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| 2. |
- Stenborg, Per, 1962, et al.
(författare)
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The Cultivated Wilderness Project – Hinterland Archaeology in the Belterra Region, Pará, Brasil
- 2014
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Ingår i: Antes de Orellana. Actas del 3er Encuentro Internacional de Arqueología Amazónica, edited by Stéphen Rostain. Actes & Mémoires de l’Institut Français d’Études Andines. - 1816-1278. - 9789942138927 ; 37:I
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Applying a broad approach, the Cultivated Wilderness Project aims at investigating the long-term dynamics of socio-political organization, resource exploitation strategies, subsistence economies and exchange networks in pre-Columbian Amazonia integrating approaches from the human, social and natural sciences. The preliminary results of our project challenge established views and models concerning pre-Columbian settlement patterns and location. Simultaneously, however, these new dates substantiates early historical information about hinterland settlements and presence of elements such as water reservoirs.
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| 3. |
- Carlsson, Ella, et al.
(författare)
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An evaluation of models for Martian gully formation using remote sensing and in situ measurments of Svalbard analogs.
- 2008
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Ingår i: Lunar and Planetary Science Conference 39. ; XXXIX:1852
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The newly discovered gully systems on Mars have been found on rather young geologi-cal surfaces such as dunes and polygons. This in combination with the general absence of superimposed impact craters suggests that the gullies are relatively young geological features. Their morphology indicates that they have been eroded by a liquid fluid, most probably water. A recent discovery suggests that gully formation is an ongoing process, which appears to occur even today. This is a paradox since water in current Martian atmospheric conditions cannot be found in a stable form on the surface due to the low pressure and temperature during normal conditions. Several formation mechanisms have been proposed for the Martian gullies such as liquid carbon dioxide reservoirs, shallow liquid water aquifer, melting ground ice, dry landslide, snow melt and deep liquid water aquifer. However, none of these models can alone explain all the gullies discovered on Mars. So far Martian gullies have only been studied from high orbit via satellites. Gullies found in Arctic climates on Earth could be an equitable analog for the Martian gullies and a com-parative analysis could help disclose the formation mechanisms of the Martian gullies as well as their eroding agent.
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| 4. |
- Carlsson, Ella, et al.
(författare)
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FIELD STUDIES OF GULLIES AND PINGOS ON SVALBARD – A MARTIAN ANALOG.
- 2008
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Ingår i: European Planetary Science Congress, 21-26 September 2008. ; 3
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Konferensbidrag (refereegranskat)abstract
- The gully systems on Mars have been found to superpose young geological surfaces such as dunes and thermal contraction polygons. This in combination with the general absence of superimposed impact craters suggest that the gullies are relatively recent geological formations. The observed gullies display a wide set of morphologies ranging from features seemingly formed by fluvial erosion to others pointing to dry landslide processes. A recent discovery suggests that this is an ongoing process, which appears to occur even today. Several formation mechanisms have been proposed for the Martian gullies, such as liquid carbon dioxide reservoirs, shallow liquid water aquifer, melting ground ice, dry landslide, snow melt and deep liquid water aquifer. However, none of these models can alone explain all the gullies discovered on Mars. So far Martian gullies have been studied only from orbit via remote sensing data. Hydrostatic pingos are perennial ice-cored mounds that may reach an elongated or circular radius of approximately 150 m. They are found in periglacial environments where they are formed by freezing processes in the continuous permafrost. The pingos go through different evolutionary stages as they mature, where the final stage leaves an annular rim left by the collapse of the summit. Images from the High Resolution Imaging Science Experiment (HiRISE) show small fractured mounds in the Martian mid-latitudes. Even though some differences are observed, the best terrestrial analogues for the observed mound morphology are pingos. Gullies and pingos found in Arctic climates on Earth could be an analog for the Martian ones. A comparative analysis might help to understand the formation mechanisms of the Martian pingos and gullies and their possible eroding agent.
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| 5. |
- Ericson, Kerstin, 1958, et al.
(författare)
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A-tents in the Central Sierra Nevada, California: A geomorphological indicator of tectonic stress
- 2004
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Ingår i: Physical Geography. - 0272-3646. ; 25:4, s. 291-312
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Tidskriftsartikel (refereegranskat)abstract
- A-tents and blisters are minor landforms associated with the release of compressive stress in combination with erosional off-loading in hard crystalline bedrock. The uplifted and westward tilted granitic batholith of the Sierra Nevada, California, comprises hundreds of Cretaceous intrusions, where sheeted bornhardts stand juxtaposed, and have been exposed to compressional stress during several time periods. Field mapping north of Yosemite Valley identified 79 A-tents with a preferred orientation ENE-WSW suggesting the application of directionally applied stress. A-tent, joint and bornhardt orientation imply NE-SW tension and NW-SE compression. The stress has probably been released after the rapid Tertiary uplift and erosional unloading in the late Quaternary. We suggest that the A-tents in this part of the Sierra Nevada are related to intrinsic compressional stress imposed on the bedrock during emplacement but before mid-Cretaceous transpression.
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| 6. |
- Ericson, Kerstin, 1958, et al.
