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Articles 1 - 30 of 39
Full-Text Articles in Geology
New Surficial Geologic Mapping In Kentucky (2021-2022), Matthew Massey, Antonia Bottoms, Max Hammond Iii, Ann Hislop, Meredith Swallom, Michele M. Mchugh
New Surficial Geologic Mapping In Kentucky (2021-2022), Matthew Massey, Antonia Bottoms, Max Hammond Iii, Ann Hislop, Meredith Swallom, Michele M. Mchugh
Research Data--KGS
New surficial geologic mapping was performed in nine new 7.5-minute quadrangles in Hardin, Meade, Breckinridge, Grayson, Hart, and Larue Counties, Kentucky.
Quadrangles include Big Clifty, Big Spring (Hardin county only), Custer (Hardin County only), Flaherty, Madrid (Hardin county only), Millerstown, Summit, Tonieville (Hardin county only), and Upton.
Mapping data for each of the nine quadrangles is captured in a ZIP file that contains an ESRI geodatabase and associated FGDC-compliant metadata files (.xml).
The geodatabase is a relational geodatabase of spatial and non-spatial data that conforms to "GeMS (Geologic Map Schema)--a standard format for digital publication of geologic maps", available at …
Size, Timing, And Landscape Impacts Of Glacial Lake Outburst Floods In The Channeled Scabland Of Eastern Washington, Usa, Karin E. Lehnigk
Size, Timing, And Landscape Impacts Of Glacial Lake Outburst Floods In The Channeled Scabland Of Eastern Washington, Usa, Karin E. Lehnigk
Doctoral Dissertations
Extreme floods have dramatically altered landscapes on Earth and Mars through bedrock erosion, sediment deposition, and canyon formation. The Channeled Scabland of the Columbia Plateau in eastern Washington, USA, is perhaps the most striking example of such a landscape, where outburst floods from an ice-dammed glacial Lake Missoula eroded immense canyons and transported large volumes of sediment during the late Pleistocene. Despite advances in numerical modeling and geochemical exposure dating methods, it has remained a challenge to untangle the complex interactions between floodwater, bedrock, and glacial ice to link the size of a flood with its impact on the landscape. …
Characterization Of Quaternary Stratigraphy In The Mississippi Sound To Evaluate The Influence Of Geologic Heterogeneity On Submarine Groundwater Transport And Discharge, Zachary Peoples
Theses and Dissertations
Submarine Groundwater Discharge (SGD) through seafloor sediments is gaining recognition as an important component of coastal water quality. Stratigraphic features creating geologic heterogeneity, such as incised paleochannels, may influence preferential pathways for SGD. The central Mississippi Sound is underlain by paleochannels that were incised into Pleistocene sediments while the area was subaerially exposed during the last glacial maximum and are now buried by transgressive Holocene deposits. In this thesis, newly collected chirp, previously published seismic reflection, and sediment core data are used to characterize the three-dimensional structure of the Holocene-Pleistocene contact. Results indicate that Pleistocene paleochannels cross-cut the study area, …
Gravel Geology And Muskoxen Paleontology Of A Late Pleistocene Fossil Site In Saltville, Virginia, Nickolas A. Brand
Gravel Geology And Muskoxen Paleontology Of A Late Pleistocene Fossil Site In Saltville, Virginia, Nickolas A. Brand
Electronic Theses and Dissertations
Two distinct studies within the Saltville Valley of southwestern Virginia revealed insights into local Pleistocene geology and paleontology. A variety of analytical techniques were applied to gravel deposits within the paleontological site of SV-5/7 that revealed this unit is very poorly sorted, has a subangular matrix, and contains significant components of silt and sand in addition to rounded cobbles. These results suggest that rather than being deposited by fluvial processes as previously suggested, these gravels were likely the result of one or many debris flows. Additionally, the identity of fossil muskoxen from Saltville was reassessed using cranial and dental material. …
Geomorphic History Of The Grand Staircase Region Of The Colorado Plateau: Understanding Arroyo Cut-Fill Dynamics, Erosion Rates, And Wildfire, Kerry E. Riley
Geomorphic History Of The Grand Staircase Region Of The Colorado Plateau: Understanding Arroyo Cut-Fill Dynamics, Erosion Rates, And Wildfire, Kerry E. Riley
