Mountain Slide Research Articles

High‐Velocity Slip and Thermal Decomposition of Carbonates: Example From the Heart Mountain Slide Ultracataclasites, Wyoming

AbstractThe Heart Mountain Slide in Wyoming is one of the largest known terrestrial gravity slides (3,500 km2) formed ∼49 Ma ago by the nearly horizontal detachment of Paleozoic‐Eocene cover sliding on top of autochthonous formations. At the White Mountain locality, exposures offer an exceptional opportunity to investigate high strain rate/high velocity processes in carbonates. Here we use the anisotropy of magnetic susceptibility (AMS) of 274 samples to shed light on ultracataclastic deformation along this detachment. Contrary to predictions, the carbonate ultracataclasite displays a consistent AMS fabric, particularly in the upper ultracataclasite. The AMS in this unit is controlled primarily by magnetite formed through the breakdown of iron sulfides caused by frictional heating. Additional thermomagnetic experiments reveal that the new magnetic fabric began forming ∼250ºC and continued up to ∼400ºC when calcination of carbonate minerals caused a major drop in friction. The main cataclastic slip direction inferred from AMS is ∼N033°, at odds with the previously accepted NNW‐SSE direction. We validate these AMS fabrics through 3D shape preferred orientation analysis and micro X‐ray scanning of the same specimens. These results, however, may only represent cataclastic flow directions at the local scale as a result of synkinematic rotation of the White Mountain block. Alternatively, these results may call for a re‐evaluation of the large scale movement of the slide. Finally, this study demonstrates the usefulness of a magnetic approach in deciphering deformation processes in carbonates, particularly in high strain rate cases such as seismic faults.

Volcanic Initiation of the Eocene Heart Mountain Slide, Wyoming, USA

AbstractThe Eocene Heart Mountain slide of northwest Wyoming covers an area of as much as 5000 km2 and includes allochthonous Paleozoic carbonate and Eocene volcanic rocks with a run-out distance of as much as 85 km. Recent geochronologic data indicated that the emplacement of the slide event occurred at ∼48.9 Ma, using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) extracted from U-Pb zircon ages from basal layer and injectite carbonate ultracataclasite (CUC). We now refine that age with U-Pb results from a lamprophyre diatreme that is temporally and spatially related to the CUC injectites. The ages for the lamprophyre zircons are 48.97 ± 0.36 Ma (LA-ICPMS) and 49.19 ±0.02 Ma (chemical abrasion isotope dilution thermal ionization mass spectrometry). Thus, the lamprophyre and CUC zircons are identical in age, and we interpret that the zircons in the CUC were derived from the lamprophyre during slide emplacement. Moreover, the intrusion of the lamprophyre diatreme provided the trigg...

Detrital Zircon U-Pb geochronology and provenance of the Eocene Willwood Formation, Northern Absaroka Basin, Wyoming

We report the results of U-Pb ages from detrital zircon populations in the lower Eocene synorogenic Willwood Formation in the northern Absaroka Basin, Wyoming. Zircons (n=229) were extracted from three sandstone beds and one ash layer in the Willwood Formation at the base of Jim Mountain in the North Fork Shoshone River Valley. K-S statistical analysis indicates that the three sandstones, which were sampled from the base, middle, and top of the formation, have identical age spectra, indicating that the sandstone provenance remained the same during the duration of Willwood deposition. The zircon age spectra are dominated by Archean zircons (61%), with peak ages at 3270 and 2770 Ma. These sandstones also have very early Paleoproterozoic zircons (∼2450 Ma), which likely were derived from the Tobacco Root Mountains. The final significant age peak is ∼70 Ma, which is likely associated with the Cretaceous Tobacco Root batholith. The Jim Mountain ash, which occurs at the top of the succession, just beneath the allocthonous volcanic rocks of the Heart Mountain slide, has a maximum depositional age of ∼50 Ma. Between 49–50 Ma, as Eocene volcanism in the northern Absaroka Range became more prominent, stratovolcanoes grew and disrupted sediment transport into the Absaroka basin. Lower Wapiti sandstones to the southwest show a mix of Eocene, recycled Proterozoic and Archean grains. The coeval Crandall Conglomerate, which was dismembered by the emplacement of the Heart Mountain slide in the northern Absaroka Range, has a distinct detrital zircon age spectrum. Thus these stream systems that deposited the Crandall did not share the headwaters with the streams that supplied sediment to the Absaroka basin.

