Geology Reference
In-Depth Information
t
The precipitation balance in the area incapable of provid-
ing the time- and space-consistent meteoric feed of the thick
reservoir members.
t
Cut-off of the main depression from the piedmont zone of a
possible charge by systems of regional faults (Santa Monica,
San Gabriel, Elsinore Chino, Christianitos and Palos Verdes).
t
The step-block structure of the basin caused by sequential
step-down of the sedimentary sequence from its flanks to the
central portion on the internal faults (Newport Englewood,
Norwalk and Wittier), which faults block and refract the
infiltration water flow down the regional dip.
t
Substantial shale-out of the Neogene section from the
periphery to the center of the basin blocking the infiltrate
migration in the same direction.
A number of factors combined with the aforementioned conditions
severely restrict the likelihood of functioning in the region of a traditional
elision mechanism involving the water flow from the depression's center
toward its flank framework. These factors are:
t
The stratigraphic pinch-out of individual intervals in the
flank zones.
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The presence of formational unconformities associated
with transgressive-regressive effects and paleo-denudation
processes.
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The absence in the sedimentary sequence of thick under-
compacted clays serving as contributors of squeezed-out
pore water and energy source for their subsequent migration
up the regional dip.
t
Poor compressibility of reservoir members determining
rather limited likelihood of releasing by them sufficient (in
time and space) volumes of laterally-mobile fluids.
The presence in the basin of powerful vertical (from the bottom upward)
interformational fluid cross-flow through a fault system mostly in the
crestal areas of local highs is supported by the following:
t
Clearly fault-associated nature of the structures forming anti-
clinal belts (Bakirov, 1959; Barbat, 1961; Levorsen, 1970).
t
The present-day spatial hydrochemical zoning.
t
Broad mosaic development in the Post-Miocene interval
(Pliocene formations Repetto and Pico) of “transitional”
