TY - CONF T1 - Larger benthic foraminifera – faunal pioneers in mixed carbonate-siliciclastic systems T2 - 2012 GSA Annual Meeting Y1 - 2012 A1 - Vibor Novak A1 - Nadiezhda Santodomingo A1 - Willem Renema AB - Larger benthic foraminifera are one of the most abundant and widespread organisms in shallow marine tropical environments. Their role as rapid colonizers of new substrates has been suggested, but little is still known to support this idea. To address this question, larger benthic foraminifera assemblages have been studied in the paleoenvironmental reconstruction of a Langhian (Middle Miocene) shallow-water patch reef, as part of a broader multitaxon fossil comunity analysis, including corals, coralline algae, and bryozoans. The studied outcrop (approx. 80 m wide and 25 m thick) is located at the northeast margin of the Kutai Basin near Bontang (Indonesia). The patch-reef was developed in mixed carbonate-siliciclastic depositional environment and despite the high terrigenous input affecting water transparency, this reef contains a diverse marine biota. Five different facies types were distinguished based on lithology and fossil content: foraminifera packstone, bioclastic packstone with foralgal communities, thin-platy coral sheetstone, platy-tabular coral platestone, and shales. Excluding the fossil barren shales facies, only larger benthic foraminifera occur in all four remaining facies types, showing the ability to rapidly adapt to changes in environment. In the current study, high siliciclastic input caused fluctuations in light levels, but also resulted in deposition of soft-bottom substrate. In newly developed conditions, the larger benthic foraminifera appear first and mark the initiation of reef growth. The persistence of LBF throughout the fossil reef succession indicates their high tolerance to terrigenous input and also highlight the role of foraminifera as primary colonizers, proving themselves as important faunal pioneers, particularly in mixed carbonate-siliciclastic systems. JF - 2012 GSA Annual Meeting CY - Charlotte, NC ER - TY - CONF T1 - Burdigalian turbid water patch reef environment revealed by larger benthic foraminifera T2 - The EGU General Assembly 2012 Y1 - 2012 A1 - Vibor Novak A1 - Willem Renema A1 - the Throughflow Project AB - Ancient isolated patch reefs outcropping from siliciclastic sediments are a trademark for the Miocene carbonate deposits occurring in East Kalimantan, Indonesia. They develop in transitional shelf sediments deposited between deltaic and deep marine deposits (Allen and Chambers, 1998). The Batu Putih Limestone (Wilson, 2005) and similar outcrops in adjacent areas have been characterized as shallow water carbonates influenced by high siliciclastic input, showing low relief patch reefs in turbid waters. Larger benthic foraminifera (LBF) are excellent markers for biochronology and paleoenvironmental reconstruction. This study aims to reveal age and paleoenvironment of a shallow water carbonate patch reef developed in mixed depositional system by using LBF and microfacies analysis. The studied section is located near Bontang, East Kalimantan, and is approximately 80 m long and 12 m high. It is placed within Miocene sediments in the central part of the Kutai Basin. Patch reef and capping sediments were logged through eight transects along section and divided into nine different lithological units from which samples were collected. Thin sections and isolated specimens of larger benthic foraminifera were analyzed and recognized to species level (where possible) providing age and environmental information. Microfacies analysis of thin sections included carbonate classification (textural scheme of Dunham, 1962) and assemblage composition of LBF, algae and corals relative abundance. Three environmentally indicative groups of LBF were separated based on test morphology, habitat or living relatives (Hallock and Glenn, 1986). Analysed foraminifera assemblage suggests Burdigalian age (Tf1). With use of microfacies analysis nine successive lithological units were grouped into five facies types. Paleoenvironmental reconstruction of LBF fossil assemblage indicate two cycles of possible deepening recorded in the section. Based on high muddy matrix ratio in analyzed thin-sections we still cannot conclude whether they were deeper water assemblage, or that they occurred in shallower water and influenced by turbid conditions as the result of terrigenous input. According to preliminary analysis and siliciclastic content in the sediments the later one should be more likely. Further work will include additional fossil groups analysis (corals, algae and bryozoans), detailed petrographical analysis and Strontium isotope stratigraphy. JF - The EGU General Assembly 2012 CY - Vienna ER - TY - CONF T1 - Environmental reconstruction of a Langhian patch reef (East Kalimantan, Indonesia) T2 - Lyell Meeting 2012 Y1 - 2012 A1 - Vibor Novak A1 - Nadiezhda Santodomingo A1 - Anja Rösler A1 - Emanuela Di Martino A1 - Juan C. Braga A1 - Paul D Taylor A1 - Kenneth G. Johnson A1 - Willem Renema JF - Lyell Meeting 2012 ER -