Sprinkel, Weiss, Fleming, Waanders REDEFINING THE LOWER CRETACEOUS STRATIGRAPHY WITHIN THE CENTRAL UTAH FO
REDEFININGREDEFINING THETHE LOWERLOWER CRETACEOUSCRETACEOUS STRATIGRAPHYSTRATIGRAPHY WITHINWITHIN THETHE CENTRALCENTRAL UTAHUTAH FORELANDFORELAND BASINBASIN
by
Douglas A. Sprinkel, Malcolm P. Weiss, Robert W. Fleming, and Gerald L. Waanders RELAND BASIN UGS Special Study 97
SPECIAL STUDY 97 UTAH GEOLOGICAL SURVEY a division of 1999 Utah Department of Natural Resources REDEFINING THE LOWER CRETACEOUS STRATIGRAPHY WITHIN THE CENTRAL UTAH FORELAND BASIN
by Douglas A. Sprinkel1, Malcolm P. Weiss2, Robert W. Fleming3, and Gerald L. Waanders4
1 Utah Geological Survey, PO Box 146100, Ste 3110, Salt Lake City, UT 84114-6100 2 Dept. of Geological Sciences, University of California, Santa Barbara, CA 93106-9630 3 U.S. Geological Survey, MS-966, PO box 25046, Denver, CO 80225-0046 4 1611-C Rancho Santa Fe Road, San Marcos, CA 92069
Cover photograph of the type section of the San Pitch Formation at Christianburg (view to the west) courtesy of Doug Sprinkel
ISBN 1-55791-643-8
Special Study 97 UTAH GEOLOGICAL SURVEY a division of
1999 Utah Department of Natural Resources UTAH GEOLOGICAL SURVEY STATE OF UTAH Michael O. Leavitt, Governor
DEPARTMENT OF NATURAL RESOURCES Kathleen Clarke, Executive Director
UTAH GEOLOGICAL SURVEY Kimm M. Harty, Acting Director
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Printed on recycled paper 2/00 In keeping with scientific practice, all measurements in this report are metric. To convert metrics to English units, use the following equivalents:
1 mm (millimeter) = 1/1000 cm = 0.04 inches 1 cm (centimeter) = 1000 mm = 0.4 inches 1 m (meter) = 1000 cm = 39 3/8 inches, or 3.28 feet 1 km (kilometer) = 1000 m = 0.621 mile
1 inch = 25.4 mm, or 2.54 cm 1 foot = 305 mm, or 30.5 cm 1 yard = 915 mm, or 91.5 cm 1 mile = 1.61 km
The following are conversion factors:
To convert millimeters to inches: multiply by 0.039 To convert centimeters to inches: multiply by 0.394 To convert meters to feet: multiply by 3.281 To convert kilometers to miles: multiply by 0.621 TABLE OF CONTENTS
ABSTRACT ...... 1
INTRODUCTION ...... 1
LOWER CRETACEOUS STRATIGRAPHY ...... 2 Nomenclature History...... 3 Current Problem and Proposed Resolution ...... 5 Value of Proposed Nomenclature ...... 5
Cedar Mountain Formation ...... 6 Definition and Description ...... 6 Contacts...... 7 Geographic Distribution and Thickness ...... 7 Age...... 8 San Pitch Formation...... 9 Definition and Description ...... 9 Member A...... 10 Member B...... 10 Member C ...... 11 Contacts...... 11 Geographic Distribution and Thickness ...... 13 Age...... 14
CONCLUSIONS...... 17
ACKNOWLEDGMENTS ...... 17
REFERENCES CITED...... 17
FIGURES
Figure 1. Distribution of Lower Cretaceous strata in central Utah ...... 2 Figure 2. History of nomenclature...... 3 Figure 3. Photograph of the type section of the San Pitch Formation ...... 6 Figure 4. Isopach map of the Cedar Mountain Formation in central Utah ...... 8 Figure 5. Diagram of the type measured section, San Pitch Formation...... 9 Figure 6. Diagram of the measured section at Chicken Creek...... 10 Figure 7. Diagram of the measured section at upper Deep Creek of member C ...... 11 Figure 8. Diagram of the measured section at Little Salt Creek of members A and B ...... 12 Figure 9. Diagram of the measured section at Salina Canyon...... 13 Figure 10. Correlation chart of Middle Jurassic (part) through Upper Cretaceous (part) strata ...... 15 Figure 11. North-south fence diagram of the Cedar Mountain and San Pitch Formations ...... 15 Figure 12. Isopach map of the San Pitch Formation in central Utah ...... 16 Figure 13. Age of the Cedar Mountain and San Pitch Formations ...... 16
TABLES
Table 1. Measured sections of the Cedar Mountain and San Pitch Formations ...... 19 Table 2. Palynologic assemblage of the San Pitch Formation ...... 19 REDEFINING THE LOWER CRETACEOUS STRATIGRAPHY WITHIN THE CENTRAL UTAH FORELAND BASIN by Douglas A. Sprinkel1, Malcolm P. Weiss2, Robert W. Fleming3, and Gerald L. Waanders4
ABSTRACT INTRODUCTION
Lower Cretaceous strata exposed in the The Lower Cretaceous section of central foreland basin of central Utah were divided into Utah consists of fluvial and lacustrine rocks that two lithostratigraphic units, the Cedar Mountain were deposited in a foreland basin along the and San Pitch Formations. Together these Sevier fold and thrust belt (Armstrong, 1968; formations correlate with both the Cedar Mountain DeCelles and others, 1995; Currie, 1997). These Formation exposed on the San Rafael Swell and strata crop out in the Canyon Mountains, Pahvant the lower part of the Canyon Range Conglomerate Range, San Pitch Mountains (Gunnison Plateau is exposed in the Canyon Mountains. the name used instead of the San Pitch Mountains The Cedar Mountain and San Pitch by many geologists), Salina Canyon, and the San Formations form an upward-coarsening Rafael Swell (figure 1); however, their regional succession of alluvial, fluvial, and lacustrine rocks correlation has been the subject of much that become finer grained and thin southeastward speculation. This study focuses on the Lower toward the San Rafael Swell. The Cedar Mountain Cretaceous strata exposed east of the Canyon Formation in central Utah consists of variegated Mountains and the Pahvant Range. Five mudstone, conglomerate, pebbly sandstone, and measured sections in the Gunnison Plateau and minor lacustrine limestone. It thickens Salina Canyon, and recovery of critical southeastward from a pinch-out near the West palynomorph assemblages are the basis for the Hills to 188 m thick in Salina Canyon and then correlation of the Lower Cretaceous strata. Most thins to 50 m in the San Rafael Swell. The Cedar of the measured sections and palynomorph data Mountain Formation in the San Rafael Swell is were obtained from the Gunnison Plateau. Barremian(?) to late Albian, but is no younger than The Lower Cretaceous of central Utah middle Albian in the Gunnison Plateau and vicinity. consists of conglomerate, sandstone, variegated The overlying San Pitch Formation (a new mudstone, and minor lacustrine limestone beds, formation and stratotype) consists of and was first mentioned by Spieker and Reeside conglomerate, sandstone, and mudstone. We (1926). Subsequent stratigraphic studies in divided it into three informal members based on central Utah intended to identify and correlate grain composition, bed geometry, and topographic these strata of late Early Cretaceous age have led expression. The San Pitch Formation thins to different interpretations and names (Spieker, southward from over 1,100 m in the western 1946; Stokes, 1972; Fouch and others, 1982; Gunnison Plateau to about 85 m in Salina Canyon; Standlee, 1982; Fouch and others, 1983; from Salina Canyon it grades eastward into the Stuecheli and Collinson, 1984; Witkind and others, upper unnamed member of the Cedar Mountain 1986; Schwans, 1988; Weiss and Roche, 1988; Formation. The San Pitch Formation is middle to Weiss, 1994). Figure 2 summarizes the major late Albian; its lower age limit is defined by the changes in nomenclature. We assign these palynomorphs Asteropollis sp., Retitricolpites controversial strata to the Cedar Mountain and georgensis, Callialasporites dampieri, and Pilosisporites trichapapillosus. Its upper limit is 1 Utah Geological Survey, PO Box 146100, Ste 3110, Salt Lake City, UT 84114-6100 based on stratigraphic position and palynomorphs 2 Dept. of Geological Sciences, University of California, Santa Barbara, from the upper part of the Cedar Mountain CA 93106-9630 3 U.S. Geological Survey, MS-966, PO box 25046, Denver, CO 80225- Formation in the San Rafael Swell and San Pitch 0046 Formation in Salina Canyon. 4 1611-C Rancho Santa Fe Road, San Marcos, CA 92069
2 Utah Geological Survey
o o
Wasatch Mtns. 113 110
o Wasatch o
40 Utah County Duchesne County 40
Nephi County
Cedar Hills
Juab
Sanpete Carbon County
West Hills County Nephi County
Price
Levan Millard
Emery County
Juab Valley Chicken Creek County
section
Moroni
Upper Deep Manti
Creek section Canyon Mountains
Castle Dale
Christianburg
Sevier
Little Salt Salina
Creek section County
Sanpete Valley
Salina Canyon
Juab County Range section
Ephraim San Rafael Swell
Sanpete County
Sevier River
Pahvant 0 50 km
38o 30' 38o 30'
113o 110o (Gunnison Plateau) San Pitch River Manti San Pitch Mountains
Wasatch Plateau
UTAH N
Christianburg section Canyon Range Conglomerate
Christianburg
Valley Mtns. Valley (type section)
Gunnison 0 10 km San Pitch Formation
Cedar Mountain Formation
Area of above map
Figure 1. Distribution of Lower Cretaceous strata in central Utah and index of important geographic features discussed in the text. The Cedar Mountain Formation is exposed as a continuous outcrop that outlines the San Rafael Swell. West of the San Rafael Swell, the Cedar Mountain and San Pitch Formations are exposed as discontinuous outcrops from the San Pitch Mountains to Salina Canyon. The equivalent Canyon Range Conglomerate is exposed as discontinuous outcrops from the Canyon Mountains to the Pahvant Range. The locations of the type and reference sections are also noted. Outcrop pattern modified from Hintze (1980).
San Pitch Formations. Separating these rocks LOWER CRETACEOUS STRATIGRAPHY into two distinctive lithostratigraphic units of equal stratigraphic rank is useful for geological mapping We here redefine the lithostratigraphic unit and interpreting the regional stratigraphy in central identified by Spieker and Reeside (1926), and that Utah. The proposed revision of the Lower Spieker (1946) defined as the Morrison(?) Cretaceous stratigraphy in central Utah builds on Formation, and that Witkind and others (1986) the stratigraphic work of previous investigators reassigned to the Cedar Mountain and San Pitch (Spieker, 1946; Witkind and others, 1986; Weiss Formations. This redefinition restricts the Cedar and Roche, 1988; Weiss, 1994). Mountain Formation and adds the overlying San This study describes the rocks assigned to Pitch Formation as a new basal formation of the the Early Cretaceous, and redefines the Lower Indianola Group. Cretaceous stratigraphy in the foreland basin of central Utah. Redefining the Lower Cretaceous 3
Nomenclature History hiatus. Spieker (1946) reported that Morrison(?) and Indianola beds could be separated by subtle Nomenclature, age, and correlation of a color differences. Despite the implication that the succession of variegated mudstone, sandstone, entire Early Cretaceous was missing, Spieker conglomerate, and minor lacustrine limestone (1946) extended the Morrison(?) Formation into beds exposed in central Utah have been persistent central Utah rather than define a new formation. stratigraphic problems (figure 2). Spieker and Stokes (1972) examined Spieker's (1946) Reeside (1926) first tentatively identified these Morrison(?) Formation in exposures near beds as the Morrison Formation of Late Jurassic Christianburg, Utah and concluded that they were age. Later, Spieker (1946) qualified the Morrison likely of Early Cretaceous age because of the identification with a query. His uncertainty was presence of polished pebbles (the polished stones based on two observations: rocks of Morrison type were identified as gastroliths by Stokes) similar to were within units of the overlying Indianola Group, those in the Cedar Mountain Formation in the San and the contact between the presumed Upper Rafael Swell. In the San Rafael Swell, Stokes Jurassic Morrison(?) Formation and Upper (1944) had divided Lower Cretaceous beds into Cretaceous Indianola Group was apparently the upper "Cedar Mountain shale" and a lower conformable in spite of an implied depositional "Buckhorn conglomerate" and assigned all Late
Witkind, Standlee, and Spieker Stokes Maley 1986 Schwans Weiss and Roche1988; This Report 1946 1972 1988 Weiss 1994 Witkind- Standlee Maley Sanpete Sanpete Sanpete Sanpete Sanpete Sanpete Sanpete Indianola Indianola Indianola Indianola Formation Formation Formation Formation Formation Formation Formation Group (part) Group (part) Group (part) Group (part) Indianola Group (part) Indianola Group (part) Indianola Group (part) upper unit upper member unnamed basal unit San Pitch Formation Pitch San
Cedar Cedar Morrison(?) Formation Morrison(?) Pigeon Creek Formation
Cedar Mountain Formation Cedar Mountain Formation Mountain Mountain unit) lower lower Cedar (lower (lower Formation Formation member member Mountain Formation
Twist Twist Twist Twist Twist Gulch Gulch Twist Gulch Formation Gulch Gulch Gulch Formation Formation Formation Formation Formation
Figure 2. History of nomenclature for the upper part of Middle Jurassic to lower Upper Cretaceous strata in the central Utah segment of the Cordilleran fold and thrust belt. Of interest is the nomenclature evolution of the Morrison(?) Formation. Although Spieker and Reeside (1926) first identified the variegated beds in central Utah as Morrison, Spieker (1946) subsequently questioned the identification, and added a query to the name, thus Morrison(?). Stokes (1972) was the first to suggest that Spieker’s Morrison(?) Formation was probably the Cedar Mountain Formation; he failed to extend the Cedar Mountain into central Utah because he lacked fossil evidence. An Early Cretaceous age for the beds was reported by Standlee (1982) and Witkind and others (1986), which led to the formal abandonment of the term Morrison(?) Formation, and the adoption of the name Cedar Mountain Formation in central Utah. Schwans (1988) proposed the name Pigeon Creek Formation for the variegated mudstone and conglomerate beds in central Utah. Weiss and Roche (1988) recommended that the name Cedar Mountain Formation be applied only to the variegated mudstone beds, and that the overlying conglomerate beds be included as a new, unnamed, basal unit of the Indianola Group. Finally, we here maintain the name Cedar Mountain Formation, and propose the name San Pitch Formation for the conglomerate beds that lie between the Cedar Mountain and Sanpete Formations. 4 Utah Geological Survey
Jurassic beds to the Morrison Formation. Stokes conglomerate beds. Witkind and his co-authors (1952) subsequently reaffirmed the name Cedar agreed that the lower (variegated mudstone) and Mountain Formation, even as he relegated the upper (conglomerate) units are not part of the Buckhorn conglomerate to member status Morrison Formation as exposed on the San Rafael because of its discontinuous distribution. Stokes Swell, and that the lower unit correlates with units (1972) suggested that the beds mapped by that form the upper unnamed member of the Spieker (1946) as Morrison(?) Formation in central Cedar Mountain Formation exposed in the San Utah really represented rocks of the Lower Rafael Swell; however, they disagreed on the Cretaceous Cedar Mountain Formation; however, nomenclature of the upper unit (figure 2). Stokes (1972) did not formally propose a Standlee (Witkind and others, 1986) favored an nomenclature change because of the lack of fossil interpretation that included the upper unit as a evidence to confirm an Early Cretaceous age in newly recognized lithofacies of the Cedar central Utah. Mountain Formation, based on the Early Fossil and radiometric data finally confirmed Cretaceous age of palynomorphs recovered from that rocks of Early Cretaceous age are in central thin mudstone beds in the Gunnison Plateau. Utah. Standlee (1982) reported palynomorphs of Witkind and Maley (Witkind and others, 1986) late Early Cretaceous age in rocks from an favored including the upper unit in the overlying unspecified location in Chicken Creek, in the Indianola Group, thus making it a new basal unit northwestern part of the Gunnison Plateau. that extends the age of the Indianola Group into Standlee (1982) subsequently applied the name the Early Cretaceous. Witkind and Maley (Witkind Cedar Mountain Formation to the conglomeratic and others, 1986) were influenced by the lithologic lithofacies of the Morrison(?) Formation in the similarity of the conglomerate beds in the upper Gunnison Plateau. Willis and Kowallis (1988) unit to the widespread conglomerate beds in the obtained an Albian age from zircon- and apatite- Indianola Group, and by the distinctive change bearing bentonite beds collected from strata from mudstone to conglomerate that provides an identified as Morrison(?) Formation in lower Salina easily recognizable contact for mapping purposes. Canyon, which they redefined as the Cedar Schwans (1988) examined the Morrison(?) Mountain Formation. Evidence of an Early Formation exposed in central Utah as part of a Cretaceous age for the Morrison(?) Formation regional sedimentologic and sequence near Christianburg was provided by Stuecheli stratigraphic study. He recognized that the rock (1984) and Stuecheli and Collinson (1984). types exposed near Christianburg are similar to Stuecheli (1984) measured three stratigraphic beds exposed elsewhere in the Gunnison Plateau. sections through the Morrison(?) Formation He also recognized that beds included in the immediately north of the Christianburg area and Jurassic Twist Gulch by Spieker (1946; 1949), found beds that contained a bivalve and leaf Hunt (1950), and Hardy and Zeller (1953) were impressions of late Early Cretaceous age. Despite also similar to beds of the Morrison(?) Formation the Early Cretaceous age for these strata, they did near Christianburg. To define formally the Lower not propose a change in nomenclature. Cretaceous strata exposed in the Gunnison Witkind, Standlee, and Maley (1986) first Plateau and place them in their correct time- recommended formal abandonment of the name stratigraphic position, Schwans (1988) abandoned Morrison(?) Formation in central Utah. They the name Morrison(?) Formation and proposed the reassigned the Morrison(?) strata exposed near name Pigeon Creek Formation (figure 2) with Christianburg to the Lower Cretaceous Cedar stratotype exposures along Pigeon Creek, the first Mountain Formation, based on striking lithologic drainage north of Chicken Creek and east of similarity (particularly the presence of the Levan, Utah. He defined the formation to reflect "polished stones," calcareous nodules, and the significance of unconformity-bounded units uncommon oncolites found in the Cedar and their regional sequence-stratigraphic Mountain), stratigraphic position, and palynologic