The Crawfordsville and Knightstown Moraines in Indiana

Indiana Geological Survey Report of Progress 28The main advance of glacial ice into central Indiana during Wisconsin time had two distinct pulsations within a span of about 1,000 years. The first, about 21,000 years ago, reached farthest south and built the segmented Shelbyville Moraine near its margin. After this first advance, the ice melted somewhat and then readvanced to a new position a few miles short of its previous position about 20,000 years ago. Because the readvance crossed and buried the Champaign and Bloomington Moraines, these names should not be used for any of the few moraines that can be traced eastward out of the interlobate complex in west-central Indiana. The name Crawfordsville Moraine is proposed for the moraine that lies near the distal margin of the drift sheet left during the second ice advance. The Knightstown Moraine is the name given to a recessional moraine that was deposited later than the Crawfordsville Moraine and that merges with the continuation into eastern Indiana of the Farmersville Moraine of Ohio.Indiana Department of Conservatio

Depositional Environment Of The Type Section Of The Seward Formation (Lower Pleistocene), Nebraska

The Seward Formation as originally described was known largely from subsurface data; the authors considered it a fine-grained facies of the Ogallala. It was later correlated with the Elk Creek Till of the Nebraskan glaciation and an outcrop selected in northeastern Seward County as a type section of the unit. Recent research has demonstrated that the Elk Creek Till is much older than the classical Nebraskan tills. The upper part of the exposure designated the type section of the Seward Formation is a massive silt unit that has a thick chernozemic paleosol, and the lower part is laminated silt and clay with a thinner CaCO3-rich paleosol. Land snails collected from a sparsely fossiliferous zone near the base of the massive silt unit represent only five species; 88% are about equally divided between Pupilla muscorum and Gastrocopta armifera, both long lived and widely distributed taxa that indicate open grassland. This faunule and the massive, nearly uniform nature of the silt from which it was collected suggest that part of the sediment may have been deposited as loess. Its thick soil profile, which is buried beneath a laminated silt and fine sand that is overlain by Cedar Bluffs Till a short distance away, is well developed. Judged by post-Wisconsinan soil profile development, it probably would have required several times as long to form. The upper part of the Seward Formation at its type section probably correlates with the Elk Creek Till, which was deposited by the earliest ice to reach the area of eastern Nebraska. The basal part of the formation probably is Pliocene. It is likely that not all the silts identified as Seward Formation from well logs and samples have the same origin as these beds at the outcrop of the type section

Mass wasting as a geologic hazard in the Province of Salta, Argentina

The north-south orient ation ofthe mo unta inous part ofthe Province ofSalta form s a massive barrier to easy communication between the more populate d region in the central pan of the provin ce and the communities to the west. Routes follow deeply entrenched valleys th at are frequ entl y th e sites ofdebris flows that cause disruptions in th e flow of traffic during the months of December through March , wh en most of the precipitation of the region is recorded . The steep topography and the tecton ic settings have resulted in nearly 150 large landslides and debris flows most ofwhich were identi fied through stereo scopic study of airphoros, scale 1/50,000 and l/70,00 0. More than 100 of these are in the Cordillera Oriental and Calchaq uenia, more than 30 were noted in the Pu na, a smaller number in the Sierra s Su bandinas. Several clus ters of large landslides in each of th ese rnorphos truc tural regions undoub tedly were trigger ed by earthquak es th at may have had a magnitude (Richter Scale) of5 .0 or greater; thus their locations provide addi tional information on the probable epicenters of preh isto ric earthq uakes. Most of the landslid es ident ified do not in themselves present any hazard or risk at thi s time. Their locat ion s and geo logic setting indicat e locations where un stabl e slopes have failed , wh ich provides a warn ing th at add itional slides co uld take place in similar setti ngs. Their identificat ion and location also serves as a guide to lan d- use planners of the pr ovince, so that if new construction is undertaken, measures to avoid reactiva ting old and now stable slide masses can be avoided. Laorientacion meridional de la parte rno n tafiosa de la Provincia de Salta ha generado una barr era que no favore ce una Hcil y fluida comunicaci6n entre las regiones pobladas de la pane central de la provin cia y los pueblos del oeste. Las ru tas siguen los valles profundos donde los flujos densos y los der rumbes de roca interrumpen con frecuencia eI rrafico entre diciembre y rnarzo , cuando se registra la mayorfa de las precipitacio nes. La ropografia empinada y el marco tectoni co dieron como resulrado casi 150 deslizamientos y flujos de escombro s qu e fu eron identificados a rraves del examen de foros aereas, escalas 1/50.000 y 1/70 .00 0. De los movimienros en masa registrado s, mas de 100 oc urrieron en la Co rdi llera Oriental y Calc haquenia, mas de 30 en la Puna, y algunos cua ntos en las Sie rras Suba nd inas/S istema Santa Barbara. En cada una de las regio nes rnorfoestructurales se ubican grupos de grandes de rrumbes que deben haber sido causados por ter remoros con una mag ni tu d (Richte r) de 5.0 0 mayor. La ubi cacion de esros rasgos distinriv os prove e la informacion necesari a para facilitar la identi ficacion de epiceritros de terremoros prehistoricos. La mayoria de los de rrumbes localiza dos no indican riesgo alguno en la acrualida d. Mas bien, los sitios geologicos seleccionados ind ican lugares donde oc urr en pend ienres inestables que advierten sobre evenruales deslizamienros que pudieran ocurrir en esros lugares. La localizaci6n de esros sitios servira de guia para quienes planifican el uso del suelo y para evitar dafiosa obras civiles, accesos viales y, au n, la vida de las personas

