Earth Sciences and Geography, Keele University, Keele, Staffordshire, ST5 5BG, UK Oliver Wakefield and Nigel Mountney Introduction & Study Location Regional Stratigraphic Setting Summary Model and Conclusions Characteristic Lithofacies Examples Preserved Sedimentary Expression of an Incised Valley-Fill Succession Within a Transgressive Shoreline System Cutler Group, Paradox Basin, Southeast Utah, USA [email protected] +44 (0) 1782 583171 http://www.esci.keele.ac.uk/ 100m 1 2 3 4 5 6 7 Lower Cutler Beds Cedar Mesa Sandstone Pennsylvanian - Lower Permian (Wolfcampian) Little Spring Canyon Sedimentary Logs: Setting Proximal to the Palaeo-Coastline Little Spring Canyon: Examples of Facies Architecture Lower Indian Creek: Examples of Facies Architecture Lower Indian Creek Sedimentary Logs: Setting Distal to the Palaeo-Coastline The study areas are located in, and adjacent to the Needles District of Canyonlands National Park, where the combined effects of both deep incision by tributary canyons of the Colorado River, & gentle anticlinal folding expose the upper and middle parts of the Lower Cutler Beds. The Lower Cutler Beds of southeastern Utah represents a Pennsylvanian-to-Permian age, mixed continental-marine shoreline succession, which accumulated under the influence of a predominantly arid climatic regime and which was subject to repeated marine transgressive-regressive cycles. The succession - which is comprises aeolian, fluvial, and shallow marine units that have previously been interpreted to have accumulated in a low relief, low gradient coastal plain and shallow marine ramp setting (Jordan, 2006). The aim of this project is to reconstruct the geometry and account for the architectural complexity of a series of well exposed incised valley systems that are thought to have been cut during episodes of relative sea level fall and then in-filled with a variety of shallow marine facies during subsequent episodes of relative sea level rise. The valley systems exhibit considerable variation in their preserved expression over distances of only 10 km, reflecting increased amounts of incision in close proximity to shoreline regions. well exposed across much of the northern and central parts of the Paradox foreland basin - The two study regions within the Lower Cutler Beds record the style of sediment infill within an incised valley complex that likely represents proximal and distal parts of the same valley system over a distance of 10 km along a transect running inland from the inferred position of the palaeo-coastline. The characteristics of the style of incised valley back-fill changes dramatically from the more coastline-proximal location at Little Spring Canyon to the more distal locality at Lower Indian Creek. The Calcarenite gritstone channels thin from thickness of 7-12 m at Little Spring Canyon to < 2 m at Lower Indian Creek. Additionally, the style of sedimentation varies with Lower Indian Creek exposing thick accumulations of laterally continuous fluvial and aeolian units, which contrasts with a more fragmentary style of preservation at Little Spring Canyon. noticeably between each location, Case Study 1: Little Spring Canyon Case Study 2: Lower Indian Creek Cedar Mesa Sandstone Lower Cutler Beds Photo showing location of Little Spring Canyon Log 1 (red). The prominent massive structureless unit at one-third height is a large, erosively-based channel infilled with calcarentite gritstone and forms part of the thicker marine unit in the correlation panel above. Cliff is 60 m high. The horizon marked in yellow signifies the top of the uppermost marine limestone that defines the top of the Lower Cutler Beds and the base of the overlying Cedar Mesa Sandstone. This horizon can be traced for over 50 km to the north. Calcarenite gritstone facies, Lower Indian Creek. Photo showing location of Lower Indian Creek Log 8 (red, 40 m high). Only three thin shallow marine units are preserved at this locality and relief on the base of these units does not exceed 1-2 m. Aeolian Fluvial Marine Aeolian, horiz. bedded Aeolian, cross bedded Aeolian, massive Fluvial, cross bedded Fluvial, horiz. bedded Fluvial, mud- & siltstone Limestone, bedded Limestone, micritic Calcarenite gritstone Gradational facies change Bioturbation Clasts Black = Extraformational Coloured = Intraformational Trough-cross bedding Planar-cross bedding Horizontal lamination Shelly debris & fragments Nodules Soft sediment deformation Bioturbated aeolian interdune facies. Cross bedded aeolian dune facies. Tape = 2 m. Wavy-to-ripple laminated fluvial sandstone facies. Horizontally laminated fluvial siltstone facies. Trough-cross bedded aeolian dune facies. Nodular marine limestone facies. Knife = 6 cm. Fossiliferous, bedded limestone facies. 