Research Paper GEOSPHERE Provenance of Cretaceous through Eocene strata of the Four Corners region: Insights from detrital zircons in the San Juan Basin, GEOSPHERE; v. 14, no. 2 New Mexico and Colorado doi:10.1130/GES01485.1 Mark E. Pecha1, George E. Gehrels1, Karl E. Karlstrom2, William R. Dickinson1,†, Magdalena S. Donahue2, David A. Gonzales3, and Michael D. Blum4 12 figures; 3 tables; 3 supplemental files 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA 2Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico 87131, USA 3Department of Geosciences, Fort Lewis College, 1000 Rim Drive, Durango, Colorado 81301, USA CORRESPONDENCE: mpecha@ email .arizona .edu 4Department of Geology, University of Kansas, Lindley Hall, 1475 Jayhawk Boulevard, Room 120, Lawrence, Kansas 66045, USA CITATION: Pecha, M.E., Gehrels, G.E., Karlstrom, K.E., Dickinson, W.R., Donahue, M.S., Gonzales, D.A., and Blum, M.D., 2018, Provenance of Creta‑ ABSTRACT this transition initiated ~8 m.y. earlier during deposition of the Campanian ceous through Eocene strata of the Four Corners Kirtland Formation beginning ca. 73 Ma. This final change in provenance is region: Insights from detrital zircons in the San Juan Cretaceous through Eocene strata of the Four Corners region provide an interpreted to reflect the unroofing of surrounding Laramide basement blocks Basin, New Mexico and Colorado: Geosphere, v. 14, no. 2, p. 785–811, doi:10.1130/GES01485.1. excellent record of changes in sediment provenance from Sevier thin-skinned and a switch to local derivation. At this time, sediment entering the San Juan thrusting through the formation of Laramide block uplifts and intra-foreland Basin was largely being generated from the nearby San Juan Mountains to Science Editor: Shanaka de Silva basins. During the ca. 125–50 Ma timespan, the San Juan Basin was flanked the north-northwest, including uplift associated with early phases of Colorado Associate Editor: Graham D.M. Andrews by the Sevier thrust belt to the west, the Mogollon highlands rift shoulder mineral belt magmatism. Thus, the detrital-zircon spectra in the San Juan to the southwest, and was influenced by (ca. 75–50 Ma) Laramide tectonism, Basin document the transition from initial reworking of the Paleozoic and Received 11 December 2016 ultimately preserving a >6000 ft (>2000 m) sequence of continental, marginal- Mesozoic cratonal blanket to unroofing of distant basement-cored uplifts Revision received 9 September 2017 marine, and offshore marine sediments. In order to decipher the influences of and Laramide plutonic rocks, then to more local Laramide uplifts. Accepted 5 January 2018 Published online 16 February 2018 these tectonic features on sediment delivery to the area, we evaluated 3228 U-Pb laser analyses from 32 detrital-zircon samples from across the entire San Juan Basin, of which 1520 analyses from 16 samples are newly reported INTRODUCTION herein. The detrital-zircon results indicate four stratigraphic intervals with internally consistent age peaks: (1) Lower Cretaceous Burro Canyon Forma- U-Pb detrital-zircon (DZ) geochronology has played an integral role in de- tion, (2) Turonian (93.9–89.8 Ma) Gallup Sandstone through Campanian (83.6– ciphering sediment-dispersal patterns in Cretaceous and Paleogene strata of 72.1 Ma) Lewis Shale, (3) Campanian Pictured Cliffs Sandstone through Cam- North America (e.g., Lawton and Bradford, 2011; Dickinson et al., 2012; Blum panian Fruitland Formation, and (4) Campanian Kirtland Sandstone through and Pecha, 2014; Bush et al., 2016; Sharman et al., 2017). DZ analyses allow Lower Eocene (56.0–47.8 Ma) San Jose Formation. Statistical analysis of the for generation of a DZ fingerprint (Ross and Parrish, 1991) of the host rock, detrital-zircon results, in conjunction with paleocurrent data, reveals three dis- establishing provenance ties between host rock and source region(s) (Gehrels tinct changes in sediment provenance. The first transition, between the Burro and Pecha, 2014), and for calculation of maximum depositional age of host OLD G Canyon Formation and the Gallup Sandstone, reflects a change from predom- rock (Surpless et al., 2006; Dickinson and Gehrels, 2009b), which can then be inantly reworked sediment from the Sevier thrust front, including uplifted compared to biostratigraphic age where available. Combining DZ ages with Paleozoic sediments and Mesozoic eolian sandstones, to a mixed signature fluvial paleocurrent information bolsters provenance ties and allows for re- indicating both Sevier and Mogollon derivation. Deposition of the Pictured gional paleogeographic reconstructions (Lawton and Bradford, 2011; Dickin- OPEN ACCESS Cliffs Sandstone at ca. 75 Ma marks the beginning of the second transition