The study of the radiolarian ribbon chert is a key in determining the
origins of associated Mesozoic oceanic terranes and may help to achieve
a general agreement regarding the basic principles on the evolution of
the Caribbean Plate. The Bermeja Complex of Puerto Rico, which contains
serpentinized peridotite, altered basalt, amphibolite, and chert
(Mariquita Chert Formation), is one of these crucial oceanic terranes.
The radiolarian biochronology presented in this work is mainly based by
correlation on the biozonations of Baumgartner et al. (1995) and
O'Dogherty (1994) and indicates an early Middle Jurassic to early Late
Cretaceous (late Bajocian-early Callovian to late early Albian-early
middle Cenomanian) age. The illustrated assemblages contain about 120
species, of which one is new (Pantanellium karinae), and belonging to
about 50 genera. A review of the previous radiolarian published works on
the Mariquita Chert Formation and the results of this study suggest that
this formation ranges in age from Middle Jurassic to early Late
Cretaceous (late Aalenian to early-middle Cenomanian) and also reveal a
possible feature of the Bermeja Complex, which is the younging of
radiolarian cherts from north to south, evoking a polarity of accretion.
On the basis of a currently exhaustive inventory of the radiolarite
facies s.s. on the Caribbean Plate, a re-examination of the regional
distribution of Middle Jurassic sediments associated with oceanic crust,
and a paleoceanographic argumentation on the water currents, we come to
the conclusion that the radiolarite and associated Mesozoic oceanic
terranes of the Caribbean Plate are of Pacific origin. Eventually, a
discussion on the origin of the cherts of the Mariquita Formation
illustrated by Middle Jurassic to middle Cretaceous geodynamic models of
the Pacific and Caribbean realms bring up the possibility that the rocks
of the Bermeja Complex are remnants of two different oceans.