@conference {2017, title = {Microbial carbonates in Miocene reefs in the Mahakam Delta in East Kalimantan, Borneo, Indonesia}, booktitle = {SAGE2013 - Southeast Asian Gateway Evolution}, year = {2013}, month = {11/03/2013}, address = {Berlin, Germany}, abstract = {

Microbial carbonates are deposits that form by the activity of bentic microbial communities. Microbialites usually form domical, columnar or conical structures and can have laminated, clotted, dendritic or homogenous macrofabric. They have a broad distribution and can grow in a variety of different environments such as hot springs, freshwater lakes, hypersaline lakes, reefs and other marine environments. This research focuses on microbialites associated to coral reefs. Coral patch reefs in the Miocene Mahakam Delta in East Kalimantan (Borneo, Indonesia) grew in shallow marine turbid waters. These patch reefs developed from delta front to deeper (prodelta) settings in areas with temporary reduced siliciclastic input. Langhian reef deposits are well exposed in limestone quarries in the Samarinda area and locally include microbial carbonates. Two different types of microbial carbonates have been found around Samarinda in two localities 2 km apart. These sections were logged in detail and 208 samples were collected. Meso and macrostructure of microbialites were identified at the outcrops. Thin sections from carbonate samples were examined under optical microscope and microfacies were classified using the Dunham (1962) and Embry and Klovan (1971) terms. The carbonate content was analyzed using Total Inorganic Carbon analysis, with 12\% carbon as a standard for carbon calibration. In the northern section, microbialites occur as low-relief domes, up to 2 m wide and 0.5 m high, with internal lamination, developed around large coral fragments at the transition from reef deposits to fine-grained siliciclastics.
The second type of microbialites has been found in the southern locality as decimeter-scale nodules (\"megaoncoids\") formed around nuclei of large coral fragments. Small nodules were bound together into bigger nodules. Microbial micrite with laminated to digitated fabrics intergrew with coralline algae to form the thick covers of these \"megaoncoids\", which laterally change into coral boundstones. In both sections microbialites are not components of the reef framework. They grew around large coral fragments on the flanks of the patch reefs. The microbialites that form low relief domes developed on a nearly flat, stable seafloor seawards of the patch reef. The \"megaoncoids\" in the southern section formed as a result of downslope movement of coral fragments coated by microbialite/coralline algal crust. The steep slope at the flank of the patch reef favoured falling and overturning of encrusted corals and continued growth of microbial crusts on other sides of nodules.

}, author = {Vedrana Pretkovi{\'c} and Juan C. Braga and Vibor Novak and Anja R{\"o}sler and Willem Renema} } @conference {2045, title = {Sub - annually resolved Miocene/Pliocene tropical palaeo - climate records from giant clams}, booktitle = {11th INTERNATIONAL CONFERENCE ON PALEOCEANOGRAPHY}, year = {2013}, publisher = {Sitges}, organization = {Sitges}, address = {Barcelona}, abstract = {

Changes in seasonality play an important role in regards to climate changes (e.g. Eldrett
et al.,
2009). To better characterize Miocene/Pliocene tropical climate and environmental change, it is
therefore crucial to reconstruct their variability on a seasonal scale. However, highly time resolve
d
palaeoenvironmental records which allow assessing
tropical intra
-
annual SST variability (like
ENSO or monsoon events) are rare, especially in \&$\#$39;deep
-
time\&$\#$39;.
Here, we present high resolution
trace element and stable isotope proxy records from well
-
preserved aragonitic Late Miocene and
Pliocene
Tridacna
spp.
shells, sampled along the coast of East Kalimantan (Indonesia) and Sabah
(Malaysia), respectively. Our multi
-
proxy approach utilizes LA
-
ICPMS El/Ca ratios (e.g. Mg/Ca,
Sr/Ca, Ba/Ca) and micromilled stable isotope profiles (

18
O,

13
C).
Records obtained fr
om our
Miocene specimens show a remarkable agreement in Mg/Ca, Sr/Ca and

18
O and can be aligned
with the shell banding pattern.

18
O intra
-
annual variability indicates a palaeoseasonality of 3
-
4\°C
(if interpreted as being temperature
-
controlled only). Ba/
Ca profiles from Pliocene tridacnin shells
are characterized by pronounced, episodically occurring peaks with a high intrashell
reproducibility. Very similar Ba/Ca signals found in modern
Tridacnagigas
have been interpreted
as palaeoproductivity indicators
(Elliot et al., 2009). Records of a modern
Tridacna
spp. from
Sabah are utilized for comparison and calibration purposes
.

