Preservation Of Foraminifera Research Articles

Well preserved Palaeogene and Cretaceous biomarkers from the Kilwa area, Tanzania

We have investigated the biomarker composition of sediments ranging in age from 30 to 70 Ma from the Kilwa area of Tanzania. They are dominated by material of terrestrial ( n-alkanols, n-alkanoic acids, n-alkanes and triterpenoids) and [bacterial hopanoids and a dipentadecyl glycerol diether (DGD)] origin with only a minor contribution of marine origin (crenarchaeol and some algal steroids). This indicates a marine setting dominated by higher plant input, which most likely stimulated sedimentary microbial activity, including sulfate reduction. The lipid composition, specifically the presence of bacteriohopanepolyols (BHPs) and the stereochemistry of hopanoids, suggests a low degree of thermal maturity. Many biomarkers have still retained functionality even after 30–70 million years. This is in good agreement with the exceptional preservation of foraminifera and nannofossils and can probably be attributed to the very low sediment permeability and burial depth. There is a clear distinction in the biomarker distributions between the Oligocene-age sediments collected at the end of the peninsula near Kilwa Masoko and the older sediments collected from elsewhere, indicating differences in depositional environment. Sediments from the end of the peninsula have higher branched and isoprenoid tetraether index values, indicating a relatively higher terrestrial input. They also contain two tentatively assigned C 28 hopenes (28,30-dinorneohop-13(18)-ene and 28,30-dinorhop-17(21)-ene), (aromatic) des- A-triterpenes, des- E-hopenes, aromatic pentacyclic triterpenoids, C 33 DGD, archaeol and BHPs, which are absent from or only present in small amounts in the other sediments. These differences likely reflect an evolution of the depositional area from a relative open shelf environment with substantial water depth to a shallower setting during the early Oligocene.

Relationships between the stable isotopic signatures of living and fossil foraminifera in Monterey Bay, California

Fossil foraminifera are critical to paleoceanographic reconstructions including estimates of past episodes of methane venting. These reconstructions rely on benthic foraminifera incorporating and retaining unaltered the ambient isotopic compositions of pore fluids and bottom waters. Comparisons are made here of isotopic compositions of abundant live and fossil foraminifera (Uvigerina peregrina, Epistominella pacifica, Bulimina mexicana, and Globobulimina pacifica) collected in Monterey Bay, CA from two cold seeps (Clam Flats and Extrovert Cliffs) and from sediments ∼5 m outside of the Clam Flats seep. Clam Flats has steep δ13CDIC gradients (to <−45‰), but DIC at Extrovert Cliffs is less enriched in 12C (to approximately −22‰). Oxygen isotope values of fossil foraminifera at Clam Flats are ∼1.5‰ enriched in 18O over the living foraminifera, as well as those of both live and fossil foraminifera at Extrovert Cliffs, suggesting they may have lived during the last glacial maximum. Statistical comparisons (Student's t and Kolmogorov‐Smirnov tests) of δ13C and δ18O values indicate that live and fossil foraminifera come from different populations at both Clam Flats and Extrovert Cliffs. At Clam Flats, the difference appears to result from alteration enriching some fossil foraminifera in 12C over live foraminifera. At Extrovert Cliffs, the fossil foraminifera are enriched in 13C over the live foraminifera, suggesting they lived prior to the onset of venting and thus that venting began recently. The short time of venting at Extrovert Cliffs may be responsible for the less alteration there compared with Clam Flats. These results indicate that preservation of foraminifera is likely to be poor within long‐lived cold seeps, but that foraminifera living in the surrounding sediment may incorporate and preserve broad basin‐wide changes in isotopic compositions of the ambient water.

INTERANNUAL VARIATION OF MARSH FORAMINIFERAL ASSEMBLAGES (BOMBAY HOOK NATIONAL WILDLIFE REFUGE, SMYRNA, DE): DO FORAMINIFERAL ASSEMBLAGES HAVE A MEMORY?