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Most streams in the southwestern United States do not flow all year, and given their delicate balance of sediment and water flow, they are sensitive to climate change. At the turn of the 20th century, many streams in the Southwest rapidly incised into their floodplains, forming arroyos with a channel entrenched into near-vertical channel banks mostly composed of sand and mud. This dissertation investigates past changes in watersheds draining the Grand Staircase region in southern Utah with the goal of understanding how changes in climate and sediment influence these types of streams. Results show sediment supply is highly variable across …
Studies Of Quaternary Depositional Systems Of The Coastal Plain And Inner Continental Shelf Along The Georgia Bight: South Carolina And Georgia, U.S.A., Joshua H. Long
Electronic Theses and Dissertations
The Quaternary stratigraphy of the continental shelf offshore of South Carolina consists of stratigraphic units deposited in coastal plain, shallow marine, and shelfal environments bound by composite erosional surfaces that developed in response to numerous glacioeustatic cycles and overprinted by regional uplift. These units are commonly distributed laterally rather than stacked vertically, a function of the long-term, low shelf gradient and the resulting lack of accommodation. This study integrates high-resolution geological and geophysical data sets acquired offshore and onshore with existing data onshore into a comprehensive conceptual model describing the Quaternary geologic evolution of the coastal plain and continental shelf …
Sedimentology And Stratigraphy Of Core Stl14: An Early Pleistocene-To-Present Paleoclimate Archive From Stoneman Lake, Arizona, Spencer Staley
Sedimentology And Stratigraphy Of Core Stl14: An Early Pleistocene-To-Present Paleoclimate Archive From Stoneman Lake, Arizona, Spencer Staley
Earth and Planetary Sciences ETDs
An 80 m lacustrine sediment core (STL14) from Stoneman Lake, Coconino County, Arizona, contains a sedimentary sequence of at least 1.5 million years, chronicling the complete history of basin infill and recording an extensive and high-resolution archive of climatic and hydrologic fluctuations. Lake levels in this small, internally-drained catchment are sensitive to changes in regional hydrologic balance. Consistent groundwater inflow, even during regionally dry episodes in the lake’s history, has prevented complete desiccation of the lake and sustained continuous lacustrine deposition except for one soil horizon. Multiproxy analysis of sedimentological indicators including lithofacies, color, wet bulk density, magnetic susceptibility, preliminary …
Miocene-Quaternary Deformation Along The Central Maynard Lake Fault, Pahranagat Shear Zone, Nevada, Alexander Peck
Miocene-Quaternary Deformation Along The Central Maynard Lake Fault, Pahranagat Shear Zone, Nevada, Alexander Peck
UNLV Theses, Dissertations, Professional Papers, and Capstones
The left-lateral Pahranagat shear zone (PSZ) and Caliente-Enterprise zone (CEZ) exist at the boundary between two sub-provinces, the Northern (NBR) and Central Basin and Range (CBR). The PSZ contains three major ENE striking sinistral faults, including the Maynard Lake fault (MLF), which is the longest fault and marks the southern boundary of the zone. The PSZ has been suggested to be a transfer zone, but little is known about the structures along these major faults that are involved in strain transfer. These left-lateral systems exist within the Central Nevada seismic belt which has experienced significant earthquakes in recent history. Possible …
Geologic Mapping Of The Bronson North And Bronson South 7.5-Minute Quadrangles, Branch County, Michigan, Karl John Backhaus
Geologic Mapping Of The Bronson North And Bronson South 7.5-Minute Quadrangles, Branch County, Michigan, Karl John Backhaus
Masters Theses
This study contributes to a better understanding of the glacial history of southwest Michigan through detailed surficial geologic and bedrock topography mapping within the Bronson North and Bronson South Quadrangles in Branch County, Michigan. This project was supported during the summer of 2017 by the USGS EDMAP program in conjunction with the Michigan Geological Survey. Hand-auger borings, grain size analysis tests, passive seismic depth-to-bedrock measurements, and ground penetrating radar transects were collected for this study. There are 350 feet of bedrock relief from west to east across the quadrangles, including a bedrock cuesta of Mississippian Coldwater Shale. This cuesta underlies …
