--> Abstract: Depositional Cycles on a Prograding Reef-Rimmed Carbonate Platform During High-Frequency Sea-Level Fluctuations, Upper Miocene Reef Complex of Mallorca, Spain, by L. Pomar, M. Esteban, and W. C. Ward; #90987 (1993).

Datapages, Inc.Print this page

POMAR, L., University of the Balearic Islands, Mallorca, Spain; M. ESTEBAN, Erico-PI, London, UK; and W. C. WARD, University of New Orleans, New Orleans, LA

ABSTRACT: Depositional Cycles on a Prograding Reef-Rimmed Carbonate Platform During High-Frequency Sea-Level Fluctuations, Upper Miocene Reef Complex of Mallorca, Spain

High-frequency fluctuations of the Mediterranean Sea influenced the architecture of the Upper Miocene coral-reef complex on the Llucmajor platform of southwestern Mallorca. The most prominent characteristic of this 90-m-thick progradational carbonate unit is the stacking of depositional units hierarchically integrated in four orders of magnitude (1M-4M) within third-order sequences. The basic building blocks are "sigmoids" (4M), which stack in "sets of sigmoids" (3M). Sigmoids and sigmoid sets stack in "cosets of sigmoids" (2M), and these stack in "sets of cosets" (1M). These depositional units, which record progradation with up and down facies shifts, are differentiated into four types of bundles: (1) low-stillstand progradational, (2) aggradational, (3) high-stillstand progradationa , and (4) downstepping (offlapping).

This model for the Mallorca reef complex has features which distinguish it from other shallow-platform models: (a) maximum accumulation throughout the depositional tracts was during sea-level rise (aggradational bundles have relatively thick open-shelf to lagoon facies); (b) there was relatively minor accumulation during sea-level stillstands (reef-core and reef-slope facies are progradational, and the open-platform facies wedges out basinward without a clear downlap surface); (c) the reef core downstepped onto the open shelf during sea-level fall (offlapping bundles are bounded by erosional truncation at the top and by downLap surfaces at the base); and (d) the high-stand and off-lapping bundles pass into condensed (few-cm-thick) open-shelf layers. These characteristics largely resul from the limited accomodation during the progradation across the relatively shallow (60-100 m) platform.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.