Lower and Middle Cambrian Stratigraphy in Northern Utah and Southeastern Idaho
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BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 69. PP. 647-688. 3 FIGS. JUNE 1958 LOWER AND MIDDLE CAMBRIAN STRATIGRAPHY IN NORTHERN UTAH AND SOUTHEASTERN IDAHO BY GEORGE B. MAXEY ABSTRACT The stratigraphic succession of Lower and Middle Cambrian sediments in northern Utah and southeastern Idaho as determined from 13 measured sections includes the basal medium- to coarse-grained Prospect Mountain Quartzite overlain by interbedded fine- and coarse-grained clastic rocks (Pioche Formation) that in turn are overlain by several hundred to a few thousand feet of carbonate rocks with a few thinly interbedded layers of fine elastics. The carbonate sequence includes the Langston Formation, Ute Limestone, Blacksmith Dolomite, and Bloomington Formation. Known occurrences of fossils are listed for the formations. Seventeen faunal groups are identified, and a sequence of faunizones is proposed. Cambrian deposits may be separated into (1) orthoquartzite; (2) greenish-brown, micaceous and arenaceous shale; (3) brown-weathering, calcareous sandstone; (4) rusty- brown-weathering dolomite; (5) green and buff fissile shale; (6) calcareous black shale; (7) mottled, silty, aphanitic, thinly bedded limestone; (8) Girvanella limestone; (9) intra- formational conglomerate; (10) oolitic limestone; (11) "undifferentiated limestone"; and (12) "undifferentiated dolomite" facies. All these sediments probably were deposited in a shallow, chiefly transgressive, though oscillating, sea. This sea transgressed a low-lying but mature topography eastward to western Utah by earliest Cambrian (pre-Olenellus?) time and to eastern Utah by the end of Early Cambrian time. The area remained submerged during Medial Cambrian and much of Late Cambrian time. CONTENTS „ Langston Formation (Lower and Middle , . Fage Cambrian) ........................... 669 Introduction ............................. 648 Ute Formation ........................ 671 Location and general description of sections Blacksmith Dolomite .................... 672 studied .............................. 649 Bloomington Formation ................. 672 General statement ...................... 649 Early an(j Medial Cambrian faunules in Utah Portneuf and Bannock ranges, Idaho ...... 649 and southeastern Idaho .... ..673 Malad Range, Idaho .................... 649 ZonatiOn of the faunules ................... 676 Bear River Range, Utah and Idaho ....... 650 General statement ...................... 676 General description ................... 650 Olenellus zone .......................... 676 High Creek section ................... 651 Glossofleura-Zacanlhoid.es zone ............ 677 Section on the North Fork of Mill Creek Bathyuriscus-Elrathina zone .............. 678 and Spence Gulch section^ .......... 655 Thompsonaspis zone ..................... 678 Section in the Left Fork of Blacksmith Asaphiscus-Bolaspidella, zone ............. 678 Fork Canyon ....................... 656 Discussion ............................. 678 South Cottonwood Canyon section, Early and Medial Cambrian sedimentation Blacksmith Fork ................... 658 and paleogeograPhy ................... 679 Blacksmith Fork section ............... 658 Description of the lithofacies ............. 679 North part of the Wasatch Range, Utah. 659 Interpretation and paleogeography ........ 685 General statement .................... 659 Selected references ........................ 686 Calls Fort section ..................... 659 Willard Peak section .................. 662 Ogden Canyon section ................. 664 ILLUSTRATIONS Big Cottonwood Creek and Neffs Canyon sections ........................... 664 Fisure Pa«e Summary ............................ 666 1. Location of the stratigraphic sections Promontory Range, Utah ................ 666 studied and outcrops of Cambrian rocks Lower and Middle Cambrian formations in in the region ......................... 648 northeastern Utah and southeastern 2. Lithologic variations within some Lower Idaho and their regional relationships .... 667 and Middle Cambrian formations in Prospect Mountain Quartzite (Lower Cam- northern Utah and southeastern Idaho. 670 brian) ............................... 667 3. Regional correlation and Early and Me- Pioche Formation ....................... 668 dial Cambrian faunules and faunizones. 673 647 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/69/6/647/3431780/i0016-7606-69-6-647.pdf by guest on 02 October 2021 648 G. B. MAXEY—LOWER AND MIDDLE CAMBRIAN STRATIGRAPHY FIGURE 1.