Abstract: Paleoclimate was reconstructed by the clay mineral
assemblages of shale units of Pabdeh (Paleocene- Oligocene), Gurpi
(Upper Cretaceous), Kazhdumi (Albian-Cenomanian) and Gadvan
(Aptian-Neocomian) formations in the Bangestan anticline. To
compare with clay minerals assemblages in these formations,
selected samples also taken from available formations in drilled wells
in Ahvaz, Marun, Karanj, and Parsi oil fields. Collected samples
prepared using standard clay mineral methodology. They were
treated as normal, glycolated and heated oriented glass slides. Their
identification was made on X-Ray diffractographs. Illite % varies
from 8 to 36. Illite quantity increased from Pabdeh to Gurpi
Formation. This may be due to dominant dry climate. Kaolinite is in
range of 12-49%. Its variation style in different formations could be a
marker of climate changes from wet to dry which is supported by the
lithological changes. Chlorite (4-28%) can also be detected in those
samples without any kaolinite. Mixed layer minerals as the mixture
of illite-chlorite and illite-vermiculite-montmorillonite are varied
from 6 to 36%, decreased during Kazhdumi deposition from the base
to the top. This result may be according to decreasing of illite
leaching process. Vermiculite was also determined in very less
quantity and found in those units without kaolinite. Montmorillonite
varies from 8 to 43%, and its presence is due to terrestrial
depositional condition. Stratigraphical documents is also supported
this idea that clay mineral distribution is a function of the climate
changes. It seems, thus, the present results can be indicated a possible
procedure for ancient climate changes evaluation.
Abstract: Oxygen and carbon isotopes records of multi-species planktonic, benthic foraminifera and bulk carbonate sample from Central Java Indonesia demonstrate that warm sea surface temperature occurred during the Miocene. Planktonic δ18O values from this study consistently lighter (-4 to -3 ‰PDB) than previous studies that indicate sea surface temperature during Miocene in this area was warm than tropical/equatorial localities. A surprising decrease of oxygen isotopic composition was recorded at ±14 Ma where the maximum of δ18O values is -4.87 ‰PDB for Orbulina universa, -5.02 ‰PDB for Globigerinoides sacculifer and -4.30 ‰PDB for Globoquadrina dehiscens, this event we predict as Middle Miocene Optimum. Warming of sea surface temperature we interpret as related to the development of Western Pacific Warm Pool where warm water from Pacific Ocean through the Indonesian seaway appears to remain during Miocene. Our result also show increasing suddenly of oxygen isotope values of planktic, benthic and bulk carbonate sample from ± 12 Ma, the increasing cooled surface water relatively high degree with Late Miocene global cooling climate or we predict that due to closing of Indonesian Gateway.