Showing papers by "Philip A. Meyers published in 2002"
01 Jan 2002
TL;DR: The organic matter content of lake sediments provides a variety of indicators, or proxies, that can be used to reconstruct paleoenvironments of lakes and their watersheds and to infer histories of regional climate changes as mentioned in this paper.
Abstract: The organic matter content of lake sediments provides a variety of indicators, or proxies, that can be used to reconstruct paleoenvironments of lakes and their watersheds and to infer histories of regional climate changes. Organic matter constitutes a minor but important fraction of lake sediments. It originates from the complex mixture of lipids, carbohydrates, proteins, and other organic matter components produced by organisms that have lived in and around the lake (e.g., Meyers, 1997; Rullkotter, 2000). As an accumulation of “geochemical fossils”, the organic matter content of lake sediments provides information that is important to interpretations of both natural and human-induced changes in local and regional ecosystems.
807 citations
TL;DR: In this paper, the authors show that the Corganic/N total values record a shift towards greater recycling rates of nitrogen-rich, relative to carbon-rich organic matter components as the flux of total organic matter to the seafloor increased.
114 citations
TL;DR: The authors examined the history of the elevated primary productivity associated with the Benguela Current upwelling system off southwest Africa using sediments from 7.5 to 4.8 Ma at Ocean Drilling Program Site 1085 in the middle Cape Basin.
102 citations
TL;DR: The results from biomarker molecule and major and trace element analyses of closely spaced samples are used to reconstruct the conditions leading to deposition of a Pliocene sapropel at Ocean Drilling Program (ODP) Site 969 on the Mediterranean Ridge as discussed by the authors.
66 citations
TL;DR: In this article, the authors investigate the paleoceanographic processes involved in creating the light-dark color cycles in sediment in three mid-Pleistocene intervals from ODP Sites 1082 and 1084.
37 citations
TL;DR: The Ocean Drilling Program Leg 175 recovered a unique series of stratigraphically continuous sedimentary sections along the SW African margin, an area which is presently affected by active coastal upwelling The accumulation rates of organic and inorganic carbon are a major component of this record.
32 citations
TL;DR: The amounts and types of carbon delivered to the sediments Seneca Lake, New York, have varied since the middle Holocene Concentrations of CaCO3 first fluctuate between 14 and 6% around 7 ka before decreasing erratically until about 5 ka and then remain 2% in younger sediments Because the amount of calcite that precipitates in hard-water lakes is related to summertime thermal stratification, the carbonate fluctuations suggest that cyclic strengthening and weakening of seasonality at intervals of about three centuries accompanied the end of the Holocene Hypsithermal in northeast North America
Abstract: The amounts and types of carbon delivered to the sediments Seneca Lake, New York, have varied since the middle Holocene Concentrations of CaCO3 first fluctuate between 14 and 6% around 7 ka before decreasing erratically until about 5 ka and then remain 2% in younger sediments Because the amount of calcite that precipitates in hard-water lakes is related to summertime thermal stratification, the carbonate fluctuations suggest that cyclic strengthening and weakening of seasonality at intervals of about three centuries accompanied the end of the Holocene Hypsithermal in northeast North America Organic C/total N values record short, decade-long intervals of enhanced delivery of land-plant material during episodes of wetter climate that are independent of the temperature variations Higher organic δ13C values indicate that recent fertilization of lake waters from soil disturbance and land-derived runoff has increased aquatic productivity
18 citations
TL;DR: In this article, the authors measured opal, total organic carbon (TOC), and CaCO3 fluxes and C and N stable isotopes in sediments deposited from 2.4 to 1.95 Ma at Sites 1082 and 1084 to explore the biogeochemical dynamics within the Benguela region.
Abstract: [1] The Matuyama Diatom Maximum (MDM) is a time of peak opal accumulation from 2.6 to ∼2.0 Ma within the Benguela Current upwelling system that was initiated by increased influence of Southern Ocean water on the eastern South Atlantic. We measured opal, total organic carbon (TOC), and CaCO3 fluxes and C and N stable isotopes in sediments deposited from 2.4 to 1.95 Ma at Sites 1082 and 1084 to explore the biogeochemical dynamics within the Benguela region. The infusion of Southern Ocean water delivered dissolved nutrients and Southern Ocean flora and fauna, resulting in local opal accumulation increasing up to 8 g/cm2ky and the production of diatom mats. Some δ15N measurements of diatom-bound organic matter indicate that the mats grew within the Benguela region. The bulk sediment δ15N records are taken to reflect changes in the δ15N of nitrate in the incoming water, where lower values at 2.4 Ma reflect less nitrate utilization in the Antarctic. A long-term increase in relative nitrate uptake in the Southern Ocean is evidenced by the gradual increase in δ15N toward 1.9 Ma.
17 citations
01 Mar 2002
TL;DR: Wefer et al. as discussed by the authors measured the sediment fraction, carbonate, and organic carbon contents of late Miocene sediments from Site 1085, Middle Cape Basin, South Africa.
Abstract: Site 1085 is located on the continental rise of southwest Africa at a water depth of 1713 m off the mouth of the Orange River in the Cape Basin. The site is part of the suite of locations drilled during Leg 175 on the Africa margin to reconstruct the onset and evolution of the elevated biological productivity associated with the Benguela Current upwelling system (Wefer, Berger, Richter, et al., 1998). Three sediment samples were collected per section from Cores 170-1085A-28H through 45X (251–419 mbsf) to provide a survey of the sediment record of paleoproductivity from the middle late Miocene to the early Pliocene (~8.7–4.7 Ma), which is a period that includes the postulated northward migration and intensification of the Benguela Current and the establishment of modern circulation off southwest Africa (Siesser, 1980; Diester-Haass et al., 1992; Berger et al., 1998). Core 170-1085A-30H (270–279 mbsf) had essentially no recovery; this coring gap was filled with samples from Cores 170-1085B-29H and 30H (261–280 mbsf). The results of measurements of multiple paleoproductivity proxies are summarized in this report. Included in these proxies are the radiolarian, foraminiferal, and echinoderm components of the sand-sized sediment fraction. Opal skeletons of radiolarians (no diatoms were found) relate to paleoproductivity and water mass chemistry (Summerhayes et al., 1995; Lange and Berger, 1993; Nelson et al., 1995). The accumulation rates of benthic foraminifers are useful proxies for paleoproductivity (Herguera 1Diester-Haass, L., Meyers, P.A., Vidal, L., and Wefer, G., 2001. Data report: Sand fraction, carbonate, and organic carbon contents of late Miocene sediments from Site 1085, Middle Cape Basin. In Wefer, G., Berger, W.H., and Richter, C. (Eds.), Proc. ODP, Sci. Results, 175, 1–23 [Online]. Available from World Wide Web: [Cited YYYY-MM-DD] 2Zentrum für Umweltforschung, Universität des Saarlandes, D-66041 Saarbrücken, Federal Republic of Germany. A.L.Haass@t-online.de 3Department of Geological Sciences, University of Michigan, Ann Arbor MI 48109-1063 USA. 4Universite Aix-Marseille, Europole de l’Arbois, BP 80, 13545 Aix en Provence Cedex, France. 5Fachbereich Geologie, Universität Bremen, D-28334 Bremen, Federal Republic of Germany.
6 citations