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- 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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| 2. |
- Franzén, Lars, 1950, et al.
(författare)
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The peatland/ice age hypothesis revised, adding a possible glacial pulse trigger
- 2007
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Ingår i: Geografiska Annaler. - 0435-3676. ; 89A:4, s. 301-330
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Tidskriftsartikel (refereegranskat)abstract
- Carbon sequestering in peatlands is believed to be a major climate-regulating mechanism throughout the late Phanerozoic. Since plant life first evolved on land, peatlands have been significant carbon sinks, which could explain significant parts of the large variations in atmospheric carbon dioxide observed in various records. The result is peat in different degrees of metamorphosis, i.e. lignite, hard coal and graphite. During phases of extensive glaciations such as the 330–240 Ma Pangea Ice Age, atmospheric carbon dioxide was critically low. This pattern repeats itself during the Pleistocene when carbon dioxide oscillates with an amplitude of c. 200–300 ppmv. This paper suggests that the ice age cycles during the Pleistocene are generated by the interglacial growth of peatlands and the subsequent sequestering of carbon into this terrestrial pool. The final initiation of ice age pulses towards the end of inter-glacials, on the other hand, is attributed to the cyclic influx of cosmic dust to the Earth surface, which in turn regulates cloud formation and the incoming shortwave radiation. These shorter cycles have a frequency of c. 1000-1250 years and might be connected to sunspot or other low frequency solar variations. In a wider context the ice age cycling could be regarded as an interplay between terrestrial life on the high latitudes of the northern hemisphere and the marine subsurface life in the southeast. If the results presented here are correct, the present global warming might just be the early part of a new warm period such as the Bronze Age and the Roman and Medieval Warm periods. This could be caused by entry into another phase of decreasing influx rates of cosmic dust. The increasing concentrations of atmospheric carbon dioxide might have contributed to this warming but, most important of all, it might temporarily have saved us from a new ice age pulse.
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