Stepwise consolidation of glacigenic sediments of the Prydz Bay

A series of samples from the five sites drilled across the continental shelf and upper slope in Prydz Bay during ODP Leg 119 were consolidation tested in an oedometer. Preconsolidation stresses increase downcore at Sites 739 and 742 in a stepwise manner, and the steps are interpreted to represent periods of increased action of grounded glaciers covering the entire shelf. By the use of theoretical ice sheet surface profiles giving the range of possible ice thicknesses, sediment loading and subsequent erosion seem to be the most important factor for increasing the overconsolidation ratios, and a total glacial erosion exceeding 1 km is possible. Four separate steps in consolidation, here termed "load events" have been identified. The lowermost load event, 1, is correlated to the onset of glaciations reaching the shelf edge and an early period of extensive glaciations, starting in early Oligocene or possibly earlier. Glacial activity related to the buildup of ice in West Antarctica in the late Miocene is tentatively correlated to load event 2. Event 3 is the trace of relatively extensive glacial erosion probably in the Pliocene, whereas the upper step in preconsolidation stress, load event 4, results from the last glaciation reaching the shelf edge, possibly during the late Weichselian. Correlations to other data related to Antarctic glacial history are, however, hampered by the poor age control of the cored diamictites. Consolidation tests may provide a tool for finding the position for hiatuses and unconformities formed subglacially and obscured by subglacial reworking.

Tab. 3: Differentiation of eroded material in the Arctic Russian Seas

Volumes of Holocene (10 000 years) terrigenous sediments and annnal sediment supply in the Laptev Sea were evaluated from average thickness of the Holocene veneer. Volumes of deposits supplied from various sediment sourees and by different proeesses (abrasion of hinterland and island shores, river discharge, eolian input, drifting ice) were diseriminating of deposition in the eoastal zone, at river/sea barrier, and in the shelf basin itself. Accumulation by drifting iee and the role of local sea bottom erosion were also considered. Total amount of sediments transported from the Laptev Sea shelf to Amundsen and Nansen Basins of the Aretie Ocean was compared with other Russian Aretie seas.

Catchment characteristics and soil and water chemistry of the San Francisco basin and subbasins, Ecuador

In this study, the Mean Transit Time and Mixing Model Analysis methods are combined to unravel the runoff generation process of the San Francisco River basin (73.5 km**2) situated on the Amazonian side of the Cordillera Real in the southernmost Andes of Ecuador. The montane basin is covered with cloud forest, sub-páramo, pasture and ferns. Nested sampling was applied for the collection of streamwater samples and discharge measurements in the main tributaries and outlet of the basin, and for the collection of soil and rock water samples. Weekly to biweekly water grab samples were taken at all stations in the period April 2007-November 2008. Hydrometric data, Mean Transit Time and Mixing Model Analysis allowed preliminary evaluation of the processes controlling the runoff in the San Francisco River basin. Results suggest that flow during dry conditions mainly consists of lateral flow through the C-horizon and cracks in the top weathered bedrock layer, and that all subcatchments have an important contribution of this deep water to runoff, no matter whether pristine or deforested. During normal to low precipitation intensities, when antecedent soil moisture conditions favour water infiltration, vertical flow paths to deeper soil horizons with subsequent lateral subsurface flow contribute most to streamflow. Under wet conditions in forested catchments, streamflow is controlled by near surface lateral flow through the organic horizon. Exceptionally, saturation excess overland flow occurs. By absence of the litter layer in pasture, streamflow under wet conditions originates from the A horizon, and overland flow.

Distribution of grain size and clay minerals in surface sediments of the Kara Sea (Fig 4, 5)

In this paper, we summarize data on terrigenous sediment supply in the Kara Sea and its accumulation and spatial and temporal variability during Holocene times. Sedimentological, organic-geochemical, and micropaleontological proxies determined in surface sediments allow to characterize the modern (riverine) terrigenous sediment input. AMS-14C dated sediment cores from the Ob and Yenisei estuaries and the adjacent inner Kara Sea were investigated to determine the terrigenous sediment fluxes and their relationship to paleoenvironmental changes. The variability of sediment fluxes during Holocene times is related to the post-glacial sea-level rise and changes in river discharge and coastal erosion input. Whereas during the late/middle Holocene most of the terrigenous sediments were deposited in the estuaries and the areas directly off the estuaries, huge amounts of sediments accumulated on the Kara Sea shelf farther north during the early Holocene before about 9 cal kyr BP. The maximum accumulation at that time is related to the lowered sea level, increased coastal erosion, and increased river discharge. Based on sediment thickness charts, echograph profiles and sediment core data, we estimate an average Holocene (0-11 cal kyr BP) annual accumulation of 194,106 t/yr of total sediment for the whole Kara Sea. Based on late Holocene (modern) sediment accumulation in the estuaries, probably 12,106 t/yr of riverine suspended matter (i.e. about 30% of the input) may escape the marginal filter on a geological time scale and is transported onto the open Kara Sea shelf. The high-resolution magnetic susceptibility record of a Yenisei core suggests a short-term variability in Siberian climate and river discharge on a frequency of 300-700 yr. This variability may reflect natural cyclic climate variations to be seen in context with the interannual and interdecadal environmental changes recorded in the High Northern Latitudes over the last decades, such as the NAO/AO pattern. A major decrease in MS values starting near 2.5 cal kyr BP, being more pronounced during the last about 2 cal kyr BP, correlates with a cooling trend over Greenland as indicated in the GISP-2 Ice Core, extended sea-ice cover in the North Atlantic, and advances of glaciers in western Norway. Our still preliminary interpretation of the MS variability has to be proven by further MS records from additional cores as well as other high-resolution multi-proxy Arctic climate records.

