Role of
Antecedent Topography and Local Environmental Controls on the Evolution and
Facies Heterogeneity of Miocene Carbonate Platforms,
Lehrmann, Daniel1, Akbar
Satria2 (1)
The Miocene Wonosari Formation forms a
series of broad, high energy platforms with patch reefs developed along the
south-central and southeastern Java. The platforms were nucleated on irregular
topography of the eroded “Old Andesite” volcanic arc. Maps depict the
unconformity as a simple surface that truncates intrusive and volcanic rocks of
the arc as well as intervening siliciclastic strata. Our mapping reveals a
complex surface that truncates intrusive and volcanic rocks on topographic
highs that may be overlain by alluvial conglomerates or upon which coral-rich
carbonates were nucleated. In topographic lows no discrete truncation surface
was found between the Wonosari and the underlying Sambipitu Fm.
In topographic lows siliciclastic
sedimentation of the Sambipitu Fm. shallowed upward from turbidites to
shoreline sands and fanglomerates containing clasts eroded from the arc and
coral clasts reworked from reefs developed as advancing seas flooded southern
Java. Although the bulk of coral clasts found within the fanglomerates were
likely derived from coeval reefs that grew and were reworked during
transgression, the presence of large lithified carbonate blocks of varied
lithologies also indicate tectonic uplift and erosion of an older carbonate
platform.
Reworked corals occur everywhere in the
basal Wonosari indicating abundant patch reefs developed during the initial
transgression, whereas later establishment of vast carbonate shelves limited
reef development. No evidence of subaerial exposure was found within the
Wonosari except for soils developed in volcaniclastic sediments formed near
landward attached areas of the platforms. Pulses of volcaniclastic influx
repeatedly filled accommodation space leading to exposure.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California