Sevier Desert Research Articles

Extensional collapse along the Sevier Desert reflection, northern Sevier Desert basin, western United States

Extensional collapse along the Sevier Desert reflection, northern Sevier Desert basin, western United States

Large-Rock Avalanche Deposits, Eastern Basin and Range, Utah: Emplacement, Diagenesis, and Economic Potential

Large-rock avalanche deposits are a common component of the basin fill within the extensional tectonic terrain of the Basin and Range; these deposits recently have been interpreted to host oil and gas within the Railroad Valley area of eastern Nevada. Large blocks of brecciated bed rock are a primary component of these avalanche deposits and are potentially excellent oil and gas reservoirs. Our work provides further insight into the emplacement and economic potential of these deposits. Exposed large-rock avalanche deposits of the Miocene Oak City Formation on the western margin of the Canyon Range, Utah, contain coherent breccia blocks up to 3.5 km long, 1 km wide, and 200 m thick. These deposits were derived from the near-vertical dipping bed rock of the adjacent Canyon Range and now are exposed as much as 5.5 km from the range front within the Sevier Desert basin. Emplacement was relatively rapid, as indicated by three well-developed breccia facies within the carbonate breccia blocks. Stratigraphically, from the base the facies include (1) matrix-rich breccia, (2) jigsaw breccia, and (3) crackle breccia. The deposits were cut and segmented by a series of syndepositional normal faults that developed during late Miocene and post-Miocene extension. Primary porosity w s reduced by cement soon after burial. Cathodoluminescence cement patterns indicate that initially the basinward breccia blocks were more deeply buried relative to the water table than the breccia blocks proximal to the Canyon Range. After initial cementation, the basinward blocks were uplifted relative to the water table. Secondary porosity approaches 8% in the carbonate blocks and is greater than 14% within the jigsaw breccia. The size and porosity of these breccia blocks indicate their potential as reservoir targets.

Western frontal fault of the Canyon Range: Is it the breakaway zone of the Sevier Desert detachment?: Comment and Reply

Western frontal fault of the Canyon Range: Is it the breakaway zone of the Sevier Desert detachment?: Comment and Reply

Is the Sevier Desert reflection of west-central Utah a normal fault?: Comment and Reply

Is the Sevier Desert reflection of west-central Utah a normal fault?: Comment and Reply

Western frontal fault of the Canyon Range: Is it the breakaway zone of the Sevier Desert detachment?

Geologic evidence developed from surface exposures demonstrates that the western frontal fault of the Canyon Range is a major structure representing the eastern breakaway zone of the Sevier Desert detachment. The western frontal fault of the Canyon Range east of Delta, Utah, is a north-trending, west-dipping, low-angle (18 °–24 ° ) normal fault that juxtaposes syntectonic conglomerates and large-rock avalanches of the Miocene Oak City Formation against footwall rocks that have been ductilely, cataclastically, and brittlely deformed. The Oak City strata dip variably to the east; dips are shallow in eastern outcrops (5 ° –15 ° ), steeper in central outcrops (20 ° –60 ° ), and shallow in the western outcrops (10 ° –20 ° ). In eastern exposures, the shallow dips of the Oak City Formation (5 ° –15 ° ) and the acute angle of 20 ° –35 ° between the western frontal fault and Oak City units limit past rotation of the fault to ≤15 ° . The systematic variation in the dip of Oak City units from east to west suggests that the western frontal fault probably flattens beneath present Oak City outcrops, linking the fault to the shallow reflector seen in the COCORP (Consortium for Continental Reflection Profiling) Utah line 1 seismic line beneath the westernmost outcrops of the Oak City Formation. Upper plate movement is constrained by Oak City clast compositions and rock-avalanche lithologies, fault geometry, and lower plate reconstruction to a maximum of 6–7 km since Oak City syntectonic deposition at ∼12–13 Ma. Maximum upper plate displacement for the entire Sevier Desert detachment cannot be determined from these breakaway-zone exposures.

Fault finding in Utah puts longstanding theories on the line

Imagine that the very fault zone a body of geological theory sprang from turns out not to exist. Besides raising some eyebrows and perhaps some ire, such a finding may well challenge the reigning paradigm that defines a whole class of normal faults, where the upper block moves downward with respect to the lower block.Well, that's exactly what a duo of geologists from Columbia University's Lamont‐Doherty Earth Observatory claim about a fault in the Sevier Desert in west‐central Utah: It frankly doesn't exist, say Mark Anders and Nicholas Christie‐Blick.

Is the Sevier Desert reflection of west-central Utah a normal fault?