implications. Schwans (1988) divided the Pigeon age control. They divided the Cedar Mountain into Creek Formation into two distinct lithologic units two informal lithologic units; a lower unit consisting much as Witkind and others (1986) did in the mostly of variegated calcareous mudstone beds Christianburg area: a lower member that consists and an upper unit consisting mostly of predominantly of red mudstone with variable Redefining the Lower Cretaceous 5 amounts of conglomerate and subordinate and Roche (1988), and that Weiss (1994) called lacustrine limestone, and an upper member that the unnamed basal unit of the Indianola Group, consists predominantly of conglomerate beds with and that Schwans (1988) defined as the upper intercalated red mudstone. member of the Pigeon Creek Formation. The Even as Schwans (1988) proposed these name San Pitch Formation is taken from the San changes, Weiss and Roche (1988) discussed the Pitch River that drains the Sanpete Valley. The stratigraphic problem of Spieker's (1946) type locality is near Christianburg, Utah and Morrison(?) Formation. They also recommended reference sections are at Chicken Creek, Deep that the name Morrison(?) Formation (in any form) Creek, Little Salt Creek, and Salina Canyon (figure be abandoned in the Gunnison Plateau and 1; table 1). Although Christianburg is not found on surrounding area and proposed that the name modern topographic maps, the farming community Cedar Mountain Formation be restricted to the still exists. Christianburg is at the extreme variegated mudstone beds with the distinctive southernmost part of the Gunnison Plateau polished stones (gastroliths), calcareous nodules, roughly 16 km southwest of Manti, Utah, and 5 km and oncolites (figure 2). Weiss and Roche (1988) west of Gunnison, Utah. We prefer to use the assigned the overlying conglomerate beds to the name Christianburg for the type section because Indianola Group as an unnamed basal unit of its proximity to the farming community of underlying the Sanpete Formation, formerly Christianburg, which is known in the geologic considered the basal formation of the Indianola literature (Spieker, 1949). Group (Spieker, 1946). Weiss and Roche (1988) Combining these distinctive lithostratigraphic argued that the name Cedar Mountain Formation units into a single formation as proposed by be used in the Gunnison Plateau region because Standlee (Witkind and others, 1986) and by of lithologic similarities to the upper unnamed Schwans (1988) is inappropriate because it would member of the Cedar Mountain Formation disregard one of the most easily mapped contacts exposed in the San Rafael Swell. in central Utah.
Current Problem and Proposed Resolution Value of Proposed Nomenclature
Each of the previously described studies Adoption of the stratigraphic nomenclature contributed significantly toward understanding the proposed in the previous section provides beds grouped as the Morrison(?) Formation in geologists with a recognizable marker both in the central Utah. Although the age of these beds is surface and subsurface. Separation of the two known and accepted, contradictions in correlation formations also gives geologists a means to map and nomenclature still exist. structural complexities, to analyze the We divide the Lower Cretaceous section in sedimentologic response to thrusting, and to central Utah into two lithostratigraphic units. The establish a temporal relationship of deformation in name Cedar Mountain Formation is assigned to the central Utah foreland basin. the predominantly variegated calcareous Geologists working in central Utah recently mudstone beds that Witkind and others (1986) proved the value of the proposed Lower assigned to the lower unit of the Cedar Mountain Cretaceous correlation. Sprinkel (1994) Formation, and that Weiss and Roche (1988), and recognized the Cedar Mountain Formation in that Weiss (1994) assigned to the Cedar Mountain exploratory wells drilled in central Utah. He Formation, and that Schwans (1988) defined as established a subsurface correlation from Juab the lower member of the Pigeon Creek Formation Valley and the Gunnison Plateau across Sanpete (figure 2). A new name, the San Pitch Formation, Valley and the Wasatch Plateau to the western is assigned to the overlying predominantly part of the San Rafael Swell. Geologic mapping in conglomerate beds that Witkind and Maley and around the Gunnison Plateau (Hunt, 1950; (Witkind and others, 1986) named the upper unit Auby, 1991; Banks, 1991; Biek, 1991; Lawton and and assigned to the Indianola Group and that Weiss, 1994; Weiss, 1994; Fong, 1995) was Standlee (Witkind and others, 1986) assigned to improved by utilizing the contact that separates the Cedar Mountain Formation, and that Weiss the variegated mudstone beds from the overlying 6 Utah Geological Survey conglomerate beds. Although Hunt (1950) Formation. The lower, discontinuous included the variegated mudstone (Cedar conglomerate beds of the Cedar Mountain Mountain Formation) with Twist Gulch strata and Formation are the Buckhorn conglomerate. In the mapped it as the Twist Gulch Formation, he San Rafael Swell, the Cedar Mountain Formation correctly mapped the contact between the fine- lies on the Upper Jurassic Morrison Formation and grained variegated mudstone and coarse-grained is overlain by the Upper Cretaceous Dakota conglomerate beds. Sandstone (Stokes, 1944; 1952; Yingling, 1987). The Cedar Mountain Formation in the Gunnison Plateau and Salina Canyon forms low, Cedar Mountain Formation smooth, unvegetated slopes that consist of variegated beds. The formation is strikingly similar Definition and Description to the upper unnamed member of the Cedar Mountain Formation at the type section. Most of The Cedar Mountain stratotype was the formation near Christianburg is mudstone, but designated by Stokes (1944; 1952) in the the more resistant sandstone and limestone beds northwestern part of the San Rafael Swell for beds form conspicuous, thin, steeply dipping ribs. In of variegated mudstone with intercalated addition, the Cedar Mountain Formation near sandstone, lacustrine limestone, and a Christianburg also contains thick zones of discontinuous basal conglomerate exposed at pedogenic carbonate that weathers out as Cedar Mountain (section 9, T. 18 S., R. 10 E., Salt carbonate nodules. These probably represent Lake Base and Meridian, Emery County, Utah). stacked paleosols that indicate slow deposition. Variegated mudstone and intercalated beds of The Cedar Mountain Formation was deposited in a pebbly sandstone, subordinate lacustrine fluvial-lacustrine environment (Yingling, 1987; limestone, and pedogenic carbonate form an Schwans, 1988). upper unnamed member. Abundant calcareous The Cedar Mountain Formation is equivalent nodules and "polished stones" (gastroliths) in the to Spieker's (1949) variegated mudstone beds of variegated mudstone are some of the more the Morrison(?) Formation, the lower unit of distinctive characteristics of the Cedar Mountain Witkind and others (1986), and Schwans' (1988)
Figure 3. Photograph of the type section of the San Pitch Formation at Christianburg (view is northwest). The contact (solid line) between the Cedar Mountain and San Pitch Formations is placed at the top of the smooth slope (Cedar Mountain Formation) and the base of the cliff (San Pitch Formation). The San Pitch is divided into three informal members, A, B, and C in ascending order, based on clast composition, bed morphology, and topographic expression. Contacts between these members are shown as white lines. The Cedar Mountain and San Pitch Formations form the east limb of the Christianburg syncline. These rocks strike north to northeast and are overturned, dipping up to 85o east. Redefining the Lower Cretaceous 7 lower member of the Pigeon Creek Formation. The upper contact conformably separates Measured sections of the Cedar Mountain the Cedar Mountain Formation from the newly Formation in the Gunnison Plateau and Salina defined San Pitch Formation. Near Christianburg, Canyon are hereby designated as reference the contact is well exposed, sharp, and is at the sections for central Utah (figure 1; table 1). base of a prominent cliff (figure 3). The contact is Additional measured sections of the Cedar placed at the base of the lowest thick, reddish- Mountain Formation are described in Stuecheli brown conglomerate and above the massive, red (1984), Roche (1985), Yingling (1987), Schwans and gray mudstone of the Cedar Mountain. At (1988), and Weiss and Roche (1988). Pigeon Creek (the next drainage north of Chicken Creek), the upper contact is at the base of the first cobble conglomerate, Schwans (1988), however, Contacts placed the contact between his lower and upper members of the Pigeon Creek Formation along a The lower contact unconformably separates fault. Similarly, the contact between the San Pitch the fluvial-lacustrine beds of the Lower Cretaceous and Cedar Mountain Formations lies at the base of Cedar Mountain Formation from the underlying the first conglomerate bed in Chicken Creek. As a fluvial-lacustrine beds of the Upper Jurassic result, the Cedar Mountain Formation is about 100 Morrison