Evaluation Of Simple Geochemical Indicators Of Aeolian Sand Provenance: Late Quaternary Dune Fields Of North America Revisited, Daniel R. Muhs
Evaluation Of Simple Geochemical Indicators Of Aeolian Sand Provenance: Late Quaternary Dune Fields Of North America Revisited, Daniel R. Muhs
United States Geological Survey: Staff Publications
Dune fields of Quaternary age occupy large areas of the world's arid and semiarid regions. Despite this, there has been surprisingly little work done on understanding dune sediment provenance, in part because many techniques are time-consuming, prone to operator error, experimental, highly specialized, expensive, or require sophisticated instrumentation. Provenance of dune sand using K/Rb and K/Ba values in K-feldspar in aeolian sands of the arid and semiarid regions of North America is tested here. Results indicate that K/Rb and K/Ba can distinguish different river sands that are sediment sources for dunes and dune fields themselves have distinctive K/Rb and K/Ba …
Origins Of Late- Pleistocene Coastal Dune Sheets, Magdalena And Guerrero Negro, From Continental Shelf Low-Stand Supply (70-20 Ka), Under Conditions Of Southeast Littoral- And Eolian-Sand Transport, In Baja California Sur, Mexico, Curt D. Peterson, Janette Murillo-Jiminez, Errol Stock, David M. Price, Steve W. Hostetler, David Percy
Origins Of Late- Pleistocene Coastal Dune Sheets, Magdalena And Guerrero Negro, From Continental Shelf Low-Stand Supply (70-20 Ka), Under Conditions Of Southeast Littoral- And Eolian-Sand Transport, In Baja California Sur, Mexico, Curt D. Peterson, Janette Murillo-Jiminez, Errol Stock, David M. Price, Steve W. Hostetler, David Percy
Geology Faculty Publications and Presentations
Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morpho-stratigraphic sections (∼2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m …
Surface Offset And Slip Rates For The Winter Rim Fault System In The Summer Lake Basin, Oregon, Jennifer Hall
Surface Offset And Slip Rates For The Winter Rim Fault System In The Summer Lake Basin, Oregon, Jennifer Hall
All Master's Theses
The 66-km-long Winter Rim Fault (WRF) system, located in the northwestern Basin and Range Province, encompasses several Holocene fault scarps within the Summer Lake basin that include the WRF system, a normal fault divided into three segments: Slide Mountain (SMF), Winter Ridge, and Ana River (ARF), and the newly-mapped Thousand Springs fault (TSF). The current least-compressive stress field is oriented ~264° (Crider, 2001). The USGS estimates a slip rate of 0.43 mm/yr, earthquake magnitudes of 6.5-7.19, and recurrence interval of 3.1 ka (Crone et al., 2009). However, these estimates are only based upon ARF and the unfavorably slip-oriented SMF. With …
Three-Dimensional Geological Model Of Quaternary Sediments In Walworth County, Wisconsin, Usa, Jodi Jau, Jason F. Thomason, David H. Malone, Eric Wade Peterson
Three-Dimensional Geological Model Of Quaternary Sediments In Walworth County, Wisconsin, Usa, Jodi Jau, Jason F. Thomason, David H. Malone, Eric Wade Peterson
Eric Wade Peterson
Modeling The Sediment Fill Of The Uppertroy Pre-Glacial Bedrock Valley,Mchenry County, Llinois, Usa, Jodi Lau, Jason F. Thomason, David H. Malone, Eric Wade Peterson
Modeling The Sediment Fill Of The Uppertroy Pre-Glacial Bedrock Valley,Mchenry County, Llinois, Usa, Jodi Lau, Jason F. Thomason, David H. Malone, Eric Wade Peterson
Eric Wade Peterson
Dating Late Quaternary Alluvial Fills In The Platte River Valley Using Optically Stimulated Luminescence Dating, Jacob C. Bruihler
Dating Late Quaternary Alluvial Fills In The Platte River Valley Using Optically Stimulated Luminescence Dating, Jacob C. Bruihler
Department of Geography: Dissertations, Theses, and Student Research
Alluvial fills underlying the Platte River Valley in Nebraska record the geologic history of the Platte River in the late Quaternary. This study investigated the alluvium underlying the valley near the cities of North Platte and Kearney, Nebraska. Data obtained from sediment cores drilled in the alluvial deposits was used to investigate the changes in Platte River dynamics on a glacial – interglacial timescale. Optically Stimulated Luminescence (OSL) dating was used to determine burial ages of recovered sediments and to quantify the thicknesses of the late Pleistocene and Holocene alluvial fills at each study area. Our geochronology depicts considerable differences …
