|
.. ~ ~ .
<br />formed in nearly horizontally bedded, lower tertiary, Wasatch %~
<br />• Formation. The Wasatch Formation, in the area, is mostly thick
<br />bedded, somewhat friable sandstone interbedded with shales, marl-
<br />stones and conglomerates. Cold Springs Mountain is Precambrian,"
<br />Uinta Mountain Group, sandstones, quartzites, and conglomerates,
<br />while Limestone Ridge, immediately west of and underlying the subject
<br />area, is composed of north-striking-east dipping limestone beds, be-
<br />lieved to be of Upper Paleozoic-age. Renewed uplifting of Cold Springs
<br />Mountain during mid-upper Tertiary times (Miocene) has faulted and
<br />warped tine Wasatch Formation along the east flank of Limestone Ridge.
<br />Following this orogeni.c~event, the Wasatch Formation was covered by
<br />Upper Tertiary, gravelly Browns Park Formation, composed of, in this
<br />area, particles eroded from the nearb}• Precambrian rocks. During
<br />. Plcistocone times, much of the Browns Park gravel was removed by heavy
<br />erosion leaving dissected terrace remnants along the east flank of `
<br />Limestone Ridge. This heavy erosion and consequent deposition re-
<br />sults in low, plunging Browns Park gravel capped ridges that have
<br />heterogenous, coarse, blocky colluvium aprons around the sides and
<br />ends of the ridges. Recent stream erosion has produced incised,
<br />dendritic patterns in the Wasatch Formation, and rectangular patterns
<br />in the older, higher relief rocks on the west side of the area.
<br />Quaternary
<br />Recent alluvium along Vermillion and Talamantes Creeks and in playa
<br />lakes at the upper end of Irish Canyon (Irish Lake) and Ponce Flat,
<br />is composed of silty-clayey sand containing randomly placed gravel and
<br />boulders. Commonly, the "desert pavement" effect can produce erroneous
<br />estimates of potential gravel quantities during cursory review. Due
<br />to the random occurrence of gravel deposits and the misleading "desert
<br />• pavement" effect, the alluvium is considered a poor source of con-
<br />• struction gravels. .
<br />". Colluvium around the flanks of the low ridges off Limestone Ridge are
<br />composed of heterogenous mixtures of sand to boulders derived from the
<br />• nearby Wasatch Formation, some Browns Park Formation gravels, and angular
<br />to sub-angular i,ragments from Limestone Ridge and Cold Springs Y,ountain.
<br />Due to the random placement, oversized end frlable nature of the i:asatch
<br />. debris, and clay-silt content,this material is considered a poor con-
<br />struction gravel source when compared to the Browns Park Formation.
<br />Tertiary
<br />Browns Fark Formation, possibly up to 50 feet or more thickness, in this
<br />area is composed of approximately 55% sub-angular to sub-rounded, bard,
<br />dense, calcareous coated gravels and cobbles to 5" size, 35X fine to
<br />" coarse sand, and 10% cobbles and elongate boulders up to about 22" x 24"
<br />_ size. S2ithin a mile or so north and south of the subject area, the
<br />gravels are covered by 6"-10" of gravelly, silty sand soil containing
<br />,. some roots and organic matter. _. _
<br />1 Wasatch Formation rocks, in the nearby area, are composed of thick
<br />bedded sandstones interbedded with shales, siltstones, marlstoaes, and
<br />
<br />
|