Formation in the San Rafael Swell m thinner there than Schwans' (1988) lower (Stokes, 1952; Yingling, 1987). West of the San member of the Pigeon Creek Formation. Rafael Swell, the Cedar Mountain Formation unconformably overlies the marginal marine beds of the Middle Jurassic Twist Gulch Formation Geographic Distribution and Thickness (Willis, 1986; Willis and Kowallis, 1988; Auby, 1991; Banks, 1991; Biek, 1991; Lawton and The Cedar Mountain Formation forms a Weiss, 1994; Sprinkel, 1994; Weiss, 1994). Thus, continuous belt of exposures around the flanks of near Salina Canyon and the Gunnison Plateau, the San Rafael Swell (figure 1). Westward from Upper Jurassic strata were either not deposited or the San Rafael Swell, it passes beneath the were eroded prior to deposition of Lower Wasatch Plateau and reappears as a Cretaceous strata (Sprinkel, 1994). This implies discontinuous belt of outcrops and isolated that a regional topographic high existed or exposures along the margins of the Gunnison emerged during Late Jurassic time. In Little Salt Plateau and at the western margin of the Wasatch Creek, the unconformable contact between Cedar Plateau in Salina Canyon (Hintze, 1980; Jefferson, Mountain and underlying Twist Gulch is angular, 1982; Stuecheli, 1984; Roche, 1985; Willis, 1986; although this may be a local feature. A basal Witkind and others, 1987; Hintze, 1988; Schwans, conglomerate with interbedded sandstone of the 1988; Weiss and Roche, 1988; Witkind, 1988; Cedar Mountain Formation dips about 20o less Auby, 1991; Biek, 1991; Lawton and Weiss, 1994; than the underlying fine-grained, reddish-orange Weiss, 1994). The Cedar Mountain Formation sandstone beds of the Twist Gulch. At Chicken also crops out at Monks Hollow and Billies Creek, the base of the Cedar Mountain Formation Mountain near Thistle, Utah, about 100 km north is placed above a conspicuous 2-m interval of fine- to northwest of Christianburg (Pinnell, 1972; grained, reddish-orange sandstone with horizontal Young, 1976; Witkind and Page, 1983). In laminae and parting lineation. No basal subsurface drill-hole data, the Cedar Mountain conglomerate or angular relation was observed at Formation can be traced westward from the Chicken Creek. Wasatch Plateau and Sanpete Valley to the Near Christianburg, the lower contact of the Gunnison Plateau and Juab Valley (Sprinkel, Cedar Mountain is generally covered; however, 1994). The Cedar Mountain Formation where exposed the Cedar Mountains is in fault thickens northwestward across the San Rafael contact with the Middle Jurassic Arapien Shale Swell from 50 m to 160 m (Craig, 1981; Yingling, (Weiss, 1994). A few hundred meters north of the 1987)(figure 4). It continues to thicken slightly exposures near Christianburg, small outcrops of north and northwestward from about 188 m in Twist Gulch, a few meters thick, underlie the Salina Canyon to a maximum thickness of a little Cedar Mountain Formation (Weiss, 1994). more than 200 m under the Sanpete Valley 8 Utah Geological Survey
(Sprinkel, 1994)(figure 4); however, Sprinkel (1994) reported only apparent thickness from drill holes in Sanpete Valley. Witkind and others Explanation of symbols used for the measured sections
Lithology Type Sedimentary Structures
(1986) measured 132 m of Cedar Mountain Formation near Christianburg, but that may not be
quartzite dominant
the total thickness for a fault may cut the formation concretion
at that location (Weiss, 1994). An anomalously
thick section (514 m) of Cedar Mountain burrows carbonate dominant
Formation, which is probably related to structural
thickening, was drilled in the Mobil Larson Unit 1 roots
(SW3SE3 section 1, T. 17 S., R. 2 E., Salt Lake mixed clast
Base and Meridian, Sanpete County, Utah) in the trough crossbeds Sanpete Valley (Sprinkel, 1994). The Cedar
mixed clast with chert Mountain Formation rapidly thins westward from
wedge crossbeds
the Sanpete Valley to about 23 m thick along the
western flank of the Gunnison Plateau and quartzarenite with chert
pinches out near the West Hills (Sprinkel, planar crossbeds
1994)(figures 1, 4).
quartzarenite wavy crossbeds
convoluted beds
Age
mudstone
The age span of the Cedar Mountain Fc flute cast
Formation has been difficult to determine because limestone the biostratigraphic and radiometric data have tool and groove come mostly from the upper half of the formation. Its age (including the age of the correlative Burro covered ripples Canyon Formation) in the San Rafael Swell is Barremian(?) to late Albian (Early
113o 110.0o
Cretaceous)
40.0o 40.0o
(Katich, 1951; Canyon Range Conglomerate
1956; Craig, 1981;
San Pitch Formation
Tschudy and
Nephi Cedar Mountain Formation
others, 1984). In
Salina Canyon, the
Cedar Mountain is
likely Albian based Castle Dale
on fission track Manti
250 dates obtained from
zircon- and apatite- 200
0 bearing bentonitic
Salina 150
mudstone beds in 50 100
the upper half of
the formation (Willis 50 0 50 km and Kowallis, 38.5o thickness in meters 38.5o 1988). 113o 110.0o
Figure 4. Isopach map of the Cedar Mountain Formation in central Utah. The Cedar Mountain Formation thickens from 50 m to more than 200 m northwestward across the San Rafael Swell into the Sanpete Valley, and then rapidly thins to about 23 m along the west flank of the Gunnison Plateau. The Cedar Mountain Formation pinches out near the West Hills. Contour interval is 50 m. Modified from Craig (1981) and Yingling (1987). Redefining the Lower Cretaceous 9
Samples collected from the Cedar Mountain 2). The San Pitch Formation is divisible into three Formation near Christianburg have yielded informal members (A, B, and C) that are palynomorphs of non-definitive Early Cretaceous geometrically, compositionally, and topographically age (Witkind and others, 1986). The Cedar distinctive and that can be recognized and traced Mountain Formation in the Gunnison Plateau is regionally. interpreted as Barremian(?) to middle Albian. The Barremian(?) age is based on the age of the Cedar Mountain and Burro Canyon Formations in east-central Utah (Tschudy and others, 1984). The middle Albian upper age limit is based on the age of the
overlying San Pitch Formation. Christianburg Section
meters
San Pitch Formation Sanpete Fm. (part)
Definition and Description
member C
300 (43.9 m) The San Pitch Formation
(a new formation and stratotype)
is applied to reddish-brown
conglomerate and interbedded
mudstone and sandstone
exposed in the low hills of the member B
southeasternmost Gunnison (96.3 m)
Fc
Plateau near Christianburg,
Utah (figures 3, 5). The type
section is in sections 12 and 13, 200
San Pitch Formation Formation Pitch San
T. 19 S., R. 1 E., Salt Lake
Base and Meridian, Sanpete
member A
County, Utah (figure 1; table 1).
Reference sections are along (56.7 m)
the western flank of the
Gunnison Plateau and in Salina
Canyon (figures 1, 6-9; table 1).
The San Pitch Formation is an
important unit that can be 100
recognized and mapped in
central Utah. We propose the Cedar Mountain
San Pitch Formation as the Formation
basal formation of Spieker's
(1946) Indianola Group. As
defined, the San Pitch
Formation replaces Spieker's
(1949) red conglomerate section of the Morrison(?) Formation, 0 the upper unit of Witkind and mud sand pebble cobble boulder others (1986), Schwans' (1988) Arapien Shale (part) upper member of the Pigeon Creek Formation, and the unnamed basal Indianola unit of Figure 5. Diagram of the type measured section of the San Pitch Formation at Christianburg. See table 1 for detailed location description. Weiss and Roche (1988) (figure 10 Utah Geological Survey
conglomerate beds consist of rounded to subrounded quartzite
Chicken Creek Section
meters and carbonates (about 50
1200 Funk Valley Fm. (equivalent) (part) percent quartzite and 45 percent
Allen Valley Shale (equivalent) carbonate). Member A also
Sanpete Formation (equivalent) contains white and grayish-red
1100 sandstone and siltstone clasts (about 5 percent). The quartzite
1000 clasts are Late Proterozoic to
member C Cambrian in age and include
(294.7 m)
900 white to light gray varieties from
the Caddy Canyon Quartzite (Late Proterozoic), purple to 800
banded purple varieties from the
Mutual Formation (Late
700 Proterozoic), and very pale
orange to pinkish varieties from the
600 Tintic Quartzite (Cambrian).
Pale-green quartzite and
member B grayish-green quartzose
500 (670.7 m)
sandstone clasts are also
San Pitch Formation Pitch San
included in member A and are
400
derived from the Dutch Peak
Formation (Late Proterozoic) 300 and the Ophir Formation
(Cambrian), respectively. Clasts
200 derived from the Ophir
Formation weather to a grayish
member A red purple and grayish olive
100 (150.9 m) green, but are grayish green on a fresh surface. The Ophir 0 Cedar Mountain Fm clasts contain coarse sand-sized mud sand pebblecobble boulder (23 m) quartz, muscovite, and glauconite. Other sandstone and siltstone clasts identified in member A were probably derived from Triassic and Jurassic formations. Figure 6. Diagram of the measured section at Chicken Creek of the Cedar Mountain and San Pitch Formations. See table 1 for detailed location description. Explanation of lithology symbols is on page 8.