Preservation And Sediment Cycling Beneath "Ghost Glaciers": How Cold-Based Ice Dictates Arctic Landscape Evolution, Lee Corbett
Preservation And Sediment Cycling Beneath "Ghost Glaciers": How Cold-Based Ice Dictates Arctic Landscape Evolution, Lee Corbett
Graduate College Dissertations and Theses
Constraining past episodes of climate change and glacial response is critical for understanding future impacts of climate change, especially in the high latitudes where warming is expected to be rapid and most of Earth's glaciers exist. Many studies of past glacier size utilize rare isotopes called cosmogenic nuclides to perform surface exposure dating. Since most areas of Earth's surface that were previously glaciated were covered by erosive ice, which stripped away pre-existing cosmogenic nuclides, surface exposure dating yields the timing of the most recent deglaciation. However, in some high latitude areas where glacial ice is cold-based and non-erosive (so-called 'ghost …
Stratigraphy And Extent Of The Pearl-Ashmore Aquifer, Mchenry County, Il, Usa, Drew C. Carlock, David H. Malone, Jason F. Thomason, Eric Wade Peterson
Stratigraphy And Extent Of The Pearl-Ashmore Aquifer, Mchenry County, Il, Usa, Drew C. Carlock, David H. Malone, Jason F. Thomason, Eric Wade Peterson
Eric Wade Peterson
Ocean Forcing Of Quaternary East Antarctic Ice Sheet Evolution: An Ice-Proximal Sedimentary Perspective, Michelle E. Guitard
Ocean Forcing Of Quaternary East Antarctic Ice Sheet Evolution: An Ice-Proximal Sedimentary Perspective, Michelle E. Guitard
USF Tampa Graduate Theses and Dissertations
Antarctica and the Southern Ocean play a critical role in Earth’s climate system. Antarctica’s ice sheets contain enough ice to raise global sea level by ~58 m, and the Southern Ocean distributes climate signals and nutrients to the major ocean basins and the deep ocean. Antarctica’s largest ice sheet, the East Antarctic Ice Sheet (EAIS), was considered stable compared to those in West Antarctica and the Antarctic Peninsula because it was thought to be grounded above sea level. However, subglacial topography now reveals vast submarine basins and measurements of ice velocity in the Pacific sector indicate marine-terminating outlet glacier thinning …
Glacial Stratigraphy Of The Ridge River Area, Northern Ontario: Refining Wisconsinan Glacial History And Evidence For Laurentide Ice Streaming, Maurice Nguyen
Glacial Stratigraphy Of The Ridge River Area, Northern Ontario: Refining Wisconsinan Glacial History And Evidence For Laurentide Ice Streaming, Maurice Nguyen
Electronic Thesis and Dissertation Repository
Detailed field studies of Quaternary sediments were undertaken during the summer of 2012 in the remote Ridge River area of the Hudson Bay Lowland. Grain size, carbonate, stone lithologic analyses and stratigraphic relations of 31 sites were compiled and revealed two main till units likely deposited by the advance and retreat of the Laurentide Ice Sheet. Based grain size, carbonate, and lithologic data the tills cannot be distinguished and the abundance of distantly transported stones suggests rapid flux of glacial debris from Quebec over the Hudson Platform to the study area. Evidence from stone fabrics, striae, and glaciotectonic structures in …
Loess Records, Daniel R. Muhs, Stephen R. Cattle, Onn Crouvi, Denis-Didier Rousseau, Jimin Sun, Marcelo A. Zárate
Loess Records, Daniel R. Muhs, Stephen R. Cattle, Onn Crouvi, Denis-Didier Rousseau, Jimin Sun, Marcelo A. Zárate
United States Geological Survey: Staff Publications
Loess is aeolian sediment, dominated by silt-sized particles, that is identifiable in the field as a distinct sedimentary body. It covers a significant portion of the land surface of the Earth and as such constitutes one of the most important archives of long-term dust deposition. Large tracts of loess cover Europe, Asia, South America, and North America, and smaller loess bodies are found covering parts of Africa, the Middle East, New Zealand, and Australia. Loess thickness, particle size, and carbonate content decrease downwind from sources, trends that are powerful tools for reconstructing paleowinds. Many loess sections consist of relatively thick …
Palaeotrophic Reconstruction And Climatic Forcing Of Mega-Lake Eyre In Late Quaternary Central Australia: A Review, Steve Webb
Steve Webb
