basin bounded to the west by the Sevier orogenic belt and to the south by the ... John Henry Member (Eaton, this volume), and correlation of the. Calico bed to ...
Geological Society of America Special Paper 260 1991
Introduction; Tectonic setting along the margin of the Cretaceous Western Interior Seaway, southwestern Utah and northern Arizona Jeffrey G. Eaton Department of Geology, Museum of Northern Arizona, Flagstaff, Arizona 86001 3. Dale Nations Department of Geology, Northern Arizona University, Flagstaff, Arizona 86011
INTRODUCTION The eastward-directed thrusting along the north-northeasttrending Sevier orogenic belt first occurred in the late Early Cretaceous (Armstrong, 1968; Villien and Kligfield, 1986); thrusting moved progressively eastward possibly through the late Paleocene (Villien and Kligfield, 1986). The orientation of the orogenic belt appears to be controlled by the western edge of the Precambrian craton (Picha, 1986). Pre-late Cenomanian uplift in the area of the Mogollon Highlands (Fig. 2) of central southern Arizona has been proposed by Harshbarger and others (1957), Drewes (1981), and Bilodeau (1986). These highlands limited southwestward transgression of the epeiric seaway, provided sediments to the foreland basin, and perhaps served as a hinge line controlling subsidence rates along the southern margin of the Grand Canyon Bight. Imposed on this structural framework were large-scale eustatic sea-level fluctuations described by Kauffman (1969, 1977) and Molenaar (1983) that resulted in a variety of complex depositional patterns reflecting the interactions of tectonics and eustacy (see this volume Elder; Kirkland; Carr). The resultant foreland basin is complex both in terms of the subtle tectonics that shaped it and the sources of the elastics that filled it.
Deposits formed along the margins of seaways record the complex interactions of uplift, subsidence, sedimentary influx, distributary systems, tides, currents, and eustacy, as well as diverse biological assemblages. It is for this reason that depositional environments along marine margins can be among the most difficult to interpret but also can provide a wealth of detailed information. This Special Paper is a result of a symposium entitled "Sedimentary facies, biostratigraphy, and paleoecology of the Cretaceous Western Interior Seaway, southern Colorado Plateau region," held at the 1987 Geological Society of America national meeting in Phoenix. The chapters included herein are intended to be data-oriented in order to augment the fundamental data base for interpreting both the evolution of the Western Interior seaway and deposits formed marginal to seaways in general. Chapters included here are presented in a sequence beginning just west of the maximum extent of the epicontinental seaway and tracing the seaway eastward across southwestern Utah, northwestern Arizona, and into New Mexico (Figs. 1, 2). The described stratigraphic sequences span the history of the seaway in the area (Fig. 3). TECTONIC SETTING
Southwestern Utah The Cretaceous strata along the southwestern margin of the Cretaceous epeiric seaway were deposited in a subsiding foreland basin bounded to the west by the Sevier orogenic belt and to the south by the Mogollon Highlands (Molenaar, 1983) (Fig. 2). This junction of two nearly perpendicular structural trends near the westernmost part of the Utah-Arizona border resulted in a Vshaped embayment, known as the "Grand Canyon Bight," at peak transgression (Stokes and Heylmun, 1963).
The basal Dakota conglomerate is variably developed across the area and was deposited by gravelly braided streams on an angular unconformity. Gustason (1989) considered the age of this basal conglomerate to be Albian (Early Cretaceous) on the basis of the occurrence of widespread conglomerates of this age in the Western Interior and its unconformable relation with the overlying middle member of Cenomanian age. However, Heller and
Eaton, J. G., and Nations, J. D., 1991, Introduction; Tectonic setting along the margin of the Cretaceous Western Interior Seaway, southwestern Utah and northern Arizona, in Nations, J. D., and Eaton, J. G., eds., Stratigraphy, depositional environments, and sedimentary tectonics of the western margin, Cretaceous Western Interior Seaway: Geological Society of America Special Paper 260.
