Some speculations on the Paleogene and Neogene tectonics of Jamaica

Abstract

AbstractMany neotectonic structures (<15 Ma) in Jamaica are best understood as reactivations (or inversion) of Paleogene structures (65–22 Ma). In the Paleocene, Jamaica underwent crustal extension which formed north‐northwest‐trending listric normal faults, including those of the Wagwater Belt which occupied a half‐graben formed over the northeast‐dipping Wagwater Fault. From the Middle Eocene (45 Ma) to Late Oligocene (23 Ma), further subsidence (possibly thermally induced following lithospheric thinning) resulted in the accumulation of a carbonate bank. Beginning in the Early to Middle Miocene, the tectonic regime changed to one of active east–west‐trending, left‐lateral, strike‐slip motion that persists to the present day. New east–west‐trending faults formed during this phase, but secondary northeast–southwest shortening produced in this regime reactivated many of the older, Paleogene north‐northwest‐trending structures. In eastern Jamaica, oblique thrust motion is concentrated on the Wagwater Fault, tectonically inverting the Wagwater Belt. The Long Mountain anticline may be a fault propagation fold over a thrust that branched from the main Wagwater Fault surface. Motion on the Silver Hill Plantain Garden Fault system resulted in the northward rotation of the Blue Mountain Block around an approximately horizontal axis and revealing the upper crustal structure of eastern Jamaica. In the central part of Jamaica, north‐northwest‐trending faults divide the terrane into a series of blocks. Evidence of right‐lateral, horizontal‐slip on some of the faults and palaeomagnetic results may suggest a domino‐style, anticlockwise rotation around vertical axis by about 10°. Copyright © 2008 John Wiley & Sons, Ltd.