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Lithofacies and environmental analysis of clastic depositional systems (view source)
Revision as of 22:15, 19 March 2014
, 22:15, 19 March 2014→Alluvial fan deposits
===Alluvial fan deposits===
===Alluvial fan deposits===
An ''alluvial fan'' is a wedge of clastic detritus that forms at the base of a mountain front as sediments eroding from the mountains are transported downslope by streams or debris flows and deposited at the base (Figure 3e). The fan-shaped body is generally characterized by a gradation from coarser sediments at the apex to finer sediments at the toe. Alluvial fans are commonly divided into [[Proximal alluvial fan|proximal]], [[Middle alluvial fan|mid-fan]], and [[Distal alluvial fan|distal]] fan subenvironments.
An ''alluvial fan'' is a wedge of clastic detritus that forms at the base of a mountain front as sediments eroding from the mountains are transported downslope by streams or debris flows and deposited at the base ([[:file:lithofacies-and-environmental-analysis-of-clastic-depositional-systems_fig3.png|Figure 3e]]). The fan-shaped body is generally characterized by a gradation from coarser sediments at the apex to finer sediments at the toe. Alluvial fans are commonly divided into [[Proximal alluvial fan|proximal]], [[Middle alluvial fan|mid-fan]], and [[Distal alluvial fan|distal]] fan subenvironments.
Vertical sequences through the proximal fan are generally dominated by gravelly deposits with subordinate sandy deposits. Sequences through the mid- and distal fan are increasingly sand dominated. [[Basic open hole tools#Gamma ray|Gamma ray]], [[Basic open hole tools#Spontaneous potential|SP]], and [[Basic open hole tools#Resistivity|resistivity]] log responses throughout a fan can generally be expected to be blocky to irregular, depending on the amount of clay.
Vertical sequences through the proximal fan are generally dominated by gravelly deposits with subordinate sandy deposits. Sequences through the mid- and distal fan are increasingly sand dominated. [[Basic open hole tools#Gamma ray|Gamma ray]], [[Basic open hole tools#Spontaneous potential|SP]], and [[Basic open hole tools#Resistivity|resistivity]] log responses throughout a fan can generally be expected to be blocky to irregular, depending on the amount of clay.