Urban Geology of Madison County, Indiana: Special Report 10

During recent years many of the population centers of Indiana have undergone growth that has resulted in expansion of urban uses into land that has been largely rural. As a result of that expansion, conflicts have arisen between expanding urban uses and the agricultural and mineral resource uses of land that lies near the centers of population. In addition, uncontrolled use of flood plains, steep slopes, and areas of soft sediments and high water tables has caused inconvenience and financial loss to individuals and industries that unknowingly have built structures in those places. Generally, these situations have developed as a result of a lack of information or understanding about the geologic materials or processes that exist in the area involved. PURPOSE OF REPORT This report was prepared to bring together information on the geologic features of Madison County, Ind., that are likely to affect the urban development of land in the county. Information of this kind is of greatest value in areas where land use is changing, because as the population density of a developing community increases, all factors likely to limit the most effective use of the land must be considered in preparing comprehensive planning studies and ordinances (Wayne, 1969). The information in this report is intended to serve as a guide in land use planning and engineering planning but is not sufficiently detailed to replace specific site evaluation studies

Relative Dating Techniques to Distinguish Late Pleistocene-Holocene Continental Sediments

Radiometric dating, particularly with 14C, provides ages for those Late Pleistocene and Holocene sediments that contain datable materials. Standard stratigraphic and morphostratigraphic techniques of superposition, geomorphic position, partial overlap, and offlap provide relative chronology in many situations. The use of multiple relative dating (RD) techniques, developed for the study of glacial deposits, makes use of these techniques where possible, but depends heavily on the additional comparison of the results of surface processes that act continuously and more or less uniformly after accumulation is complete. For sediments at the surface that have not been buried, the most important of these processes are weathering and morphological alteration. Soil profile development is progressive; careful field description plus laboratory analysis provide data to distinguish soils of differing maturity, hence, of different ages. Clasts at the surface and within the soil profile weather continuously, and quantification of the degree of their decay permits recognition of age differences. In mountains adjacent to deserts, a veneer of loess accumulates slowly, and is thicker on older alpine deposits. Quantification of gully development provides still another morphometric approach to dating young sediments. These RD methods have been effective in distinguishing relative ages of continental sediments from 102 to 107 yr. old in the western U.S.A. mountains and in the Central Andes

Provenance of sand in periglacial sand wedges and sheet sand, northeastern Nebraska, USA

Sand-wedge polygons on upland surfaces beneath thin loess in northeastern Nebraska record existence of permafrost around the margin of the Wisconsinan glacier at its maximum advance. Strong unidirectional wind not only kept the upland surfaces free of snow, allowing frost to penetrate deeply and thermal contraction cracks to develop, but also dessicated the surface material so that frost action and sublimation of pore ice could loosen surface material. The strong NW-SE winds deflated soils from upland surfaces, made ventifacts of the cobbles in the lag that remained and created fields of yardangs oriented NW-SE. Sand derived from the soils and underlying till was carried only a short distance to fill the thermal contraction cracks and in some places leave a thin sheet of sand covering the former surface