8 7 6 5 100m 1 2 3 4 Lower Cutler Beds Canyonlands National Park, Needles District The Lower Cutler Beds exhibit a variety of complex architectural relationships between marine, fluvial and aeolian depositional units. These represent the preserved stratigraphic expression of a marginal marine, shoreline and arid terrestrial system that was subject to repeated marine transgressive and regressive events. Whilst the marine units, which represent the product of transgressive events, are typically only 2-5 m thick, in places they infill broad incised valley systems where they attain thicknesses of 12-15 m and exhibit a complex array of facies interactions and architectural styles. A series of high-resolution sedimentary logs, measured from two study regions within the Lower Cutler Beds, record the style of sediment infill within an incised valley complex that likely represents shore- proximal and shore-distal parts of the same valley system over a distance of 10 km. Regional Stratigraphy Regional palaeogeography Study Locations N UTAH 0 5 km Study area 1: Little Spring Canyon Study area 2: Lower Indian Creek The extent of the Paradox foreland basin and associated major structural elements in adjacent areas with the study locality shown. The area in yellow denotes the limits of the Paradox Formation salt that defines the extent of the main basin. Modified after Kelley (1958), cited in Nuccio and Condon (1996). ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä DEFIANCE PLATEAU Carrizo Mtns. SAN JUAN BASIN UNCOMPAHGRE PLATEAU SAN RAFAEL SWELL PARADOX FOLD FAULT BELT AND UINTA BASIN TYENDE SADDLE BLACK MESA BASIN KAIBITO SADDLE PIUTE FOLDS Navajo Mtn BLANDING BASIN WHITE CANYON SlLOPE Henry Mtns. HENRY BASIN CIRCLE CLIFFS UPLIFT Abajo Mtns ä La Sal Mtns 0 25 Mi 0 25 Km Utah Arizona Colorado New Mexico 111 00' 110 30' 110 00' 109 30' 109 00' 108 30' 108 00' 107 30' Durango Farmington Hanksville Hite Montrose Navajo Reservoir Lake Powell FOUR CORNERS PLATFORM Sleeping Ute Mountain MONUMENT UPWARP H O G B A CK M O NOCLINE RED ROCK BENCH ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä ä C O M B R I D G E M ONOCLINE San Miguel Mtns La Plata Mtns Green River Grand Junction Gateway Naturita Ouray Cortez Blanding Moab Bluff Slick Rock Monticello S a n J u a n R i v e r Green R iver C o l o r a d o R i v e r Mexican Hat Kayenta C o lorado Ri v er Rico SAN JUAN DOME Rico Mtns Needle Mtns OILETO SAG 39 30' 39 00' 38 30' 38 00' 37 30' 37 00' 36 30' LISBON VALLEY ANTICLINE Palaeo - windflow Palaeo - Fluvial Shafer Basin Lockhart Basin Canyonlands District Grabens District N Lower Cutler Beds facies interaction summary. a) Palaeogeographic model for the multiple styles of interactions observed between aeolian, fluvial, nearshore and shallow marine environments. While the model shows each of the three principal environment types active simultaneously, it should be noted that this is not necessarily always the case. b) Schematic regional model of stratigraphic relationships in the Lower Cutler Beds and the inter-tonguing of the unit with the undifferentiated Cutler Group. Modified after Jordan (2006). Lower Cutler Beds Cedar Mesa Sandstone NE SW Cutler Group Undivided Summary depositional model Regional Stratigraphy aeolian facies assoc. fluvial facies assoc. shallow marine facies association Little Spring Canyon Lower Indian Creek Deeply incised channels with marine infill Fluvial channel sandstone with abundant water escape structures Gradational transition between calcarenite gritstone and micritic limestone Abundant shell debris: lags of crinoid and bivalve fragments Planar-cross bedded fluvial units with erosive bases Non-marine bioturbation Marine units with lags of extraformational clasts Fluvial-to-aeolian transition marked by unit of wind- rippled sandsheet strata Very thin but extensive fine-grained fluvial unit Nodular limestone Erosively-based channel with calcarenite gritstone infill. Note lateral thinning. Erosively-based channel (12 m deep) with calcarenite gritstone infill. Channel lag with marine fossil debris. Limestone bedding surface with . Scolicia 1 2 1 2 1 3 4 3 5 7 2 4 6 8 3 4 5 6 7 8 9 10 5 6 9 6 8 7 8 5 3 4 7 1 10 2 0 8 m 0 8 m 0 1 km 1 2 3 4 5 6 7 A A’ UNCOMPAHGRE UPLIFT CANYONLANDS CAPITOL REEF RICHFIELD MOAB Circle Cliffs Trough Emery Arch Cutler Foredeep Undivided Cutler Gp Lower Cutler Beds Pre-Cambrian Rocks Pennsylvanian & Mississippian Rocks Triassic Rocks Organ Rock Fm Cedar Mesa Sst White Rim Sst Toroweap Fm Kaibab Fm W E 120 m 0 0 10 20 30 40 km Cross-bedded sst: aeolian dune Gypsum/evap: sabkha/restricted marine Carbonate: marine/restricted marine Sst/mst: sabkha/fluvial Mst/evap: restricted marine/sabkha Arkosic sst/cong: fluvial Arkosic sst/ms: fluvial Sst/mst: mixed aeolian/marine/sabkha Stratigraphic panel of Permian units on the Colorado Plateau. Not all the unit boundaries can be correlated with confidence over the distances shown, rather the diagram reflects a generalised stratigraphy. Numbers 1, 3 and 4 refer to the regionally extensive sequences of Blakey (1996), from which the figure is taken. Four Corners Utah Arizona Nervada 2000 ft 1000 ft 300 m 0 0 0 0 100 km 100 miles Cedar Mesa Sst Halgaito Fm Lower Cutler Beds Organ Rock Fm Monument Valley Monument Valley Canyonlands Canyonlands Undivided Cutler Gp Organ Rock Fm Cedar Mesa Sst Pakoon Lst Pakoon Lst Hermit Fm Esplanade Sst Esplanade Sst Supai Fm Sedona Holbrook Defiance Plateau Magollon Rim Lower Cutler Beds Elephant Canyon Fm See insert in upper left-hand corner. Pavant Range Virgin River Grand Wash Cliffs Grand Canyon San Rafael Swell Uncompahgre Uplift Paradox Basin Grand Canyon Zuni - Defiance Arch Sedona Arch Circle Cliffs Insert Sandstone, mostly cross-strata: aeolian Sandstone, variable, tan: marine/sabkha/aeolian Sandstone/mudstone, red: fluvial/sabkha/marine Evaporite: sabkha/restricted marine Carbonate: marine/restricted marine Arkosic conglomerate, sandstone, mudstone: fluvial Pre-Cambrian rocks vertical exaggeration 150x Fence diagram showing the distribution of major units within Permian sequence 1 (Blakey (1996), as identified within southern Utah & northern Arizona (after Blakey, 1996). Note that the Lower Cutler Beds are time equivalent to the Pakoon Limestone of Arizona. Uncompahgre Uplift Arkosic sst and cong. Mixed sst, mst, lst & cong. Sst, mst & local lst. Sst with large cross-beds Evaporites Limestone & dolomite 0 0 100 km 100 miles 0 0 100 km 100 miles Epicontinental Sea Lower Cutler Beds Pakoon Lst Esplanade Sst Cedar Mesa Sst Halgaito Fm Coastal sabkha/tidal flats Arid coastal lowlands Dune field/erg Alluvial fans Alluvial Plain Cutler Gp Cutler Gp Esplanade - Cedar Mesa erg Inland Sabkha Pakoon Lst Cedar Mesa Sst Supai Fm Esplanade Sst Upper part of interval removed by pre-White Rim Erosion Edge of significant aeolian deposits Queantoweap Sst Approximate facies limits (left) and inferred palaeogeography (right) for Lower Cutler Beds times. Modified after Blakey (1996). The position of the study localities are indicated. Approximate facies limits (left) and inferred palaeogeography (right) for Cedar Mesa times. Modified after Blakey (1996). The position of the study localities are indicated. Facies Facies Palaeogeography Palaeogeography Limit of Paradox salt in subsurface Limit of Paradox salt in subsurface Study localities Study localities The Lower Cutler beds exposed in the Paradox basin of southeastern Utah represent the preserved remnant of a large, shallow epicontinental sea that occupied a position across much of what is now south-central Utah and north-central Arizona. The incised valley systems replete with nearshore and non-marine facies, which represent the focus of this study, record the coastline of this sea in southeast Utah. To the south and west of the Canyonlands region, strata composed of the Lower Cutler Beds, are known by a variety of names including the Elephant Canyon Formation and the Pakoon Limestone. shallow marine limestones and calcarenites, which are time-equivalent to 0 1 km 1 4 3 2 8 7 6 5 Fluvial architectural elements, characterised by cross-bedded and planar-laminated sandstones and sandy-siltstones, are arranged into multi-storey channel complexes that commonly exhibit relief on both their basal and upper surfaces. Aeolian architectural elements, characterised by homogeneous and large-scale cross-bedded sandstone facies, are arranged into sharp-based units that usually infill topography at the top of the underlying fluvial units. Shallow marine architectural elements are characterised by both calcarenite gritstone facies, arranged into erosively-based co-sets, and micritic limestone facies, with abundant marine macro-fossils. The coarse-grained calcarenite gritstone facies occur most commonly as complex co-sets of strata, which form the fill of deeply-incised channelised elements that cut down into underlying aeolian and fluvial units. These channels are interpreted to represent incised valleys that were cut by fluvial systems during periods of relative sea-level lowstand and which were later infilled by shallow marine strata during subsequent transgression. A variety of onlap relationships are recognized between strata of marine and non-marine origin at the channel margins. At least five separate marine transgressions are known to have occurred during Lower Cutler Beds times and incised valley systems with marine stratal infills are associated with each of these flooding events, though only the uppermost three are recorded here. Study area Study area study area Blakey, R.C. (1996) Permian eolian deposits, sequences and sequence boundaries, Colorado Plateau. In: (Eds M.W. Longman, and S.D. Sonnenfeld), Rocky Mountain Section SEPM (Society for Sedimentary Geology, 405-426. Jordan O.D. (2006) . Unpublished PhD thesis, University of Keele, UK, 328 pages. Nuccio, V.F. and Condon, S.M. (1996) . U.S. Geol. Surv. Bull., , 41 pages. Paleozoic Systems of the Rocky Mountain Region Sedimentology and stratigraphic evolution of the Pennsylvanian-Permian Lower Cutler Beds, Paradox basin, SE Utah Burial and Thermal History of the Paradox Basin, Utah and Colorado, and the Petroleum Potential of the Middle Pennsylvanian Paradox Formation 2000-O