Details
| Original language | English |
|---|---|
| Pages (from-to) | 341-355 |
| Number of pages | 15 |
| Journal | Swiss journal of geosciences |
| Volume | 112 |
| Issue number | 2-3 |
| Publication status | Published - 1 Dec 2019 |
| Externally published | Yes |
Abstract
We reveal the subsurface bedrock topography and sedimentary succession of one of the deepest glacially-formed basins in the Eastern Alps: the Lienz Basin in the Upper Drau Valley (Tyrol), by means of seismic reflection. A dense source-receiver spacing, supplied by autonomous receivers, and a prestack depth-migration processing scheme were essential to distinguish the various deposits in fine detail, such as slumping, fan delta deposits, and a modified monocline on the basin flank. These details support our interpretation of the seismic stratigraphy that consists of, e.g., subglacial till of last glacial maximum (LGM) age and possibly older, laminated basin fines, and gravel/coarse sand. The maximum depth of the basin is 622 m, at the junction of two major basement faults that are not clearly visible in the seismic reflections. We regard the overdeepening in this longitudinal valley as the result of glacier confluence during the LGM. Subglacial meltwaters utilized the higher erodibility of faulted rocks, as indicated by channel structures. The adverse slope (2.6%) along the valley axis exceeds the gradient ice-surface slope (0.4–0.5%) during the LGM by more than fivefold. We thus suggest this feature is a product of a pre-LGM phase, since adverse slopes greater than ~ 1.2 times the ice surface slope promote the freezing of water in subglacial channels and prevent efficient water flushing of sediments. Integrating other studies allows us to estimate the local overdeepening of the Lienz Basin and that of the whole Upper Drau Valley to be 146 m and 530 m, respectively. At the beginning of lacustrine sedimentation, we estimate the paleo-water depth to be at least 216 m.
Keywords
- Basin morphology, Glacial sediments, Lienz Basin, Overdeepening, Seismic facies, Seismic imaging
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
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In: Swiss journal of geosciences, Vol. 112, No. 2-3, 01.12.2019, p. 341-355.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Unravelling the shape and stratigraphy of a glacially-overdeepened valley with reflection seismic
T2 - the Lienz Basin (Austria)
AU - Burschil, Thomas
AU - Tanner, David C.
AU - Reitner, Jürgen M.
AU - Buness, Hermann
AU - Gabriel, Gerald
N1 - Funding information: The project was funded by German Research Foundation DFG, Grants KR2073/3-1, GA749/5-1, BU2467/1-2. We acknowledge the Geophysical Instrument Pool Potsdam at the GFZ German Research Centre for Geosciences Helmholtz Centre Potsdam for providing seismic equipment, Grant GIPP201623, and the help of Christian Haberland and Manfred Stiller. We thank our colleagues, among others, Markus Fiebig (BOKU Vienna), Harald Haider and Andreas Gander (Baubezirksamt Lienz), and Paul Herbst (GWU) for support and advice; Philip Nagy and the LIAG field crew, who carried out the seismic surveys and Manfred Linner for discussions on the tectonic setting. A special thanks to the editor-in-chief Wilfried Winkler and the reviewers, Darell A. Swift and Wilfried Gruber, who carefully revised and improved our manuscript.
PY - 2019/12/1
Y1 - 2019/12/1
N2 - We reveal the subsurface bedrock topography and sedimentary succession of one of the deepest glacially-formed basins in the Eastern Alps: the Lienz Basin in the Upper Drau Valley (Tyrol), by means of seismic reflection. A dense source-receiver spacing, supplied by autonomous receivers, and a prestack depth-migration processing scheme were essential to distinguish the various deposits in fine detail, such as slumping, fan delta deposits, and a modified monocline on the basin flank. These details support our interpretation of the seismic stratigraphy that consists of, e.g., subglacial till of last glacial maximum (LGM) age and possibly older, laminated basin fines, and gravel/coarse sand. The maximum depth of the basin is 622 m, at the junction of two major basement faults that are not clearly visible in the seismic reflections. We regard the overdeepening in this longitudinal valley as the result of glacier confluence during the LGM. Subglacial meltwaters utilized the higher erodibility of faulted rocks, as indicated by channel structures. The adverse slope (2.6%) along the valley axis exceeds the gradient ice-surface slope (0.4–0.5%) during the LGM by more than fivefold. We thus suggest this feature is a product of a pre-LGM phase, since adverse slopes greater than ~ 1.2 times the ice surface slope promote the freezing of water in subglacial channels and prevent efficient water flushing of sediments. Integrating other studies allows us to estimate the local overdeepening of the Lienz Basin and that of the whole Upper Drau Valley to be 146 m and 530 m, respectively. At the beginning of lacustrine sedimentation, we estimate the paleo-water depth to be at least 216 m.
AB - We reveal the subsurface bedrock topography and sedimentary succession of one of the deepest glacially-formed basins in the Eastern Alps: the Lienz Basin in the Upper Drau Valley (Tyrol), by means of seismic reflection. A dense source-receiver spacing, supplied by autonomous receivers, and a prestack depth-migration processing scheme were essential to distinguish the various deposits in fine detail, such as slumping, fan delta deposits, and a modified monocline on the basin flank. These details support our interpretation of the seismic stratigraphy that consists of, e.g., subglacial till of last glacial maximum (LGM) age and possibly older, laminated basin fines, and gravel/coarse sand. The maximum depth of the basin is 622 m, at the junction of two major basement faults that are not clearly visible in the seismic reflections. We regard the overdeepening in this longitudinal valley as the result of glacier confluence during the LGM. Subglacial meltwaters utilized the higher erodibility of faulted rocks, as indicated by channel structures. The adverse slope (2.6%) along the valley axis exceeds the gradient ice-surface slope (0.4–0.5%) during the LGM by more than fivefold. We thus suggest this feature is a product of a pre-LGM phase, since adverse slopes greater than ~ 1.2 times the ice surface slope promote the freezing of water in subglacial channels and prevent efficient water flushing of sediments. Integrating other studies allows us to estimate the local overdeepening of the Lienz Basin and that of the whole Upper Drau Valley to be 146 m and 530 m, respectively. At the beginning of lacustrine sedimentation, we estimate the paleo-water depth to be at least 216 m.
KW - Basin morphology
KW - Glacial sediments
KW - Lienz Basin
KW - Overdeepening
KW - Seismic facies
KW - Seismic imaging
UR - http://www.scopus.com/inward/record.url?scp=85062938025&partnerID=8YFLogxK
U2 - 10.1007/s00015-019-00339-0
DO - 10.1007/s00015-019-00339-0
M3 - Article
AN - SCOPUS:85062938025
VL - 112
SP - 341
EP - 355
JO - Swiss journal of geosciences
JF - Swiss journal of geosciences
SN - 1661-8726
IS - 2-3
ER -