Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM

Gulf of Cadiz (Western Spain):
Characterized by a Complex Petroleum System
Luis Somoza
ITGE: Geological Survey of Spain
Rio Rosas 23 E-28003
Madrid, Spain
e-mail: Luis.Somoza@itge.es
Bradley M. Battista
Consultant
1507 Dunbar Avenue
Bay Saint Louis, Mississippi 39520
U.S.A.
Joan Gardner
Code 7420
Naval Research Labs
4555 Overlook Drive
Washington, D.C. 20375-5320
U.S.A.
e-mail: gardner@qur.nrl.navy.mil
Allen Lowrie
Consultant
238 F. Z. Goss Road
Picayune, Mississippi 39466-9458
U.S.A.
e-mail: alowrie@webtv.net
Abstract
The petroleum system is that series of interrelated processes by which hydrocarbons are generated and migrate to
reservoirs from which they can be extracted commercially. The complex geology of the Gulf of Cadiz provides three
separate heat sources for thermal maturation, while energetic downslope movement of crustal blocks has created reservoirs
and traps that result from both structure and stratigraphic complexity.
Westward extension by continental margin collapse of the Alboran Sea microplate in the Early Neogene has initiated
large slump-block movements along the Iberic and Moroccan continental margins. Extensive allochthonous Late
Cretaceous-Paleogene salt, deposited in a paleobasin having a western limit of 10°W to 12°W may underlie the
slump-blocks at depths from 20 to 25 km and temperatures from 450° to 600°C, assuming 25°C/km gradient, and
could serve as a lubricant for gravity-driven translation. Overall movement may exceed 400 km. The migrating
blocks, operating as thin-skinned tectonics, and associated down-dip debris flows may be trapping mechanisms for
hydrocarbons. Migrating debris covers an area as great as 90,000 km2, an area approximately equivalent to that covered
by salt in the Gulf of Mexico.
The eastern terminus of the Azores triple junction is well marked by shallow earthquakes (