Structure and tectonics of the Yucatan Basin, caribbean Sea, as determined from seismic reflection studies

Abstract

The Yucatan Basin preserves a record of the Late Cretaceous to Paleogene Caribbean‐North American convergent history that is largely unaffected by Neogene strike‐slip tectonics of the current plate boundary. An examination of seismic basement within the Yucatan Basin, based upon available seismic reflection data including extensive multichannel data, shows that the basement comprises nine domains distinguished on the basis of internal reflection character and surface topography. These domains encompass three distinct crustal types or blocks. The first underlies the western flank of the basin and represents the offshore continuation of the adjacent Yucatan platform. The second includes the topographically heterogeneous domains of the eastern two‐thirds of the basin, and is dominated by a subsided volcanic rise or arc (Cayman rise) resting upon probable oceanic crust of pre‐Tertiary age. The eastern edge of the rise and adjacent basins dips northeast beneath the Cuban margin along a sediment filled trench. The third type of crust occupies a rectangular deep within the western third of the basin. Available evidence indicates that this crust is oceanic in character, and represents a large, mature pull‐apart basin set within a wide paleo‐transform zone between the western platform and eastern oceanic basin. This zone defines the northwestern portion of the Caribbean‐North American convergent plate boundary. Paleocene to Middle Eocene transform motion was left‐lateral along north‐south to NNE‐SSW trends, with a displacement of about 350 km. A long Middle Eocene transcurrent fault of about 50 km left‐lateral displacement cuts the basin diagonally from SW to NE and continues onland in Cuba as La Trocha fault. This reconstruction is consistent with known Eocene regional tectonics, but the timing of regional events raises questions about present interpretations of plate geometry in the northwestern Caribbean.