Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic sedimentation and tectonics

Abstract

Exposed along the southeast fl ank of the Colorado Front Range are rocks that beautifully illustrate the interplay of sedimentation and tectonics. Two major rangebounding faults, the Ute Pass fault and the Rampart Range fault, converge on the Garden of the Gods region west of Colorado Springs. Cambrian through Cretaceous strata upturned by these faults reveal in their grain compositions, textures, and bedforms radically different styles of sedimentation. The Cambrian/Ordovician marine transgressive deposits appear to have come to rest on a passive and tectonically inactive craton. In contrast, coarse-grained Pennsylvanian/Permian marine deposits of the Fountain Formation and Lyons Sandstone reveal deposition by suspension and tractive currents in a very dynamic tectonic setting. These styles are contrasted with the alternating eustatics of the Western Interior Seaway which led to the local Cretaceous section. Finally, the powerful imprint of the Laramide orogeny is evident in the sandstone dikes of Sawatch Sandstone which are found within the hanging wall of the Ute Pass fault.

Experimental Relationship Between Compressional Wave Attenuation and Surface Strains in Brittle Rock

“…Figure a shows the plot of ε yy versus ε xx strain for LSP‐2, through which the specimen‐scale ε c value was estimated to be −2e − 4 (positive (+) and negative (−) strains represent contraction and extension, respectively). For estimation of ε c at the grain‐scale, the tensile cracking limit of the clay cement present between the quartz grains was calculated as shown in Figure c (Ross et al, ). From this, the grain‐scale ε c value was estimated to be −22e − 4.…”

“…All the peripheral surfaces of the specimens were smooth, flat, and leveled to within 0.01 mm under dry conditions using mechanized grinding. Lyons sandstone has an average grain size of about 190 μm (Bathija et al, ; Henao, ; Mighani et al, ; Ross et al, ; Shukla et al, ; Xu, Hofmann, et al, ). The bulk density of Lyons sandstone specimens was 2.52 g/cm 3 , which is similar to the value reported by Xu, Hofmann, et al ().…”

“…The Lyons sandstone was obtained from Lyons, Colorado, which is in the front range of the Colorado Rocky Mountains (United States). It is aeolian in origin and was formed through the long‐term consolidation of moderately sorted fine‐grained quartz sand dunes (Mighani et al, ; Ross et al, ; Shirole et al, , ; Thompson, ). Because of this, Lyons sandstone is primarily composed of quartz (85–90%) with some presence of clay minerals (10–12%; Henao, ; Ross et al, ; Shukla et al, ).…”

The significance of angular K-feldspar grains in ancient sandstones

“…Colorado (Permian) Brill 1952*;Hubert 1960;McKee and Bigarella 1979*;Maher 1954*;Ross et al 2010;Thompson 1949;Walker and Harms 1972* The Lyons Sandstone is best known from the Colorado Front Range where it extends into the subsurface of southeastern Colorado, western Kansas, and parts of Wyoming and Nebraska (Maher 1954). The Lyons can be traced into New Mexico and is correlative with the Glorieta Sandstone (Brill 1952) The Navajo Sandstone covers most of eastern Utah and parts of Arizona, New Mexico and Colorado.…”