Toni Simo, AAPG Distinguished Lecture

Title: Toni Simo, AAPG Distinguished Lecture

Event: AAPG Distinguished Lecture

Event Date: January 14, 2010

Publication: The Outcrop, January 2010, p. 18-19

(This luncheon is jointly sponsored by RMAG and RMS/SEPM at the Marriot downtown on Thursday, January 14th, 2010.) This talk focuses on Tertiary and modern ICPM from Southeast Asia, drawing general conclusions on ICPM initiation, growth and demise.

Abstract:

Isolated Carbonate Platforms and Mounds (ICPM): Initiation, Growth and Demise
Isolated carbonate platforms and mounds (ICPM) originate on topographic highs in shallow marine waters and are surrounded on all sides by deeper-water environments. Comparative studies of modern and ancient isolated platforms allow insights into mechanisms that control the platforms. Modern examples provide information especially relevant to Tertiary platforms because the carbonate-secreting organisms that built the platforms are very similar and occupied similar ecologic zones.

In the modern detailed information on the organisms and environments of deposition can provide insights into the dominant controls on facies type and dimensions today. However, there is a challenging lack of information regarding how the facies and size change through time. This challenge can be addressed through high-resolution seismic images, which provide sequential and spatial information and allow for comprehensive analysis on ICPM initiation, amalgamation, and demise. A unique combination of insights gathered from modern and ancient datasets on isolated carbonate platforms and mounds can be used to make predictions, create conceptual models, and guide geologic model inputs.

Two- and three-dimensional seismic surveys from SE Asia show internal seismic geometries and positions of margins, providing clues on the evolution of the ICPM. Mounds initiate as small positive features that amalgamate to form platforms of different sizes and geometries prior to drowning. The distance between the mounds appears to be the first-order control on amalgamation and ultimate platform size. However, amalgamation may be inhibited if strong currents redistribute sediment transported off-bank and away from the mounds, leaving unfilled accommodation space.

Understanding the feedbacks between mound amalgamation and carbonate production will have implications for predicting control mechanisms and building conceptual models. High amalgamation rates imply large areas of shallow-water carbonate deposition and high carbonate production resulting in the formation of mega-platforms. Smaller areas of shallow water deposition tend to drown faster when environmental conditions deteriorate and platforms cannot keep up with increased accommodation.

Satellite images over several modern platforms in SE Asia provide an opportunity to investigate the importance of oceanographic processes such as tides and currents as well as tectonic subsidence and chemistry on carbonate deposition and the impact on ICPM evolution. In the Tertiary, however, special consideration is needed for sea-surface temperature and salinity residence times. These parameters are thought to be the major difference in biologic controls on the types of organisms building shallow-water platforms in the Tertiary versus today.

Modern and ancient datasets are used in parallel to evaluate what and how certain processes control initiation, growth, and demise of isolated carbonate platforms and mounds. This allows us to predict the controls for ancient ICPM, thus establishing a framework of rules for predictive conceptual models.

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