Member B Member A Member B consists of cobble and boulder Member A consists of cobble and pebble conglomerate interbedded with sandstone and conglomerate interbedded with calcareous to mudstone (figures 5, 6, 8) and forms distinctive noncalcareous mudstone (figures 5, 6, 8). The stacked tabular beds. Many of the conglomerate conglomerate is thick to medium bedded with beds in member B contain carbonate-cobble channel-form geometry and subtle, large-scale, conglomerate (nearly 100 percent carbonate), trough cross-stratification. The conglomerate is which is not common in members A and C. clast supported and cemented with a reddish- Carbonate clasts are mostly dolostone cemented brown calcareous matrix. Clasts within the in a dolomite to dolomitic matrix. This Redefining the Lower Cretaceous 11
Upper Deep Creek Section Sandstone beds also contain
meters
450 Sanpete Formation (part) burrows and roots, rare leaf
impressions, and a few
gastropods. The mudstone beds
400 are reddish orange, silty in part,
and calcareous.
Member C
Member C is the uppermost
300 unit of the San Pitch Formation.
At its type section near Christianburg, member C is
member C
(443 m) mostly covered; however, where
exposed it consists of calcareous,
reddish-brown to gray, silty
mudstone interbedded with
200 limonitic sandstone and
conglomerate. Member C was
also inspected in Chicken Creek,
San Pitch Formation (part) Pitch San
upper Deep Creek, and Salina
Canyon (figure1). In Chicken
Creek, it consists of mudstone 100 and sandstone interbedded with thick tabular beds of cobble
conglomerate (figure 6). In upper Deep Creek, member C consists
of interbedded pebbly sandstone with abundant limonite nodules,
0 pebble conglomerate, and member B (part) mud sand pebblecobbleboulder mudstone (figure 7). The conglomerate beds contain quartzite and few lithic clasts cemented in a calcareous matrix. In Salina Canyon, member C is mostly mudstone with a few thin Figure 7. Diagram of the measured section at upper Deep Creek of member C of the San Pitch Formation. Table 1 has detailed location descriptions. Explanation of lithology beds of sandstone and pebbly symbols is on page 8. sandstone (figure 9). Mudstone beds are generally light to characteristic gives member B the appearance of medium gray and slightly calcareous to being grayer and lighter in color than the calcareous. underlying conglomerate beds of member A. Member B also consists of conglomerate beds that Contacts contain subrounded to subangular quartzite and carbonate clasts (about 50 percent quartzite and At the type section near Christianburg, the 50 percent carbonate). The distinctive grayish- base of the San Pitch Formation rests conformably green quartzose sandstone and pale-green on the Cedar Mountain Formation (figures 3, 5, 6, quartzite clasts in member A are also in member 8, 9). This contact is placed at the base of the first B. Sandstone beds are light pinkish orange to reddish-brown cobble- and pebble-conglomerate light gray, fine to medium grained, and display bed. The lower contact of the San Pitch Formation trough cross-stratification, asymmetrical ripples, is generally distinctive because the San Pitch flute casts, and tool and groove marks. commonly forms the first prominent cliff above the 12 Utah Geological Survey
Little Salt Creek Section easily recognized in the subsurface on lithologic and petrophysical logs
meters
North Horn Formation
fault (Sprinkel, 1994). The San Pitch Formation
700
unconformably underlies the Sanpete
Formation. Regionally, the upper
contact of the San Pitch Formation is
placed at the base of a distinctive,
600 light-colored quartzite-boulder
conglomerate (about 90 to 100
percent quartzite clasts) of the
Sanpete Formation (figures 5, 6, 7,
500 9). This light-colored quartzite-
boulder conglomerate consists of
member B (part) quartzite boulders derived mostly
(643.6 m) from the Tintic Quartzite, but also
from the Caddy Canyon Formation
400 and the Eureka Quartzite. Locally,
this unit contains grayish-red-purple
cobbles of the Mutual Formation,
pale-green cobbles of the Dutch 300 Peak Formation, and grayish-green
cobbles of the Ophir Formation. The
San PitchFormation (part) basal boulder conglomerate of the
Sanpete Formation is indurated where freshly exposed; however, it 200 weathers readily to produce an
abundance of loose boulders lying on
covered slopes.
For the following reasons we
100 believe the contact between the San Pitch and overlying Sanpete
member A (51 m)
Formations is unconformable: (1) the
dramatic change in grain size from 0 Cedar Mountain Fm. (part) mudstone and sandstone to the light- mud sand pebblecobbleboulder colored quartzite-boulder conglomerate; and (2) commonly, basal conglomerate beds are Figure 8. Diagram of the measured section at Little Salt Creek of members A and B associated with regional of the San Pitch Formation. At Little Salt Creek, the upper part of member B unconformities. Schwans (1995) also contains a thick amalgamation of stacked, tabular beds of quartzite-dominant cobble interpreted this contact as a regional conglomerate. Elsewhere member B contains a thick succession of tabular beds, unconformity. but they are generally separated by finer grained units. See table 1 for detailed The contacts between members location description. Explanation of lithology symbols is on page 8. A, B, and C of the San Pitch Formation are based on notable grain-size smooth slopes of the Cedar Mountain Formation. changes, changes in clast composition and matrix It is one of the most obvious and best described color, and changes in general bed geometry. At contacts used for mapping in the region (Hunt, the type section, the contact between members A 1950; Hardy and Zeller, 1953; Witkind and Page, and B is placed at the top of a calcareous pebbly 1983; Witkind and others, 1986; Weiss and sandstone bed and at the base of a calcareous Roche, 1988; Auby, 1991; Biek, 1991; Weiss, mudstone bed (figures 3, 5). The contact 1994; Fong, 1995). The lower contact is also separates the reddish-brown, channel-form Redefining the Lower Cretaceous 13
Geographic Distribution and Thickness
meters Salina Canyon Section
The known geographic distribution of
Sanpete Fm (part)
the San Pitch Formation is restricted to
300 easternmost Juab County (West Hills, Juab
Valley, and western Gunnison Plateau),
Sanpete County (eastern Gunnison
San Pitch Fm Plateau, Sanpete Valley, and western
member C Wasatch Plateau) and Sevier County
(84.4 m) (western Wasatch Plateau) (Sprinkel,
1994). The westernmost outcrop of the
San Pitch Formation is along the west flank of the Gunnison Plateau where it forms an
200 apparent continuous belt from an area east
of Nephi, Utah southward to immediately
south of Little Salt Creek Canyon (figure 1).
Elsewhere in central Utah, the San Pitch
Formation forms discontinuous outcrops
along the east flank of the Gunnison
Cedar Mountain Plateau and in Salina Canyon (figure 1).
Formation The lower part of the Canyon Range (188 m)
Conglomerate, exposed in the Canyon
100 Mountains some 30 km west of the
Gunnison Plateau, is correlative with the
San Pitch Formation (figures 1, 10).
