Deep Seismic Imaging across the Cameroon Volcanic Line

MEYERS, JAYSON B., and BRUCE R. ROSENDAHL, Project PROBE, University of Miami, Miami, FL

The Cameroon Volcanic Line (CVL) is a southwest-trending line of volcanic centers that extends from near Lake Chad to at least the island of Pagalu. The Sao Tome and Principe Islands along the CVL have intrigued explorationists for decades because oil seeps and windows of sediments occur on them. Recently the "PROBE Study" acquired a grid of deep-imaging multifold seismic data across submarine portions of the CVL. Profiles crossing the CVL show upward flexure of oceanic crust and Moho reflections of more than 3 km locally. Upper Cretaceous/lower Tertiary drift sequence reflectors are concordant to crustal uplift, and shoal toward the islands where they are enmeshed with volcanics. These sediments are apparently the source of oil seeps on Sao Tome and Principe. On the flanks of CVL isl nds and seamounts, regionally continuous sequence boundaries are observed onlapping rotated older sediment reflectors. These sequence boundaries display either base-discordant onlap patterns or divergent onlap patterns, both indicative of uplift, not eustatic fluctuation.

The "uplift sequence boundaries" probably result from uplift associated with pulses of volcanism in the Miocene. It is likely this arching is the equivalent of the Miocene Adamawa uplift that occurs on land. We hypothesize crustal uplift was produced by upwelling of the asthenosphere and upward percolation of light mantle fluids. Features which may be the tops of magma bodies 2-20 km wide are imaged in some of the reflection profiles, and possible shear zones and fluid conduits are observed as sub-Moho dipping reflector events.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)