A prominent west-dipping reflection that can be traced in seismic-reflection profiles over an area of 7000 km 2 beneath the Sevier Desert basin of west-central Utah is generally referred to as the Sevier Desert detacbment and is widely regarded as one of tbe best examples of an upper-crustal low-angle normal fault. The absence of evidence for fault-related deformation in drill cuttings and core from two industry boreholes that intersect this feature casts doubt on the fault interpretation. The existing interpretation is based mainly on the observation that high­ angle normal faulting is restricted largely to Tertiary sedimentary and volcanic rocks above the reflection. An alternative explanation is tbat the bigh-angle faults are related to the withdrawal of early deposited lacustrine salt, which even today is as much as 2 km thick. Reevaluation of the seismic data suggests that the Sevier Desert reflection consists of two spatially and genetically distinct segments: a shallow segment here interpreted as an unconformity between Paleozoic and Tertiary strata and a fortuitously aligned deeper segment that is traceable to mid- and lower­ crustal levels and that appears to represent a thrust fault related to the Cretaceous Sevier orogeny.

Case of the phantom foredeep: Early Cretaceous in west-central Utah

A reconstruction of the structure in west-central Utah shows that a major foredeep with sedimentary deposits possibly as thick as 6 km (now eroded) probably existed at the present site of the Sevier Desert during Early Cretaceous time and conceivably during Late Jurassic time. Concurrent emplacement and erosion of the Canyon Range thrust sheet provided the load and sediment, much like the Willard-Paris thrust sheet did for the better documented Early Cretaceous foredeep in northern Utah and eastern Idaho. The onset of major thrusting in western Utah may have been as early as Callovian or as late as Albian, a 50 m.y. time span.

Cenozoic extension and evolution of the Sevier Desert Basin, Utah, from seismic reflection, gravity, and well log data

Seismic reflection profiles (∼550 km), gravity data, and well log information from west central Utah, have been interpreted to reveal an asymmetric west‐dipping Cenozoic basin beneath the Sevier Desert. The basin is underlain by a 10°–12° westward dipping, slightly undulatory, detachment surface, the Sevier Desert detachment. Finite difference synthetic seismograms were used to constrain the geometry of the interpreted reflectors in the basin. A two‐dimensional, one‐layer gravity inversion of three gravity profiles in the basin, using a 0.35 g/cm³ density contrast, corroborated the structure determined from the seismic interpretations. Physical properties and lithological data from eight wells were interpreted to acquire velocity‐depth and density‐depth functions and to obtain stratigraphic control. A minimum width of the Sevier Desert detachment of 80 km to 130 km and an area of 5600 km² to 9100 km² was estimated primarily from the reflection data. On the basis of geological and geometrical information, we estimated a minimum post‐middle Pliocene extension of 2.5 km to 3.5 km at a rate of 0.6 mm/yr to 0.8 mm/yr, corresponding to a strain rate of 2.7 10−16 s−1 to 3.5 10−16 s−1. Up to 4.0±0.6 km of predominantly post Eocene lacustrine and fluvial sediments overlie the Sevier Desert detachment including a well‐defined reflection that is interpreted as a middle Pliocene 4.2 m.y. basaltic flow that is present throughout the central and western part of the basin. The geometry of the middle Pliocene reflector, a variable ∼300 to ∼1500 m post‐middle Pliocene offset of a ∼40° eastward dipping western basin‐bounding fault, and up to ∼6 km east and west stepping of the generally north‐trending western basin‐bounding fault, suggests a complex late Tertiary deformational history. The varying deformational pattern may be a response to a changing geometry of the underlying detachment surface.

Late Pleistocene basaltic ash and volcanic eruptions in the Bonneville basin, Utah

Microprobe analyses of glass and radiocarbon dating of samples associated with three basaltic volcanic ashes in the deposits of Lake Bonneville make the ashes useful stratigraphic markers for correlation within the Bonneville basin. Two of the ashes were derived from tuff cones (Pavant Butte and Tabernacle Hill) that erupted into Lake Bonneville in what is now the Black Rock Desert of south-central Utah. Near Kanosh, Utah, the Pavant Butte ash is interbedded with barrier-beach lagoon marl that is slightly less than 16,000 yr old. Five radiocarbon dates on carbonate materials stratigraphically associated with the ash elsewhere in the Sevier Desert average 15,300 yr B.P. Lake Bonneville was in its transgressive phase, about 15 m below the Bonneville Shoreline, when the Pavant Butte eruption began. At the Tabernacle Hill tuff cone, a basalt flow that has pillows, wave-rounded cobbles, and tufa on its outer margins was erupted into Lake Bonneville shortly after the tuff cone at or near the Provo Shoreline. The Tabernacle Hill tuff cone and basalt flow are older than a radio-carbon date of about 14,300 yr B.P. on tufa collected from the outer margin of the basalt flow, but younger than the Bonneville Flood at about 14,500 yr B.P. The third ash, informally termed the Thiokol ash, has been found interbedded with Lake Bonneville deposits in two exposures in northern Utah and in sediment cores from the Great Salt Lake. It is about 25,000 yr old, and may have been erupted from a volcanic field on the northwest shore of Great Salt Lake or from the Snake River Plain. Microprobe analyses of glass from samples of the Black Rock Desert ashes show them to have similar chemical compositions, but glass from Tabernacle Hill can be distinguished from Pavant Butte glass by its higher concentrations of CaO and P 2 O 5 . Systematic differences in chemical composition between samples of Pavant Butte glass can be explained by comagmatic processes. Thiokol glass has less SiO 2 , AI 2 O 3 , MgO, and Na 2 O but greater total iron and P 2 O 5 than do the Black Rock Desert glasses.

