https://doi.org/10.1130/G46338.1 Manuscript received 3 April 2019 Revised manuscript received 10 July 2019 Manuscript accepted 11 August 2019 © 2019 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 4 September 2019 Earliest Jurassic U-Pb ages from carbonate deposits in the Navajo Sandstone, southeastern Utah, USA Judith Totman Parrish1*, E. Troy Rasbury2, Marjorie A. Chan3 and Stephen T. Hasiotis4 1 Department of Geological Sciences, University of Idaho, P.O. Box 443022, Moscow, Idaho 83844, USA 2 Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, USA 3 Department of Geology and Geophysics, University of Utah, 115 S 1460 E, Room 383, Salt Lake City, Utah 84112-0102, USA 4 Department of Geology, University of Kansas, 115 Lindley Hall, 1475 Jayhawk Boulevard, Lawrence, Kansas 66045-7594, USA ABSTRACT with the lower part of the Navajo Sandstone New uranium-lead (U-Pb) analyses of carbonate deposits in the Navajo Sandstone in across a broad region from southwestern Utah southeastern Utah (USA) yielded dates of 200.5 ± 1.5 Ma (earliest Jurassic, Hettangian Age) to northeastern Arizona (Blakey, 1989; Hassan and 195.0 ± 7.7 Ma (Early Jurassic, Sinemurian Age). These radioisotopic ages—the first re- et al., 2018). The Glen Canyon Group is under- ported from the Navajo erg and the oldest ages reported for this formation—are critical for lain by the Upper Triassic Chinle Formation, understanding Colorado Plateau stratigraphy because they demonstrate that initial Navajo which includes the Black Ledge sandstone (e.g., Sandstone deposition began just after the Triassic and that the base of the unit is strongly Blakey, 2008; Fig. DR1A). time-transgressive by at least 5.5 m.y. Age assignments of the Glen Canyon Group and underlying formations have been in a state INTRODUCTION These are lithostratigraphic units, and definition of flux (Marsh, 2014), partly because of dis- The Navajo Sandstone in southeastern Utah of the boundaries between them is commonly crepancies between the geochronological and (United States) represents the largest erg in Earth arbitrary, particularly where they interfinger and/ biostratigraphic records—a global problem in history (e.g., Blakey et al., 1988), cropping out or have gradational relationships. The literature chronostratigraphy—but also because of pos- on much of the Colorado Plateau (Fig. 1). Fos- on the Glen Canyon Group is voluminous, and sible overreliance on the continental biostrati- sils are generally lacking, poorly preserved, and/ a comprehensive review is outside the scope of graphic record (Olsen et al., 2010; see also Irmis or not age diagnostic. Determining the age of this report. Useful general reviews are Blakey et al., 2010; Marsh, 2014). Quantitative age esti- the Navajo Sandstone has, therefore, been chal- (2008) and Dickinson (2018), and additional mates have come from detrital zircon (DZ) and lenging. The Navajo Sandstone contains car- reviews can be found in Peterson and Pipirin- magnetostratigraphy (Fig. 2). bonate deposits laid down in lakes and springs gos (1979), Blakey (1989), and Sprinkel et al. The Kayenta Formation, Moenave Forma- (Parrish et al., 2017) from which we report the (2011), as well as others. tion, and Black Ledge sandstone have yielded first radioisotopic ages, acquired by U-Pb dat- The Wingate and Navajo Sandstones are DZ ages broadly consistent with their deposi- ing. The dates reported here set the stage for predominately eolian (Blakey, 1989); the Moe- tional ages as determined from biostratigraphy future work on the development of the Navajo nave and Kayenta Formations contain inter- or magnetostratigraphy (Dickinson and Geh- erg and provide a framework for understanding bedded eolian, fluvial, and lacustrine deposits rels, 2009a; Table DR1 in the Data Reposito- mechanisms of the evolution of the basin in the (e.g., Clemmensen et al., 1989; Blakey, 2008; ry). Marsh (2014) dated the Kayenta Formation Jurassic Period. Suarez et al., 2017). The Moenave Formation is with DZ in northern Arizona at 183.7 ± 1.7 Ma, divided into two members, the Dinosaur Can- ∼12 m.y. younger than the dates obtained by PREVIOUS WORK ON THE AGE OF yon Member and the overlying Whitmore Point Dickinson and Gehrels (2009a) from their clos- THE NAVAJO SANDSTONE Member. The Moenave Formation is overlain est sample location of the Kayenta Formation The Navajo Sandstone is the upper formation by the Springdale Sandstone, which has been near Moenkopi, Arizona (Fig. 1; Table DR2). of the Glen Canyon Group, which in southern assigned variously as the upper member of the DZ ages from the Moenave Formation west of Utah and northern Arizona includes the Wing- Moenave Formation (Steiner, 2014a) or, more Kanab, Utah, yielded dates ca. 201.3 Ma (Su- ate Sandstone, Moenave Formation, Kayenta commonly, the lower member of the overlying arez et al., 2017; Fig. 2; Table DR2). The Chinle Formation, and Navajo Sandstone (generalized Kayenta Formation (Lucas and Tanner, 2006; Formation, which underlies the Glen Canyon in Fig. DR1A in the GSA Data Repository1). Dickinson, 2018, p. 93). In east-central Utah, the Group, is well dated using DZ (Irmis et al., Glen Canyon Group consists solely of the Wing- 2011; see also Riggs et al., 2003; Ramezani ate Sandstone, Kayenta Formation, and Navajo et al., 2011). The youngest dates from the Chinle *E-mail: [email protected] Sandstone. The Kayenta Formation interfingers Formation are 203–204 Ma (Rhaetian) from the 1GSA Data Repository item 2019359, details of methods, sample descriptions, and supplementary tables and figures, is available online athttp://www.geosociety. org/datarepository/2019/, or on request from [email protected]. CITATION: Parrish, J.T., et al., 2019, Earliest Jurassic U-Pb ages from carbonate deposits in the Navajo Sandstone, southeastern Utah, USA: Geology, v. 47, p. 1015–1019, https://doi.org/10.1130/G46338.1 Geological Society of America | GEOLOGY | Volume 47 | Number 11 | www.gsapubs.org 1015 Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/47/11/1015/4852055/1015.pdf by guest on 23 September 2021 Figure 1. Map of study 180 San Rafael area and sample loca- GS3 RT US191 N 8 Navajo Ss (this study) 110°W 111°W Swell 109°W 39°N tions, southeastern Utah 182 * Kayenta Fm 39°N 4 and surrounding areas TC * Springdale Ss HR I-70 Green Rive * Whitmore Point Mbr, Moenave Fm COL Dinosaur Canyon Mbr, Moenave Fm 200 m (USA) (see Table DR3 [see 184 * 5 km ORADO Wingate Ss 2,10,11 footnote 1] for more infor- * Black Ledge ss r Moab * Chinle Fm 2 mation). Colors indicate 100 m 186 114°W North Wash formations sampled; see 7 38°N 38°N KU 112°W 113°W UTAH Figure 2 for color expla- 400 m 188 Dolores2 nation. Inset at lower right DAVA Black Kitchen shows outline of Colorado M11 NE I-15 Corral Canyon9 Comb Plateau (UT—Utah; CO— 190 2 TC4 800 m Canyon Ridge1 Colorado; NV—Nevada; 2 37°N 37°N CA—California; AZ—Ari- 192 MO Potter Kanab5,6,7 NEW MEXIC zona; NM—New Mexico). Canyon9 Inset at upper left is loca- Echo 194 er tion enlargement near KC2 2 Riv 1 DO do * a O r 4 Moab, Utah (black outline 6 2 2 lo Tuba City KU KC M o 196 36°N C 36°N box in main map), marking M2 Moenkopi2 sample locations for this * W ARIZONA study: Rocky Tops (RT), 198 109° M11 38.62881°N, 109.77227°W; KU5 * * 200 I-40 3 Horsethief Road (HR), PC/ Gold Spring 1 UT 9 EC 10 CO BC M 1 35°N 38.597°N, 109.88651°W. * * CR NV * Solid yellow line shows 202 W W W W I-17 W generalized outline of SR8 112° 113° 114° 111° 110° ? * 100 km NM Navajo Sandstone out- 204 CA AZ crop; dotted yellow lines are isopachs (Dickinson, 206 2018, his figure 55). Local- ities are from: 1—Molina-Garza et al. (2003); 2—Dickinson and Gehrels (2009a); 3—Marsh (2014); 4—Bazard and Butler (1991); 5—Steiner (2014a); 6—Steiner (2014b); 7—Steiner and 208 Tanner (2014); 8—Umbarger (2018); 9—Suarez et al. (2017); 10—Steiner and Helsley (1974); Ma 11—this study. Figure 2. Summary of geochronological data on Glen Canyon Group (southwestern USA) lower part of the Church Rock Member in the of such intervals in the Hettangian in the Newark and selected subjacent strata. Asterisks are San Rafael Swell (Umbarger, 2018). Basin (Kent et al., 2017). detrital zircon (DZ) dates; triangles are U-Pb dates from this study. Thin vertical lines Efforts to define ages based on magneto- (error bars) on DZ dates were provided by stratigraphy of the Glen Canyon Group have METHODS their respective authors, except for DZ ages also yielded age estimates. These results were Samples were collected from six carbonate at Potter Canyon and Black Canyon (Suarez calibrated against the Newark Basin (north- units described by Parrish et al. (2017) in the et al., 2017); those two ages and their error bars not resolvable at this scale. Thick vertical eastern United States) magnetostratigraphy erg margin of the Navajo Sandstone (Fig. 1; lines are ages specified from magnetostratig- (Molina-Garza et al., 2003; Kent et al., 2017; see sample descriptions in Table DR3). They raphy as reported by their respective authors. Suarez et al., 2017), paleopole paths (Steiner were analyzed by laser ablation for U/Pb (Table Data are arranged roughly west (left) to east and Helsley, 1974; Bazard and Butler, 1991), or DR4); three samples were then chosen for iso- (right). PC/BC—Potter Canyon, Arizona (AZ), the Paris Basin (France) (Steiner, 2014a, 2014b; tope dilution analyses.