Arizona State and Local Government Documents Collection

Throughout the southwestern United States, vegetation in what historically was grassland has changed to a mixture of trees and shrubs; exotic grass species and undesirable shrubs have also invaded the grasslands at the expense of native grasses. The availability and amount of soil nutrients influence the relative success of plants, but few studies have examined fire effects on soil characteristics in a temporal, spatial, and species group-specific fashion. Likewise, few studies have tied fire effects and ecological aspects to the underlying geology. Our research investigates the effects of fire events on selected soil characteristics pH, nitrate (NO3-), plant-available phosphorus (PO4-3), and total organic carbon (TOC) on native grass-, exotic grass-, and mixed grass-dominated plots distributed on four different geological surfaces. Treated and control plots were sampled prior to burn treatment and at intervals after the burns. In addition to new geologic mapping of the study areas, results indicate the geologic substrate is the most important variable for explaining pH, NO3- and PO4-3 values in the soils. Dominant grass type – native, non-native, or mixed – had little effect on the response of soil geochemistry to fire events: post-burn results indicate vegetation was a significant factor only for TOC. Recovery to pre-burn levels varies with characteristic: there were no significant initial differences between vegetation types, but significant differences in NO3-, PO4-3, and TOC amounts occur as a result of fire events, geological characteristics, and time. The research helps identify the soil response to fire and the recovery times of soil characteristics, further defines which fire frequency is optimal as a management strategy to maximize soil macronutrient contents, and illustrates the important role geology plays in grassland ecosystems.

Seven sinkholes surround the city of Sedona in Coconino and Yavapai Counties, Arizona. They occur in surface bedrock of Permian age Esplanade Sandstone, Hermit formation, and Schnebly Hill Sandstone, but the causative source is from the collapse of subsurface water-filled caves in Mississippian Redwall Limestone that underlies those formations. The original Mississippian-age Redwall karst surface has undergone two additional phases of dissolution enlargement in later geologic time. The first occurred after the Laramide uplift of the Mogollon Highlands when northeast flowing streams penetrated the exposed Redwall Limestone erosion surface, and the second took place following the generation of the Verde graben ~10 million years ago when regional drainage reversal took place. Pre-graben Miocene basalt lava flows that overlie eroded Paleozoic strata are present on either side of, and faulted within, the Verde graben closed depression. Post-graben erosion generated the Mogollon Rim escarpment in the northern portion of the Verde Valley and allowed surface streams to erode the broad Dry Creek and Margs Draw valleys. Oak Creek fault, and the erosion of its canyon, is much younger than the faulting that generated the Verde graben.

Over time, water flow through the Sedona area evolved from surface flow to dominantly groundwater flow, mainly due to leakage through abundant northwest-southeast oriented rock joints and permeable fault zones into underlying cavernous Redwall Limestone. USGS oxygen isotope studies show that water recharge entering the northeastern part of the Upper Verde watershed, and passing beneath the greater Sedona area, originated high on the Colorado Plateau above 6900 feet before discharging at a rate of ~15 millions of gallons per day at artesian springs in the Page Springs area to the southwest of Sedona. Dissolution caves in the underlying Redwall Limestone have now enlarged to the point where their sandstone roof rocks have collapsed into limestone caves over the past several thousand years. Devils Kitchen sinkhole has historic records of collapse in the 1880s, 1989 and 1995, and it will continue to collapse in future years.

Six additional sinkholes are in various stages of collapse from modern time and possibly to the end of the last Ice Age. While the danger of future collapse is probably minimal to humans, unregulated septic leakage into hidden sinkhole breccias within the town limits could contaminate groundwater being tapped for municipal use or the contamination of the Page Springs outflow. The report contains geologic maps, cross sections, photographs and individual features of the sinkholes as of the end of 2009.

At the request of the U.S. Forest Service to Red Rock Jeep Tours of Sedona a geologic report on the condition of the Devils Kitchen sinkhole was required for the safe continuation of Jeep visits to the site (Fig. 1). Mark Avery of the jeep company contacted me to study the site and write up my findings. The study of sinkholes in the Sedona area has been of interest to the writer for some time and the present study is hoped to shed some light on these fascinating geologic features. This report is offered as a public contribution at the cost of publication and without fee.

