Field trip no. 22 from “Geologic Excursions to the Rocky Mountains and Beyond,” field trip guidebook of the 1996 Annual Meeting of the Geological Society of America. Cretaceous-Tertiary Boundary in the Beloc Formation, Southern Peninsula of Haiti, West Indies. (SP-44 has the complete set.) 20 pages. Digital PDF download. OF-96-04-22D
The southern Peninsula comprises the southwestern portion of the island of Hispaniola which extends westward to form the Gulf of La Gonave, separated from the rest of the Caribbean Sea to the south. The eastern portion of the Peninsula also extends into the mainland areas where it curves southward into the Barahona Peninsula and becomes the landward extension of the Beata Ridge. This whole southern unit of Hispaniola is distinctly separated from the rest of the island by a remarkable fault-bounded depression, the Cul-de-Sac!Enriquillo valley (Plaine du Cul-de-Sac and Hoy a de Enriquillo. The Peninsula is characterized by some of the highest reliefs of the island, which can be grouped into two distinct geomorphologic areas separated by a narrow north-south-trending graben, the Jacmel-Fauche depression. … The general physiography is essentially fault controlled, and the most prominent such feature is the TransXaragua fault system that transects the entire length of the Peninsula diagonally.
The remarkable orographic system that constitutes the southern Peninsula can be essentially related to transcurrent faulting (also called strike-slip faulting) associated with tectonic activities along the northern boundary of the Caribbean plate. Transpressional stresses acting along this particular area of the Caribbean played an important role in the uplift and the present structural mode of southern Hispaniola. This portion of the island shows a complex orthogonal fabric of dislocation that controls the patterns of the mountain ranges. The uplift involved terranes equivalent to the Caribbean Sea crust to several thousand meters above the sea floor. Gravity surveys suggest that igneous rocks of oceanic character probably underlie most of the southern Peninsula. … In addition to relief influenced by tectonism, the topography is further accentuated by relief inversion caused by faster weathering of the older basaltic terranes relative to the overlying limestone rocks, as will be observed during the crossing to Jacmel.