Geology of the Coamo area, Puerto Rico, and its relation to the volcanic arc-trench association

Abstract

___ ________________________________________ Introduction. _ _____________________________________ Petrographic methods ___________________________ Definitions of some terms._______________________ Acknowledgments ______________________________ General geologic setting.____________________________ Cretaceous rocks.__________________________________ Pre-Robles rocks_ ______________________________ Robles Formation._____________________________ Bedded volcaniclastic rocks__________________ Rio Maton Limestone Member.______________ Lapa Lava Member._ ______________________ Las Tetas Lava Member.____ ______________ Some chemical peculiarities of the lavas____ __ Age ______________________________________ Source and conditions of deposition__ ________ Cariblanco Formation-__________________________ Volcaniclastic rocks_________________________ Conglomerate: mixtures of gravel, ash, and reworked pyroclastics_ ____________ Gravel. ___________________________ Conglomerate matrix and coarse volcaniclastic strata _________________ Mudstone, chert, and tuff___________.

Cretaceous-Paleogene thrust emplacement of serpentinite in southwestern Puerto Rico

“…Northwest-striking thrust faults within the serpentinite are geographically associated and kinematically compatible with the ESE-striking left-lateral faults in the serpentinite (Laó-Dávila and Anderson, 2009). Many of these structures have oblique slip indicators and show strain compatibility with late Eocene-early Oligocene structures recorded in the Cerrillos belt (Glover, 1971;Erikson et al, 1990;Laó-Dávila, 2002;Laó-Dávila and Anderson, 2009), suggesting that some structures that formed during the Maastrichtian-Paleocene transpression were reactivated and that new structures formed during late Eocene-early Oligocene transpression. This evidence suggests two periods of early Cenozoic deformation in SW Puerto Rico: (1) an older transpressional event during the MaastrichtianPaleocene that was responsible for the second emplacement of the serpentinite belts, and (2) a younger late Eocene-early Oligocene transpression event, manifested principally in the Cerrillos belt, that formed new faults in the serpentinite belts and also reactivated old faults, as shown by stratigraphic relations and our fi eld investigation.…”

“…The NW-striking Northern and Southern Puerto Rico fault zones divide the pre-Oligocene rocks on the island into three blocks: the Northeast block, the Central block, and the Southwest block (Briggs and Akers, 1965;Pease, 1968aPease, , 1968bGlover, 1971;Erikson et al, 1990Erikson et al, , 1991. The Northeast and Central blocks contain Early Cretaceous vol cani clastic, sedimentary, and volcanic rocks, the oldest in Puerto Rico, which are part of a primitiveisland-arc suite of rocks (Jolly et al, 2006).…”

Toward an integrated understanding of Holocene fault activity in western Puerto Rico: Constraints from high-resolution seismic and sidescan sonar data

“…Faults in Mona Passage identifi ed by Grindlay et al (1997) and van Gestel et al (1998). Structural lineaments onland from Glover (1971 (1971) and Mann et al (this volume,Ch. 6) and location of South Lajas fault from Glover (1971), Meltzer and Almy (2000), and Prentice and Mann (this volume Erikson et al, 1990Erikson et al, , 1991.…”

Circum-Caribbean Explosive Volcanic Activity: Evidence from Leg 15 Sediments

“…All of these formations contain calc-alkalic minerals. For instance, the Hacienda Larga Tuff of the Cariblanco Formation has been described (Glover, 1971) as dominantly plagioclase bearing, but with hornblende, biotite, minor sanidine and quartz. In addition, I have seen conspicuous apatite from one locality.…”

“…Stratigraphic equivalents of this activity in surrounding land areas are well known: the Summerfield Formation of Jamaica (Coates, 1968;Roobol, in press), the Cariblanco Formation of Puerto Rico (Glover, 1971), the Knip Group of Curacao (Beets, 1971), and the Washikemba Formation of Bonaire (Beets and Lodder, 1967). All of these formations contain calc-alkalic minerals.…”