Annotated record of the detailed examination of Mn deposits from the SO 79 (SEDIPERU - TUSCH) expedition from R/V Sonne

The research cruise SO79 with RV SONNE (April 18 to June 09 1992) aimed to assess the impact of a potential mining activity on the sensitive deep-sea ecosystem of the Peru Basin. Up to now only results of reconnaissance surveys of the extended manganese nodule field discovered in 1978 in the Peru Basin are available. The hydroacoustic, sedimentological, and geochemical studies on data and sample material of SO79 came to the following results: a small-scaled variation in thickness respectively type of surface sediments shown by the sediment echosounder respectively the side-scan-sonar is assumably due to variations in deposition or erosion. The composition of sediments is controlled by climatic cycles of different length which were caused by the variable influence of glaciation of the northern hemisphere. We think that during the quaternary a deep-water circulation reduced in intensity and O2-content may have produced a suboxic diagenetic environment which led to a remobilization and redeposition of Mn forming manganese nodules in the oxic surface sediments. Near the distinct redox boundary at about 10 cm depth the growth conditions for nodules are extremely favourable. Due to the great variability of sediments the impact of deep-sea mining will be highly variable and the disturbance of the seafloor will change the ecosystem considerably.

(Table 1) Summary of maximum clast size and bed thickness of ODP Leg 126 samples

Subaerial debris flows, with water contents ranging from as little as 10 wt% up to no more than about 25 wt% (Pierson, 1986; Pierson and Costa, 1987), are non-Newtonian fluids that move as fairly coherent masses with yield strength (owing to bulk densities and viscosity that are much greater than those of clear water), which enables them to suspend and transport large clasts. Their flow behavior is thought to be predominantly laminar, although the relative importance of laminar and turbulent flow has not been established and is debatable. They leave deposits (debrites) that are characteristically poorly sorted with large clasts in their middle portions and commonly protruding from their tops. Although generally ungraded or normally graded in their upper portions, many have centimeter- to decimeter-thick inversely graded basal zones (Arguden and Rodolfo, 1990, doi:10.1130/0016-7606(1990)102<0865:SADDBH>2.3.CO;2).

Location, intervals and thickness of Cretaceous sections in Indian Ocean DSDP and ODP sites (Table 2)

The Indian Ocean covers approximately 73.5 * 10**6 km**3 from 25°N to 67°S and from 20° to 120°E. Several legs of the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) have operated in its waters, many penetrating the Cretaceous. Most of the scientific drill sites are DSDP related and thus pre-dated modern biostratigraphic conventions. Foraminifers and calcareous nannoplankton were by far the dominant fossil groups studied in the earlier work, supplemented occasionally by studies of other fossil groups, The results of the Ocean Drilling Project phase are yet too young to be fully integrated but have been based on a broader range of techniques and fossil groups. During most of the Cretaceous, the proto-Indian Ocean basin lay in middle to high latitudes. Thus, it is unrealistic to expect successful routine application of low-latitude zonations. No planktonic foraminifer zonal scheme has been developed for the Indian Ocean basin for several reasons. There are no sections with complete or even significant partial sections to allow development of such a zonation. Carbonate compensation depth (CCD) effects have been marked in most sections, and significant intervals are devoid of planktonic foraminifers. The Indian Ocean now covers a great latitudinal range from tropics to polar regions and, at first glance, no scheme can be expected to be applicable over that entire range. In the Cretaceous the area was much smaller, though expanding progressively, and the paleolatitude range was quite small. Calcareous nannoplankton have proved valuable in dating Indian Ocean Cretaceous sediments and have, perhaps in contrast with the foraminifers, been consistently a more reliable means of applying zonal schemes developed elsewhere. For the Albian-Aptian, zonations based on well-known benthic foraminifer lineages (Scheibnerova, 1974) have been useful when nothing else was available or effective. Palynology has been used little, but where used, has proved excellent. It has the added value of providing valuable information on nearby terrestrial vegetation as the fossils were resistant to dissolution. Normally, when different fossil groups have been applied to a section, the results have been compatible or compatible to an acceptable degree. There are a few instances where incompatibility is noteworthy, and Site 263 is a classic example, as even two calcareous nannoplankton studies show irreconcilable differences here. All groups gave different results, but one benthic foraminifer analysis agreed with one calcareous nannoplankton study.

An assessment of the operational impact of the longer and wider combination vehicles on the geometry of diamond interchanges. Final report.

Texas State Department of Highways and Public Transportation, Austin

Understanding the limits of the seasonal prediction of sea ice in the Arctic

Thesis (Master's)--University of Washington, 2016-06