Extreme Quaternary climatic variation in Australia brought radical environmental changes to various parts of the continent. In this article, I discuss these changes in terms of mega-lake development in Central Australia, and in particular the southern Lake Eyre Basin (SLEB). The formation of these features, together with the fossil record of the region, throws light on the palaeoclimatic and palaeobiological relationships of megafauna and other animal groups, and the trophic development required to support them. Australian continental drying during the late Quaternary has been noted by many workers, but this process was punctuated by strong pluvial episodes of decreasing strength …
Stratigraphic Constraints On Groundwater Flow: Examples From York College, Cuny Campus In Queens, New York City, Nazrul I. Khandaker, Stanley Schleifer, Ezazul Haque, Coreyn Goddard, Shirley Jackson
Stratigraphic Constraints On Groundwater Flow: Examples From York College, Cuny Campus In Queens, New York City, Nazrul I. Khandaker, Stanley Schleifer, Ezazul Haque, Coreyn Goddard, Shirley Jackson
Publications and Research
Surficial geology of the York College campus is dominated by recent glacial deposits dating back to late Wisconsinan event. Several shallow excavation-type trenches reaching a depth of approximately 6 to 10 feet were dug in the wide greeneries adjacent to the parking lot to determine soil texture and collect in-situ permeability data. Based on these shallow pits, an apparent subsurface stratigraphy has been constructed. In general, the uppermost 8 to 18 inches is mostly clayey-and-silty sand and organic-rich top soil overlying stratified drift. The uppermost horizons are observed to also contain fill materials such as bricks, concretes, broken glasses, and …
Sh-Wave Refraction And Reflection Investigation Of Quaternary Geology―Central United States Seismic Observatory, Carrington L. Wright
Sh-Wave Refraction And Reflection Investigation Of Quaternary Geology―Central United States Seismic Observatory, Carrington L. Wright
Theses and Dissertations--Earth and Environmental Sciences
The Central United States Seismic Observatory (CUSSO) consists of an array of vertical strong motion accelerometers and medium period seismometers that penetrate 585 m into the Mississippi Embayment sediments and terminates into Paleozoic bedrock. The array is located in the New Madrid Seismic Zone within the upper embayment. The thick unconsolidated Quaternary sediments have the potential to influence strong motions; understanding how these sediments affect ground motion is the goal of the CUSSO array. Nine SH-wave refraction and five P-wave common midpoint reflection surveys were collected within a 1 km radius around the CUSSO borehole in order to characterize the …
Quaternary Evolution Of The Colorado River At Lees Ferry, Arizona, William Scott Cragun
Quaternary Evolution Of The Colorado River At Lees Ferry, Arizona, William Scott Cragun
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
A well-exposed suite of Colorado River fill terraces preserved at Lees Ferry records the oscillating history of this major river superimposed on its overall downcutting of the Colorado Plateau. Detailed mapping, sedimentology, cross-sectional surveys, and the use of two geochronometers have been used in order to establish a detailed chronostratigraphy for the area. Eight distinct deposits have been identified along the Colorado River (Ml -M7, and S3), and four deposits have been identified along the Paria River (Pl -P4).
Geochronology of six of these deposits using optically stimulated luminescence and cosmogenic 10Be exposure techniques indicates a long-term average bedrock …
Effects Of Quaternary Climate Change On Tributary Sedimentation And Geomorphology In Eastern Grand Canyon, Benjamin D. Dejong
Effects Of Quaternary Climate Change On Tributary Sedimentation And Geomorphology In Eastern Grand Canyon, Benjamin D. Dejong
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Climate variability has had a dramatic impact on eastern Grand Canyon tributaries over the past ~100 ky. This is readily observed in the Lava Chuar and Comanche catchments, which host well preserved colluvial remnants and river terraces that resulted from several climate-induced cycles of aggradation and incision. This study investigates these climate responses using surveying, sedimentology, and luminescence geochronology methods to investigate the mechanisms and timing of their deposition.