}, url = {http://www.icp2013.cat/USB/PDF/P-183.PDF}, author = {Viola Warter and Wolfgang M{\"u}ller and Willem Renema} } @conference {2015, title = {Diversity and palaeoecology of Miocene coral-associated molluscs from East Kalimantan}, booktitle = {SAGE2013: Southeast Asian Gateway Evolution}, year = {2013}, address = {Museum fuer Naturkunde, Berlin}, abstract = {

Currently, SE Asia is the global marine centre of diversity. High diversity is concentrated in and around reefs. A large variety of organisms, including corals and fish, but also molluscs, crustaceans and echinoderms contribute to this high diversity. In order to understand the timing and the context of the origin of the modern biodiversity hotspot, the fossil record needs to be documented. However, reef facies often suffer strong diagenesis, compromising the fossil record of reef and reef-associated organisms. Here we present an assessment of a well-preserved Late Miocene mollusc fauna from Bontang (East Kalimantan, Indonesia). The fauna is found in association with branching corals, dominated by Dictyaraea. The mollusc fauna is dominated by predatory and browsing carnivorous snails and includes reefal indicators such as the gastropod Coralliophyla and the bivalve Tridacna. The new Bontang fauna gives a glimpse of the diversity and ecological composition of a Late Miocene mollusc fauna from a so-called coral-carpet environment.

}, author = {Aires Kusworo and Sonja Reich and Frank P. Wesselingh and Nadiezhda Santodomingo and Willem Renema} } @conference {2014, title = {Mollusks as seagrass indicators in the Miocene of Indonesia}, booktitle = {SAGE 2013: Southeast Asian Gateway Evolution}, year = {2013}, address = {Museum fuer Naturkunde, Berlin}, abstract = {

Today\’s centre of maximum marine biodiversity is located in the Indo-Malayan region. Understanding the development of this biodiversity hotspot through the Cenozoic could answer numerous questions about the responses of highly diverse faunal associations to small and large scale environmental changes. When assessing marine biodiversity through time comparisons of taxon diversity are only meaningful when comparing faunas from similar habitats. To evaluate diversity through time within the same ecological setting, it is indispensable to reliably discriminate different habitats. A good example for the difficulties which may occur when identifying marine paleo-habitats is the challenge of recognizing seagrass vegetation in the fossil record. Due to the low preservation potential of marine angiosperms, indirect indicators, e.g. associated organisms with a higher potential for preservation, are commonly used to infer the presence of seagrass meadows in the geological past. Because of their high fossilization potential and their abundance in marine habitats mollusks yield the possibility to be useful paleo seagrass indicators. Here we assess the potential use of indicator species, species and feeding guild composition of whole assemblages, as well as stable isotope signals in shells for their suitability to determine seagrass vegetation in the Miocene of Indonesia.

}, author = {Sonja Reich and Frank P. Wesselingh and Willem Renema and Warter, Viola} } @conference {2006, title = {Foraminiferal assemblages in Miocene carbonates of Indonesia}, booktitle = {Southeast Asian Gateway Evolution: SAGE2013}, year = {2013}, month = {11/03/2013}, address = {Museum fuer Naturkunde, Berlin}, abstract = {Neogene carbonates in Indonesia are characterised by different depositional environments. We studied localities outcropping on Mangkalihat Peninsula, Kutai Basin, and Java, that were deposited in a time interval from Early (Te5) to Middle Miocene (Tf2). In order to reconstruct depositional environments and obtain biostratigraphic information, larger benthic foraminifera (LBF) assemblages were analysed from these three locations. The northernmost, and stratigraphically oldest, from the studied carbonates are exposed on Mangkalihat Peninsula. They were formed in shallow-water environment on carbonate platform. Stratigraphically important LBF indicate Early to Middle Miocene age (Te5-Tf1). Towards the south, in the Kutai Basin, isolated patch reefs occur within siliciclastic sediments, developed in mixed carbonate-siliciclastic depositional systems. In general, LBF assemblage is indicative of low-light conditions typical for mesophotic reefs. Based on LBF late Early to Middle Miocene age (Tf1-Tf2) can be suggested. The southernmost carbonate exposures are located on Central Java, in the Bulu Limestone member. The LBF assemblage composition indicate environmental conditions typical for continental shelf edge. Middle Miocene (Tf2) can be inferred for these limestones based on LBF. Here we present an overview of Indonesian Early to Middle Miocene LBF assemblages in a range of depositional environments. We will assess the interplay between stratigraphical and environmental control on LBF assemblages. }, author = {Vibor Novak and Willem Renema} }