Late Pleistocene and Holocene lake fluctuations in the Sevier Lake basin, Utah, USA

Sevier Lake is the modern lake in the topographically closed Sevier Lake basin, and is fed primarily by the Sevier River. During the last 12000 years, the Beaver River also was a major tributary to the lake. Lake Bonneville occupied the Sevier Desert until late in its regressive phase when it dropped to the Old River Bed threshold, which is the low point on the drainage divide between the Sevier Lake basin and the Great Salt Lake basin. Lake Gunnison, a shallow freshwater lake at 1390 m in the Sevier Desert, overflowed continuously from about 12000 to 10000 yr B.P., into the saline lake in the Great Salt Lake basin, which continued to contract. This contrast in hydrologic histories between the two basins may have been caused by a northward shift of monsoon circulation into the Sevier Lake basin, but not as far north as the Great Salt Lake basin. Increased summer precipitation and cloudiness could have kept the Sevier Lake basin relatively wet.

Conjunctive Use in Sevier River System, Utah

The Sevier Desert and Sanpete Valley are two subbasins within the Sevier River System in south‐central Utah in which groundwater is extensively used in conjunction with surface water for irrigation. The conjunctive use has developed more by accident than by deliberate planning. The surface‐water supply in the two areas was basically developed by 1920. Severe droughts in the early 1920s and early 1950s focused attention on groundwater development as a supplemental supply. Well construction gradually increased between the mid‐1940s and 1960 in both basins until the problems of water rights and overdraft essentially halted further development. Groundwater pumpage in both the Sevier Desert and Sanpete Valley has fluctuated inversely with the available surface‐water supplies and climatic conditions. Overdraft has not occurred and the sustained yield of the groundwater basins seems to have been established.

History of Cenozoic Extension in Central Sevier Desert, West-Central Utah, from COCORP Seismic Reflection Data: REPLY

COCORP seismic reflection data show that Cenozoic extension beneath the Sevier Desert has had movement along a major, west-dipping surface. Reflections were obtained from several stratigraphic zones of known age within the Sevier Desert basin. The geometric relationships of these zones indicate that extension has occurred in at least two stages. A large first stage of movement (20-30 km or 12-18 mi) began after the middle Oligocene (26-28 Ma) and continued into the Miocene. This activity was followed by a probably short period of quiescence and erosion. A later episode of movement of smaller proportions (< 8 km or < 5 mi) began during or after the eruption of a middle Pliocene (4.2 Ma) basalt. This later stage is still active, as indicated by fault scarps which offs t recent sediments in the basin. The record of extension within the Sevier Desert reflects the history of movement along the underlying Sevier Desert detachment, a major, low-angle normal fault that has been traced over 70 km (43 mi) perpendicular to strike and to depths of 12-15 km (7.5-9.3 mi). The record of displacement along the Sevier Desert detachment may have implications for the general history of extension in the Basin and Range Province.

Relationship of late Quaternary fault scarps to subjacent faults, eastern Great Basin, Utah