Structure, Timing, and Kinematics of the Early Eocene South Fork Slide, Northwest Wyoming, USA

AbstractThe South Fork slide (SFS) is exposed over an area of 800 km2 in northwest Wyoming, and its evolution is connected in space and time to the adjacent and overlying 48.87 Ma Heart Mountain slide (HMS). The youngest rocks deformed as part of the SFS are the Eocene Willwood Formation sands and mudstones, which have a U/Pb detrital zircon youngest depositional age (TuffZirc calculation) of 51.80 +1.04/−1.08 Ma as well as a spectrum of older zircons that were eroded from the Sevier Highlands to the west and the Archean Beartooth uplift to the north (n = 379 U-Pb zircon ages). The SFS is overlain by allochthonous Paleozoic carbonate and Eocene volcanic rocks of the HMS. The SFS deformation involves shallowly plunging thin-skinned folds that trend northeast-southwest, where the slip surface could have been the top of the Jurassic Gypsum Springs Formation. Detailed mapping reveals the absence of any cleavage or joints and a plethora of minor structures unreported in any thin-skinned belt as well as the fac...

Constraints on the Emplacement Age of the Heart Mountain Slide, Northwestern Wyoming

The Heart Mountain slide is the largest terrestrial landslide deposit as yet recognized on Earth. The slide covers an area of at least 3400 km2, and the upper-plate rocks include 2–4 km of Paleozoic carbonate and Eocene volcanic rocks thrust out over 45 km of Eocene landscape. The precise age and duration of sliding is critical to emplacement models as well the slide’s effect on regional Eocene river systems. To address the timing issues, we sampled zircons from the basal fluidized layer 2 km from the slide’s breakaway fault (Silver Gate, MT) and 40-km downslope, nearer the slide’s toe (White Mountain, WY). Within this basal layer, we have identified mineral content and features consistent with a partially solidified magma. We interpret these observations to be consistent with the slide catastrophically dismembering an active magma body that mixed with the basal fault layer. The results yield remarkably similar U/Pb zircon crystallization ages at the proximal and distal locations: 48.78 ± 0.51 Ma at Silver Gate (n = 48) and 48.88 ± 0.22 Ma at White Mountain (n = 22). These zircon ages from the basal layer are tightly bracketed using various radiometric ages of Eocene Absaroka volcanic units involved in the movement phase of the slide and those deposited after emplacement, including detrital U/Pb zircon ages from the dissected Crandall Conglomerate river system. Our interpretation of the data is that the slide was catastrophically emplaced at 48.87 ± 0.20 Ma.

Vertical injectites of detachment carbonate ultracataclasite at White Mountain, Heart Mountain detachment, Wyoming

Research Article| May 01, 2012 Vertical injectites of detachment carbonate ultracataclasite at White Mountain, Heart Mountain detachment, Wyoming John P. Craddock; John P. Craddock * 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA *E-mail: Craddock@Macalester.edu. Search for other works by this author on: GSW Google Scholar Jesse Geary; Jesse Geary 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA Search for other works by this author on: GSW Google Scholar David H. Malone David H. Malone 2Department of Geography, Geology, Illinois State University, Campus Box 4400, Normal, Illinois 61790, USA Search for other works by this author on: GSW Google Scholar Author and Article Information John P. Craddock * 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA Jesse Geary 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA David H. Malone 2Department of Geography, Geology, Illinois State University, Campus Box 4400, Normal, Illinois 61790, USA *E-mail: Craddock@Macalester.edu. Publisher: Geological Society of America Received: 10 Aug 2011 Revision Received: 03 Jan 2012 Accepted: 05 Jan 2012 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (5): 463–466. https://doi.org/10.1130/G32734.1 Article history Received: 10 Aug 2011 Revision Received: 03 Jan 2012 Accepted: 05 Jan 2012 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation John P. Craddock, Jesse Geary, David H. Malone; Vertical injectites of detachment carbonate ultracataclasite at White Mountain, Heart Mountain detachment, Wyoming. Geology 2012;; 40 (5): 463–466. doi: https://doi.org/10.1130/G32734.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Carbonate ultracataclasite (CUC) is found as a veneer along the bedding plane portion of the Eocene Heart Mountain detachment (Wyoming, United States). At White Mountain, where the CUC is thickest, we report the discovery of six dikes, as much as 1 m wide, that were intruded vertically ∼120 m from the detachment into the overlying Madison and Bighorn Formations. The horizontal basal detachment and injectite material is texturally, petrographically, geochemically, and isotopically identical, containing sparse, sand- to pebble-sized andesitic clasts, various quartz-calcite melt spherules, and armored lapilli in a matrix (95%) of fine-grained calcite. The relationship of hanging wall displacement to fault gouge generation, and the presence of vertical, 120 m, fault gouge injectites, makes the Heart Mountain slide anomalous to all fault systems, especially as this fault system had only one episode of motion. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Heart Mountain and South Fork fault systems: Architecture and evolution of the collapse of an Eocene volcanic system, northwest Wyoming: COMMENT

