Evolution of a Tectonically Controlled Carbonate Platform and Adjacent Basin (Cretaceous of Gorbea, Basque-Cantabrian Basin, N Iberia)

Irene Gomez-Perez, Pedro Angel Fernandez-Mendiola, Joaquin Garcia Mondejar

The formation and evolution of the Basque Cantabrian Basin as a pericratonic rift was related to the opening of the Bay of Biscay and the North Atlantic during the Mesozoic. Distensional tectonics resulted during Aptian-Albian in a horst-graben configuration: shallow reefal rudist-coral-orbitolinid limestones formed on tectonically controlled paleohighs whereas adjacent basins infilled with deeper water sediments.

In this contest, the Gorbea platform evolved on an isolated paleohigh from the Late Aptian to Late Albian. During latest Aptian a mixed ramp depositional system developed, evolving to a carbonate ramp system during earliest Albian. Later on, a siliciclastic shelf system formed locally during a short period of interruption of carbonate production. Late Early Albian is characterized first by shallow water carbonate platform progradation and later establishment of an aggrading rimmed platform to basin system. A carbonate slope system developed during latest Early Albian-earliest Middle Albian, preluding subaerial exposure of the platform. An important paleokarstic horizon developed on the platform during mid Albian. Meanwhile a thick wedge of distal shelf to slope siltstones and turbidit s infilled the adjacent basin. During early Late Albian carbonate deposition recovered and a residual bank coexisted with shallow shelf siliciclastics. Deltaic sediments eventually flooded the area and ended carbonate production during mid Late Albian.

The described depositional systems formed during about 12 million years, and are organized in two transgressive-regressive cycles made up of seven depositional sequences and sequence groups. Their origin is linked to relative-sea level changes related to active tectonics, which in turn controlled the sedimentary and paleogeographic evolution of the basin.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995