440 resultados para Mounds


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Shell mounds ceased to be built in many parts of coastal northern Australia about 800-600 years ago. They are the subject of stories told by Aboriginal people and some have been incorporated in ritual and political activities during the last 150 ears. These understandings emerged only after termination of the economic and environmental system that created them, 800-600 years ago, in a number of widely separated coastal regions, Modern stories and treatments of these mounds by Aboriginal people concern modern or near-modern practices. Modern views of the mounds, their mythological and ritual associations, may be explained by reference to the socioeconomic transitions seen in the archaeological record; but the recent cultural, social and symbolic statements about these places cannot inform us of the process or ideology concerned with the formation of the mounds. Many Aboriginal communities over the last half a millennium actively,formed understandings of new landscapes and systems of land use. Attempts to impose historic ideologies and cosmologies on earlier times fail to acknowledge the magnitude and rate of economic and ideological change on the tropical coastline of Australia.

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Epigeous termite mounds are frequently observed in pasture areas, but the processes regulating their population dynamics are poorly known. This study evaluated epigeous termite mounds in cultivated grasslands used as pastures, assessing their spatial distribution by means of geostatistics and evaluating their vitality. The study was conducted in the Cerrado biome in the municipality of Rio Brilhante, Mato Grosso do Sul, Brazil. In two pasture areas (Pasture 1 and Pasture 2), epigeous mounds (nests) were georeferenced and analyzed for height, circumference and vitality (inhabited or not). The area occupied by the mounds was calculated and termite specimens were collected for taxonomic identification. The spatial distribution pattern of the mounds was analyzed with geostatistical procedures. In both pasture areas, all epigeous mounds were built by the same species, Cornitermes cumulans. The mean number of mounds per hectare was 68 in Pasture 1 and 127 in Pasture 2, representing 0.4 and 1 % of the entire area, respectively. A large majority of the mounds were active (vitality), 91 % in Pasture 1 and 84 % in Pasture 2. A “pure nugget effect” was observed in the semivariograms of height and nest circumference in both pastures reflecting randomized spatial distribution and confirming that the distribution of termite mounds in pastures had a non-standard distribution.

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Earthen mounds with archaeological artifacts have been well known in Marajo Island since the 19th century. Their documented dimensions are impressive, e.g., up to 20m high, and with areas large as 90 ha. The mounds, locally known as lesos, impose a significant. relief on the very low-lying landscape of this region, which averages 4 to 6 in above present. sea level. These features have been traditionally interpreted as artificial constructions of the Marajoara culture, designed for defense, cemetery purposes, or escape from flooding. Here, we provide sedimentological and geomorphological data that suggest an alternative origin for these structures that is more consistent with their monumental sizes. Rather than artificial, the Marajoara tesos seem to consist of natural morphological features related to late Pleistocene and Holocene fluvial, and possibly tidal-influenced, paleochannels and paleobars that became abandoned as depositional conditions changed through dine. Although utilized and modified by the Marajoara since at least 2000 years ago, these earthen mounds contain a significant non-anthropogenically modified sedimentary substratum. Therefore, the large Marajoara tesos are not entirely artificial. Ancient, Marajoara cultures took advantage of these natural, preexisting elevated surfaces to base their communities and develop their activities, locally increasing the sizes of these fluvial landforms. This alternative interpretation suggests less cumulative labor investment, in the construction of the mounds and might. have significant implications for reconstructing the organization of the Marajoara culture. (C) 2009 Wiley Periodicals, Inc.

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The growth rate of mounds of Nasutitermes sp. was evaluated by taking monthly measurements of the diameter and the height of ten mounds during twelve months. Through these data, the monthly volumes were calculated for each of them and, later, a dispersion diagram between the volume of each mound and the number of days from the first observation was obtained. From this diagram, it was observed that during the 335 days of observation, the rate of growth of these mounds was null.

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Longstanding debates concerning the origin of the Kess Kess Emsian carbonate mounds exposed at Hamar Laghdad Ridge (eastern Anti-Atlas, Morocco) centre around the processes that induced precipitation of carbonate mud and the preservation of steep morphologies. Although in the last years an origin related to hydrothermalism seemed to be more likely, to date the Kess Kess are still considered controversial vent deposits. This study combines in updated research review information from previous work and new detailed field observations coupled with new analytical results to define a consistent framework and some new insight of current knowledge about the origin of these mounds. We obtain a complete minero-petrographic and palaeobiological data set and a detailed geochemical characterization of the different lithologies and facies of the Hamar Laghdad stratigraphic succession, including mounds, and we compared the results with the data from Maïder Basin mounds (Anti-Atlas, Morocco). Our data support the hydrothermal model proposed for the genesis and development of the Kess Kess mounds. The mechanisms linked to the mounds formation and growth are discussed in the light of the new finding of fluid-sediment interaction within a scenario driven by late magmatic fluids circulation. Conical mounds and other fluids related morphologies were also reported from Crommelin crater area (Arabia Terra, Mars). These mounds consist in meter-sized conical buildups hosted in the Equatorial Layered Deposits (ELDs) deposed during a regional groundwater fluid upwelling. Geometries and geological conditions that might have controlled the development of such morphologies were discussed. According to our data the morphological and stratigraphical characteristics of Crommelin area mounds are most consistent with a formation by fluids advection. Then we compare terrestrial and Martian data and examine the geological settings of hydrothermal mound occurrences on Earth in order to describe potential target areas for hydrothermal structures on Mars.

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During DSDP Leg 70, a 1.60 m thick manganese oxide layer was sampled in hole 509B. This deposit is formed of alternating layers of hard plates of pure todorokite, about 2 mm thick, and of a more powdery material deeply impregnated with manganese oxide, about 3 mm thick. A SEM study of the plates and the associated powder shows that the powdery material is a transformation of a pre-existing sediment, while the plates are a direct precipitation from a hydrothermal solution. The uranium series disequilibrium method was used to determine the ages of the plates. They are found to be in good chronological sequence and in accordance with the sedimentation rate of the area (4.9 cm/10^3 years) which implies that they have been formed at the sediment-seawater interface during a pulsed injection of hydrothermal solution. The powder presents systematically an "older age" which is explained by a slowing down of the injection while the normal sediment settles; the older age is due to the 230Th excess of the sediment.

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The Darwin Mounds are a series of small (<=5 m high, 75-100 m diameter) sandy features located in the northern Rockall Trough. They provide a habitat for communities of Lophelia pertusa and associated fauna. Suspended particulate organic matter (sPOM) reaching the deep-sea floor, which could potentially fuel this deep-water coral (DWC) ecosystem, was collected during summer 2000. This was relatively "fresh" (i.e. dominated by labile lipids such as polyunsaturated fatty acids) and was derived largely from phytoplankton remains and faecal pellets, with contributions from bacteria and microzooplankton. Labile sPOM components were enriched in the benthic boundary layer (~10 m above bottom (mab)) relative to 150 mab. The action of certain benthic fauna that are exclusively associated with the DWC ecosystem (e.g. echiuran worms) leads to the subduction of fresh organic material into the sediments. The mound surface sediments are enriched in organic carbon, relative to off-mound sites. There is no evidence for hydrocarbon venting at this location.