نتایج جستجو برای: foraminifera
تعداد نتایج: 4350 فیلتر نتایج به سال:
We propose a new calculation method to better estimate the deep water ventilation age from benthic-planktonic foraminifera 14C ages. Our study is motivated by the fact that changes in atmospheric A14C through time can cause contemporary benthic and planktonic foraminifera to have different initial A14C values. This effect can cause spurious ventilation age changes tobe interpreted from the geol...
Chronologies for Late Quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera. Signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information. A key premise is that microfossils and other indicators within a given sediment horizon are of equal age. We show here that haptophyte-derived alkenones ...
asmari formation was deposited in the foreland zagros basin (southwest iran). in this research, biostratigraphy related to the asmari formation in north of khorram abad, robat namaki section, is discussed. in the studied stratigraphic section, the asmari formation overlies the shahbazan formation and underlies gachsaran formation and consists of cream to gray medium to thick limestone and marl....
Biological response and ecological indices of benthic communities, such as greater mortality of foraminifera and shell abnormalities, have been used to document pollution effects on ecosystems. Shadegan Wetland was damaged from a deposition of huge amounts of soot and products of burning oilwells of Kuwait as well as chronic exhaust fumes of refinery and industrial furnaces. In this investigati...
Microbiostratigraphy of the Oligo-Miocene Asmari Formation, Kuh Siah Anticline (Izeh Basin), SW Iran
This research focusses on the biostratigraphy and paleoecological implications of the carbonatesof the Asmari Formation. The Asmari Formation is located in the Siah Kuhanticline of Izeh, Zagros Basin, SW Iran. It is of Late Oligocene (Chattian) - Early Miocene (Burdigalian) age. In this stratigraphic section, the Asmari Formation overlies the Pabdeh Formation and underlies the Gachsaran Formati...
Planulina ornata (d'Orbigny), a coarsely perforate species of foraminifera having a low trochospiral test, was recovered attached to phosphatic hardgrounds from the lower oxygen-minimum zone off Peru. Above the base of individual pores are calcified, perforate sieve plates, the largest so far described. Structure of the pores suggests a possible association with mitochondria and respiratory fun...
The geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo-climatic, -oceanographic and -ecological changes. However, dissolution of biogenic calcite and precipitation of inorganic calcite (overgrowth and recrystallization) at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test...
Barium (Ba) incorporated in the calcite of many foraminiferal species is proportional to the concentration of Ba in seawater. Since the open ocean concentration of Ba closely follows seawater alkalinity, foraminiferal Ba /Ca can be used to reconstruct the latter. Alternatively, Ba /Ca from foraminiferal shells can also be used to reconstruct salinity in coastal settings in which seawater Ba con...
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