Breccia pipes and associated mineralization in the Grand Canyon region, Northern Arizona

Author(s):  
Karen J. Wenrich ◽  
Peter W. Huntoon
Geosphere ◽  
2020 ◽  
Vol 16 (2) ◽  
pp. 533-545
Author(s):  
Ivo Lucchitta ◽  
Richard Holm

Abstract An ancient drainage, named Crooked Ridge river, is unique on the Colorado Plateau in extent, physiography, and preservation of its alluvium. This river is important for deciphering the generally obscure evolution of rivers in this region. The ancient course of the river is well preserved in inverted relief and in a large valley for a distance of several tens of kilometers on the Kaibito Plateau–White Mesa areas of northern Arizona. The prominent landform ends ∼45 km downstream from White Mesa at a remarkable wind gap carved in the Echo Cliffs. The Crooked Ridge river alluvium contains clasts of all lithologies exposed upstream from the Kaibito Plateau to the San Juan Mountains in Colorado, so we agree with earlier workers that Crooked Ridge river was a regional river that originated in these mountains. The age of Crooked Ridge river cannot be determined in a satisfactory manner. The alluvium now present in the channel is the last deposit of the river before it died, but it says nothing about when it was born and lived. Previous research attempted to date this alluvium, mostly indirectly by applying a sanidine age obtained ∼50 km away, and directly from six sanidine grains (but no zircon grains), and concluded that Crooked Ridge river was a small river of local significance, because the exotic clasts were interpreted to have been derived from recycling of nearby preexisting piedmont gravels; that its valley was not large; and that it only existed ca. 2 Ma. Our proposition in 2013 was that Crooked Ridge river came into being in Miocene and possibly Oligocene time, which is when the very high San Juan Mountains were formed, thus giving rise to abundant new precipitation and runoff. To address some of this ambiguity, we examined all available evidence, which led us to conclude that several of the interpretations by previous researchers are not tenable. We found no evidence for a preexisting piedmont from which the Crooked Ridge river exotic clasts could be recycled. Furthermore, the principal advocate of the piedmont discounted it in a later publication. Tributaries to Crooked Ridge river in the White Mesa area contain no exotic clasts that could have been derived from a local clast-rich piedmont; only the Crooked Ridge river channel contains exotic clasts. So, we conclude that Crooked Ridge river was the principal stream, that it was of regional significance, that it was headed in the San Juan Mountains, and that it existed long before it died, perhaps as early as Oligocene time, until it was captured by the San Juan River, maybe ca. 2 Ma. West and downstream from The Gap, no deposits or geomorphic features attributable to the Crooked Ridge river have been preserved, but we infer that the river joined the Colorado and Little Colorado paleorivers somewhere on the east side of the Kaibab Plateau, and then crossed the plateau along a paleovalley that approximated the present alignment of the eastern Grand Canyon. West of the Kaibab Plateau, the combined rivers perhaps flowed in a northwest-trending strike valley to an as-yet-unknown destination.


2007 ◽  
Vol 72 (2) ◽  
pp. 322-333 ◽  
Author(s):  
Alan P. Sullivan III ◽  
Philip B. Mink II ◽  
Patrick M. Uphus

It is generally presumed that intensive survey yields reliable representations of regional archaeological variability. We evaluate this assumption with an analysis of the results of two intensive surveys of the same terrain in the Upper Basin, a heavily forested upland ecosystem located south of Grand Canyon National Park in Kaibab National Forest, northern Arizona. By comparing differences between the results of site-based surveys with those of mapping-unit-based surveys, we demonstrate that units of observation have a profound effect on how archaeological landscapes and their variability are characterized and interpreted. In addition, results of four analyses of survey data show that the archaeological resource inventories created by the application of these two different units of observation cannot be reconciled. We suggest that because some units of observation may be more appropriate for certain problems and for different kinds of surface and near-surface archaeological records, additional studies of the effects of units of observation on characterizing the archaeological content of the same terrain should become a research priority in survey archaeology. Without such studies, the identification of archaeologically sensitive areas, particularly those that necessitate active management and vigilant protection on public lands, will be underdetermined, thereby placing those heritage properties at risk.


