ABSTRACT: Late Quaternary Carbonate Sequence Stratigraphy in Walton Basin, Northeastern Nicaragua Rise, Caribbean Sea

GLASER, KAREN S., and ANDRE W. DROXLER, Rice University, Houston, TX

Sequence stratigraphic models for carbonate rocks were primarily developed in ancient carbonate settings, applying concepts derived from siliciclastic sequence stratigraphic models. The sequence stratigraphic model for the accumulation of late Quaternary sediments on the northern Nicaragua Rise differs significantly from that based on fossil carbonate systems, particularly in the large proportion of highstand sediments on the basin margins.

Late Quaternary glacial and interglacial stage sediments deposited in Walton Basin onlap the steep margins of Pedro Bank and the southern Jamaica shelf. This onlapping relationship is seen on 3.5 kHz seismic profiles. The thick package of interglacial sediments (up to 10 m) and the thin (<1 m) glacial package onlapping the shelf do not fit models for carbonates in ancient systems.

Glacial stage sediments, deposited during times of low sea level when the bank and shelf were exposed, correspond to the lowstand systems tract. They are characterized by low sediment accumulation rates and lateral removal of fine sediment by strong currents. Interglacial sediments were deposited when the bank and shelf were submerged and are characterized by large accumulations of neritic carbonate and greater input of pelagic carbonate and bank-margin derived sediment gravity flow deposits. The majority of the interglacial stage sediments are contained within the highstand systems tract, although a thin transgressive systems tract is present.

Transgressive systems tracts in the study area are thin due to the rapid flooding of the flat-topped bank and shelf. They are too thin (30 cm) to be resolved from the highstand systems tract even on high resolution 3.5 kHz seismic profiles. They can, however, be identified by subtle compositional changes in the interglacial sediments associated with the eustatic sea level maximums that mark the top of the transgressive systems tract.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)