Holocene Paleofloods of the Ross River, Central Australia

1993 ◽  
Vol 40 (2) ◽  
pp. 201-212 ◽  
Author(s):  
Peter C. Patton ◽  
Geoff Pickup ◽  
David M. Price
Keyword(s):  
Silty Sand ◽  
Dynamic Nature ◽  
Alluvial Deposits ◽  
Long Wavelength ◽  
Red Earth ◽  
Central Australia ◽  
River Plain ◽  
Large Floods ◽  
Flood Flow ◽  
Eolian Origin

AbstractThe rivers of central Australia rise in the MacDonnell Ranges and flow out across broad, low-relief plains into the surrounding desert. The stratigraphy of the Ross River plain records the areal extent and frequency of Holocene floods. This floodout plain is underlain by deeply weathered alluvial deposits, characterized by red earth soils dated by thermoluminesence at >59,000 yr. This old alluvium is covered by a sheet-like deposit of very silty sand of probable eolian origin dated by thermoluminesence at 9200 ± 900 yr. The oldest Holocene alluvium occurs as broad, low-relief bars and levee deposits flanking the modem channel and as low-relief long-wavelength bedforms that fan out across the plain. This deposit resulted from a flood flow, up to 10 km wide, that covered the entire plain. Evidence for several large floods between 1500 and 700 yr B.P. is also preserved in a 500- to 1500-m-wide paleochannel. Thus, the surface features on the floodout plains are the product of a few rare large flood events. This paleohydrologic record is additional evidence of the dynamic nature of the hydrometerological regime of central Australia.

Relations entre la tectonique et la morphologie de la plaine du Rhin, en Alsace et au grand duche de Bade

1945 ◽  
Vol S5-XV (1-3) ◽  
pp. 69-80
Author(s):  
R. A. Schlumberger
Keyword(s):  
Rhine River ◽  
Regional Structure ◽  
Geophysical Prospecting ◽  
Alluvial Deposits ◽  
Crustal Movements ◽  
River Plain

Abstract The morphologic features of the Rhine river plain in Alsace (France) and Baden (Germany), observed during airplane reconnaissance, corroborate and supplement data obtained by geologic investigations, borings, and geophysical prospecting relating to the structure of the Rhine trough and associated surface forms. It is concluded that, below the alluvial deposits of the plain, the terrain is highly folded and faulted and that crustal movements, which produced a regional structure resembling a piano keyboard, continued to the present time.

The Tunguska event and Cheko lake origin: dendrochronological analysis

2014 ◽  
Vol 14 (3) ◽  
pp. 345-357
Author(s):  
Fantucci Rosanna ◽  
Serra Romano ◽  
Kletetschka Gunther ◽  
Di Martino Mario
Keyword(s):  
Basal Area ◽  
Forest Trees ◽  
Alluvial Deposits ◽  
Continuous Growth ◽  
Dendrochronological Analysis ◽  
Lake Formation ◽  
Growth Increase ◽  
Vigorous Growth ◽  
Tunguska Event ◽  
River Plain

AbstractDendrochronological research was carried out on 23 trees samples (Larix sibirica and Picea obovata) sampled during the 1999 expedition in two locations, close to the epicentre zone and near Cheko lake (N 60°57′, E 101°51′). Basal Area Increment (BAI) analysis has shown a general long growth suppression before 1908, the year of Tunguska event (TE), followed by a sudden growth increase due to diminished competition of trees that died due to the event. In one group of the trees, we detected growth decrease for several years (due to damage to the trunk, branches and crown), followed by growth increase during the following 4–14 years. We show that trees that germinated after the TE, and living in close proximity of Cheko lake (Cheko lake trees) had different behaviour patterns when compared to those trees living further from Cheko lake, inside the forest (Forest trees). Cheko lake trees have shown a vigorous continuous growth increase. Forest trees have shown a vigorous growth during the first 10–30 years of age, followed by a period of suppressed growth. We interpret the suppressed growth by the re-established competition with the surroundings trees. Cheko lake pattern, however, is consistent with the formation of the lake at the time of TE. This observation supports the hypothesis that Cheko lake formation is due to a fragment originating during TE, creating a small impact crater into the permafrost and soft alluvial deposits of Kimku River plain. This is further supported by the fact that Cheko lake has an elliptical shape elongated towards the epicentre of TE.

Geotechnical Characterization of the Weber River Crossing, Utah, for HDD Feasibility for the 2003 Kern River Pipeline Expansion

2002 ◽  
Author(s):  
Jeffrey R. Keaton ◽  
Roy L. Steelman
Keyword(s):  
Southern California ◽  
Normal Fault ◽  
Silty Sand ◽  
Preliminary Evaluation ◽  
Silty Clay ◽  
Directional Drilling ◽  
Alluvial Deposits ◽  
Sandy Gravel ◽  
Pilot Hole ◽  
Road Geometry

The 2003 Kern River Pipeline Expansion will loop 635 miles of 36-inch high-pressure natural gas pipeline between southwest Wyoming and southern California and 82 miles of 42-inch pipeline in southern California. The Weber River near Coalville in Summit County, Utah, will be crossed using horizontal directional drilling (HDD) techniques. The original Kern River Pipeline was constructed across the Weber River using conventional open-cut methods in 1991, but environmental factors and the close proximity to other pipelines made HDD a reasonable option to consider. The Weber River floodplain is approximately 3500 feet wide at the pipeline crossing, and contains Interstate Highway 80, US Highway 189, and a paved frontage road. Geometry of the slopes above the floodplain results in an overall HDD horizontal length of 4750 feet with an elevation difference of 88 feet. The geologic setting of the Weber River crossing consists of Cretaceous marine and non-marine sedimentary rocks and Quaternary alluvial and colluvial deposits. The rocks are chiefly sandstone, siltstone, and claystone, with local limestone and coal. Sedimentary beds dip to the west at 10 to 30 degrees, and fractures dip at 60 to 80 degrees. The siltstone and claystone are soft to moderately soft, whereas the sandstone and limestone are moderately hard to hard. The alluvial deposits consist of silty sand to sandy gravel, and the colluvial deposits consist of silty clay to silty sand. A north-trending, west-dipping normal fault shown on published maps nearly coincides with Interstate 80. Geotechnical conditions at the proposed HDD crossing were evaluated by drilling six borings to depths ranging from 100 to 150 feet, and collecting ground penetrating radar (GPR) data at 11 profile lines covering 2170 feet of floodplain. The GPR profile lines were interrupted by channels of the Weber River, canals, and Interstate 80. A 25 MHz antenna was used to obtain radar penetration to effective depths of 50 feet or more. The contact between alluvial deposits and bedrock was detected at depths ranging from 20 to 50 feet. Local relief of the alluvial/bedrock contact was found to be on the order of 10 feet. DrillPath 2 and DrillMud programs were used for a preliminary evaluation of the HDD feasibility. A maximum HDD installation depth of approximately 105 feet was used, and fracture pressures were evaluated for a pilot hole and four stages of back-reaming. Locations of frac-out concern were identified. Final HDD design was performed by others.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

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