Chapter 10: Structural features and emplacement of surficial gravity-slide sheets, northern Idaho-Wyoming thrust belt

Boyer, Steven E.; Hossack, John R.

doi:10.1130/mem179-p197

Cited by 10 publications

(13 citation statements)

References 13 publications

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“…Anders et al (Fig. 1C in Anders et al, 2000) described lamination of this character from material at the bases of the Heart Mountain allochthon and two other large rockslides, the Palisades slide of Wyoming (Boyer and Hossak, 1992) and Horse Creek slide of Idaho (Beutner, 1972). We have also observed lamination at the base of a Miocene rockslide in the Halloran/Silurian Hills area of southeastern California (Bishop, 1997).…”

Section: Laminations and Striationssupporting

confidence: 65%

Catastrophic emplacement of the Heart Mountain block slide, Wyoming and Montana, USA

Beutner

Gerbi

2005

Geol Soc America Bull

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The mechanism that allowed many tens of km of movement of the enormous block slide fl oored by the rootless Heart Mountain detachment fault in NW Wyoming has long been a puzzle. Carbonate-rich microbreccia that is widespread along the fault and in dikes in the upper plate contains accreted grains indistinguishable from those observed as fallout from volcanic eruption clouds (accretionary lapilli) and impact ejecta clouds and in intrusive diatremes. In these settings and also in industrial processing, accreted grains form when particles in a turbulent gaseous suspension containing limited water adhere to a nucleating grain or to each other. Elongate grains in thick microbreccia have strong but diverse shape-preferred orientations unlike those reported from other fault rocks but instead suggestive of turbulent fl ow, and the microbreccia contains layering and other features of sedimentary character that appear to record deposition from suspension rather than frictional processes along a fault. We suggest that frictional heating led to dissociation of carbonate rock along the fault, producing supercritical CO 2 as the suspending medium. High CO 2 pressure drastically reduced friction along the fault and allowed continuation of catastrophic movement, probably initiated by a volcanic or phreatomagmatic explosion, resulting in very large displacement on a lowdipping surface. Earlier slower sliding may have occurred but fi nal emplacement was rapid (minutes) and spectacular.

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Section: Laminations and Striationssupporting

confidence: 65%

Catastrophic emplacement of the Heart Mountain block slide, Wyoming and Montana, USA

Beutner

Gerbi

2005

Geol Soc America Bull

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“…Many other features seen in the Shadow Valley glide blocks are similar to those of other case studies (Pierce, 1973;Braddock, 1978;Hauge, 1990;Boyer and Hossack, 1992). These include a lack of internal brecciation, no mixing, and foliated muds along the basal surface.…”

Section: Mass-wasting Depositssupporting

confidence: 74%

Sedimentology and stratigraphy of the Shadow Valley basin, eastern Mojave Desert, California

Friedmann¹

1999

Cenozoic Basins of the Death Valley Region

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“…Some of these blocks are kilometers in length and several tens to a few hundred of meters in thickness. Explanations for the duration and causal mechanism of the massive slide block movement are controversial (Moore et al, 1987;Anders, 1990;McCalpin et al, 1990;Boyer and Hossack, 1992). Whereas Oriel and Moore (1985) inferred that these slide masses moved from the crest and southwest fl ank of the Snake Range, they did not propose a triggering mechanism for such large detachments.…”

Section: Timing Of Tectonic Events Seismically Triggered Slide Blocksmentioning

confidence: 99%

“…Whereas Oriel and Moore (1985) inferred that these slide masses moved from the crest and southwest fl ank of the Snake Range, they did not propose a triggering mechanism for such large detachments. Boyer and Hossack (1992) inferred that these slide blocks were emplaced over a relatively long time and "crept" into place. They interpreted this from lithologic characteristics within various slide blocks mostly along the Grand Valley Fault and the contact between them and the underlying blocks.…”

Section: Timing Of Tectonic Events Seismically Triggered Slide Blocksmentioning

confidence: 99%

Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA

Morgan

McIntosh

2005

Geol Soc America Bull

180

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The Snake River Plain (SRP) developed over the last 16 Ma as a bimodal volcanic province in response to the southwest movement of the North American plate over a fi xed melting anomaly. Volcanism along the SRP is dominated by eruptions of explosive high-silica rhyolites and represents some of the largest eruptions known. Basaltic eruptions represent the fi nal stages of volcanism, forming a thin cap above voluminous rhyolitic deposits. Volcanism progressed, generally from west to east, along the plain episodically in successive volcanic fi elds comprised of nested caldera complexes with major caldera-forming eruptions within a particular fi eld separated by ca. 0.5-1 Ma, similar to, and in continuation with, the present-day Yellowstone Plateau volcanic fi eld. Passage of the North American plate over the melting anomaly at a particular point in time and space was accompanied by uplift, regional tectonism, massive explosive eruptions, and caldera subsidence, and followed by basaltic volcanism and general subsidence. The Heise volcanic fi eld in the eastern SRP, Idaho, represents an adjacent and slightly older fi eld immediately to the southwest of the Yellowstone Plateau volcanic fi eld. Five large-volume (>0.5 km 3) rhyolitic ignimbrites constitute a time-stratigraphic framework of late Miocene to early Pliocene volcanism for the study region. Field relations and high-precision 40 Ar/ 39 Ar age determinations establish that four of these regional ignimbrites were erupted from the Heise volcanic fi eld and form the framework of the Heise Group. These are the Blacktail Creek Tuff (6.62 ± 0.03 Ma), Walcott Tuff (6.27 ± 0.04 Ma), Conant Creek Tuff (5.51 ± 0.13 Ma), and Kilgore Tuff (4.45 ± 0.05 Ma; all errors reported at ± 2σ). The fi fth widespread ignimbrite in the region is the Arbon Valley Tuff Member of the Starlight Formation (10.21 ± 0.03 Ma), which erupted from a caldera source outside of the Heise volcanic fi eld. These results establish the Conant Creek Tuff as a distinct and widespread ignimbrite in the Heise volcanic fi eld, eliminating former confusion resulting from previous discordant K/Ar and fi ssion-track dates. New 40 Ar/ 39 Ar determinations, when combined with geochemical, lithologic, geophysical, and fi eld data, defi ne the volcanic and tectonic history of the Heise volcanic fi eld and surrounding areas. Volcanic units erupted from the Heise volcanic fi eld also provide temporal control for tectonic events associated with late Cenozoic extension in the Snake Range and with uplift of the Teton Range, Wyoming. In the Snake Range, movement of large (≥0.10 km 3) slide blocks of Mississippian limestone exposed 50 km to the east of the Heise fi eld occurred between 6.3 and 5.5 Ma and may have been catastrophically triggered by the caldera eruption of the 5.51 ± 0.13-Ma Conant Creek Tuff. This slide block movement of ~300 vertical meters indicates that the Snake Range had signifi cant relief by at least 5.5 Ma. In Jackson Hole, the distribution of outfl ow facies of the 4.45 ± 0.05-Ma Kilgore Tuff rel...

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Chapter 10: Structural features and emplacement of surficial gravity-slide sheets, northern Idaho-Wyoming thrust belt

Cited by 10 publications

References 13 publications

Catastrophic emplacement of the Heart Mountain block slide, Wyoming and Montana, USA

Catastrophic emplacement of the Heart Mountain block slide, Wyoming and Montana, USA

Sedimentology and stratigraphy of the Shadow Valley basin, eastern Mojave Desert, California

Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA

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