Drainage Patterns and Glaciations in Eastern Nebraska

Most of the stream courses of eastern Nebraska came into existence during the recession of an ice margin. Their patterns include many drainage anomalies that suggest both the manner and the times of ice disappearance. Rivers coming from the west flow down the regional slope of the High Plains. Along and east of the Kansan glacial border most streams are subparallel, trend S300 _40 0 E, and probablY mark pauses of an actively retreating ice margin. Logan Creek, an underfit stream, flows S4SoE from Hartington to the Thurston/Burt c\u3c;mnty line, then directly southward to the Elkhorn. East of Logan Creek and above the bend, South Blackbird, Omaha, and Cow creeks flow parallel to Logal Creek then bend abruptly back northward to the Missouri. The Bow creeks in Cedar and Knox counties describe a series of arcs that surely mark successive retreatal positions of an ice lobe that crossed the Missouri trench around Yankton, South Dakota. Bazile Creek in the Santee Sioux Reservation flows northward to the Missouri, but the gravel and sand along it indicate a southeastward flow for the currents that deposited them. These sediments can be traced into the North Fork of the Elkhorn, thence to the Platte Valley near Fremont. These drainage lines define the lobate margins of the ice through the J ames and Red River lowlands. The degree of dissection and alteration of the associated tills suggests the relative lengths of time since the ice melted from them. The compact and weathered tills in east-central Nebraska are oldest (classical Kansan); the softer, less weathered tills near the Missouri are younger (Illinoian?); Wisconsinan ice may have blocked the Missouri River near Yankton and shunted it to the Elkhorn, but left little till on the south side of the Missouri

Provenance of sand in periglacial sand wedges and sheet sand, northeastern Nebraska, USA

Sand-wedge polygons on upland surfaces beneath thin loess in northeastern Nebraska record the existence of permafrost around the margin of the Wisconsinan glacier at its maximum advance. Strong unidirectional wind not only kept the upland surfaces free of snow, allowing frost to penetrate deeply and thermal contraction cracks to develop, but also dessicated the surface material so that frost action and sublimation of pore ice could loosen surface material. The strong NW-SE winds deflated soils from upland surfaces, made ventifacts of the cobbles in the lag that remained and created fields of yardangs oriented NW-SE. Sand derived from the soils and underlying till was carried only a short distance to fill the thermal contraction cracks and in some places leave a thin sheet of sand covering the former surface

Provenance of sand in periglacial sand wedges and sheet sand, northeastern Nebraska, USA

Sand-wedge polygons on upland surfaces beneath thin loess in northeastern Nebraska record the existence of permafrost around the margin of the Wisconsinan glacier at its maximum advance. Strong unidirectional wind not only kept the upland surfaces free of snow, allowing frost to penetrate deeply and thermal contraction cracks to develop, but also dessicated the surface material so that frost action and sublimation of pore ice could loosen surface material. The strong NW-SE winds deflated soils from upland surfaces, made ventifacts of the cobbles in the lag that remained and created fields of yardangs oriented NW-SE. Sand derived from the soils and underlying till was carried only a short distance to fill the thermal contraction cracks and in some places leave a thin sheet of sand covering the former surface

Glacial Chronology of the Ruby Mountains–East Humboldt Range, Nevada

The Ruby Mountains-East Humboldt Range, one of the interior mountain groups of the Basin and Range Province, lies about midway between the Wasatch Mountains and the Sierra Nevada. After Blackwelder’s description in his review of glaciation in the western mountains, Sharp mapped and named the deposits of the Lamoille and Angel Lake glaciations and correlated them with early and late Wisconsin deposits of the Great Lakes area. The refinement of relative dating (RD) methods, the availability of air photos and modem topographic maps, and new road cuts have aided the restudy of these alpine glacial deposits and the basis for their correlation. Lamoille moraines are smooth ridges and show little detail of constructional topography. Valleys glaciated only by Lamoille ice still show the characteristics of a glaciated trough, but they have been greatly modified by weathering and erosion. Granite boulders on Lamoille moraines are pitted, and pegmatites have grotesque shapes with 30-cm-deep pits. Cuts through Lamoille end moraines (and alluvial talus cones) expose a thick soil profile with a well-developed blocky structure in a reddish brown argillic B horizon. Subsurface granitic boulders in the B horizon of Lamoille tills show much greater weathering than do those in Angel Lake tills. In contrast, Angel Lake moraines are irregular and rugged, contain closed depressions, and have been little altered since deposition. Surfaces scoured by Angel Lake ice are fresh and unweathered. Granites of Angel Lake moraines have weathered surfaces but show little pitting; pegmatites have pits up to 10 cm deep. The thin soil profiles on Angel Lake tills and alluvial talus cones display brown colors, minor clay accumulation, and no B-horizon structure. These weathering and morphological differences suggest that the Lamoille deposits have been exposed to weathering and erosion for a period of time as much as an order of magnitude longer than the Angel Lake deposits. Thus only the Angel Lake is Wisconsinan in age, and the Lamoille drift is more reasonably correlated with the Illinoian Stage of the Great Lakes regio