Mapping sediment acoustic impedance using remote sensing acoustic techniques in a shallow-water carbonate environment

 Real-time trackline plots of surficial sediment acoustic impedance delineate several sedimentary facies off Garden Key in the Dry Tortugas. The sea floor within a 6×6 km surveyed area consists of carbonate muds (silts), sands and shell, rock, and live corals. The 4-kHz acoustic data supports this finding by providing a pictographic representation of the distribution and structure of several sediment facies types. Plotting the gridded acoustic data with commercial mapping software (Surfer) provides a three-dimensional (3D) perspective of the bottom topography with a color contour map of surficial sediment impedance (upper 0.4 m) draped over the 3D surface.     

On the assessment of hydrodynamic coefficients of cylinders in heaving

A detailed comparison is made of the common two-dimensional methods for the evaluation of the hydrodynamic coefficients. Special attention was given to the conformal transformation method and the parameters which influence the accuracy of this method are studied. The results were compared with the Frank close-fit method with respect to accuracy and time taken. Finally the correlation between the geometric and hydrodynamic errors is examined and some relations are proposed.     

Trace element fractionation and distribution in turbidites,homogeneous and pelagic deposits; the Zaire Fan,Southeast Atlantic Ocean

In turbidites, homogeneous and pelagic deposits of the Zaire Fan Th, La, Sm, and Rb and to a lesser extent Yb and Ta correlate strongly. La, Sm, Yb, Rb, Ta, and Th increase two-fold in Te3 turbidite intervals relative to Te 1 due to an increase in clay fraction with which these elements occur associated preferentially.Hf and Zr are anomalously high in Tel and Tel intervals which is probably a result of mineral separation. Zr is absent in Te3 intervals and the homogenous and pelagic deposits. Ba, Br. and U are lowest in turbidites and highest in homogenous continental slope deposits which is probably caused by upwelling. Cc anomalies may be related to the crystallinity of smectite.     

Concentrations of unsubstituted polynuclear aromatic hydrocarbons in bay mussels (Mytilus edulis) from Oregon, USA

Concentrations of fifteen unsubstituted polynuclear aromatic hydrocarbons (PNAH) were measured in Mytilus edulis from two sites in Yaquina Bay, Oregon, USA, during 1979–1980. There were significant differences in PNAH levels between the two populations. The average total concentration in mussels inhabiting the more industrialized bayfront was 986·2 μg/kg compared with 273·9 μg/kg in mussels from a more remote site across the bay. Substantial differences were found in the concentrations of different PNAH in M. edulis examined during this study. The smaller more water soluble, compounds were concentrated to one or two orders of magnitude above the larger, less soluble PNAH.     

Past and future sea-level rise along the coast of North Carolina,USA

We evaluate relative sea level (RSL) trajectories for North Carolina, USA, in the context of tide-gauge measurements and geological sea-level reconstructions spanning the last ~11,000 years. RSL rise was fastest (~7 mm/yr) during the early Holocene and slowed over time with the end of the deglaciation. During the pre-Industrial Common Era (i.e., 0–1800 CE), RSL rise (~0.7 to 1.1 mm/yr) was driven primarily by glacio-isostatic adjustment, though dampened by tectonic uplift along the Cape Fear Arch. Ocean/atmosphere dynamics caused centennial variability of up to ~0.6 mm/yr around the long-term rate. It is extremely likely (probability P=0.95) that 20th century RSL rise at Sand Point, NC, (2.8 ± 0.5 mm/yr) was faster than during any other century in at least 2,900 years. Projections based on a fusion of process models, statistical models, expert elicitation, and expert assessment indicate that RSL at Wilmington, NC, is very likely (P=0.90) to rise by 42–132 cm between 2000 and 2100 under the high-emissions RCP 8.5 pathway. Under all emission pathways, 21st century RSL rise is very likely (P>0.90) to be faster than during the 20th century. Due to RSL rise, under RCP 8.5, the current ‘1-in-100 year’ flood is expected at Wilmington in ~30 of the 50 years between 2050-2100.     

Some properties of flows in unsaturated soils with an exponential dependence of the hydraulic conductivity upon the pressure head

A systematic development of the consequences of an exponential dependence of the hydraulic conductivity upon the pressure head is presented. Alternative expressions for the flux are discussed in detail. For steady flows, partial differential equations in terms of the matric flux potential, the pressure head, and the total head are derived. For steady, plane and axially symmetric flows, partial differential equations for the stream function are given. A theoretical basis for the construction of viscous flow analogs for steady, plane and axially symmetric flows is also presented.     

A comparative mineralogical study of gas-related sediments of the Gulf of Cádiz

The Gulf of Cádiz area has been extensively surveyed in recent years and several gas-related fluid escape seafloor structures have been identified. In this study, gravity cores, collected during the ANASTASYA/00 and ANASTASYA/01 cruises, on mud volcanoes, hemipelagic sediments and dredged material from diapiric structures, have been studied. A comparative mineralogical analysis by XRD and SEM of samples from different areas has been performed in order to determine whether there is a characteristic mineralogy related to these fluid escape structures, and also to determine the origin of the mud matrix and constrain the depth of the parent units. The mineralogical analysis reflects the different origins of the different units described in the cores: hemipelagic material of the slope, clays that underlie the mud volcanoes and are discharged at the sea bottom surface, and authigenic and diagenetic minerals possibly involved in the anaerobic oxidation of methane in the mud volcano sediments.