UPPER ZEOLITE FACIES BURIAL METAMORPHISM IN PALEOCENE-EOCENE REDBEDS OF THE WAGWATER GROUP, EASTERN JAMAICA

Cenozoic strata in eastern Jamaica reflect three tectonic stages: (1) Early Paleocene to Middle Eocene redbeds and volcanic rocks of the Wagwater Group occupy a NW-trending half-graben that relates to transtensional tectonics. The Group is at least 6.8 km thick. (2) Middle Eocene to Miocene platform limestone overlies the Wagwater Group and varies in thickness from ~0.9 km to ~2.5 km. The limestone relates to epeirogenic subsidence. (3) Late Miocene (c. 10 Ma) to Pleistocene carbonate reef deposits relate to ongoing transpressional uplift.

This research focuses on clasts of volcanic rock in Early Paleocene (c. 65 Ma) conglomerate near the base of the Wagwater Group. Relict augite (Mg#68), plagioclase (An₆₀) and Fe-Ti oxides in the clasts are consistent with basalt. Mineral assemblages, thermodynamic calculations, and stratigraphy define a P-T path for the following paragenesis: (1) During burial, augite was partially to completely replaced by celadonite and chlorite, and expansion fractures were filled by calcite, laumonite and orthoclase (adularia). P-T conditions reached ~260°C, ~1.4 kbars (4.2 km), c. 61 Ma. Cooling began during the deposition of the youngest strata of the Wagwater Group. (2) Plagioclase was partially replaced by heulandite in response to intermittent hydration during continued cooling and burial beneath a thickening limestone platform. P-T conditions approached ~80°C, 2.6-3.1 kbars (7.7-9.3 km), c. 10 Ma. (3) Plagioclase and heulandite were partially replaced by chabazite in response to hydration during final transpressional uplift. The P-T path is interesting because it involves “hot” burial (low dP/dT) and “cool” uplift (high dP/dT). The results contribute to understanding the evolution the northern margin of the Caribbean plate.