Geochemistry and mineralogy of selected carbonaceous claystones at DSDP Hole 76-534

Four dominant depositions of carbonaceous claystones are recognized to have occurred during the early Aptian to middle Albian at Site 534. There are correlations of stable isotope ratios with organic carbon content and of clay content with clay mineralogy of the samples. Almost all organic carbon in these sequences has very negative terrestrial isotope ratios, and the clay of that age indicates predominance of aluminous montmorillonite, which is thought to be of terrigenous origin. It is suggested that development of coastal vegetation belts and deltaic outbuilding with consequent outpouring of land-plant detritus and terrigenous elastics into the deep basins probably led to formation of the "black shale" facies.

Geotechnical properties of shelf sdiments from the Prydz Bay

This paper presents a geotechnical characterization of the glacigenic sediments in Prydz Bay, East Antarctica, based on the shipboard physical properties data obtained during Leg 119, combined with results of land-based analyses of 24 whole-round core samples. Main emphasis is placed on the land-based studies, which included oedometer consolidation tests, triaxial and simple shear tests for undrained shear strength, permeability tests in oedometer and triaxial cell, Atterberg limits, and grain-size analyses. The bulk of the tested sediments comprise overconsolidated diamictites of a relatively uniform lithology. The overconsolidation results from a combination of glacial loading and sediment overburden subsequently removed by extensive glacial erosion of the shelf. This leads to downhole profiles of physical properties that have been observed not to change as a function of the thickness of present overburden. A number of fluctuations in the parameters shows a relatively systematic trend and most likely results from changes in the proximity to the ice sheet grounding line in response to variations in the glacial regime. Very low permeabilities mainly result from high preconsolidation stresses (Pc'). Pc' values up to 10,000 kPa were estimated from the oedometer tests, and empirical estimates based on undrained shear strengths (up to 2500 kPa) indicate that the oedometer results are conservative. The diamictites generally classify as inactive, of low to medium plasticity, and they consolidate with little deformation, even when subjected to great stresses. This is the first report of geotechnical data from deep boreholes on the Antarctic continental shelf, but material of similar character can also be expected in other areas around the Antarctic.

Holocene sediment transport from the glaciated margin of East/Northeast Greenland to the N Iceland shelves

We examine variations in the ice-rafted sources for sediments in the Iceland/East Greenland offshore marine archives by utilizing a sediment unmixing model and link the results to a coupled iceberg-ocean model. Surface samples from around Iceland and along the E/NE Greenland shelf are used to define potential sediment sources, and these are examined within the context of the down-core variations in mineralogy in the <2 mm sediment fraction from a transect of cores across Denmark Strait. A sediment unmixing model is used to estimate the fraction of sediment <2 mm off NW and N Iceland exported across Denmark Strait; this averaged between 10 and 20%. Both the sediment unmixing model and the coupled iceberg-ocean model are consistent in finding that the fraction of "far-travelled" sediments in the Denmark Strait environs is overwhelmingly of local, mid-East Greenland, provenance, and therefore with a significant cross-channel component to their travel. The Holocene record of ice-rafted sediments denotes a three-part division of the Holocene in terms of iceberg sediment transport with a notable increase in the process starting ca 4000 cal yr BP. This latter increase may represent the re-advance during the Neoglacial period of land-terminating glaciers on the Geikie Plateau to become marine-terminating. The contrast in spectral signals between these cores and the 1500-yr cycle at VM28-14, just south of the Denmark Strait, combined with the coupled iceberg-model results, leads us to speculate that the signal at VM28-14 reflects pulses in overflow waters, rather than an ice-rafted signal.

Documentation, profile descriptions and analytical results of loes profiles from Bavaria, southern Germany

This study investigates the landscape evolution and soil development in the loess area near Regensburg between approximately 6000-2000 yr BP (radiocarbon years), Eastern Bavaria. The focus is on the question how man and climate influenced landscape evolution and what their relative significance was. The theoretical background concerning the factors that controlled prehistoric soil erosion in Middle Europe is summarized with respect to rainfall intensity and distribution, pedogenesis, Pleistocene relief, and prehistoric farming. Colluvial deposits , flood loams, and soils were studied at ten different and representative sites that served as archives of their respective palaeoenvironments. Geomorphological, sedimentological, and pedological methods were applied. According to the findings presented here, there was a high asynchronity of landscape evolution in the investigation area, which was due to prehistoric land-use patterns. Prehistoric land use and settlement caused highly difIerenciated phases of morphodynamic activity and stability in time and space. These are documented at the single catenas ofeach site. In general, Pleistocene relief was substantially lowered. At the same time smaller landforms such as dells and minor asymmetric valleys filled up and strongly transformed. However, there were short phases at many sites, forming short lived linear erosion features ('Runsen'), resulting from exceptional rainfalls. These forms are results of single events without showing regional trends. Generally, the onset of the sedimentation of colluvial deposits took place much earlier (usually 3500 yr BP (radiocarbon) and younger) than the formation of flood loams. Thus, the deposition of flood loams in the Kleine Laaber river valley started mainly as a consequence of iron age farming only at around 2500 yr BP (radiocarbon). A cascade system explains the different ages of colluvial deposits and flood loams: as a result of prehistoric land use, dells and other minor Pleistocene landforms were filled with colluvial sediments. After the filling of these primary sediment traps , eroded material was transported into flood plains, thus forming flood loams. But at the moment we cannot quantify the extent ofprehistoric soil erosion in the investigation area. The three factors that controlled the prehistoric Iandscapc evolution in the Ioess area near Regensburg are as follows: 1. The transformation from a natural to a prehistoric cultural landscape was the most important factor: A landscape with stable relief was changed into a highly morphodynamic one with soil erosion as the dominant process of this change. 2. The sediment traps of the pre-anthropogenic relief determined where the material originated from soil erosion was deposited: either sedimentation took place on the slopes or the filled sediment traps of the slopes rendered flood loam formation possible. Climatic influence of any importance can only be documented as the result of land use in connection with singular and/or statistic events of heavy rainfalls. Without human impact, no significant change in the Holocene landscape would have been possible.