1
Eaton and Nations
Figure 1. The Western Interior seaway during maximum transgression in early Turonian time (modified from Kauffman, 1984). Arizona, Utah, New Mexico, and Colorado are outlined.
Paola (1989) have suggested that the widespread distribution of Altaian conglomerates indicates that these could not have been generated as a direct result of Sevier thrusting, leaving the relation of the Dakota conglomerate to conglomerates of known Albian age uncertain. The stratigraphically lowest syntectonic conglomerate bounded by Cretaceous rocks is the Calico bed of the Smoky Hollow Member of the Straight Cliffs Formation (Peterson, 1969b). The westernmost documented occurrence of this conglomerate is east of Cedar City (Gustason, 1989), but a conglomerate stratigraphically high in the Pine Valley Mountains sequence may be equivalent. The distinctive Calico conglomerate is well developed in the western Markagunt Plateau region and is continuous to the eastern side of the Kaiparowits Plateau. The age of the Calico conglomerate is uncertain. Peterson (1969a, b) inferred the presence of an unconformity spanning the late Turonian through the Coniacian between the Calico bed and the overlying John Henry Member. Field examination of relations at the base and top of the Calico bed, dating of the lower part of the John Henry Member (Eaton, this volume), and correlation of the Calico bed to the upper part of the Toreva Formation at Black
Mesa (Eaton and others, 1987) suggest that if an unconformity is present, it occurs between the base of the Calico and the underlying fine-grained deposits of the Smoky Hollow Member (Fig. 3). This would imply a latest Turonian age for the Calico bed itself, with the unconformity restricted to the late Turonian. Other regional syntectonic conglomerates have distributions similar to that of the Calico. A conglomerate in the latest Santonian or early Campanian (Eaton, this volume) Drip Tank Member of the Straight Cliffs Formation, is variably developed on the Kaiparowits Plateau, and a conglomerate in the same stratigraphic position is well developed on the east side of the Paunsaugunt Plateau. It may be correlative with a gritty sandstone present on the west side of the Markagunt Plateau. A thick conglomerate present at the top of the Wahweap Formation in the northwestern part of the Kaiparowits Plateau (but not in the central part; Eaton, this volume) has been tentatively traced into a gravel deposit on the Paunsaugunt Plateau. None of these conglomerates are well developed in westernmost Utah adjacent to the thrust belt. They occur east of the thrust belt as widespread, possibly northeast-oriented bodies, with each successively younger conglomerate more completely developed east of the previous. This suggests that the coarse elastics were transported from the area of southern California and southeasternmost Nevada across northwestern Arizona, as has been proposed for later deposits (Schmitt and others, this volume). The progressive eastward development of conglomerates through time and the greater eastward thickening of progressively younger units (e.g., Kaiparowits Formation, Eaton, this volume) may reflect eastward migration of the axis of subsidence in the foreland basin through time. Previous interpretations of southwestern Utah represented by the Utah State Geologic Map (Hintze, 1980) and based on Gregory and Moore (1931),
Figure 2. Index map showing areas of Upper Cretaceous outcrops (shaded pattern), maximum extent of the epeiric sea (dashed line), major tectonic features, and geographic location of subject matter of chapters presented in this volume (numbers represent the sequence in which chapters are presented) (after Molenaar, 1983).