DeCelles and others (1995) described the
Canyon Range Conglomerate as having a
lower quartzite petrofacies, a middle
carbonate petrofacies with an
approximately 10-m thick unit of marine fan-
Jurassic (part) delta deposits, and an upper mixed 0 petrofacies. Although no age data are mud sand pebblecobbleboulder available for the marine fan-delta unit, DeCelles and others (1995) correlated this unit with pollen-bearing strata of similar Figure 9. Diagram of the measured section at Salina Canyon of the Cedar Mountain and San Pitch Formations. See table 1 for detailed location stratigraphic position in the Placid Oil description. Explanation of lithology symbols is on page 8. Company WCX-USA 1-2 well (section 24, T. 19 S., R. 2 W., Salt Lake Base and conglomerate beds of member A from the lighter Meridian, Millard County, Utah) and the Placid Oil colored tabular conglomerate, sandstone, and Company WXC-Barton 1 (section 32, T. 16 S., R. mudstone beds of member B. At Chicken Creek, 1 W., Salt Lake Base and Meridian, Juab County). the base of member B is placed under the The age of the pollen-bearing strata in those wells lowermost carbonate-cobble conglomerate bed is believed to be late Cenomanian to Turonian (figure 6). Above this contact, beds in member B (Villien and Kligfield, 1986; DeCelles and others, are typically tabular beds of stacked mudstone, 1995). Thus, if the correlation is valid, the lower sandstone, and conglomerate. The conglomerate quartzite and middle carbonate petrofacies below beds are typically composed of cobble clasts the fan-delta deposits are probably correlative to cemented with a light-gray calcareous matrix. The the San Pitch Formation (figure 10). contact between members B and C at the type All three members (A, B and C) are recogniz- section of the San Pitch Formation is placed able in about a 5-km strip from Christianburg between the uppermost thickly bedded pebble- northward to the Gunnison Reservoir (figure 1). conglomerate bed and the base of a mudstone Farther north along the eastern flank of the (figures 3, 5). Gunnison Plateau, only incomplete sections (mostly of members A and B) of the San Pitch 14 Utah Geological Survey
Formation are exposed because of structural exposed in Chicken Creek; however, Standlee complexities. All three members are also (1982) failed to properly locate the palynology recognizable in about a 25-km strip along the west sample. Subsequently, the location of the flank of the Gunnison Plateau. In Salina Canyon, Standlee sample within the stratigraphic section only member C is identified. Members A and B was incorrectly reported by Yingling (1987) and pinch out east and south of the Gunnison Plateau Schwans (1988). An Aptian to Albian age was first (figure 11). assigned by Witkind and others (1986) for the The San Pitch Formation is thickest along predominantly conglomerate unit exposed near the west flank of the Gunnison Plateau and thins Christianburg. Samples were also collected during to the south and east (figure 12). The San Pitch this study for palynologic age determinations from Formation in Chicken Creek measured 1,116.3 m. Southward in upper Deep Creek and Little Salt exposures of the San Pitch Formation near Creek, the total thickness of the San Pitch Christianburg and Chicken Creek in the Gunnison Formation is 1,137.6 m. Near Christianburg, the Plateau and Salina Canyon (figure 13; table 2). type section of the San Pitch is 196.9 m thick and Most of the datable samples that we collected it continues to thin southward to 85.4 m at Salina were from the same sample locations as in Canyon. The San Pitch Formation thins Witkind and others (1986) near Christianburg and southeastward from 1,116.3 m at Chicken Creek a sample site presumably near the Standlee to 223.4 m in the Hanson Oil Moroni 1AX well (1982) location in Chicken Creek. (section 14, T. 15 S., R. 3 E., Salt Lake Base and Concurrent ranges of palynomorphs col- Meridian, Sanpete County, Utah) in Sanpete lected from near the base of the San Pitch Valley (Sprinkel, 1994). It continues to thin to 66.8 Formation in Chicken Creek and Christianburg m in the Phillips Petroleum USA E-1 well, on the indicated a middle Albian age. At Chicken Creek, Wasatch Plateau (Sprinkel, 1994). The San Pitch samples collected from a mudstone near the base Formation grades eastward from the Salina of member A of the San Pitch Formation contained Canyon exposure and the Phillips USA E-1 well Asteropollis sp., Liliacidites reticulatus, and into the upper unnamed member of the Cedar Retitricolpites georgensis. These taxa do not Mountain Formation. range below middle Albian (figure 13). From the Thickness of the informal members generally same horizon, palynomorph species Pilosisporites varies concordantly with the thickness of the San trichapapillosus, Callialasporites dampieri, and Pitch Formation. Member A is thickest at Chicken Trilobosporites apiverrucatus were also present. Creek (150.9 m). It thins southward to 51.2 m and These taxa do not range above middle Albian 56.7 m at Little Salt Creek and Christianburg, (figure 13). respectively, and pinches out between The late Albian age of the San Pitch Christianburg and Salina Canyon (figure 11). Formation is based on: (1) palynomorphs reported Member B is 670.7 m thick at Chicken Creek, from Cedar Mountain beds in the San Rafael Swell 643.4 m thick in an incomplete section at Little Salt (Tschudy and others, 1984), (2) palynomorphs Creek, and 96.3 m thick at Christianburg. It collected for this study from San Pitch beds in pinches out between Christianburg and Salina Salina Canyon, and (3) the stratigraphic position of Canyon. Member C is 294.7 m thick at Chicken these palynomorph-bearing beds beneath an Creek, 443 m thick at upper Deep Creek, 43.9 m unconformity. Palynomorph-bearing samples thick at Christianburg, and 84.4 m thick at Salina within the top 20 m of the Cedar Mountain Canyon. Formation in the San Rafael Swell contained an assemblage tentatively of late Albian age (Tschudy and others, 1984). In Salina Canyon, a Age palynomorph-bearing sample collected at the top of member C contained the palynomorph The San Pitch Formation ranges in age from Tigrisporites scurrandus, with a range of middle to middle to late Albian. Standlee (1982) reported an late Albian. Thus, the upper part of member C of Early Cretaceous age (Aptian to late Albian) for the San Pitch Formation is likely late Albian in age. rocks now designated as the San Pitch Formation Redefining the Lower Cretaceous 15
Canyon SE San Pitch W Colorado Mountains Mountains Plateau
Turonian Canyon Range Allen Valley Tununk Member of the Conglomerate Mancos Shale (part) (part) Shale (part) (hanging wall) Sanpete Fm. (part)
Upper Dakota Sandstone Cenomanian Cretaceous
San Pitch
Indianola Group Formation Albian upper shale Canyon Range member Conglomerate (footwall) Cedar Mountain Aptian Formation Buckhorn Barremian Cedar Mountain Fm. Conglomerate
Lower Cretaceous ? ? ? Neocomian
Upper Jurassic Morrison Fm. San Rafael Group Middle Jurassic (part) Twist Gulch Fm. (part)
Figure 10. Correlation chart of Middle Jurassic (part) through Upper Cretaceous (part) strata in central and east-central Utah.
1 2 and 3 4 5
Chicken Creek upper Deep Creek (2) Christianburg Salina Canyon
Little Salt Creek (3)
Sanpete Fm.
San Pitch Fm.
member C Cedar
Mountain
Fm.
Jurassic
fault
113o 110o
o o 40 40
meters
member B Nephi Price
300 1
2
3
200
Manti
Castle Dale
4 100
Salina
0 5
050 km
member A 38o 30' 38o 30'
113o 110o
Figure 11. North-south fence diagram of the Cedar Mountain and San Pitch Formations from Chicken Creek to Salina Canyon. The Cedar Mountain Formation thickens southward from 23 m at Chicken Creek to 188 m at Salina Canyon. The San Pitch Formation dramatically thins from more than 1,100 m at Chicken Creek to about 85 m at Salina Canyon. Members A and B are interpreted to pinch out between Christianburg and Salina Canyon. Member C pinches out east of Salina Canyon. Explanation of lithology symbols is on page 8. Distance between sections is not to scale. 16 Utah Geological Survey
113o 110.0o
40.0o 40.0o
Canyon Range Conglomerate
San Pitch Formation
Cedar Mountain Formation Nephi
500
Castle Dale
Manti
Salina
300
0
100 050 km 38.5o thickness in meters 38.5o 113o 110.0o
Figure 12. Isopach map of the San Pitch Formation in central Utah. The San Pitch Formation is over 1,000 m thick along the west flank of the Gunnison Plateau and represents the depositional axis of the foredeep. The formation thins and interfingers with the upper part of the Cedar Mountain Formation to the south and east. The contour interval is 100 m and the innermost enclosing contour represents greater than 800 m of strata.
1 and 2 3 4
San Pitch Mtns. Salina Canyon San Rafael Swell sp.
Ks Ks Kd
Late Albian Late Albian
Asteropollis Liliacidites reticulatus Callialasporites damperi Trilobosporites apiverrucatus
Tigrisporites Asteropollis Retitricolpites georgensis Pilosisporites trichapapillosus
Retitricolpites ?
Pilosisporites Late
No tricolporates Cretaceous
Albian San Pitch Fm.
Aptian
San Pitch Formation Barremian
Middle Albian
Asteropollis Cretaceous Early
Neocomian
Liliacidites
Retitricolpites Cedar Mountain Formation
Callialasporites Jurassic
Pilosisporites
Trilobosporites
113o 110o
Cedar Mountain Fm. 40.0o 40.0o
Cedar Mtn. Fm. Mtn. Cedar
1
Jur.
Jur.