Contents and isotopic composition of black carbon from ODP Sites 184-1147 and 184-1148

A 30 m.y. stable isotopic record of marine-deposited black carbon from regional terrestrial biomass burning from the northern South China Sea reveals photosynthetic pathway evolution for terrestrial ecosystems in the late Cenozoic. This record indicates that C3 plants negatively adjusted their isotopic discrimination and C4 plants appeared gradually as a component of land vegetation in East Asia since the early Miocene, a long time before sudden C4 expansion occurred during the late Miocene to the Pliocene. The changes in terrestrial ecosystems with time can be reasonably related to the evolution of East Asian monsoons, which are thought to have been induced by several intricate mechanisms during the late Cenozoic and could contribute significantly to the post-Miocene marine carbonate isotope decline.

Establishment, expansion and regeneration of aspen (Populus tremula) in the Torneträsk area, subarctic Sweden

In subarctic Sweden, recent decadal colonization and expansion of aspen (Populus tremula L.) were recorded. Over the past 100 years, aspen became c. 16 times more abundant, mainly as a result of increased sexual regeneration. Moreover, aspen now reach tree-size (>2 m) at the alpine treeline, an ecotone that has been dominated by mountain birch (Betula pubescens ssp. czerepanovii) for at least the past 4000 years. We found that sexual regeneration in aspen probably occurred seven times or more within the last century. Whereas sexual regeneration occurred during moist years following a year with an exceptionally high June-July temperature, asexual regeneration was favored by warm and dry summers. Disturbance to the birch forest by cyclic moth population outbreaks was critical in aspen establishment in the subalpine area. At the treeline, aspen colonization was less determined by these moth outbreaks, and was mainly restricted by summer temperature. If summer warming persists, aspen spread may continue in subarctic Sweden, particularly at the treeline. However, changing disturbance regimes, future herbivore population dynamics and the responses of aspen's competitors birch and pine to a changing climate may result in different outcomes.

Organic geochemistry of Cretaceous black shales

Organic-carbon-rich 'black shales' and adjacent organic-carbon-poor rocks from three different Cretaceous settings encountered during ODP Leg 103 have been studied by organic geochemical methods. Rock-Eval analysis, carbon isotope data, and lipid biomarkers show organic matter to contain varying proportions of marine and continental materials. In Hauterivian-Barremian organic-carbon-rich marlstone turbidites, large amounts of land-derived organic matter are found. Aptian-Albian black-colored shales are interspersed within green claystones, from which they differ by containing more marine organic matter. An abbreviated layer of black shale from the Cenomanian/Turonian boundary is dominated by well-preserved marine organic matter. Downslope transport and rapid reburial within a predominantly oxygenated deep-water setting created most of these examples of black shales, except for the Cenomanian-Turonian deposits in which deep-water anoxia may have been involved.

Survey of Western Palestine 1880, Palestine Exploration Fund 1:63,360 mosaicked map

The Palestine Exploration Fund (PEF) Survey of Western Palestine (1871-1877) is highly praised for its accuracy and completeness; the first systematic analysis of its planimetric accuracy was published by Levin (2006). To study the potential of these 1:63,360 maps for a quantitative analysis of land cover changes over a period of time, Levin has compared them to 20th century topographic maps. The map registration error of the PEF maps was 74.4 m using 123 control points of trigonometrical stations and a 1st order polynomial. The median RMSE of all control and test points (n = 1104) was 153.6 m. Following the georeferencing of each of the 26 sheets of the PEF maps of the Survey of Western Palestine, a mosaicked file has been created. Care should be taken when analysing historical maps, as it cannot be assumed that their accuracy is consistent at different parts or for different features depicted on them.