Introduction Gregory (1944, 1950, 1951), and Cook (1957) indicate that the stratigraphic sequence present on the Kaiparowits Plateau is continuous westward across Utah. If the sequence is representative of a simple progradational wedge generated west to east from the orogenic belt, it would be expected that conglomerates would thin away from the thrust belt, and as thrusting progressed eastward, successively younger conglomerates might be distributed farther into the basin (Fig. 4A). An alternative model presented in Figure 4B suggests that subsidence was greater initially near the Sevier orogenic belt, resulting in very thick deposits equivalent in time to the Dakota, Tropic Shale, and lower Straight Cliffs formations to the east. Maximum subsidence may have occurred during the Cenomanian-Turonian in the Pine Valley Mountains area where the very thick Cretaceous section consists of braided GUNLOCK AREA I
I
stream sandstones separated by relatively thick mudstone deposits. This thick western section may have thinned between the Pine Valley Mountains and the Cedar City area as a result of syndepositional folding (Moir, 1974). The easterly migration of the foreland basin axis was apparently not laterally uniform (Fig. 5). Cretaceous sediments thin markedly across the Paunsaugunt Plateau, suggesting that through much of the Cretaceous this area subsided more slowly than adjacent parts of the basin. Recent examination of Cretaceous strata overlying the Tropic Shale on the Paunsaugunt Plateau indicates marked lithostratigraphic changes across the mid-Tertiary Sevier and Paunsaugunt faults that bound the plateau (Eaton and Morrow, 1989). Controls on deposition of the Dakota Formation and Tropic Shale along these fault trends have GALLUP SAG 10
KAIPAROWITS BASIN BLACK MESA BASIN, 2,3,4 I 5,6,7,8,9 I PINE HOLLOW FM.
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WAHWEAP FM.
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Figure 5. Stratigraphic cross section interpreted from measured sections: (1) Fillmore, this volume; (2) Cook, 1957, Section 3 (3) Gregory, 1950, Section 15; (4) Gregory, 1950, Section 16; (5) Gregory, 1951, Section 10; and (6) Bowers, 1972; Eaton, 1987). Circled numbers refer to the major conglomerates: (1) basal Dakota Formation; (2) Calico bed, Smoky Hollow Member, Straight Cliffs Formation; (3) John Henry Member (?), middle Straight Cliffs Formation; (4) Drip Tank Member, upper Straight Cliffs Formation; and (5) capping sandstone member (Eaton, this volume) of the Wahweap Formation. Path of section shown at the top of the figure. DISPERSAL SYSTEMS Cretaceous fluvial systems in the southwestern Utah area usually flowed to the northeast (Peterson, 1969a, b; Molenaar, 1983; Lawton, 1986; Fillmore, this volume). Gustason (1989) has suggested that for the basal Cretaceous unit in the area, the Dakota Formation, stream transport was to the east or southeast
during periods of stability and flowed down the northnortheast-trending basin axis during periods with higher rates of subsidence. This may have been the pattern for the entire Cretaceous sequence. Arkosic sediments were shed northeastward from the Mogollon Highlands into the Black Mesa Basin (Fig. 6) during the late Cenomanian through the late Turonian (Eaton and others,
Eaton and Nations land, 1983). These folds generally have dips of only a few degrees and are typified by the Black Mesa syncline. Depositional thinning of the lower Mancos Shale over the anticlines and thickening over the synclines indicate that the folding had begun by late Cenomanian time (Peterson, 1969a; Kirkland, 1983). LARAMIDE STRUCTURE
Figure 6. Transport directions and sources of elastics that filled the Sevier foreland basin in southwestern Utah and northern Arizona (LS = limestone, VL = volcanic lithics, SS = sandstone).
1987). Lawton (1986) suggested the possibility that volcanic fragments and feldspars were transported northeastward from southeastern Nevada or southern California across the northwestern corner of Arizona into the foreland basin during late Campanian time. The westernmost exposures of Cretaceous rocks in southwestern Utah are preserved in the Gunlock area (Fig. 5) adjacent to the thrust belt. The 1,000 m of Iron Springs Formation found there is dominantly fine grained (Fillmore, this volume) except for a basal Dakota(?) conglomerate. Thirty kilometers due east of the Gunlock section is a thick (1,200 m) Cretaceous section preserved along the eastern flank of the Pine Valley Mountains (Cook, 1957). In this section, a conglomerate is locally present at the base, and another near the top (Cook, 1957). It is apparent that elastics shed from the thrust sheets immediately to the west were dominantly sand size or finer. Thus, the combination of southwestern source areas and a northeasttrending depositional basin has produced a counterintuitive result in southwestern Utah: Sediments directly adjacent to the thrustbelt are overall finer grained than probable time-equivalent distal deposits to the east.