—LOCATION OF THE STRATIGRAPHIC SECTIONS STUDIED AND OUTCROPS OF CAMBRIAN ROCKS IN THE REGION INTRODUCTION plex and partly in error on the basis of modern principles and concepts of regional stratig- As part of a regional investigation of the raphy. Many of the conclusions here presented Cambrian rocks of the Great Basin which has are tentative because the field and laboratory been conducted sporadically since 1939, the study is still in progress. Additional informa- writer studied several sections of Lower and tion and more dependable conclusions will be Middle Cambrian rocks in northeastern Utah made available as the study progresses. and southeastern Idaho (Fig. 1). New informa- The writer gratefully acknowledges the tion resulting from this study constitutes the advice and assistance of Dr. Charles Deiss main body of this paper. Suggestions are also and Dr. J. Stewart Williams, both of whom included for simplifying and correcting Cam- encouraged him to begin and continue these brian formational and biostratigraphic nomen- studies. Dr. B. F. Howell consistently and clature which seems to be unnecessarily com- patiently advised the writer throughout the Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/69/6/647/3431780/i0016-7606-69-6-647.pdf by guest on 02 October 2021 INTRODUCTION 649 study; assisted him with many problems, Porlneuf and Bannock Ranges, Idaho chief among these the identification of most of the fossils; and finally read the manuscript. Detailed descriptions of sections of Cambrian Without this advice and assistance the study rocks in the north part of the Bannock Range would probably have never been completed, have been published by Ludlum (1943, p. 973- and for this the writer is sincerely grateful. 986). In the vicinity of Pocatello and Inkom, Dr. Erling Dorf and Dr. Franklin Van Houten Idaho, he found that 3200 feet of Prospect also read the manuscript and offered helpful Mountain ("Brigham") Quartzite unconform- suggestions. Thanks are extended to Dr. ably overlies the Precambrian Blackrock Lime- Norman Denson, Mr. Donald Duncan, Dr. stone. This is one of the few localities in Idaho Franco Rasetti, the late Dr. Charles E. Resser, and northern Utah, outside the Wasatch Range, Dr. John F. Mason, and the late Mr. Frank where the base of the Prospect Mountain For- Beckwith, all of whom contributed much time mation is exposed. The formation is pink to and many ideas. red, thick-bedded, vitreous, medium-grained Funds to finance the field and laboratory quartzose sandstone interbedded with beds work were furnished in part by the Depart- of coarse sandstone and pebble conglomerate. ments of Geology of Princeton University and The upper 600 feet of the formation as de- Utah State Agricultural College. The Univer- scribed by Ludlum is thin-bedded and contains sity of Connecticut also contributed funds for much green or buff siltstone and shale. The laboratory equipment and freed the writer lower part of this shaly and silty sequence may from excessive academic tasks during 1949 and be the lithogenetic equivalent of the Pioche 1950. Field assistants included John W. Wetz- Shale, and the upper part the equivalent of the ler (Summer, 1939), Kent O. Bushnell, and Spence Shale Member of the Langston Forma- Arthur Reimer (Summer, 1950). To these tion. The quartzite is conformably overlain by organizations and individuals the writer is 4250 feet of sparsely fossiliferous limestones indebted and extends his warmest thanks. interbedded with a little shale and sandstone. All sections described for the first time by In the vicinity of Scout Mountain about 10 the writer were measured with a Brunton com- miles south of Pocatello, Idaho, the writer pass and steel tape; adjustments were made to identified lithologic equivalents of the Lang- obtain the correct thicknesses of stratigraphic ston, Ute, and Bloomington Formations which units where necessary. These adjustments were also crop out in adjacent areas of Idaho and usually made by reference to Mertie's chart northern Utah. Time did not allow detailed (1922, PL VI). Rock colors were determined in measurement of this section, but several litho- the field by use of a standard rock color chart logic units and formations were recognized, (Goldman and Merwin, 1928). The color names including the Spence Shale Member of the corresponding to the color chips on the chart Langston Formation and the Hodges and Calls are from Ridgway (1912, p. 1-53). Fort Shale Members of the Bloomington For- mation. An equivalent of the Blacksmith Dolo- LOCATION AND GENERAL DESCRIPTION OF mite probably is absent in this locality. SECTIONS STUDIED A section in the south part of the Bannock Range, about 3 miles north of Malad City, General Statement Idaho, was also examined. Lithologic equiva- lents of the above-mentioned formations, ex- Most of the outcrop areas (Fig. 1) in north- cept the Blacksmith Dolomite, were also rec- eastern Utah and southern Idaho were visited ognized in this area. by the writer during the period