Petrology and Diagenesis of Arc-Derived Lithic Sandstones--Wagwater Trough, East-Central Jamaica: ABSTRACT

Abstract

The Wagwater trough is a fault-bounded block of lower Tertiary sedimentary and volcanic rocks that cuts across east-central Jamaica in a southeast direction. Detrital sandstone and conglomeratic sequences within this block include the early Eocene and Paleocene(?) Wagwater and Richmond Formations. The Wagwater Formation is a red-bed sequence of breccias, conglomerates, sandstones, and mudstones with minor amounts of limestone and gypsum deposited as a subaerial fan-delta complex. Sedimentary rocks of the Wagwater Formation are laterally equivalent to sandstones, conglomerates, shales, and limestones of the Richmond Formation, which were deposited in submarine-slope and fan environments. Lithic arenites are the dominant sandstone type within the trough. Principal framework constituents include volcanic and carbonate lithic fragments, plagioclase, quartz, and fossil fragments with minor amounts of plutonic lithic fragments and opaque heavy minerals. Authigenic minerals are abundant in some sandstones and include phyllosilicates (chlorite and clay minerals), calcite, and iron oxide. The progressive sequence of diagenetic features from earliest to latest in marine sandstones of the Richmond Formation is: (1) development of clay coats around framework grains, (2) precipitation of calcite pore-fill cement, (3) development of a second clay coat on calcite cement in incompletely filled pores, (4) crystallization of radiating pore-fill chlorite after development of clay coats in either stage 1 or stage 3, and (5) late-stage calcite replacement. Despite minor differences in diagenetic features, the Richmond sandstones are similar to other arc-derived sandstones from five other basins. These separate occurrences suggest that sands deposited in arc basins have the same compositional range, and that postdeposition processes produce a common diagenetic sequence. End_of_Article - Last_Page 447------------