Jur. 2 4
3 0 50 km 38o 30' 38o 30' 113o 110o Figure 13. Age of the Cedar Mountain and San Pitch Formations as determined by palynologic assemblages. Palynomorphs collected from member A of the San Pitch Formation in Chicken Creek (1) and Christianburg (2), San Pitch Mountains, provided a middle Albian age. Palynomorphs collected from near the top of the San Pitch Formation in Salina Canyon (3) and the Cedar Mountain Formation in the San Rafael Swell (4) provided a late Albian age. Tschudy and others (1984) used the lack of tricolporates as negative evidence to restrict the age of the Cedar Mountain to late Albian in the San Rafael Swell. The Cedar Mountain Formation in the San Rafael Swell (4) was measured by Yingling (1987). The age-range chart of critical palynomorph species illustrates the restrictive middle Albian age of member A of the San Pitch Formation. These palynomorphs were collected from a bed near the base of member A at Chicken Creek and Christianburg. Explanation for symbols is on page 8. Redefining the Lower Cretaceous 17
CONCLUSIONS REFERENCES CITED
The Cedar Mountain and San Pitch Armstrong, R.L., 1968, Sevier orogenic belt in Nevada and Utah: Geological Society of America Bulletin, v. 79, no. Formations are mappable lithostratigraphic units 4, p. 429-458. that redefine the Lower Cretaceous stratigraphy Auby, W.L., 1991, Provisional geologic map of the Levan within the foreland basin of central Utah. Together quadrangle, Juab County, Utah: Utah Geological these formations are correlative with the Cedar Survey Map 135, 13 p., scale 1:24,000. Banks, R.L., 1991, Provisional geologic map of the Fountain Mountain Formation as exposed on the San Green North quadrangle, Sanpete and Juab Counties, Rafael Swell, and with the lower part of the Utah: Utah Geological Survey Map 134, 21 p., scale Canyon Range Conglomerate as exposed in the 1:24,000. Canyon Mountains. Biek, R.F., 1991, Provisional geologic map of the Nephi quadrangle, Juab County, Utah: Utah Geological The Cedar Mountain and San Pitch Survey Map 137, 21 p., scale 1:24,000. Formations form an upward-coarsening Craig, L.C., 1981, Lower Cretaceous rocks, southeastern succession of alluvial, fluvial, and lacustrine rocks Utah and southwestern Colorado, in Wiegand, G.L., that become finer grained southeastward toward editor, Geology of the Paradox Basin: Rocky Mountain Association of Geologists, p. 195-200. the San Rafael Swell. The Cedar Mountain Currie, B.S., 1997, Sequence stratigraphy of nonmarine Formation attains a maximum thickness of about Jurassic-Cretaceous rocks, central Cordilleran 200 m in the Sanpete Valley area and then thins foreland-basin system: Geological Society of America westward toward the Gunnison Plateau and Bulletin, v. 109, no. 9, p. 1206-1222. DeCelles, P.G., Lawton, T.F., and Mitra, Gautam, 1995, eastward toward the San Rafael Swell. The San Thrust timing, growth of structural culminations, and Pitch Formation attains a maximum thickness of synorogenic sedimentation in the Sevier orogenic belt, more than 1,100 m in the western part of the western United States: Geology, v. 23, no. 8, p. 699- Gunnison Plateau, and then rapidly thins south 702. Fong, A.W., 1995, Geologic map of the Fountain Green South and east toward the Wasatch Plateau where it quadrangle, Juab and Sanpete Counties, Utah: Utah pinches out and grades laterally into the upper Geological Survey Miscellaneous Publication 95-1, 18 part of the Cedar Mountain Formation. p., scale 1:24,000. The age of the Cedar Mountain is Fouch, T.D., Lawton, T.F., Nichols, D.J., Cashion, W.B., and Cobban, W.A., 1982, Chart showing preliminary Barremian(?) to late Albian in the San Rafael Swell correlation of major Albian to middle Eocene rock units region but is no younger that middle Albian in the from Sanpete Valley in central Utah to the Book Cliffs Gunnison Plateau and surrounding area. The age in eastern Utah, in Nielson, D.L., editor, Overthrust belt of the San Pitch Formation is middle to Late of Utah: Utah Geological Association Guidebook 10, p. 267-272. Albian. Fouch, T.D., Lawton, T.F., Nichols, D.J., Cashion, W.B., and Cobban, W.A., 1983, Patterns and timing of synorogenic sedimentation in Upper Cretaceous rocks ACKNOWLEDGMENTS of central and northeast Utah, in Reynolds, M.W., and Dolly, E.D., editors, Mesozoic paleogeography of west- central United States Rocky Mountain: Society of We were fortunate to work in a geologically Economic Paleontologists and Mineralogists challenging and interesting area of Utah. We Paleogeography Symposium 2, p. 305-336. were also fortunate to interact with many Hardy, C.T., and Zeller, H.D., 1953, Geology of the west- central part of the Gunnison Plateau: Geological knowledgeable geologists who also work in this Society of America Bulletin, v. 64, no. 11, p. 1261- area. We thank all of the geologists who, over the 1278. course of this work, have shared their knowledge Hintze, L.F., compiler, 1980, Geologic map of Utah: Utah and insight about the geology of central Utah, Geological and Mineral Survey Map A-1, scale 1:500,000. especially Lehi F. Hintze, Timothy F. Lawton, and Hintze, L.F., 1988, Geologic history of Utah, Provo: Brigham Grant C. Willis. We thank Will Aubrey, Ray Young University Geology Studies Special Publication Banks, and Paul Mycka for their assistance in 7, 202 p. measuring the thick and difficult sections. Finally, Hunt, R.E., 1950, The geology of the northern part of the Gunnison Plateau, Utah: Columbus, The Ohio State we thank Timothy F. Lawton, Irving J. Witkind, University, Ph.D. dissertation, 267 p. Bryce T. Tripp, and Grant C. Willis, for reviewing Jefferson, W.S., 1982, Structural and stratigraphic relations of the manuscript. Their suggestions and comments Upper Cretaceous to lower Tertiary orogenic were very helpful and significantly improved the sediments of the Cedar Hills, Utah, in Nielson, D.L., editor, Overthrust belt of Utah: Utah Geological manuscript. Association Guidebook 10, p. 65-80. 18 Utah Geological Survey
Katich, P.J., Jr., 1951, Recent evidence for Lower Cretaceous Association Guidebook 2, p. 21-28. deposits in the Colorado Plateau: American Stuecheli, P.J., 1984, The sedimentology, depositional Association of Petroleum Geologists Bulletin, v. 35, no. setting, and age of the Morrison(?) Formation in central 9, p. 2093-2094. Utah: Columbus, The Ohio State University, Master's Katich, P.J., Jr., 1956, Some notes on the Cretaceous faunas thesis, 104 p. of eastern Utah and western Colorado, in Peterson, Stuecheli, P.J., and Collinson, J.S., 1984, Sedimentology of J.A., editor, Geology and economic deposits of east- synorogenic conglomerates of the Lower Cretaceous central Utah: Intermountain Association of Petroleum Morrison(?) Formation, central Utah [abs.]: Geological Geologists, 7th Annual Field Conference Guidebook, Society of America Abstracts with Programs, v. 16, p. p. 116-119. 200. Lawton, T.F., and Weiss, M.P., 1994, Interim geologic map of Tschudy, R.H., Tschudy, B.D., and Craig, L.C., 1984, the Wales quadrangle, Sanpete County, Utah: Utah Palynological evaluation of Cedar Mountain and Burro Geological Survey Open-File Report 312, 94 p., scale Canyon Formations, Colorado Plateau: U.S. 1:24,000. Geological Survey Professional Paper 1281, 24 p. Pinnell, M.L., 1972, Geology of the Thistle quadrangle, Utah: Villien, Alain, and Kligfield, R.M., 1986, Thrusting and Provo, Brigham Young University Studies, v. 19, pt. 1, synorogenic sedimentation in central Utah, in p. 89-130. Peterson, J.A., editor, Paleotectonics and Roche, M.G., 1985, Morrison(?) Formation of central Utah sedimentation in the Rocky Mountain region: American reassigned: DeKalb, Northern Illinois University, Association of Petroleum Geologists Memoir 41, p. Master's thesis, 176 p. 281-306. Schwans, Peter, 1988, Depositional response of Pigeon Weiss, M.P., 1994, Geologic map of the Sterling quadrangle, Creek Formation, Utah, to initial fold-thrust belt Sanpete County, Utah: Utah Geological Survey Map deformation in a differentially subsiding foreland basin, 159, 26 p., scale 1:24,000. in Schmidt, C.J., and Perry, W.J., editors, Interaction of Weiss, M.P., and Roche, M.G., 1988, The Cedar Mountain the Rocky Mountain foreland and Cordilleran thrust Formation (Lower Cretaceous) in the Gunnison belt: Geological Society of America Memoir 171, p. Plateau, central Utah, in Schmidt, C.J., and Perry, 531-556. W.J., editors, Interaction of the Rocky Mountain Schwans, Peter, 1995, Controls on sequence stacking and foreland and Cordilleran thrust belt: Geological Society fluvial shallow-marine architecture in a foreland basin, of America Memoir 171, p. 557-569. in Van Wagoner, J.C., and Bertram, G.T., editors, Willis, G.C., 1986, Geologic map of Salina quadrangle, Sevier Sequence stratigraphy of foreland basin deposits: County, Utah: Utah Geological and Mineral Survey American Association of Petroleum Geologists Memoir Map 83, 20 p., scale 1:24,000. 64, p. 55-102. Willis, G.C., and Kowallis, B.J., 1988, Newly recognized Spieker, E.M., 1946, Late Mesozoic and Early Cenozoic Cedar Mountain Formation in Salina Canyon, Sevier history of central Utah: U.S. Geological Survey County, Utah: Provo, Brigham Young University Professional Paper 205-D, p. 117-161. Geology Studies, v. 35, p. 57-61. Spieker, E.M., 1949, The transition between the Colorado Witkind, I.J., 1988, Geologic map of the Huntington 30' x 60' Plateau and the Great Basin in central Utah: Salt Lake quadrangle, Carbon, Emery, Grand, and Uintah City, Utah Geological Society Guidebook to the counties, Utah: U.S. Geological Survey Miscellaneous Geology of Utah, no. 4, 106 p. Investigations Series Map I-1631, scale 1:100,000. Spieker, E.M., and Reeside, J.B., Jr., 1926, Upper Witkind, I.J., and Page, W.R., 1983, Geologic map of the Cretaceous shoreline in Utah: Geological Society of Thistle area, Utah County, Utah: Utah Geological and America Bulletin, v. 37, p. 429-438. Mineral Survey Map 69, scale 1:24,000. Sprinkel, D.A., 1994, Stratigraphic and time-stratigraphic Witkind, I.J., Standlee, L.A., and Maley, K.F., 1986, Age and cross sections: A north-south transect from near the correlation of Cretaceous rocks previously assigned to Uinta Mountains axis across the Basin and Range the Morrison(?) Formation, Sanpete-Sevier Valley transition zone to the western margin of the San Rafael area, central Utah: U.S. Geological Survey Bulletin Swell, Utah: U.S. Geological Survey Miscellaneous 1584, 9 p. Investigations Series I-2184-D, 31 p., scale 1:500,000. Witkind, I.J., Weiss, M.P., and Brown, T.L., 1987, Geologic Standlee, L.A., 1982, Structure and stratigraphy of Jurassic map of the Manti 30' x 60' quadrangle, Carbon, Emery, rocks in central Utah: their influence on tectonic Juab, Sanpete, and Sevier counties, Utah: U.S. development of the Cordilleran foreland thrust belt, in Geological Survey Miscellaneous Investigations Map I- Powers, R.B., editor, Geologic studies of the 1631, scale 1:100,000. Cordilleran thrust belt: Rocky Mountain Association of Yingling, V.L., 1987, Timing of initiation of the Sevier Geologists, p. 357-382. Orogeny: Morrison and Cedar Mountain Formations Stokes, W.L., 1944, Morrison and related deposits in and and Dakota Sandstone, east-central Utah: Salt Lake adjacent to the Colorado Plateau: Geological Society City, University of Utah, Master's thesis, 169 p. of America Bulletin, v. 55, no. 8, p. 951-992. Young, G.E., 1976, Geology of Billies Mountain quadrangle, Stokes, W.L., 1952, Lower Cretaceous in Colorado Plateau: Utah: Provo, Brigham Young University Geology American Association of Petroleum Geologists Bulletin, Studies, v. 23, pt. 1, p. 205-280. v. 36, no. 9, p. 1766-1776. Stokes, W.L., 1972, Stratigraphic problems of the Triassic and Jurassic sedimentary rocks of central Utah, in Baer, J.L., and Callaghan, E., editors, Plateau-Basin and Range transition zone: Utah Geological Redefining the Lower Cretaceous 19
Table 1. Measured sections of Cedar Mountain and San Pitch Formations.
