Interpretation of Faults in Glaciofluvial Sediments

Mcdonald, B C; Shilts, W W

doi:10.2110/pec.75.23.0123

Cited by 42 publications

(22 citation statements)

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“…Some offset refl ections can be observed throughout the grid, with individual offsets typically <1 m. Although the frequency of offset refl ections is minimal, they are interpreted as normal faults refl ecting structural collapse of the landform sediments (cf. McDonald and Shilts, 1975) due to melting of the supporting ice walls, similar to offset refl ections observed in glaciofl uvial sediments at Skeiðarárjökull (Woodward et al, 2008).…”

Section: Interpretation Of Gpr Profilessupporting

confidence: 65%

The sedimentary architecture of outburst flood eskers: A comparison of ground-penetrating radar data from Bering Glacier, Alaska and Skeithararjokull, Iceland

Burke

Woodward

Russell

et al. 2010

Geological Society of America Bulletin

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We present ground-penetrating radar (GPR) profi les that reveal the sedimentary architecture of an esker deposited during a surge-associated outburst fl ood at the Bering Glacier, Alaska. The wide, up-fl ow end of the esker contains a transition from large backset beds to large foreset beds interpreted to refl ect composite macroform development in an enlarged part of the conduit. By contrast, the narrow, down-fl ow portion of the esker is dominated by plane beds interpreted to have been deposited where the conduit was constricted and the fl ow was faster. A previously studied outburst esker at Skeiðarár-jökull, Iceland has a similar morphology and stratigraphic architecture. This suggests that outburst fl oods generate distinct depositional signatures in eskers, both in terms of morphology and sedimentary architecture. Identifi cation of these distinct signatures in ancient eskers will help assess the paleohydraulic conditions under which ancient eskers formed and, by extension, the nature of meltwater drainage systems beneath the Laurentide and Eurasian ice sheets.

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Section: Interpretation Of Gpr Profilessupporting

confidence: 65%

The sedimentary architecture of outburst flood eskers: A comparison of ground-penetrating radar data from Bering Glacier, Alaska and Skeithararjokull, Iceland

Burke

Woodward

Russell

et al. 2010

Geological Society of America Bulletin

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“…It seems that the overhang developed by collapse of rectangular blocks of frozen sand into the channel. The fault pattern bears a strong superficial resemblance to those produced experimentally by Sanford (1959) and recognized by McDonald and Shilts (1975) in the Oak Ridges Moraine, southern Ontario which they ascribed to melting of buried ice. However, unfaulted channels in Member 2 (Figure 14) of similar cross-sectional dimensions occur on either side of the faulted channel described above.…”

Section: B the Red-brown Sand And Gravel Membersupporting

confidence: 60%

The Origin of late Devensian sands and gravels, southeast Anglesey, N. Wales

Helm

Робертс

1984

Geological Journal

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The Lleiniog Sand and Gravel Formation, of late Devensian age, has been divided into four Members. The sediments are interpreted as the sequential products of the wasting of a single ice lobe. Member I formed where subglacial streams debouched into a pro‐glacial lake and is noteworthy for the occurrence of a bedform, hitherto undescribed but which may be common in many outwash sequences; Member 2 consists of channel sands and gravels deposited by pro‐glacial streams; Member 3 has the characters of a melt‐out till deposited after a readvance; and Member 4 accumulated in pools of meltwater on the irregular surface of Member 3. Clasts above granule grade are dominantly of locally‐derived Carboniferous rocks although a far travelled component from northern England and southern Scotland can be distinguished as well as a small but constant input of Lower Palaeozoic rock types from the Conwy area. The sand grade is dominated by quartz grains released from Permo‐Triassic sandstones. Clay grade material has been derived from Carboniferous shales.

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“…Up thrusts caused by melting dead ice reveal three characteristics [Sanford, 1959;McDonald and Shilts, 1975]: (1) a series of reverse faults rather than a single fault form, (2) the initial high-angle reverse fault curves convex upward toward the block that was relatively downthrown to become a low-angle reverse fault, and (3) a given vertical displacement would result in a fracture length approximately twenty times the amount of the displacement. None of these characteristics apply to the thrusted Raphstreng moraine thus weakening the hypothesis of melting dead ice in the underground.…”

Section: Interpretation Of Deformation Features In the Raphstreng Andmentioning

confidence: 99%

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Meyer

Wiesmayr

Brauner³

et al. 2006

Tectonics

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Paleoseismological investigations, brittle fault analysis, and paleostrain calculations combined with the interpretation of satellite imagery and flood wave modeling were used to investigate the seismic and associated glacial hazard potential in Eastern Lunana, a remote area in NW Bhutan. Seismically induced liquefaction features, cracked pebbles, and a surface rupture of about 6.8 km length constrain the occurrence of M ≥ 6 earthquakes within this high‐altitude periglacial environment, which are the strongest earthquakes ever been reported for the Kingdom of Bhutan. Seismicity occurs along conjugate sets of faults trending NE‐SW to NNW‐SSE by strike‐slip and normal faulting mechanism indicating E‐W extension and N‐S shortening. The strain field for these conjugate sets of active faults is consistent with widespread observations of young E‐W expansion throughout southern Tibet and the north Himalaya. We expect, however, that N‐S trending active strike‐slip faults may even reach much farther to the south, at least into southern Bhutan. Numerous glacial lakes exist in the investigation area, and today more than 100 × 106 m3 of water are stored in moraine‐dammed and supraglacial lakes which are crosscut by active faults. Strong earthquakes may trigger glacial lake outburst floods, and the impact of such flash floods may be worst 80 km downstream where the valley is broad and densely populated. Consequently, tectonic models of active deformation have to be closely linked with glacial hazard evaluation and require rethinking and modification.

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Interpretation of Faults in Glaciofluvial Sediments

Cited by 42 publications

References 0 publications

The sedimentary architecture of outburst flood eskers: A comparison of ground-penetrating radar data from Bering Glacier, Alaska and Skeithararjokull, Iceland

The sedimentary architecture of outburst flood eskers: A comparison of ground-penetrating radar data from Bering Glacier, Alaska and Skeithararjokull, Iceland

The Origin of late Devensian sands and gravels, southeast Anglesey, N. Wales

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

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