fills make up system. Although all them can be compared with valley modern Mississippi Fan, thus their bases interpreted as sequence boundaries, only lowermost uppermost are documented allocyclic boundaries. was deposited immature passive margin subjected to transtensional movements. filled composite pull apart depression clastics derived narrow platform north present invaded fan deltas. A major pattern sinistral strike‐slip faulting linked opening Bay Biscay invoked explain appearance its tectonic confinement.