Section name Location Quadrangle Measured by Christianburg1 NE¼NE¼ sec. 13, T. 19 S., R. 1 E. to Sterling D.A. Sprinkel SE¼SE¼ sec. 12, T. 19 S., R. 1 E. Sanpete County Christianburg 2 NW¼ sec. 18, T. 19 S.,R. 2 E. to Sterling K.F. Maley (Witkind et al., 1986) SE¼ sec. 12, T. 19 S.,R. 1 E. Sanpete County Chicken Creek3 SW¼SE¼ sec. 2, T. 15 S., R. 1 E., Levan D.A. Sprinkel, W. Aubrey, P. Mycka Juab County Little Salt Creek3 SW¼SW¼ sec. 33, T. 15 S., R. 1 E. Chriss D.A. Sprinkel, M.P. Weiss, R.L. Juab County Canyon Banks upper Deep Creek3 SE¼SE¼ sec. 23, T. 15 S., R. 1 E. Chriss D.A. Sprinkel, M.P. Weiss, R.L. Juab County Canyon Banks Salina Canyon3 SE¼NE¼ sec. 33, T. 21 S., R. 1 E. Salina D.A. Sprinkel, W. Aubrey, P. Mycka Sevier County
1 Type section of the San Pitch Formation 2 Reference section of the Cedar Mountain Formation 3 Reference section of the Cedar Mountain and San Pitch Formations
Table 2. Palynologic assemblage of the San Pitch Formation.
Relative1 Location Sample Formation Age Species Site Abundance
Chicken SW¼NE¼NE¼ CC10 San Pitch Aptian to SPORES AND POLLEN Creek sec. 11, member A middle Araucariacites australis R T. 15 S., R. 1 E., Albian Undifferentiated bisaccates R Juab County, Utah Exesipollenites tumulus R Schizopris parvus R S. retulatus R Taxodiaceae R Cicatricosisporites australiensis R Cingulatisporites sp. R Deltoidospora spp. R Foraminisporites dailyi R Lycopodiumsporites sp. A R
MICROPLANKTON Micrhystridium sp. R
Chicken SW¼NE¼NE¼ CC72893-1 San Pitch middle to SPORES AND POLLEN Creek sec. 11, member A early late Araucariacites australis A T. 15 S., R. 1 E., Albian Undifferentiated bisaccates F Juab County, Utah Classopollis classoides F ?Classopollis spinosus R Exesipollenites tumulus R Callialasporites dampieri R Taxodiaceae R Appendicisporites potomacensis R Cicatricosisporites australiensis R C. brevilaesuratus R C. hallei R C. venustus R Cingulatisporites distaverrucosus R Concavissimisporites punctatus R Deltoidospora spp. F 20 Utah Geological Survey
Foveotriletes sp. R Foraminisporis dailyi R Gleicheniidites senonicus R Pilosisporites trichopapillosus F Trilobosporites minor R T. perverulentus R Eucommiidites minor R Retitricolpites georgensis R Asteropollis/Clavatipollenites complex F
Chicken SW¼NE¼NE¼ 3739-1 San Pitch Aptian to SPORES AND POLLEN Creek2 sec. 11, member A middle Arauacariacites australis A T. 15 S., R. 1 E., Albian Callialasporites dampieri F Juab County, Utah Classopollis classoides A Exesipollenites tumulus R Schizosporis parvus R Appendicisporites potomacensis R Cingulatisporites distaverrucosus R Concavissimisporites punctatus F Deltoidaspora spp. R Foraminisporis dailyi R Gleicheniidites senonicus R Perotrilites sp. R Pilosisporites trichopapillosus C P. verus R Trilobosporites apiverrucatus R Trilobosporites marylandensis F Undifferentiated bisaccates R
Chicken SW¼NE¼NE¼ P4507-1 San Pitch Aptian to SPORES AND POLLEN Creek1 sec. 11, member A middle Araucariacites australis A T. 15 S., R. 1 E., Albian Undifferentiated bisaccates R Juab County, Utah Classopollis classoides A Eucommiidites minor R Exesipollenites tumulus R Callialasporites dampieri A Taxodiaceae R Apiculatisporites sp. A R Balmeisporites sp. R Concavissimisporites punctatus R Coptospora sp. A R Coronatispora valdensis R Deltoidospora spp. R Foraminisporis dailyi R Asteropollis asteroides A Clavatipollenites tenellus A C. rotundus C C. hughesii C Liliacidites tricotomosulcus R L. spp. R
MICROPLANKTON Cometosphaeridium sp. R ?Muderongia sp. A R Micrhystridium sp. R Miscellaneous Acritarch R Christianburg SW¼NW¼NW¼ X-1 San Pitch Aptian to SPORES AND POLLEN sec. 13, member A middle Appendicisporites potomacensis R T. 19 S., R. 1 E., Albian Chomotriletes fragilis R Sanpete County, Cicatricosisporites australiensis R Utah C. hallei R Deltoidospora spp. R Exexsipollenites tumulus F Foveosporites labiosus F Klukisporites pseudoreticulatus R Lycopodiumsporites spp. R Matonisporites crassiangulatus R Ornamemtifera echinata R Osmundacidites comaumensis R Pilosisporites trichopapillosus R Undifferentiated bisaccates R Redefining the Lower Cretaceous 21
Undulatisporites pannuceus R Verrucosisporites rotundus R
MICROPLANKTON Tasmanaceae R
Christianburg SW¼NW¼NW¼ X-2 San Pitch Aptian to SPORES AND POLLEN sec. 13, member A middle Appendicisporites potomacensis R T. 19 S., R. 1 E., Albian Araucariacites australiensis R Sanpete County, Cicatricosisporites australiensis R Utah C. hallei R C. venustus R Concavissimisporites punctatus R Concavissimisporites sp. 2 R Deltoidospora spp. R Foraminisporis wonthaggiensis R Gleicheniidites senonicus R Klukisporites pseudoreticulatus R Laevigatosporites sp. R Lycopodiumsporites sp. A R L. spp. R Permonolites allensis R Pilosisporites trichopapillosus F Punctatosporites scabratus R Undifferentiated bisaccates R Undulatisporites pannuceus R ?Tigrisporites sp. R
MICROPLANKTON Tasmanaceae R
Salina NE¼SW¼SE¼ SC1 San Pitch middle to SPORES AND POLLEN Canyon sec. 33, member C late Albian Undifferentiated bisaccates R T. 21 S., R. 1 E., Concavissimisporites punctatus R Sevier County, Deltoidospora spp. R Utah Gleicheniidites senonicus R Tigrisporites scurrandus R
1 A = abundant (>30); C = common (16-30); F = frequent (6-15); R = rare (1-5) 2 Chevron samples