Alluvial fans

For example, the many deepwater fields located in the Gulf of Mexico are of Tertiary age and are comprised of complex sand bodies which were deposited in a deepwater turbidite sequence. The BP Prudhoe Bay sandstone reservoir in Alaska is of Triassic/ Cretaceous age and was deposited by a large shallow water fluvial-alluvial fan delta system. The Saudi Arabian Ghawar limestone reservoir is of Jurassic age and was deposited in a warm, shallow marine sea. Although these reservoirs were deposited in very different depositional environments they all contain producible accumulations of hydrocarbons, though the fraction of recoverable oil varies. In fact, these three fields are some of the largest in the world, containing over 12 billion barrels of oil each ... 

Contrary to popular concepts, sands do not always dominate arid and semi-arid zones. Aridisols occur on a wide variety of landforms, lithological formations and are of different ages. They are most common on stable land surfaces of Late Pleistocene or greater age in tectonically active deserts where they comprise alluvial fan, alluvial flats or stream terraces. Arid zones also include mountainous terrain with steep slopes (Nettleton and Peterson, 1983). Many arid or semi-arid zones include fluvial and aeolian materials of Pleistocene age. 

Concentrations of selenium in shallow groundwater generally were less than 20 pg/L in the middle alluvial fan deposits (Figure 3). 

Water Alluvium Flood plains Deltas and alluvial fans... 

Nilsen, T. H., 1982, Alluvial Fan Deposits In Sandstone Depositional Environments (edited by P. A. Scholle and D. Spearing), American Association of Petroleum Geologists, Memoir No. 31, Tulsa, OK, pp. 49-86. 

USA California Kerr River Alluvial Fan (San Joaquin Valley)... 

USA California Kerr River Alluvial Fan (San Joaquin Valley) aquifer soils 1.3-8.2 Klinchuch et al. (1999)... 

Virtually over its entire extension, the continental slope of the Black Sea is dissected by numerous faults and underwater canyons. These canyons, confined to tectonic dislocations (fracture zones or grabens), are later transformed by turbidity flows, which use them as channels for the transport of mineral particulate matter from the near-shore zone to the foot of the continental slope. At the places of discharge of turbidity flows, alluvial fans are formed, which may be cut by runoff channels [10]. 

The Danube underwater canyon system is crowned by a thick alluvial fan. The relative height of this topographic feature reaches 500 m at a width changing from 40 km in its upper part to 60 km at its base. The alluvial fan is advanced by 100 km in the southeastern direction into the western depression of the sea. At the center of the fan, one observes an underwater valley rimmed by high (up to 300-400 m) near-channel bars [11]. 

The continental footstep of the Black Sea occupies an intermediate position between the continental slope and the floor of the central depression at depths from 1100-1200 to 1800-2000 m. Morphologically, it is represented by a slightly inclined plain that borders the base of the continental slope. It is a kind of accumulative tail formed owing to the merging of numerous alluvial fans near the mouths of underwater canyons and to the sedimentation matter supplied from the shelf and continental slope due to the sediment runoff and landslide processes. 

Unit C at Nekhen is clearly different from the sediments above and below it. Comparing all features (including the location of its occurrences), it is clear that Unit C is material washed from the wadi and deposited in a small alluvial fan during the period from 3200 to 2500 B.C. At this time, Nile flooding must not have reached the site, but there were substantial amounts of water to wash sediments from the wadi. This evidence supports other paleoclimatic studies that suggest periods of moist conditions on the Egyptian desert (18). 

During the middle Holocene era, occasional summer rainy intervals (see ref. 22) carried desert sediments down the Great Wadi into the modern flood plain, building up a succession of alluvial fans under what would later be the site of the walled city of Nekhen (Kom el Ahmr). The level of Nile flooding in this area (marked by the Nekhen lithozone) reached to within about 100 m of the modern boundary between the cultivation and the low desert, at an elevation of approximately 80 m above sea level. 

Kreitler C. W. (1979) Nitrogen-isotope ratio studies of soils and groundwater nitrate from alluvial fan aquifers in Texas. J. Hydrol. 42, 147-170. 

Figure 3 Sheigra paleosol (bleached and reduced zone 1 m thick to right) under Torridonian (1,000 Ma) alluvial fan deposits, and Staca paleosol at same unfoncormity but on amphibolite (left-hand side) near the hamlet of Sheigra, northwest Scotland (photo courtesy of G. E. Williams geological age revised hy Williams and Schmidt, 1997).

Eitaor M. I. and Keigley R. B. (1991) Geochemical equilibria of iron in sediments of the Roaring river alluvial fan, Rocky Mountain National Park, Colorado. Earth Surf. Process. Landforms 16, 533—546. 

Bierman, P. R., Lini, A., Zehfuss, P., Church. A., Davis, P. T., Southon, J., and Baldwin, L., 1997, Postglacial ponds and alluvial fans recorders of Holocene landscape history, GSA Today 1 no. 10 1-8. 

Figure 2.1 Settings for calcrete development. In fluvial settings pedogenic calcretes can develop on floodplains and terraces, whereas groundwater calcretes may form in channel deposits or around the capillary fringe and upper part of the phreatic zone in more permeable parts of the floodplain. In alluvial fans paired calcretes may develop on the fans, with hydromorphic calcretes near discharge zones.

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