son et al., 2012). and is indicated by the spate of near-depositional-age zircons, likely derived Cretaceous through Lower Eocene strata preserved in the San Juan Basin from the Laramide porphyry copper province of southern Arizona and south- (SJB) in northwestern New Mexico and southwestern Colorado provide a western New Mexico. Paleoflow indicators suggest the third change in prove- unique opportunity to study spatial and temporal variations in sediment prov- nance was complete by 65 Ma as recorded by the deposition of the Paleocene enance using DZ geochronology. During the deposition of these sediments, Ojo Alamo Sandstone. However, our new U-Pb detrital-zircon results indicate the SJB region was flanked by the Sevier thrust belt, the Mogollon highlands This paper is published under the terms of the rift shoulder, and was also influenced by Laramide tectonism (ca. 75–50 Ma). CC‑BY‑NC license. †Deceased 21 July 2015, during preparation of manuscript Understanding how these surrounding tectonic elements influenced sediment © 2018 The Authors GEOSPHERE | Volume 14 | Number 2 Pecha et al. | Detrital zircons from the San Juan Basin Downloaded from https://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/doi/10.1130/GES01485.1/4110452/ges01485.pdf 785 by University of Kansas user on 08 November 2019 Research Paper delivery to the Four Corners region, particularly the SJB, is the overall goal of morphology (Elston and Young, 1991). Estimates of the thickness of pre-Cre- this research. taceous Mesozoic strata eroded from the Colorado Plateau range from Here we synthesize new and existing DZ data from Cretaceous and Paleo- ~3000 to 5000+ ft (~1000–1500 m), with thickness increasing from south-south- gene strata and combine the observations with paleoflow information to make east to north-northwest (Wilson, 1967; Pederson et al., 2002; Lazear et al., provenance assessments and paleogeographic interpretations. We also use 2013). It is also estimated that an additional ~1000–3000 ft (~300–1000 m) the DZ ages to refine maximum depositional ages of the units by comparing of Cretaceous strata were removed during Cenozoic beveling (Wilson, 1967; them with biostratigraphic ages. Our new U-Pb DZ data indicate that three Epis and Chapin, 1975; Evanoff and Chapin, 1994; Pazzaglia and Kelley, 1998). distinct changes in sediment provenance occur in the Cretaceous through Eo- This extensive erosion resulted in removal of most Cretaceous and younger cene section of the SJB. The results track changes in sediment routing from rocks, leaving a wide region around Four Corners predominantly devoid of initial reworking of the Paleozoic and Mesozoic cratonal blanket to unroofing of the entire Cretaceous section. The San Juan Basin (SJB) in northwestern distant basement-cored uplifts and Laramide plutonic rocks, then to more local New Mexico and southwestern Colorado is an exception, preserving a se- Laramide uplifts. The results also provide additional clarity in sediment routing quence of Cretaceous and younger sediments exceeding 6000 ft (~2000 m) during the transition from Sevier retroarc thrusting through foreland basin par- in total thickness. The SJB represents the best preserved, deepest, and most titioning during the Laramide, providing important insights into sediment-dis- comprehensive section that characterizes the Cretaceous/Paleogene stratig- persal patterns and paleogeographic reconstructions. These new results fill raphy of the region. in gaps from previous DZ studies (e.g., Dickinson and Gehrels, 2008; Gehrels et al., 2011; Lawton and Bradford, 2011; Dickinson et al., 2012) of Paleozoic and Mesozoic Colorado Plateau stratigraphy and Paleogene units (Dickinson et al., San Juan Basin 2010; Donahue, 2016). We define the SJB as the contiguous area that encompasses Lower Cre- taceous through Eocene strata preserved in northwestern New Mexico and GEOLOGIC SETTING southwestern Colorado (Figs. 1 and 2). It is a structurally-bound intra-foreland basin that encompasses more than 46,000 km2. It developed coevally with the The Four Corners region was part of an expansive late Mesozoic Cor- adjacent Laramide tectonic features: San Juan (Needle Mountains) uplift to di lleran foreland basin system (Fig. 1) related to loading of the Sevier retroarc the north, Archuleta anticlinorium and/or San Juan sag to the northeast, Naci- fold and thrust belt to the west (Armstrong, 1968; Jordan, 1981; DeCelles, miento uplift on the east, Zuni uplift to the south, Defiance uplift on the west, 2004) and flanked on the southwest by the Mogollon highlands rift shoulder, and Hogback monocline to the northwest (Kelley, 1950, 1951, 1957) (Fig. 2). a high-standing structural feature that formed at the same time as