Several anticlinal, synclinal, and monoclinal folds trend northeast-southwest across the north side of the Black Mesa basin. Monoclines define the northwestern margin of Black Mesa basin, which is separated from the Kaiparowits basin by the Kaibito saddle (Fig. 7). These prominent folds are imposed upon earlier northwest-trending folds (Kelley, 1958; Peterson, 1969a; Wilson and others, 1969). Deep-seated faults do not commonly cut Cretaceous rocks in northern Arizona (Wilson and others, 1969). The final regression of the Cretaceous seas was caused by the broad uplift of the area as a result of the Laramide orogeny accompanied by global lowering of sea level (Haq and others, 1987). Laramide deformation in northern Arizona was reflected in crustal shortening of the Sevier foreland basin. This resulted in the formation of several large anticlinal uplifts, synclinal basins, and numerous smaller folds, all with generally north-trending axes (Chapin and Gather, 1981) (Fig. 7) often along trends of the earlier Sevier folds. A large-scale Laramide fold preserves the Cretaceous rocks of the Black Mesa and Kaiparowits basins.
SYNDEPOSITIONAL STRUCTURAL DEFORMATION The regional structural pattern of northern Arizona and adjacent areas exerted a dominant influence on Cretaceous depositional patterns. Compressional tectonics during the Late Cretaceous resulted in a series of parallel northwest-trending anticlines and synclines, the early movements of which are detectable by thinning and local erosion of Cretaceous units along anticlinal axes and thickening along synclinal axes (Peterson, 1969a; Kirk-
Figure 7. Large-scale Laramide folds in Cretaceous rocks of northeastern Arizona (modified from Kelley, 1958; Chapin and Gather, 1981; Nations and others, 1985; Davis and Kiven, 1975).
Introduction ACKNOWLEDGMENTS We thank Emily Mead for drafting the figures and Lehi Hintze and Tim Lawton for thoughtful reviews of the manuscript. REFERENCES CITED Armstrong, R. L, 1968, The Sevier erogenic belt in Nevada and Utah: Geological Society of America Bulletin, v. 79, p. 229-258. Bilodeau, W. L., 1986, The Mesozoic Mogollon Highlands, Arizona; An Early Cretaceous rift shoulder: Journal of Geology, v. 94, p. 724-735. Bowers, W. E., 1972, The Canaan Peak, Pine Hollow, and Wasatch formations in the Table Cliff region, Garfield County, Utah: U.S. Geological Survey Bulletin 1331-8,39 p. Carr, D. A., 1987, Depositional environments of the upper carbonaceous member of the Wepo Formation (Upper Cretaceous), northeastern Black Mesa [M.S. thesis]: Flagstaff, Northern Arizona University, 238 p. Chapin, C. E., and Gather, S. M., 1981, Eocene tectonics and sedimentation in the Colorado Plateau-Rocky Mountain area, in Dickinson, W. R., and Payne, W. D., eds., Relations of tectonics to ore deposits in the southern Cordillera: Arizona Geological Society Digest, v. 14, p. 173-198. Cook, E. F., 1957, Geology of the Pine Valley Mountains: Utah Geological and Mineralogical Survey Bulletin 58, 111 p. Cumella, S. P., 1983, Relation of Upper Cretaceous regressive sandstone units of the San Juan Basin to source area tectonics, in Reynolds, M. W., and Dolly, E. D., eds., Mesozoic paleogeography of west-central United States: Society of Economic Paleontologists and Mineralogists Rocky Mountain Paleogeography Symposium 2, p. 189-199. Davis, G. H., and Kiven, C. W., 1975, Tectonic analysis of folds in the Colorado Plateau of Arizona: Tucson, University of Arizona, Office of Arid Land Studies Bulletin 9, 68 p. Dickenson, W. R., 1981, Plate tectonic evolution of the southern Cordillera, in Dickinson, W. R., and Payne, W. D., eds., Relations of tectonics to ore deposits in the southern Cordillera: Arizona