Subdubccion En El Caribe

TECTONICS, VOL. 1,

NO. 3,

PAGES 251-276,

JUNE 1982

SUBDUCTION OF THE IN THE OVERRIDING

CARIBBEAN PLATE AND BASEMENT SOUTH AMERICAN PLATE

UPLIFTS

J. N. Kellogg andW. E. Bonini 1
Department of Geological and Geophysical Sciences, Princeton University, Princeton, New Jersey 08540

Abstract. The new tectonic interpretations presented in this paper are based on geologic fieldmapping and gravity data supplemented by well logs, seismic profiles, and radiometric and earthquake data. The present Caribbean-South American plate boundary is the South Caribbean marginal fault, where subduction is indicated by folding and thrusting in the deformed belt and a seismic zone that dips 30o to the southeast
and terminates 200 km below the Maracaibo Basin. The Caribbean-SouthAmerican convergence rate is estimated as 1.9 +_. 0.3 cm/yr on the basis of the 390-km length of the seismic zone and a thermal equilibration time of 10 n.y. The Caribbean-South American convergence has produced a northwest-southeast maximum principal stress direction o1 in the overriding South American plate. The mean Ol direction for the Maracaibo-Santa Marta block is 310ø _+ 10ø based on earthquakefocal mechanism determinations, and structural and gravity data. On the overriding South American plate, basement blocks have been uplifted

7-12 km in

the last 10 n.y. to form the VenezuelanAndes• Sierra de

Perija, and the Colombian Santa Marta massif. Crystalline basement of the Venezuelan Andes has been thrust to the northwest over Tertiary sediments on a fault dipping about 25ø andextending to the mantle.
In the Sierra de Perija, Mesozoic sediments have been thrust 16-26 km

to the northwest over Tertiary sandstones along the Cerrejon fault. A thrust fault dipping 15ø +_ 10ø to the southeast is consistent with field mapping, and gravity and density data. The Santa Marta massif has been uplifted 12 km in the last 10 n.y. by northwest thrusting over sediments. The basementblock overthrusts of the Perijas,
Venezuelan Andes, and the Santa Marta massif are Pliocene-Pleistocene

analogs for Laramide orogenic structures in the middle and southern Rocky Mountains of the United States. The no•magmatic basement block

uplifts along low-angle thrust faults reveal horizontal compression in the overriding plate over 500 km from the convergent margin. Present-day eastnortheast-west southwest (080 ø) compression is indicated by earthquake focal mechanismsand strike slip motion on the
Bocono fault.
INTRODUCTION

These earthquakes are intraplate

deformation

associated

with east-west (080ø) Nazca-South American convergence.

the
,

The Caribbean-northwestern South American plate boundary has been most controversial and difficult Caribbean boundary tointerpret

tectonically

(Figures 1 and 2).

The high seismicity

and Holocene

1 Now Hawaii Institute of Geophysics, at University of Hawaiiat Manoa,
Honolulu, Hawaii 96822.

Copyright 1982 by the American Geophysical Union. Paper number 2T0861. 0278-7407/82/002T-0861510.00

252
I I

Kellogg and Bonini:
I I

Caribbean Suhduction and Andean Uplift
I
I I

90 o

o

70o

6o ø

NORTH AM ERICAN PLATE
20 ø --

Bønmbe•

t/ SOUTH PLATE AMERICAN
ß I I

'

Fig.

1.

Circum-Caribbean

plate

motions relative

to the Caribbean

plate

[after

Jordan, 1975].

Earthquake focal mechanismsare shown
1978].

for event 9 [Kafka and Weidner, 1979] and event 10 [Rial,

displacement
prompted

on the

northeast trending Bocono fault
theBocono fault

(Figure 2) have
zone as the

some to

interpret

Caribbean-South American plate

boundary [Molnar and Sykes, 1969;

Dewey, 1972]. Kafka and Weidner [1981] determined surface wave focal mechanisms for five earthquakes near the Bocono fault zone. The determinations were consistent with compression in an east-west direction, which they interpreted as the direction of...