Research Article| May 01, 1984 Relationship of late Quaternary fault scarps to subjacent faults, eastern Great Basin, Utah Anthony J. Crone; Anthony J. Crone 1U.S. Geological Survey, Box 25046, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Samuel T. Harding Samuel T. Harding 1U.S. Geological Survey, Box 25046, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information Anthony J. Crone 1U.S. Geological Survey, Box 25046, Denver, Colorado 80225 Samuel T. Harding 1U.S. Geological Survey, Box 25046, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1984) 12 (5): 292–295. https://doi.org/10.1130/0091-7613(1984)12<292:ROLQFS>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Anthony J. Crone, Samuel T. Harding; Relationship of late Quaternary fault scarps to subjacent faults, eastern Great Basin, Utah. Geology 1984;; 12 (5): 292–295. doi: https://doi.org/10.1130/0091-7613(1984)12<292:ROLQFS>2.0.CO;2 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 High-resolution seismic reflection profiles in the Sevier Desert basin in western Utah help clarify the relationship between some late Quaternary fault scarps and subjacent faults. A profile crossing the Clear Lake fault confirms that Holocene(?) displacement has occurred on a high-angle normal fault that is directly connected to the Sevier Desert detachment. If detachment faults can act as seismogenic source zones, then the young movement on the normal fault suggests that the Sevier Desert detachment may be unstable and perhaps the source of future earthquakes. A swarm of late Quaternary scarps near the Drum Mountains overlies a network of steep faults in competent rock that have had recurrent movement. Many subsurface faults are not associated with scarps, suggesting that selected faults ruptured during the last episode of surface faulting. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Cenozoic and Mesozoic structure of the eastern Basin and Range province, Utah, from COCORP seismic-reflection data

COCORP seismic-reflection data collected from the eastern Basin and Range in west-central Utah provide information on Cenozoic extensional tectonics, Mesozoic thrusting, and their interrelationships. Those data show a series of remarkably continuous, low-angle reflectors that extend more than 120 km perpendicular to strike and can be traced as deep as 15–20 km. Over that distance, none of these events are significantly cut by any high-angle normal faults. A major detachment beneath the Sevier Desert can be traced from a surface zone of normal faulting to a depth of 12–15 km, with a regional apparent westward dip of 12°. Tentative correlation of upper- and lower-plate events suggests 30–60 km of extensional displacement on this detachment. Whether this structure is a reactivated Mesozoic thrust is uncertain. West-steepening splays off the end of the detachment reach depths of 20 km and may represent a major Mesozoic ramp or zones of distributed ductile shearing during extension. Some events are interpreted to be Mesozoic thrusts, of which at least one (beneath the House Range) has been reactivated during the Cenozoic. The Snake Range decollement dips gently east and has a sense of Cenozoic displacement opposite to that of other Cenozoic detachments farther east. Deep events are most numerous beneath the east side of the Sevier Desert where they occur to depths of 30 km, at the top of or perhaps partly within the anomalously low velocity upper mantle.

Upper Oligocene Evaporites in Basin Fill of Sevier Desert Region, Western Utah

The basin fill beneath the Sevier Desert of western Utah contains evaporites of late Oligocene age that were deposited in a broad closed basin. All of the basin fill penetrated by the Gulf Oil 1 Gronning (2,458 m TD), one of only three deep holes in the basin, contains abundant volcanic detritus and its alteration products of Cenozoic age, when volcanism was intense in western Utah. Fission-track dating of tuffaceous sandstone, interbedded with evaporite minerals and representative of sandstone in the lower formations penetrated, yields ages of 26 to 28 m.y.; concordance of ages indicates no thermal resetting. Fossil pollen from mudstone in the evaporite-bearing strata includes forms no older than late Oligocene, in good agreement with the fission-track ages. Thus the age of the evaporites, and of all the basin fill penetrated by drilling, is late Oligocene and younger; previous work had assigned them ages ranging from Triassic to Eocene. Evaporite-bearing rocks were deposited during late Oligocene time in a broad closed basin under arid or semiarid conditions much like those of the Great Basin today. Anhydrite is present throughout approximately 900 m of volcaniclastic rocks in the lower part of the section cut by the Gulf hole, and more than 1,500 m of anhydrite and halite is present in possibly equivalent strata in the nearby Argonaut dry hole. Fossil pollen from anhydrite-bearing rocks in the Gulf hole are indicative of an arid to semiarid flora, including plants similar to Mormon tea and possibly saltbush or buffalo berry. Evaporite minerals formed in the basin during dry periods; tuff was erupted from nearby volcanic centers, reworked by water, and deposited in the basin.

Pumping from wells on the floor of the Sevier Desert, Utah

Data collected at the Topaz Relocation Center provide an excellent record of the development and subsequent disappearance of a cone of depression caused by pumping. This Center occupied temporarily an area of natural ground‐water discharge on the floor of the Sevier Desert in west‐central Utah. Water for a population of 6500 was pumped from artesian wells which tapped aquifers of sand. Overlying these sand beds are lake‐bed sediments too impermeable to yield water to wells, but apparently permeable enough to permit slow upward movement of water from the artesian aquifers. The water table is near the surface, and there is natural discharge by evapotranspiration, accumulation of “alkali” in the soil, and a need for drainage of irrigated lands. The wells were abandoned when the Relocation Center was closed, apparently because these handicaps were so great that the ground water could not be used profitably for irrigation.