Geological Society Digest, v. 14, p. 113-136. Drewes, D. H., 1981, Tectonics of southeastern Arizona: U.S. Geological Survey Professional Paper 1144, 96 p. Eaton, J. G., 1987, Stratigraphy, depositional environments, and age of Cretaceous mammal-bearing rocks in Utah, and systematics of the Multituberculata (Mammalia) [Ph.D. thesis]: Boulder, University of Colorado, 308 p. Eaton, J. G., and Cifelli, R. L., 1988, Preliminary report on Late Cretaceous mammals of the Kaiparowits Plateau, southern Utah: University of Wyoming Contributions to Geology, v. 26, p. 45-55. Eaton, J. G., and Morrow, J. R., 1989, Problems of Cretaceous stratigraphy, Paunsaugunt Plateau, southwestern Utah, in Abstracts of the Symposium on Southwestern Geology and Paleontology, 1989: Flagstaff, Museum of Northern Arizona, p. 6. Eaton, J. G., Kirkland, J. I., Gustason, E. R., Nations, J. D., Franczyk, K. J., Ryer, T. A., and Carr, D. A., 1987, Stratigraphy, correlation, and tectonic setting of Late Cretaceous rocks in the Kaiparowits and Black Mesa basins, in Davis, G. H., and VandenDolder, E. M., eds., Geologic diversity of Arizona and its margins; Excursions to choice areas; Geologic Society of America 100th Annual Meeting Field-Trip Guidebook: Arizona Bureau of Geology and Mineral Technology Special Paper 5, p. 113-125. Franczyk, K. J., 1988, Stratigraphic revision and depositional environments of the Upper Cretaceous Toreva Formation in the northern Black Mesa area, Navajo and Apache Counties: U.S. Geological Survey Bulletin 1685, 32 p. Gregory, H. E., 1944, Geologic observations in the upper Sevier River Valley, Utah: American Journal of Science, v. 242, p. 577-606. , 1950, Geology and geography of the Zion Park region, Utah and Arizona: U.S. Geological Survey Professional Paper 220, 200 p.
, 1951, Geology and geography of the Paunsaugunt region, Utah: U.S. Geological Survey Professional Paper 226, 116 p. Gregory, H. E., and Moore, R. C., 1931, The Kaiparowits region; Geographic and geologic reconnaissance of parts of Utah and Arizona: U.S. Geological Survey Professional Paper 164, 161 p. Gustason, E. R., 1989, Stratigraphy and sedimentology of the middle Cretaceous (Albian-Cenomanian) Dakota Formation, southwestern Utah [Ph.D. thesis]: Boulder, University of Colorado, 376 p. Haq, B. U., Hardenbol, J., and Vail, P. R., 1987, Chronology of fluctuating sea levels since the Triassic: Science, v. 235, p. 1156-1167. Harshbarger, J. W., Repenning, C. A., and Irwin, J. H., 1957, Stratigraphy of the uppermost Triassic and Jurassic rocks of the Navajo country: U.S. Geological Survey Professional Paper 291, 74 p. Hattin, D. E., 1962, Stratigraphy of the Carlile Shale (Upper Cretaceous) in Kansas: Kansas Geological Survey Bulletin 156, 155 p. Heller, P. L., and Paola, C., 1989, The paradox of Lower Cretaceous gravels and the initiation of thrusting in the Sevier orogenic belt, United States Western Interior: Geological Society of America Bulletin, v. 101, p. 864-875. Hintze, L. F., 1980, Geologic map of Utah: Utah Geological and Mineral Survey, scale 1:500,000. Hook, S. C., Molenaar, C. M., and Cobban, W. A., 1983, Stratigraphy and revision of nomenclature of upper Cenomanian to Turanian (Upper Cretaceous) rocks of west-central New Mexico, in Contributions to midCretaceous paleontology and stratigraphy of New Mexico, Part 2: New Mexico Bureau of Mines and Mineral Resources Circular 185, p. 7-28. Kauffman, E. G., 1969, Cretaceous marine cycles of the Western Interior: The Mountain Geologist, v. 6, p. 227-245. , 1977, Geological and biological overview; Western Interior Cretaceous basin: The Mountain Geologist, v. 14, p. 75-99. , 1984, Paleobiogeography and evolutionary response