The peri-Caribbean
ophiolites: structure, tectono-magmatic significance and geodynamic
implications
G. Giunta, L. Beccaluva, M. Coltorti, D.
Mortellaro, F. Siena and D. Cutrupia
ABSTRACT.
New geological and petrological data on ophiolitic complexes deformed and
dismembered along the Caribbean Plate margins are presented in the framework of
IGCP 433, in order to contribute to the debate on the origin and evolution of
the Caribbean Plate. A “near Mid-America” original location of the
Jurassic-Cretaceous Caribbean oceanic realm (proto-Caribbean phase) is
suggested. Generation of oceanic crust can be initially referred to multiple
spreading centres (LREE depleted MORB, in Venezuela, Costa Rica, Cuba, Guatemala,
Hispaniola), evolving, into a thickened oceanic plateau (REE-flat MORB locally
associated with picrites, in Costa Rica, Hispaniola, Venezuela, Dutch and
Venezuelan Islands). At the same time, both the South and North American
continental margins were affected by rifting and within-plate tholeiitic
magmatism (Venezuela and Cuba). From
Early to Late Cretaceous (eo-Caribbean phases), one subcontinental subduction
zone, with melange formation (recorded only in Venezuela), and two main stages
of intraoceanic subduction may be recognised: 1) an initial NE- and SE-dipping
sinking of unthickened proto-Caribbean lithosphere, recorded by deformed and
HP/LT metamorphosed ophiolitic melanges and volcano plutonic sequences with
island-arc tholeiitic affinity (IAT) in Venezuela, calc-alkaline affinity (CA)
in Cuba and both IAT and CA affinity in Guatemala and Puerto Rico; 2) followed
by intraoceanic subduction, with reverse polarity, responsible for the first
tectonic arrangement of the Caribbean margins, recorded by unmetamorphosed
tonalitic intrusives, and related to the onset of the Aves-Lesser Antilles arc
system and its eastward migration. In the Late Cretaceous, the undeformed
interior of the Caribbean Plate, i.e. the Colombian and
Venezuelan Basins,
was restricted by subduction of the Pacific plate, building the Central
American Isthmus. The Tertiary to Present eastward displacement of the
Caribbean Plate led to the progressive dismembering of the deformed ophiolitic
belts and their obduction at its margins. Presented at IGC-BRAZIL/2000.
Two very
fossiliferous rudist sites from the Marchmont Inlier, northwestern Jamaica
Gavin C. Gunter
ABSTRACT. The Marchmont Inlier of
north-western Jamaica
exposes Upper Cretaceous rudist bearing limestones and intervening clastics.
The purpose of this note is to document the presence of two localities in this
inlier that yield abundant, well-preserved rudist specimens belonging to the Titanosarcolites fauna. Collections from
these sites have significantly increased our knowledge of the rudist
assemblages present within the inlier, and may prove invaluable in future
studies on the biostratigraphy and palaeoecology of Jamaican rudists.
Field guide to the
geological evolution of the Maastrichtian rocks of the Central Inlier, Jamaica
Simon F. Mitchell
ABSTRACT.
This field guide describes the geology found in the central part of the Central
Inlier. The oldest rocks present, the Arthurs Seat Formation represent the
deposits of a volcanic arc. These are succeeded unconformably by a
Maastrichtian (Upper Cretaceous) transgressive-regressive cycle consisting of
the Slippery Rock, Thomas
River and Guinea Corn
formations, and the Summerfield Group. The various stops show how this
transgressive-regressive cycle developed.
The trace fossil Schaubcylindrichnus coronus Frey and
Howard, 1981, from the White Limestone Group of northeast Jamaica
Donovan J. Blissett and Ron K. Pickerill
ABSTRACT.
The upper Lower-Middle Miocene Pelleu Island Formation of the Middle Eocene to
Middle Miocene White Limestone Group, northeast Jamaica, has yielded the trace
fossil Schaubcylindrichnus coronus
Frey and Howard, 1981. The documentation of this bundled trace fossil is
important because it is the first report of this ichnotaxon from Jamaica and indeed the Caribbean
region. As a corollary it therefore adds to the geographical distribution of
the trace fossil, and it is the first record that extends its
palaeoenvironmental range to a deep-water setting.
Field guide to the
geology of the Eocene Chapelton Formation (Yellow Limestone Group), western
Central Inlier
Stephen K. Donovan
ABSTRACT.
This field guide provides details of an excursion that demonstrates the faunas
and sedimentary facies of the Yellow Limestone Group in the western part of the
Central Inlier, between Dump (near Christiana), parish of Manchester,
and Stettin, parish of Trelawny. Units
examined include the Freemans Hall beds, Stettin Member, Guys Hill Member and
Dump Limestone, representing a range of shallow water, near shore palaeoenvironments.