We would like to begin by paying tribute to Ed Beutner who passed away in 2008. Ed made significant contributions to the continuing debate over one of the most enigmatic features on the surface of the Earth, the Heart Mountain slide block. Ed will be greatly missed and we wish that he were here to respond to our discussion of his most recent paper—we are certain his comments would have been insightful and of interest to all working on the Heart Mountain problem. In lieu of having Ed's response, we are confident that Tom Hauge will provide a vigorous defense picking up the mantle so aptly held by Ed. We have a number of concerns about the slow/fast model presented by Beutner and Hauge (2009). In our view, many of their arguments supporting slow or incremental movement of the Heart Mountain slide block are not supported by the evidence. In addition, we wish to correct certain erroneous statements and omissions about previous work. In reference to the “phreatomagmatic-hydraulic” model of Straw and Schmidt (1981a, b), Beutner and Hauge (2009, p. 159) state that “… Aharonov and Anders (2006) provided a refined version of the last model.” The Aharonov and Anders model is not a “refined version” of the Straw and Schmidt model as presented in their 1981a and 1981b abstracts. Straw and Schmidt (1981a) wrote: “eruptive centers exerted explosive pressure on water in the regional fracture system” and that the groundwater “exceeded normal lithostatic stress and ‘lift’ the upper plate.” Aharonov and Anders (2006) proposed that the intrusion of dikes heated trapped ground water and reduced pore space via the Skempton effect (Skempton, 1954), thus causing elevated basal pore pressure, enabling sliding of the upper plate along the extremely low 2° gradient. These two models are only …

The long runout of the Heart Mountain landslide: Heating, pressurization, and carbonate decomposition

The Heart Mountain landslide of northwestern Wyoming is the largest subaerial landslide known. This Eocene age slide slid ∼50 km along a shallow 2° slope, posing a long‐standing enigma regarding its emplacement mechanism. We suggest here a mechanism for the catastrophic emplacement of the Heart Mountain landslide that is independent of slide triggering. The mechanism is a feedback between shear heating, thermal pressurization, and thermal decomposition of carbonates at the slide shear zone. Such a feedback arises when a porous, fluid‐filled shear zone heats up because of frictional sliding. If the shear zone is confined, the generated heat leads to pore pressure rise, which in turn reduces frictional resistance to sliding, leading to acceleration. Temperatures at the shear zone quickly reach the decomposition temperature of carbonates. Since the shear zone of the Heart Mountain slide is located within a dolomite layer, it is expected that thermal decomposition of dolomite occurred within the Heart Mountain shear zone. This prediction is supported by ample field evidence for carbonate decomposition during the emplacement. Simulation of the sliding dynamics of the Heart Mountain block, accounting for feedback between shear heating, thermal pressurization, and thermal decomposition of carbonates, successfully reproduce the travel distance of the Heart Mountain block. The simulation results also predict that the maximum sliding velocity ranged between tens of meters per second to more than 100 m s−1 (depending on model assumptions) and that the duration of sliding was of the order of a few tens of minutes, in agreement with previous assessments.

The Role of Calcining and Basal Fluidization in the Long Runout of Carbonate Slides: An Example from the Heart Mountain Slide Block, Wyoming and Montana, U.S.A.

