Abstract

The western portion of the Sanga Sanga PSC, located in the Kutei Basin, encompasses the Samarinda Anticlinorium. Structuring in this area is characterized by long, linear, tightly folded and faulted anticlines separated by broad, minimally deformed synclines. Each of the synclines is isolated. Seismic data correlation of horizons must be jump-correlated over the anticlines. Well data are limited and for the most part are located on the structurally complex anticlines. Biostratigraphic data collected from well control, outcrops, and seismic shotholes were used with seismic and SAR data in VICO's stratigraphic and structural interpretation of this complex area.

This project was one component of a three year basin study. It had three primary objectives, i.e.: providing sediment age control to constrain syncline to syncline correlation, determining depositional environment of surface exposures and outlining the biostratigraphic sequence component within a regional sequence stratigraphic interpretation. The Oligocene to Recent sequence chronostratigraphy, based on planktonic foraminifera, calcareous nannofossils and larger foraminifera index species found in the Sanga Sanga PSC as well as the distribution of benthonic foraminifera in the Miocene onshore Kutei Basin, were summarized and applied. However, the interpretation results of the early Early Miocene Blow Zone N4 to N6 biostratigraphic data varied significantly over the course of the study. The presence of reworked fossils was probably the most frequent error in age and facies analysis of the sedimentary succession. In the end, it was the strength of the multi-discipline integrated interpretation approach that permitted us to examine critically the biostratigraphic database and discover more viable alternate solutions.

In poorly constrained, tectonically complex, clastic sediment fill basins such as the Kutei Basin, correlation of sections is best achieved by utilizing foraminifera diversity/abundance histograms within a regional interpretation framework. Because of extensive reworking of fossils, a biostratigraphic stand-alone correlation technique is prone to significant error in deriving age, depositional environment, and the sequence stratigraphy context.