Research Article| April 01, 2002 INTERANNUAL VARIATION OF MARSH FORAMINIFERAL ASSEMBLAGES (BOMBAY HOOK NATIONAL WILDLIFE REFUGE, SMYRNA, DE): DO FORAMINIFERAL ASSEMBLAGES HAVE A MEMORY? Scott P. Hippensteel; Scott P. Hippensteel Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. 1Present address: Department of Geography and Earth Sciences, 9201 University City Boulevard, University of North Carolina, Charlotte, NC 28223-0001. Search for other works by this author on: GSW Google Scholar Ronald E. Martin; Ronald E. Martin 2 Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. 2Corresponding author: Phone: 302-831-6755; Fax: 302-831-4158; E-mail: Daddy@Strauss.Udel.Edu Search for other works by this author on: GSW Google Scholar Daria Nikitina; Daria Nikitina Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. Search for other works by this author on: GSW Google Scholar James E. Pizzuto James E. Pizzuto Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. Search for other works by this author on: GSW Google Scholar Author and Article Information Scott P. Hippensteel 1Present address: Department of Geography and Earth Sciences, 9201 University City Boulevard, University of North Carolina, Charlotte, NC 28223-0001. Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. Ronald E. Martin 2 Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. Daria Nikitina Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. James E. Pizzuto Department of Geology, University of Delaware, Newark, DE 19716 U.S.A. 2Corresponding author: Phone: 302-831-6755; Fax: 302-831-4158; E-mail: Daddy@Strauss.Udel.Edu Publisher: Cushman Foundation for Foraminiferal Research Received: 12 Dec 2000 Accepted: 07 May 2001 First Online: 03 Mar 2017 Online ISSN: 1943-264X Print ISSN: 0096-1191 © 2002 Journal of Foraminiferal Research Journal of Foraminiferal Research (2002) 32 (2): 97–109. https://doi.org/10.2113/0320097 Article history Received: 12 Dec 2000 Accepted: 07 May 2001 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Scott P. Hippensteel, Ronald E. Martin, Daria Nikitina, James E. Pizzuto; INTERANNUAL VARIATION OF MARSH FORAMINIFERAL ASSEMBLAGES (BOMBAY HOOK NATIONAL WILDLIFE REFUGE, SMYRNA, DE): DO FORAMINIFERAL ASSEMBLAGES HAVE A MEMORY?. Journal of Foraminiferal Research 2002;; 32 (2): 97–109. doi: https://doi.org/10.2113/0320097 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Seasonal reproduction and preservation of foraminifera were monitored for three years at Bombay Hook National Wildlife Refuge (Smyrna, DE). Cluster analysis of “seasonally artificially time-averaged” (SATA) assemblages indicates that assemblages reflect the most recent test inputs, and that test inputs record subtle variations in porewater chemistry related to rates of sulfate reduction, pyrite oxidation, and vertical differentiation of geochemical gradients. Changes in geochemical gradients are caused by interannual variation of rainfall: more rainfall damps pyrite oxidation and weakens geochemical gradients, whereas less rainfall allows more pyrite oxidation and strengthens vertical gradients. Geochemical overprinting of assemblages related to rainfall tended to occur during the summer and early fall. Therefore, as assemblages pass into the historical layer, they may have a “memory” of the most recent test inputs and environmental conditions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Benguela Current and associated upwelling on the southwest African Margin: a synthesis of the Neogene-Quaternary sedimentary record at DSDP sites 362 and 532

Abstract Sediments cored at DSDP Sites 362 and 532 on the Walvis Ridge provide a Neogene-Quaternary history of the development of the upwelling system on the southwest African margin. Upwelling occurs principally on the landward side of the Benguela Current. The upwelling centres have shifted northward since the Middle Miocene as the current has intensified and has flowed farther to the north. Changes in productivity are recorded in the types, proportions and preservation of foraminifera, radiolaria, diatoms, organic matter, and clay minerals in the sedimentary record. Prior to the Late Miocene (10 Ma), the Benguela Current did not reach the Walvis Ridge, and enhanced productivity is not evident in the sediments at this location. Between 10 to 5.2 Ma, upwelling was recorded in the DSDP sites in glacial periods, indicating that the Benguela Current intensified during glacial periods and transported evidence of upwelling to Sites 362/532 from near-coastal areas. During interglacial periods the current was not as strong and did not reach the Walvis Ridge, turning instead to the west within the Cape Basin. Strengthening of the current continued such that by the Pliocene and Quarternary the upwelling signal is contained in interglacial sediments. Sediments deposited in these more recent glacial times contain a weak or absent upwelling signal because glacial intensification shifts the Benguela Current system northward to reach the Angola Basin before it turns westward away from its coast-parallel direction.

Paleoecology of Middle and Late Miocene Monterey Formation, Upper Newport Bay, Newport Beach, California: ABSTRACT

The Miocene Monterey Formation exposed along the cliffs of Upper Newport Bay represents a lower calcareous facies dominated by foraminifera and coccoliths, indicating warm climate and low nutrient waters, and a siliceous facies consisting of diatomaceous rocks, which records high productivity as a result of climatic deterioration and intensified upwelling. Using the distribution and preservation of foraminifera in the California continental borderland basins as a modern analog, they interpret the effect of changing environmental (climatic and oceanographic) conditions during the middle and late Miocene on the distribution and preservation of foraminifera, calcareous nannofossils, radiolarians, diatoms, and sediments. Two stratigraphic sections were sampled: (1) middle Miocene (Luisian) section 1, and (2) late Miocene (upper Mohnian) section 2. Section 1 best correlates with the middle Miocene Sphenolithus heteromorphus nannofossil zone. Benthic foraminifera indicate deposition in upper bathyal to upper middle bathyal depths. Poor preservation of calcareous tests is generally associated with homogeneous sediments, whereas better preservation is correlated with indistinctly laminated rocks. Stratigraphic section 2, which accumulated in upper bathyal depths, covers parts of the early late Miocene (upper Mohnian) Denticulopsis hustedtii-D. lauta and D. hustedtii diatom zones. Foraminifera and nannofossils are generally more abundant and better preserved in well laminated sedimentsmore » than in sediments with homogeneous to indistinct laminations. Benthic foraminifera favoring low oxygen conditions have low diversities in rocks with poorly preserved laminations, but have higher densities in well laminated intervals.« less