In order to understand the movement of large rock masses or allochthons on low-angle surfaces, we have studied the 3400-km2 Heart Mountain slide block of northwestern Wyoming and southwestern Montana. The Heart Mountain slide block was initiated on a 2° gradient, with its toe thrust a minimum of 45 km across an early Eocene landscape. The slide block moved on a basal layer that ranges in thickness from a few tens of centimeters to several meters. This basal layer commonly has a concrete-like appearance of rounded, mixed-lithology grains in a fine-grained carbonate matrix, and in some locations it has features similar to sedimentary deposits, including both normal and inverse grading, flow banding, turbidite-like structures, and clastic dikes containing pieces of carbonized wood. Nowhere did we observe crosscutting relationships in the basal layer or overlying clastic dikes, as would be expected from incremental or noncatastrophic emplacement. Results from cathodoluminescence and δ18O, δ13C, and 87Sr/86Sr isotopic compositions from the basal layer support a single movement event followed by hydrothermal and meteoric fluids percolating through a permeable basal layer. These observations suggest that a catastrophic movement on the detachment resulted in frictional heating at the base of the slide. When the generated heat was at least 800°C, calcining of carbonates occurred, yielding calcium and magnesium oxide powders and carbon dioxide gas. The calcium oxide powder became mechanically fluidized by the pressurized carbon dioxide gas, leading to a reduced coefficient of friction at the base of the slide, which in turn permitted the long runout on such a low-angle surface. This mechanism might be applied to explain a wide range of catastrophic sliding events where carbonate rocks are involved.

Rincon Mountain megaslide: La Conchita, Ventura County, California

The 1995 and 2005 landslides in the 200-m high sea cliff above the community of La Conchita, California, are known to be part of a reactivated Holocene prehistoric landslide. We propose that the prehistoric Holocene slide is part of a much larger, several hundred million cubic meter late Pleistocene slide complex composed of upper slumps and lower flows, informally termed as the Rincon Mountain megaslide. An approximate age of 30 ka for the Rincon Mountain landslide is derived based on a 25-m high fault scarp produced in earthflow deposits that overlie the megaslide deposits and a known rate of faulting (~ 0.8 m/ky). Geomorphic evidence for the megaslide includes a prominent 100-m high amphitheater-shaped head scarp, back-tilted landslide benches, hummocky topography, and numerous smaller landslides and earthflow deposits. Geologic evidence includes deposits composed of slide breccia with fragments of the late Pleistocene (45 ka) emergent marine platform and terrace deposits displaced several tens of meters. Isolated parts of the Rincon Mountain landslide are active in the La Conchita area, but no evidence exists that the entire slide mass is moving as a unit. Landslides from the 200-m high slope behind La Conchita will reoccur and future development on the proposed Rincon Mountain slide should be very carefully evaluated to avoid reducing slope stability and reactivation of the megaslide.

Der Totalpbergsturz bei Davos aus bodenkundlicher Sicht

Abstract. The soils of a deposition hill of an ancient mountain slide, from a serpentinitic region called Totalp, were investigated and mapped. The investigation area lies east of Wolfgang (1631 m above sea level) near Davos, Switzerland. In spite of the subalpine climate, which generates iron-humus-podsols on acid Silicates, acid brown earth was found on serpentinitic parent material. Slightly visible eluvial horizons that were found occasionally below the raw humus consisted primarily of quartzsilt, which was thought to be of aeolian origin. Mapping elucidated the boundary between two mountain slide depositions. The first slide to occur (deposition area: Drussetschawald/Lusiwald) consisted mainly of acid Silicates mixed with some serpentinite, whereas the slide that followed (Delenwald/Budlerboden) consisted of pure serpentinite. This second slide only covered the first marginally.

Analysis of Landslides during the 1978 Izu-Ohshima-Kinkai Earthquake

Using the so-called pseudo-static method, a stability analysis was made for the mountain slide that took place at Mitaka-iriya village at the time of the Izu-Ohshima-Kinkai earthquake of January 14, 1978. Undisturbed samples of volcanic clay were obtained in blocks from the exposed surface of the deposit identified to have been the sliding surface. The partially saturated clay samples were tested under consolidated undrained conditions using the triaxial test equipment. Dynamic axial stresses with irregular time histories were applied to the specimens in combination with statically sustained axial stresses to determine the soil strength under the conditions simulating in-situ states of stress during the earthquake. The results of the tests were expressed in terms of the Mohr-Coulomb type failure criterion which showed that, while the angle of internal friction remained almost unchanged, the cohesion component in irregular loading increased above values obtained in the static loading. Using the strength parameters thus determined, a pseudo-static analysis was made to check the stability of the soil masses that had actually slid during the 1978 earthquake. The maximum horizontal acceleration required to cause the slide was computed. The computed accelerations were shown to cover a range between 400 and 500 gals which is consistent with the range estimated by other investigators on the basis of overturning of tombstones in the vicinity of the slide area.