A brief reconnaissance (5-8 November 2008) of the Big Sandy Formation near Wikieup (on US Highway 93 in Mohave County, Arizona) was undertaken to reconcile a reported dominance of lacustrine beds (Sheppard and Gude, 1972, 1973) with the largely terrestrial mammalian fauna reported from the formation (MacFadden et al., 1979; Lindsay and Mead, 2005). The issue is resolved satisfactorily by appreciation that nearly all fossil localities occur in fluvial beds that intertongue with and grade laterally into the dominant lacustrine strata.

To provide insight into provenance relations for multiple mid-Oligocene to mid-Miocene subbasins
(typically half-grabens) dissected by erosion in uplands lying north of the Catalina core complex and west of the San Pedro trough, 136 outcrop counts were made of clast types in tilted conglomerates of the Cloudburst and San Manuel Formations and their lateral equivalents in exposures as far north as the Gila River near Kearny. Clast counts were not made for younger conglomerates of the post-mid-Miocene Quiburis Formation, which fills the San Pedro trough and onlaps flanking uplands (Dickinson, 1998), because Quiburis clast assemblages in all cases match bedrock sources exposed uphill on the modern landscape. By contrast, paleotopography during Cloudburst and San Manuel deposition can only be inferred from local paleocurrent indicators (clast imbrications; figure 39 of Dickinson, 1991, p. 70-71) and clast assemblages in tilted strata. Areas included in this study were the Guild Wash allochthon between the Tortolita and Suizo Mountains, the Star Flat allochthon on the east flank of the Black Mountains, the
Black Hills (west of Mammoth), Camp Grant Wash (and Putnam Wash) between the Black Mountains and the Black Hills, multiple drainages of the Tortilla Mountains (Eagle Wash, Jim Thomas Wash, Hackberry Wash, Indian Camp Wash), and Ripsey Wash on the west flank of the Tortilla Mountains (Figs. 1-4).

This white paper has been created by Arizona Land Subsidence Group to help educate stakeholders and decision makers by describing the geological features and processes of land subsidence and earth fissures, and the hazards they create. This paper presents the current and future technical needs that exist in terms of basic knowledge, available data, and the state of professional practice.

This report details geothermal resource exploration done for Arizona Public Service and the U.S. Department of Energy in 2005 to evaluate the geothermal resources of the Clifton Hot Springs area in Greenlee County, eastern Arizona for electric power production. The intent of the evaluation was to determine the local geologic controls of the geothermal system and, using publicly available data and original mapping performed for this project, to recommend locations for Controlled Source Audiomagnetotelluric (CSAMT) cross sections. The results of the geophysics were then combined with the geologic mapping to site three gradient holes, two of which were drilled to depths of 635 feet and 1,000 feet, respectively.

This summary report overviews a State of Arizona and U. S. Department of Energy funded drilling project to determine if near-term hot dry rock (HDR) geothermal potential exists in the eastern portion of the White Mountains region of Arizona. A 4,505 feet deep slim-hole exploratory well, Alpine1/Federal, was drilled within the Apache-Sitgreaves National Forest at Alpine Divide near the Alpine Divide camp ground about 5 miles north of Alpine, Arizona in Apache County (Figure 1). A comprehensive technical report, in two parts, details the results of the project. Part 1, Alpine1/Federal, Drilling Report, discusses the drilling operations,
logging program, permitting and site selection for the hole. Part 2, Temperature Gradients, Geothermal Potential, and Geology, summarizes the temperature gradients, heat flow, geothermal potential, and subsurface geology.

In March 1971, the Arizona Bureau of Mines—predecessor of today’s Arizona Geological Survey—published the first issue of Fieldnotes. For nearly 40 years, Fieldnotes, and its successor, Arizona Geology, showcased all things geologic in Arizona. From the onset, the quarterly magazine printed topical pieces on Arizona’s mineral resources, energy potential, and environmental geology. In Fall 1988, Fieldnotes became Arizona Geology, and the newsletter was retailored to meet the needs of Arizona’s exploding population. There was increased focus on articles describing geologic phenomena—flash floods and regional floods, earthquakes, landslides, volcanism, swelling and shrinking soils, earth fissures, and more—with the most immediate and adverse impact on the lives and properties of our fellow Arizonans. But that was then and this is now! As print publication costs rise through the stratosphere, we simply can no longer afford to print and mail 4100 copies of Arizona Geology quarterly. Arizona Geology is going digital. We are suspending the print publication immediately and we are moving from a quarterly schedule to three times annually.