(författare)
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Fractures and drainage in the granite mountainous area - A study from Sierra Nevada, USA
- 2005
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X. ; 64:1-2, s. 97-116
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides an analysis of relationships between drainage patterns and fractures in the part of Sierra Nevada, California, north of the Yosemite Valley. Bedrock is Cretaceous granite and cut by numerous lineaments of various orientation, length and geomorphic expression. We have mapped fractures and drainage lines from aerial photographs, 1:40000 scale, in four test areas ranging in size from 32.5 to 266km(2). Azimuths are shown on rose diagrams for fractures and drainage lines and then visually and statistically compared. The coincidence of drainage and fracture patterns is strong, which implies causal relationships. In plan, the majority of valleys follow fractures even if this locally means a different orientation in respect to the regional slope arising from tectonic tilt of the range. Main streams occupy deeply incised troughs coincident with 'master fractures' of regional extent. Among two principal fracture directions, SSW-NNE to SW-NE and WSW-ENE, the former exerts more control on the drainage lines. The presence of a central zone of structural weakness within the major valleys provided significant constraints for the course of glacial erosion and may explain why multiple Pleistocene glaciers did not succeed in transforming valley cross-sections into expected U-shapes. (C) 2004 Elsevier B.V. All rights reserved.
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| 7. |
- Franzén, Lars, 1950, et al.
(författare)
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Small Scale Glacial Erosion Forms and Their Possible Relation to Post-Glacial Weathering
- 1991
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Ingår i: Geografiska Annaler. - 0435-3676 .- 1468-0459. ; 73:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes several types of small scale forms on the stoss side of a roche moutonnee surface, recently exposed in a gravel pit in the Fjaras bracka complex, SW Sweden. The forms were filled with weathered rock debris. When excavated, they showed a striking resemblance to 5 forms generally accepted to be shaped by glacial/glaciofluvial erosion. In addition to these forms there were irregular cavities for instance smoothly rounded throughs and irregular rough surfaces resembling those claimed to be preglacial weathering forms. In spite of the few observations made, many small scale glacial erosion forms are likely to be the result of a three-step process i.e. glacial pressure deformation of the bedrock, subsequent weathering of the deformed rock, and finally excavation of the deformed rock by exogenic processes. Further on it seems probable that many rough surfaces of the type described in the paper are the result of glacial pressure deformation and subsequent weathering
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| 8. |
- Hauber, Ernst, et al.
(författare)
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DEBRIS FLOW FANS AND PERMAFROST LANDFORMS ON SVALBARD (NORWAY): TERRESTRIAL ANALOGUES FOR MARTIAN MID-LATITUDE PERIGLACIAL LANDSCAPES.
- 2010
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Ingår i: 41st Lunar and Planetary Science Conference. ; :1922
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Konferensbidrag (refereegranskat)abstract
- Many young landforms on Mars that were probably formed by exogenic processes show a latitude- dependent geographic distribution. They include surface mantling, lobate debris aprons, lineated valley fill, and concentric crater fill, viscous flow features, gullies, and patterned ground. Collectively, these landforms are hypothesized to represent the surface records of Martian ice ages that were induced by astronomical forcing and associated climate changes. Previous studies often considered just one of the features in isolation (e.g., gullies), without taking into account the geomorphologic context. A more comprehensive investigation of the full assemblage of landforms (landscape analysis), however, has the potential to reduce the ambiguity in interpreting landforms (the problem of equifinality, e.g., in the case of pingos), and to reveal the evolution of the climatic environment in more detail. Here we present permafrost landforms of Svalbard (Norway) as useful terrestrial analogues for the suite of possible periglacial landforms that are typically found at mid-latitudes on Mars. We build on our previous investigations of gullies and fans, and include a number of classical periglacial landforms (patterned ground, rock glaciers, pingos) that all have close morphological analogues on Mars. Based on this comparison, we propose an evolutionary scenario which helps to understand the sequential formation of the Martian landforms into their present state.
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| 9. |
- Hauber, Ernst, et al.
(författare)
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Landscape evolution in Martian mid-latitude regions: Insights from analogous periglacial landforms in Svalbard.
- 2011
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Ingår i: Geological Society, London, Special Publications. ; 356, s. 111-131
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Tidskriftsartikel (refereegranskat)abstract
- Periglacial landforms on Spitsbergen (Svalbard, Norway) are morphologically similar to landforms on Mars that are probably related to the past and/or present existence of ice at or near the surface. Many of these landforms, such as gullies, debris-flow fans, polygonal terrain, fractured mounds and rock-glacier-like features, are observed in close spatial proximity in mid-latitude craters on Mars. On Svalbard, analogous landforms occur in strikingly similar proximity, which makes them useful study cases to infer the spatial and chronological evolution of Martian coldclimate surface processes. The analysis of the morphological inventory of analogous landforms on Svalbard and Mars allows the processes operating on Mars to be constrained. Different qualitative scenarios of landscape evolution on Mars help to better understand the action of periglacial processes on Mars in the recent past.
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| 10. |
- Hauber, Ernst, et al.
(författare)
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MORPHOMETRY OF ALLUVIAL FANS IN A POLAR DESERT (SVALBARD, NORWAY): IMPLICATIONS FOR INTERPRETING MARTIAN FANS.
- 2009
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Ingår i: 40th Lunar and Planetary Science Conference. ; :1648
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Konferensbidrag (refereegranskat)abstract
- Alluvial fan-like landforms have been identified on Mars. Since alluvial fans are recorders of processes that are sensitive to climatic conditions, the investigation of possible Martian fans can reveal information about the planet`s climate. In lieu of direct observations of active depositional processes on Martian fans, comparisons with terrestrial analogues can constrain models of Martian fan formation derived from remote sensing data. Since present-day Mars is cold and dry, alluvial fans formed in cold deserts should be considered as useful analogues. The probably closest climatic analogue to Mars on Earth are the Antarctic Dry Valleys , but polar deserts can also be found in the Arctic. We report on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSC-AX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express. The results are compared with measurements of Martian fans, based on HRSC DEM.
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