An Afternoon of Pocket Billiards by Henry Taylor (review)

part of this well-organized work. In addition to formal lexical repetitions and the obvious lyricism of his Whitmanesque "song of myself," Mard's poem exhibits complex phonological patterning which constitutes the basis of the poem's recognized melodic construction. Davison's presentation of phonological patterning is a unique contribution to die study of poetic musicality. Each stanza is printed in published form. On a facing page appears a line-by-line analysis of phonemic patterns for each stanza. In each line of poetry Davison highlights the repetition of phonemic material in red characters. Such a graphic representation of sound patterning facilitates the reader's comprehension of Mard's virtuosity. Below each stanza, there appears a prose discussion of the sound patterns in blue. Here, Davison indicates only the presence of patterning without reading into die patterns any emotional or conceptual significance. Rather, he invites the reader to discover his own impressions aroused by the interplay of phonic and conceptual aspects of the poem. Perhaps the most appealing feature of the book is its accurate depiction of musical qualities without the distraction of statistical data. The text is, in a sense, a handbook which can easily serve as a model for future studies of Modernist poetry. It is fitting, then, that the work captures in a pleasing visual approach, the sonorous experiments in one of Modernism's sonatas and symphonies in verse. HOWARD M. FRASER Howard M. Fraser teaches at the College of William and Mary, Williamsburg , Virginia. AN AFTERNOON OF POCKET BILLIARDS BY HENRY TAYLOR (Salt Lake City: University of Utah Press, 1975. x+78 pages, $6.00.) With this most recent collection, An Afternoon of Pocket Billiards, Henry Taylor continues to develop a poetic stance that marks him as a unique, eclectic writer whose concern for form and content is at once academic as well as popular: he can speak to all of us. An Afternoon of Pocket Billiards offers a variety of styles and themes; no two poems are the same just as no two billiard shots are the same. The voice shifts from personal, almost confessional, as in "To Hear My Head 102BOOK REVIEWS Roar," to a character mask, such as "The New York Poet." Mr. Taylor is skilled at both. In "Goodbye to the Old Friends," an elegant, moving sestina , he speaks warmly and philosophically; the language is clear, precise; the voice is personal, yet not exclusive of the reader. In "Snapshot" Mr. Taylor again shows his remarkable talent for developing unforgettable characters , especially in humorous situations. Though mosdy recognized as a "Southern" poet by the setting of many of his poems, Mr. Taylor uses the Western experience of place in several of the poems in An Afternoon of Pocket Billiards. "Storm Mountain Slide Area" shows a shift of form to enhance subject, idea, and place — more of an open form, yet with a strong sense of control and boundary. And in "Buildings and Grounds" the Southerner is placed in the West, in Salt Lake City, with hilarious results: I will station an iron jockey by die driveway to stare back into die pitiless eyes of my neighbors' pink plastic flamingoes, I will keep a Tennessee Walking Horse in die garage and give him a foxhound for company, I will stand out in front in a white linen suit surveying my plantation, I will plant a magnolia tree. If one seeks in poetry a philosophical or mythic experience, An Afternoon of Pocket Billiards offers "Burning a Horse": Burning at last, die horse was blackening and shrinking into the tall meadow grass; and then, before us, there, from coals that had caught hold in the horse's bones, we saw a horse, made whole, with heavy flesh and shining skin, rippling against the pull, rising from the grass around the dying fire . . . Or if one seeks the clear, strong, simple expression of the human condition, Mr. Taylor gives "Breakings": So nothing changes, nothing stays the same, and I have returned from a broken home alone, to ask for a job breaking horses. ROCKY MOUNTAIN REVIEW103 I watch a colt on a long line making tracks in dust, and think of the kinds of breakings there are...