1000 resultados para Cape Floristic Region


Relevância:

30.00% 30.00%

Publicador:

Resumo:

This layer is a georeferenced raster image of the historic, paper manuscript map entitled: Map of country between the N.E. Cape-Fear River and Topsail sound, made under the direction of Capt. Wm. H. James, Chf. Engineer, by B.L. Blackford, Top. Engrs. It was drawn in 1865. Scale 1:40,000. The image inside the map neatline is georeferenced to the surface of the earth and fit to the North Carolina State Plane NAD 1983 coordinate system (in Meters) (Fipszone 3200). All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as roads, railroads, bridges, drainage, troop camps, lines of defense, selected buildings with names of landowners, mills and salt works, ground cover, swamps, and more. Relief shown by hachures. Includes also ill. of Confederate soldier with a plane table and Confederate flag, at left within margin. This layer is part of a selection of digitally scanned and georeferenced historic maps of the Civil War from the Harvard Map Collection. Many items from this selection are from a collection of maps deposited by the Military Order of the Loyal Legion of the United States Commandery of the State of Massachusetts (MOLLUS) in the Harvard Map Collection in 1938. These maps typically portray both natural and manmade features, in particular showing places of military importance. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This layer is a georeferenced raster image of the historic paper map entitled: Stanford's new map of the Orange Free State, the southern part of the South African Republic, the northern frontier of Cape Colony, Natal, Basutoland and Delagoa Bay. It was published by E. Stanford in 1899. Scale 1:1,000,000 The image inside the map neatline is georeferenced to the surface of the earth and fit to the Africa Lambert Conformal Conic projected coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, roads, railroads and stations, administrative and territorial boundaries, shoreline features, and more. Relief shown by shading and spot heights.This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We analysed long-chain alkenones in sinking particles and surface sediments from the filamentous upwelling region off Cape Blanc, NW Africa, to evaluate the transfer of surface water signals into the geological record. Our study is based on time-series sediment trap records from 730 m (1990-1991) to 2195-3562 m depth (1988-1991). Alkenone fluxes showed considerable interannual variations and no consistent seasonality. The average flux of C37 and C38 alkenones to the deep traps was 1.9 µg/m**2/d from March 1988 to October 1990 and sevenfold higher in the subsequent year. Alkenone fluxes to the shallower traps were on average twice as high and showed similar temporal variations. The alkenone unsaturation indices UK'37, UK38Me and UK38Et closely mirrored the seasonal variations in sea-surface temperature (weekly Reynolds SST). Time lags of 10-48 days between the SST and unsaturation maxima suggest particle sinking rates of about 80 and 280 m/d for the periods of low and high alkenone fluxes, respectively. The average flux-weighted UK'37 temperature for the 4-year time series of the deeper traps was 22.1°C, in perfect agreement with the mean weekly SST for the same period. This and the comparison with seasonal temperature variations in the upper 100 m of the water column suggests that UK'37 records principally the yearly average of the mixed-layer temperature in this region. A comparison between the average annual alkenone fluxes to the lower traps (2400 µg/m**2/yr) and into the underlying sediments (4 µg/m**2/yr) suggests that only about 0.2% of the alkenones reaching the deep ocean became preserved in the sediments. The flux-weighted alkenone concentrations also decreased considerably, from 2466 µg/gC in the water column to 62 µg/gC in the surface sediments. Such a low degree of alkenone preservation is typical for slowly accumulating oxygenated sediments. Despite these dramatic diagenetic alkenone losses, the UK'37 ratio was not affected. The average UK'37 value of the sediments (0.796±0.010 or 22.3±0.3°C) was identical within error limits to the 4-year average of the lower traps. The unsaturation indices for C38 alkenones and the ratio between C37 and C38 alkenones also revealed a high degree of stability. Our results do not support the hypothesis that UK'37 is biased towards higher values during oxic diagenesis.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Non-glaciated Arctic lowlands in north-east Siberia were subjected to extensive landscape and environmental changes during the Late Quaternary. Coastal cliffs along the Arctic shelf seas expose terrestrial archives containing numerous palaeoenvironmental indicators (e.g., pollen, plant macro-fossils and mammal fossils) preserved in the permafrost. The presented sedimentological (grain size, magnetic susceptibility and biogeochemical parameters), cryolithological, geochronological (radiocarbon, accelerator mass spectrometry and infrared-stimulated luminescence), heavy mineral and palaeoecological records from Cape Mamontov Klyk record the environmental dynamics of an Arctic shelf lowland east of the Taymyr Peninsula, and thus, near the eastern edge of the Eurasian ice sheet, over the last 60 Ky. This region is also considered to be the westernmost part of Beringia, the non-glaciated landmass that lay between the Eurasian and the Laurentian ice caps during the Late Pleistocene. Several units and subunits of sand deposits, peat-sand alternations, ice-rich palaeocryosol sequences (Ice Complex) and peaty fillings of thermokarst depressions and valleys were presented. The recorded proxy data sets reflect cold stadial climate conditions between 60 and 50 Kya, moderate inderstadial conditions between 50 and 25 Kya and cold stadial conditions from 25 to 15 Kya. The Late Pleistocene to Holocene transition, including the Allerød warm period, the early to middle Holocene thermal optimum and the late Holocene cooling, are also recorded. Three phases of landscape dynamic (fluvial/alluvial, irregular slope run-off and thermokarst) were presented in a schematic model, and were subsequently correlated with the supraregional environmental history between the Early Weichselian and the Holocene.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The palaeoenvironmental development of the western Laptev Sea is understood primarily from investigations of exposed cliffs and surface sediment cores from the shelf. In 2005, a core transect was drilled between the Taymyr Peninsula and the Lena Delta, an area that was part of the westernmost region of the non-glaciated Beringian landmass during the late Quaternary. The transect of five cores, one terrestrial and four marine, taken near Cape Mamontov Klyk reached 12 km offshore and 77 m below sea level. A multiproxy approach combined cryolithological, sedimentological, geochronological (14C-AMS, OSL on quartz, IR-OSL on feldspars) and palaeoecological (pollen, diatoms) methods. Our interpretation of the proxies focuses on landscape history and the transition of terrestrial into subsea permafrost. Marine interglacial deposits overlain by relict terrestrial permafrost within the same offshore core were encountered in the western Laptev Sea. Moreover, the marine interglacial deposits lay unexpectedly deep at 64 m below modern sea level 12 km from the current coastline, while no marine deposits were encountered onshore. This implies that the position of the Eemian coastline presumably was similar to today's. The landscape reconstruction suggests Eemian coastal lagoons and thermokarst lakes, followed by Early to Middle Weichselian fluvially dominated terrestrial deposition. During the Late Weichselian, this fluvial landscape was transformed into a poorly drained accumulation plain, characterized by widespread and broad ice-wedge polygons. Finally, the shelf plain was flooded by the sea during the Holocene, resulting in the inundation and degradation of terrestrial permafrost and its transformation into subsea permafrost.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

