959 resultados para Per unit length
(Table 2) Thysanoessa raschii clearance rate, ingestion rate and daily ration in feeding experiments
Resumo:
Black shales possessing high concentrations of organic carbon (Foresman, 1978, doi:10.2973/dsdp.proc.40.111.1978) were deposited in many parts of the proto South Atlantic Ocean during the Cretaceous period (Bolli et al., 1978, doi:10.2973/dsdp.proc.40.104.1978). The way such sediments accumulated is not fully understood, but is likely to have occurred through a combination of low oxygen availability and abundant supply of organic matter. Thin, centimetre-thick layers of black shales are commonly interbedded with thicker layers of organic carbon-deficient, green claystones, as found in strata of Aptian to Coniacian age, at Deep Sea Drilling Project (DSDP) Site 530, in the southern Angola Basin (Hay et al., 1982, doi:10.1130/0016-7606(1982)93<1038:SAAOOC>2.0.CO;2) and elsewhere. These differences in carbon content and colour reflect the conditions of deposition, and possibly variations in the supply of organic matter (Summerhayes and Masran, 1983, doi:10.2973/dsdp.proc.76.116.1983; Dean and Gardner, 1982). We have compared, using organic geochemical methods the compositions of organic matter in three pairs of closely-bedded black and green Cenomanian claystones obtained from Site 530. Kerogen analyses and distributions of biological markers show that the organic matter of the black shales is more marine and better preserved than that of the green claystones.
Resumo:
Data on contents and compositions of hydrocarbons (HCs)-aliphatic (AHCs) and polycyclic aromatic (PAHs) are provided in comparison with contents of total organic carbon (Corg), lipids in suspended matter, and Corg in bottom sediments. Particular attention is paid to distribution of HCs in the area of the Kravtsov oil field. It is established that concentrations of AHCs in water are governed by concentrations of suspended matter and elevated AHC concentrations are confined to coastal areas. In the area of D-6 platform sandy bottom sediments are notable for great variability of HC concentrations, both laterally and from year to year. In summer of 2010 average content of AHCs was 40 ppm (19% of Corg) and that of PAHs was 0.023 ppm. Natural seepage from sediment mass is considered to be a source of HCs along with oil contamination.
Resumo:
Calcareous nannofossils, pollen, and spores were examined on samples from Ocean Drilling Program Leg 178 Site 1095 on the continental rise and Sites 1097, 1100, and 1103 on the outer continental shelf of the western Antarctic Peninsula. Stratigraphically useful specimens of calcareous nannofossils occur in Site 1095 sediments assigned to Zones CN15, CN13b, and CN11. Calcareous nannofossils are rare but occur throughout the sedimentary sequences from seismic Units S1 to S3 on the continental shelf. Most of the calcareous nannofossils in Units S1 and S2 are composed of Cretaceous specimens that have been recycled by glacial processes. The occurrence of Dictyococcites in samples within Unit S3 upper Miocene sediments without any reworked specimens suggests those sediments are deposited in an open-ocean environment. These results are consistent with those from foraminifer and radiolarian studies. Pollen and spores including Nothofagidites, the genus for fossil pollen referred to as Nothofagus, are also observed in Unit S3 sediments. The sparse occurrence of pollen and spores, however, makes it difficult to assess the nature of the Antarctic terrestrial vegetation.
Resumo:
The basalts recovered at Holes 651A and 655B appear to carry a single component remanent magnetization, which is generally of reversed polarity. These magnetizations are consistent with eruption during the Matuyama (651A) and Gilbert (655B) polarity epochs. The blocking temperature spectra and the Js/T curves indicate that titanomaghemite is the principal remanence carrier. The lower mean destructive field (MDF) and higher susceptibility at 651A probably indicates a lower mean oxidation state at this hole relative to 655B, which may simply reflect the age difference between the two basalt sequences. At both holes, a decreasing downcore trend both in natural remanent magnetization (NRM) and susceptibility probably indicates that maghemitization (from primary titanomagnetite) increases downcore. An interval of high coercivity at hole 655B (119.80-151.45 mbsf) appears to define a magnetically distinct unit within the basalt sequence.
Resumo:
The PELMED-ECOPEL dataset contains mesozooplankton data collected in 1995-1996 in the Gulf of Lion (North Western Mediterranean Sea) between 43°35' N, 2°50' E and 42°15' N, 6°15' E. Zooplankton taxonomy-related abundance per unit volume of the water column.