2018 ◽  
Vol 92 (S77) ◽  
pp. 1-33 ◽  
Author(s):  
John-Paul M. Hodnett ◽  
David K. Elliott

AbstractTwo chondrichthyan assemblages of Late Mississippian/Early Pennsylvanian age are now recognized from the western Grand Canyon of northern Arizona. The latest Serpukhovian Surprise Canyon Formation has yielded thirty-one taxa from teeth and dermal elements, which include members of the Phoebodontiformes, Symmoriiformes, Bransonelliformes, Ctenacanthiformes, Protacrodontoidea, Hybodontiformes, Neoselachii (Anachronistidae), Paraselachii (Gregoriidae, Deeberiidae, Orodontiformes, and Eugeneodontiformes), Petalodontiformes, and Holocephali. The euselachian grade taxa are remarkably diverse with four new taxa recognized here; the Protacrodontidae:Microklomax carrieaenew genus new species andNovaculodus billingsleyinew genus new species, and the Anchronistidae:Cooleyella plateranew species andAmaradontus santuciinew genus new species The Surprise Canyon assemblage also has the youngest occurrence of the elasmobranchClairina, previously only known from the Upper Devonian. The Surprise Canyon Formation represents a nearshore fluvial infilling of karstic channels, followed by a shallow marine bioherm reef, and finally deeper open water deposition. The early Bashkirian Watahomigi Formation represents open marine deposition and contains only two taxa: a new xenacanthiform,Hokomata parvanew genus new species, and the holocephalanDeltodus. The relationship between the Surprise Canyon and Watahomigi chondrichthyan assemblages and other significant coeval chondrichthyan assemblages suggests that there may have been eastern and western distinctions among the Euamerican assemblages during the Serpukhovian due to geographic separation by the formation of Pangea.UUID:http://zoobank.org/54a906b6-4873-4f84-92b5-ca0752de01aa


2011 ◽  
Vol 8 (1) ◽  
pp. 115-122
Author(s):  
Dennis Foster ◽  
Craig Bain

In the summer of 1997, the Kaibab National Forest released the Draft Environmental Impact Statement for Tusayan Growth. This report analyzed various scenarios involving the transfer of National Forest land at the boundary of the Grand Canyon National Park to a private developer, in exchange for private inholdings scattered throughout the Kaibab National Forest in northern Arizona. The resulting private development was to be called Canyon Forest Village, and would include hotels, visitor facilities, private housing, community facilities and a transportation center for tourists accessing the Grand Canyon. The proposed build out of Canyon Forest Village (CFV) was to take place from 1999 to 2010. Consequently, the Forest Service analysis used that time frame as the basis for calculating the economic impacts CFV would be expected to have on local economies in the northern Arizona region. The Draft Environmental Impact Statement (EIS) concluded that overall growth in demand for lodging in northern Arizona would be robust over those years, and that CFV would have no net negative impacts. The results of the Draft EIS were sharply contested during the public comment phase, and, in the summer of 1998, a Supplement to the Draft Environmental Impact Statement for Tusayan Growth was issued. This document used a different modeling procedure and changed its primary focus to two, smaller, CFV proposals, involving only 900 and 1,270 hotel rooms. The Supplement did conclude that there would be some negative impacts to the communities surrounding Grand Canyon. The results of the Supplemental Draft EIS were also contested during the public comment phase following its release, although a year later, in the summer of 1999, the Forest Service issued a Final EIS and adopted the CFV proposal for 1,270 rooms. One peculiarity of the Forest Service reports, throughout this process, was the failure to identify an explicit discount rate of interest in order to identify costs and benefits in terms of their present value. While EIS documentation has been required for many years, the obvious focus is on purely environmental concerns and the analyses tend to be based on scientific findings. The inclusion of a socioeconomic analysis necessitates a careful accounting of benefits and costs. While this EIS is not the first to include an explicit accounting of economic benefits and costs, it may serve as a harbinger of more reporting of this type. Unless those with an appreciation of the discounting process, especially economists and accountants, are included in these analyses, present values may be employed only on an erratic basis, making the results of such reports difficult, if not impossible, to adequately interpret. This article applies basic and commonly accepted time value of money principles to an EIS report. Although an economic analysis was provided as part of the report, the time value of money was ignored. In order to present a viable economic impact, these basic financial tenants must be employed. The authors used basic time value of money principles with reasonable discount rates. The result is that impacts could be as much as six times greater than the values given by the Forest Service, representing upwards of one hundred and fifty million dollars.


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