dynamic in the Cretaceous Western Interior Seaway of North America, in Westermann, G.E.G., ed., Jurassic-Cretaceous biochronology and paleogeography of North America: Geological Association of Canada Special Paper 27, p. 273-306. Kelley, V. C., 1958, Tectonics of the Black Mesa Basin region of Arizona, in Anderson, R. Y., and Harshbarger, J. W., eds., 9th Field Conference Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, p. 146-150. Kirkland, J. I., 1983, Paleontology and paleoenvironments of the Greenhorn marine cycle, southwestern Black Mesa, Coconino County, Arizona [M.S. thesis]: Flagstaff, Northern Arizona University, 224 p. Lawton, T. F., 1986, Fluvial systems of the Upper Cretaceous Mesaverde Group and Paleocene North Horn Formation, central Utah; A record of transition from thin-skinned to thick-skinned deformation in the foreland region, in Peterson, J. A., ed., Paleotectonics and sedimentation in the Rocky Mountain region, United States: American Association of Petroleum Geologists Memoir 41, p. 423-442. Moir, G. J., 1974, Depositional environments and stratigraphy of the Cretaceous rocks, southwestern Utah [Ph.D. thesis]: Los Angeles, University of California, 316 p. Molenaar, C. M., 1983, Major depositional cycles and regional correlations of Upper Cretaceous rocks, southern Colorado Plateau and adjacent areas, in Reynolds, M. W., and Dolly, E. D., eds., Mesozoic paleogeography of west-central United States: Rocky Mountain Section, Society of Economic Paleontologists and Mineralogists Rocky Mountain Paleogeography Symposium 2, p. 201-224. Nations, J. D., Wilt, J. C., and Hevly, R. H., 1985, Cenozoic paleogeography of Arizona, in Flores, R. M., and Kaplan, S. S., eds., Cenozoic paleogeography of the west-central United States: Rocky Mountain Section, Society of Economic Paleontologists and Mineralogists Rocky Mountain Paleogeography Symposium 3, p. 335-355. Peterson, F., 1969a, Cretaceous sedimentation and tectonism in the southeastern Kaiparowits region, Utah: U.S. Geological Survey Open-File Report, 259 p.
Eaton and Nations , 1969b, Four new members of the Upper Cretaceous Straight Cliffs Formation in the southeastern Kaiparowits region, Kane County, Utah: U.S. Geological Survey Bulletin 1224-J, 28 p. Peterson, F., and Kirk, A. R., 1977, Correlation of the Cretaceous rocks in the San Juan, Black Mesa, Kaiparowits, and Henry basins, southern Colorado Plateau: New Mexico Geological Society 28th Field Conference Guidebook, San Juan Basin III, p. 167-178. Picha, F., 1986, The influence of preexisting tectonic trends on geometries of the Sevier Orogenic Belt and its foreland in Utah, in Peterson, J. A., ed., Paleotectonics and sedimentation in the Rocky Mountain region, United States: American Association of Petroleum Geologists Memoir 41, p. 309-320. Stokes, W. L., and Heylmun, E. B., 1963, Tectonic history of southwestern Utah, in Heylmun, E. B., ed., Guidebook to the geology of southwestern Utah: Intermountain Association of Petroleum Geologists 12th Annual Field Conference, p. 19-25.
Villien, A., and Kligfield, R. M., 1986, Thrusting and synorogenic sedimentation in central Utah, in Peterson, J. A., ed., Paleotectonics and sedimentation in the Rocky Mountain region, United States: American Association of Petroleum Geologists Memoir 41, p. 281-308. Wilson, E. D., Moore, R. T., and Cooper, J. R., 1969, Geologic map of Arizona: Tucson, Arizona Bureau of Mines and U.S. Geological Survey, scale 1:500,000. Wolfe, D. G., 1989, The stratigraphy and paleoenvironments of middle Cretaceous strata along the central Arizona-New Mexico border [M.S. thesis]: Boulder, University of Colorado, 221 p.
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