Comparative Geomorphology and Dynamics of Holocene Isolated Carbonate Buildups, South China Sea

Abstract

Carbonate strata form important reservoirs in southeast Asia, including Eocene-Miocene isolated buildups. Although seismic data from some platforms illustrate internal geometries such as platformward progradation of reef sand aprons, in most, such direct facies indicators are absent. In such scenarios, analogs provide both conceptual models and data to constrain facies dimensions, orientation, and configuration. The overall objective of this study is to use remote sensing data to systematically examine and quantify spatial facies patterns of Holocene isolated carbonate buildups (ICB) in the South China Sea. The fundamental data for the study are high-resolution (<2.4 m² multispectral, 0.6 m² panchromatic) remote sensing images of 27 ICB. Each ICB is captured by at least one image collected between 2003 and 2014; 11 ICB include two or more temporally distinct images that permit assessing temporal changes on these platforms. Analysis of remote sensing data of ICB of the South China Sea includes platforms ranging in size from 5 – 195 km², and include circular, ovoid, and elongate shapes. The mean orientation of the long axis for ICB of both the Spratly (73°) and the Paracel (96°) chains are slightly different, probably related to tectonic framework. ICB facies bodies include reefs and reef sand aprons that are non-uniformly distributed within and among platforms. Platforms range from incipiently drowned to almost fully aggraded, and include reef sand aprons and reefs that can exceed 1500 m width. Despite the variability, a pronounced trend of marked asymmetry of the spatial distribution reef sand aprons is evident: 89% of ICB include the widest reef sand apron on the north- or west-facing flank. These systems are not static. Although some ICB show no changes between multi-temporal images, several ICB illustrate rather pronounced changes; in one case (Mischief), reef-derived debris migrated over 300 m towards the platform interior in 8 years (2004–2012). A database of processes (characteristics of waves, tides, currents, and winds, for example) provides a process-based understanding of the genesis and potential evolution of these systems. These results provide conceptual models and data that could be used as input on facies attributes for geologic models.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015