The pre-drift Central Atlantic; A model based on tectonomagmatic and sedimentological evidence

Abstract

Geological data from islands and deep sea drill sites of the Central Atlantic have been examined in the light of problems such as the pre-drift relative position of North America and Africa, and the time of commencement of seafloor spreading. Observations of particular concern, and which are difficult to accomodate in the present spreading model, are 1. the wide distribution of the Lower Cretaceous “black shales”, 2. the mid-Cretaceous tectonomagmatic event, and 3. the pronounced Upper Cretaceous sedimentary hiatus. Based on these data a new evolutionary model, including a major pre-drift basin (of the order of 2000 km across) and onset of sea-floor spreading around late Cenomanian time, is proposed. A possible relationship between sea-floor spreading and the major intracontinental sedimentation in Africa and North America in Middle-Upper Cretaceous is suggested, giving a reasonable explanation of the well-known “Cenomanian” transgression.