New pollen and radiocarbon data from an 8.6-m coastal section, Cape Shpindler (69°43' N; 62°48' E), Yugorski Peninsula, document the latest Pleistocene and Holocene environmental history of this low Arctic region. Twelve AMS 14C dates indicate that the deposits accumulated since about 13,000 until 2000 radiocarbon years BP. A thermokarst lake formed ca. 13,000-12,800 years BP, when scarce arctic tundra vegetation dominated the area. By 12,500 years BP, a shallow lake existed at the site, and Arctic tundra with Poaceae, Cyperaceae, Salix, Saxifraga, and Artemisia dominated nearby vegetation. Climate was colder than today. Betula nana became dominant during the Early Preboreal period about 9500 years BP, responding to a warm event, which was one of the warmest during the Holocene. Decline in B. nana and Salix after 9500 years BP reflects a brief event of Preboreal cooling. A subsequent increase in Betula and Alnus fruticosa pollen percentages reflects amelioration of environmental conditions at the end of Preboreal period (ca. 9300 years BP). A decline in arboreal taxa later, with a dramatic increase in herb taxa, reflects a short cold event at about 9200 years BP. The pollen data reflect a northward movement of tree birch, peaking at the middle Boreal period, around 8500 years BP. Open Betula forest existed on the Kara Sea coast of the Yugorski Peninsula during the Atlantic period (8000-4500 years BP), indicating that climate was significantly warmer than today. Deteriorating climate around the Atlantic-Subboreal boundary (ca. 4500 years BP) is recorded by a decline in Betula percentages. Sedimentation slowed at the site, and processes of denudation and/or soil formation started at the beginning of the Subatlantic period, when vegetation cover on Yugorski Peninsula shifted to near-modern assemblages.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The Canary Islands region occupies a key position with respect to biogeochemical cycles, with the zonal transition from oligotrophic to nutrient-rich waters and the contribution of Saharan dust to the particle flux. We present the distribution of geochemical proxies (TOC, carbonate, d15N, d13Corg, C/N-ratio) and micropaleontological parameters (diatoms, dinoflagellates, foraminifera, pteropods), in 80 surface-sediment samples in order to characterise the influence of coastally upwelled water on the domain of the subtropical gyre. Results of the surface-sediment analyses confirmed the high biomass gradient from the coast to the open ocean inferred from satellite data of surface chlorophyll or SST. The distribution of total dinoflagellate cysts, the planktic foraminifera species Globigerina bulloides, the diatom resting spore Chaetoceros spp., and TOC concentration coincided well with the areas of strong filament production off Cape Ghir and Cape Yubi. The warm-water planktic foraminifera Globigerinoides ruber (white), the diatom Nitzschia spp., and the d15N-values showed the opposite trend with high values in the open ocean. Factor analyses on the planktic foraminifera species distribution indicated three major assemblages in the Canary Islands region that represent the present surface-water conditions from the upwelling influenced region via a mixing area towards the subtropical gyre.