The survey data demonstrate that the concavity of terrace treads is lower than modern drainages. The sedimentology suggests the prevalence of stream-flow reworking of debris flow deposits and portrays an expected …
Caves And Speleogenesis At Blomstrandsøya, Kongsfjord, W. Spitsbergen, Stein-Erik Lauritzen
Caves And Speleogenesis At Blomstrandsøya, Kongsfjord, W. Spitsbergen, Stein-Erik Lauritzen
International Journal of Speleology
Blomstrandsøya, at Kongsfjord (78° 57’N), Spitsbergen, is within the high arctic, a completely permafrozen zone. The bedrock consists of Paleozoic marbles and has yielded a surprising amount of karst features. Early phases of hydrothermal, possibly Caledonian, speleogenesis and subsequent Devonian karstification with redbed deposits is well documented. 62 active seacaves, and more than 30 relict karst caves were found in the coastal cliffs and in escarpment faces around the island. All caves have very limited extent; they are either quite short, like most of the active sea caves, or they are soon choked by frozen sediments and ground ice after …
The Quaternary Tectonic And Structural Evolution Of The San Felipe Hills, California, Stefan M. Kirby
The Quaternary Tectonic And Structural Evolution Of The San Felipe Hills, California, Stefan M. Kirby
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
We examine the transition between extension and strike-s lip in the San Felipe Hills, western Salton Trough, southern California using new and compiled geologic mapping, measured stratigraphic sections, magnetostratigraphy, and structural analysis. A 625 m measured section describes the Borrego, Ocotillo , and Brawley formations in the SE San Felipe Hills and constrains a regional disconformity and correlative angular unconformity at ~ 1 Ma. Sedimentation rates for the Brawley Formation above the disconformity range from 1.0 to 1.2 mm/yr, palcoflow was to the ENE. The Brawley Formation consists of three interbeddcd lithofac ics; (I) fluvial and fluvio-d eltaic, (2) lacustrinc, …
Quaternary Geology And Landscape Evolution Of Eastern Grand Canyon, Arizona, Matt D. Anders
Quaternary Geology And Landscape Evolution Of Eastern Grand Canyon, Arizona, Matt D. Anders
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Tectonics and drainage evolution are controlling overall landscape incision in eastern Grand Canyon. Superimposed on downcutting are dynamic responses of hillslopes, tributary streams, and the Colorado River to glacial-interglacial climate cycles. Five tributary stream fill terraces have been identified, and luminescence dating indicates aggradation was occurring 50- 34 ka {S3), 12-7 ka (S2), and 5-3.5 ka (S1). Seven Colorado River fill terraces have been identified, and luminescence and U-series dating indicate deposition was occurring 343-322 ka (M5), 151-118 ka (M4), and 71-64 ka (M3).
Aggradation by the Colorado River in eastern Grand Canyon begins during glacial advances and continues into …
Quaternary Loess-Paleosol Sequences As Examples Of Climate-Driven Sedimentary Extremes, Daniel R. Muhs, E. Arthur Bettis Iii
Quaternary Loess-Paleosol Sequences As Examples Of Climate-Driven Sedimentary Extremes, Daniel R. Muhs, E. Arthur Bettis Iii
United States Geological Survey: Staff Publications
Loess is a widespread, wind-transported, silt-dominated deposit that contains geologic archives of atmospheric circulation and paleoclimate on continents. Loess may cover as much as 10% of the Earth’s land surface. It is composed mainly of quartz, feldspars, and clay minerals, with varying amounts of carbonate minerals. The geochemistry of loess differs from region to region, depending on source materials, but all loess is very high in SiO2 with lesser amounts of other major elements. Trends in loess downwind from source areas include systematic decreases in thickness and amounts of sand and coarse silt, and increases in amounts of fine silt …
Late Quaternary Slip Rates Across The Central Tien Shan, Kyrgyzstan, Central Asia, Stephen C. Thompson, Ray J. Weldon, Charles M. Rubin, Kanatbek Abdrakhmatov, Peter Molnar, Glenn W. Berger
Late Quaternary Slip Rates Across The Central Tien Shan, Kyrgyzstan, Central Asia, Stephen C. Thompson, Ray J. Weldon, Charles M. Rubin, Kanatbek Abdrakhmatov, Peter Molnar, Glenn W. Berger
All Faculty Scholarship for the College of the Sciences
Slip rates across active faults and folds show that late Quaternary faulting is distributed across the central Tien Shan, not concentrated at its margins. Nearly every intermontane basin contains Neogene and Quaternary syntectonic strata deformed by Holocene north‐south shortening on thrust or reverse faults. In a region that spans two thirds of the north‐south width of the central Tien Shan, slip rates on eight faults in five basins range from ∼0.1 to ∼3 mm/yr. Fault slip rates are derived from faulted and folded river terraces and from trenches. Radiocarbon, optically stimulated luminescence, and thermoluminescence ages limit ages of terraces and …