Geochemistry of Albian to Santonian black shale sequences on the Demerara Rise, South American margin

Ocean Drilling Program Leg 207 recovered thick sequences of Albian to Santonian organic-carbon-rich claystones at five drill-sites on the Demerara Rise in the western equatorial Atlantic Ocean. Dark-colored, finely laminated, Cenomanian-Santonian black shale sequences contain between 2% and 15% organic carbon and encompass Oceanic Anoxic Events 2 and 3. High Rock-Eval hydrogen indices signify that the bulk of the organic matter in these sequences is marine in origin. However, d13Corg values lie mostly between -30 per mil and -27 per mil, and TOC/TN ratios range from 15 to 42, which both mimic the source signatures of modern C3 land plants. The contradictions in organic matter source indicators provide important implications about the depositional conditions leading to the black shale accumulations. The low d13Corg values, which are actually common in mid-Cretaceous marine organic matter, are consequences of the greenhouse climate prevailing at that time and an associated accelerated hydrologic cycle. The elevated C/N ratios, which are also typical of black shales, indicate depressed organic matter degradation associated with low-oxygen conditions in the water column that favored preservation of carbon-rich forms of marine organic matter over nitrogen-rich components. Underlying the laminated Cenomanian-Santonian sequences are homogeneous, dark-colored, lower to middle Albian siltstones that contain between 0.2% and 9% organic carbon. The organic matter in these rocks is mostly marine in origin, but it occasionally includes large proportions of land-derived material.

Pigment concentrations in surface sediments of the Arabian Sea

As part of the large-scale, interdisciplinary deep-sea study "BIGSET", the relationship between the monsoon-induced regional and temporal variability of POC deposition and the small-sized benthic community was investigated at several sites 2316-4420 m deep in the Arabian Sea during four cruises between 1995 and 1998. Vertical and horizontal distribution patterns of chloroplastic pigments (a measure of phytodetritus deposition), readily soluble protein and activity, and biomass parameters of the small-sized benthic community (Electron Transport System Activity (ETSA); bacterial ectoenzymatic activity (FDA turnover) and DNA concentrations) were measured concurrently with the vertical fluxes of POC and chloroplastic pigments. Sediment chlorophyll a (chl. a) profiles were used to calculate chl. a flux rates and to estimate POC flux across the sediment water interface using two different transport reaction models. These estimates were compared with corresponding flux rates determined in sediment traps. Regional variability of primary productivity and POC deposition at the deep-sea floor creates a trophic gradient in the Arabian Basin from the NW to the SE, which is primarily related to the activity of monsoon winds and processes associated with the topography of the Arabian Basin and the vicinity of land masses. Inventories of sediment chloroplastic pigments closely corresponded to this trophic gradient. For ETSA, FDA and DNA, however, no clear coupling was found, although stations WAST (western Arabian Sea) and NAST (northern Arabian Sea) were characterised by high concentrations and activities. These parameters exhibited high spatial and temporal variability, making it impossible to recognise clear mechanisms controlling temporal and spatial community patterns of the small-sized benthic biota. Nevertheless, the entire Arabian Basin was recognised as being affected by monsoonal activity. Comparison of two different transport reaction models indicates that labile chl. a buried in deeper sediment layers may escape rapid degradation in Arabian deep-sea sediments.

Occurrence of interlayers in sediment cores collected in the East Indian Ocean

In the East Indian Ocean direct contribution of land volcanism to sedimentation appears as interlayers of tephra and tuffaceous sediments, pumice fragments, and dispersed volcanoclastic materials of silty grain size. Similarity of distribution of tephra, tuffaceous sediments, Ethmodiscus ooze, and turbidites in the Pleistocene section results from deposition of all these materials under controll of a single factor, namely synchronous redistribution owing to seismic activity on the ocean floor and on the Sunda Islands. Burial of layers of oxidized deposits and formation of iron-manganese nodules is at least partly related to global climate cooling and to circulation of ocean waters.

Coastal erosion dynamics and storm characteristics of Bykovsky Peninsula

This study investigates the rate of erosion during the 1951-2006 period on the Bykovsky Peninsula, located north-east of the harbour town of Tiksi, north Siberia. Its coastline, which is characterized by the presence of ice-rich sediment (Ice Complex) and the vicinity of the Lena River Delta, retreated at a mean rate of 0.59 m/yr between 1951 and 2006. Total erosion ranged from 434 m of erosion to 92 m of accretion during these 56 years and exhibited large variability (sigma = 45.4). Ninety-seven percent of the rates observed were less than 2 m/yr and 81.6% were less than 1 m/yr. No significant trend in erosion could be recorded despite the study of five temporal subperiods within 1951-2006. Erosion modes and rates actually appear to be strongly dependant on the nature of the backshore material, erosion being stronger along low-lying coastal stretches affected by past or current thermokarst activity. The juxtaposition of wind records monitored at the town of Tiksi and erosion records yielded no significant relationship despite strong record amplitude for both data sets. We explain this poor relationship by the only rough incorporation of sea-ice cover in our storm extraction algorithm, the use of land-based wind records vs. offshore winds, the proximity of the peninsula to the Lena River Delta freshwater and sediment plume and the local topographical constraints on wave development.