Preserved Sedimentary Expression of an Incised Valley-Fill ...
Transcript of Preserved Sedimentary Expression of an Incised Valley-Fill ...
Earth Sciences and Geography, Keele University, Keele, Staffordshire, ST5 5BG, UKOliver 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 SystemCutler Group, Paradox Basin, Southeast Utah, USA
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Cedar
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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 arelocated in, and adjacent tothe Needles District ofCanyonlands NationalP a r k , w h e r e t h ecombined effects of bothdeep incision by tributarycanyons of the ColoradoRiver, & gentle anticlinalfolding expose the upperand middle parts of theLower Cutler Beds.
The Lower Cutler Beds of southeastern Utah represents a Pennsylvanian-to-Permian age, mixedcontinental-marine shoreline succession, which accumulated under the influence of a predominantlyarid climatic regime and which was subject to repeated marine transgressive-regressive cycles. Thesuccession - which is
comprises aeolian, fluvial, and shallow marine units that have previously beeninterpreted to have accumulated in a low relief, low gradient coastal plain and shallow marine rampsetting (Jordan, 2006). The aim of this project is to reconstruct the geometry and account for thearchitectural complexity of a series of well exposed incised valley systems that are thought to havebeen cut during episodes of relative sea level fall and then in-filled with a variety of shallow marinefacies during subsequent episodes of relative sea level rise. The valley systems exhibit considerablevariation in their preserved expression over distances of only 10 km, reflecting increased amounts ofincision in close proximity to shoreline regions.
well exposed across much of the northern and central parts of the Paradoxforeland basin -
The two study regions within the Lower Cutler Beds record the style of sediment infillwithin an incised valley complex that likely represents proximal and distal parts of thesame valley system over a distance of 10 km along a transect running inland from theinferred position of the palaeo-coastline. The characteristics of the style of incised valleyback-fill changes dramatically from the more coastline-proximal location at Little SpringCanyon to the more distal locality at Lower Indian Creek. The Calcarenite gritstonechannels thin from thickness of 7-12 m at Little Spring Canyon to < 2 m at Lower IndianCreek. Additionally, the style of sedimentation varieswith Lower Indian Creek exposing thick accumulations of laterally continuous fluvial andaeolian units, which contrasts with a more fragmentary style of preservation at LittleSpring Canyon.
noticeably between each location,
Case Study 1: Little Spring Canyon Case Study 2: Lower Indian Creek
Cedar Mesa Sandstone
Lower CutlerBeds
Photo showing location of Little Spring CanyonLog 1 (red). The prominent massive structurelessunit at one-third height is a large, erosively-basedchannel infilled with calcarentite gritstone andforms part of the thicker marine unit in thecorrelation panel above. Cliff is 60 m high. Thehorizon marked in yellow signifies the top of theuppermost marine limestone that defines the topof the Lower Cutler Beds and the base of theoverlying Cedar Mesa Sandstone. This horizoncan be traced for over 50 km to the north.
Calcarenite gritstone facies, Lower Indian Creek.
Photo showing location of LowerIndian Creek Log 8 (red, 40 m high).Only three thin shallow marine unitsare preserved at this locality andrelief on the base of these units doesnot exceed 1-2 m.
Ae
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lM
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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
ClastsBlack = ExtraformationalColoured = 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.
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CanyonlandsNational Park,Needles District
The Lower Cutler Beds exhibit a variety of complex architectural relationships between marine, fluvialand aeolian depositional units. These represent the preserved stratigraphic expression of a marginalmarine, shoreline and arid terrestrial system that was subject to repeated marine transgressive andregressive events. Whilst the marine units, which represent the product of transgressive events, aretypically only 2-5 m thick, in places they infill broad incised valley systems where they attainthicknesses of 12-15 m and exhibit a complex array of facies interactions and architectural styles. Aseries of high-resolution sedimentary logs, measured from two study regions within the Lower CutlerBeds, 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
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Study area 1:Little Spring Canyon
Study area 2:Lower Indian Creek
The extent of the Paradox foreland basin and associatedmajor structural elements in adjacent areas with the studylocality shown. The area in yellow denotes the limits of theParadox Formation salt that defines the extent of the mainbasin. Modified after Kelley (1958), cited in Nuccio andCondon (1996).
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DEFIANCEPLATEAU
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LISBON
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LINE Palaeo - windflow
Palaeo - Fluvial
Shafer Basin
Lockhart Basin
Canyonlands
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Grabens
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NLower Cutler Beds faciesinteraction summary. a)Palaeogeographic model fort h e m u l t i p l e s t y l e s o fi n t e r a c t i o n s o b s e r v e dbetween aeolian, fluvial,nearshore and shallow marineenvironments. While themodel shows each of the threeprincipal environment typesactive simultaneously, itshould be noted that this is notnecessarily always the case.b) Schematic regional modelof stratigraphic relationships inthe Lower Cutler Beds and theinter-tonguing of the unit withthe undifferentiated CutlerGroup. Modified after Jordan(2006).
Lower CutlerBeds
Cedar Mesa SandstoneNE SW
Cutler GroupUndivided
Summary depositional model
Regional Stratigraphy
aeolian facies assoc.
fluvial facies assoc.
shallow marinefacies association
Little SpringCanyon
Lower IndianCreek
Deeply incised channels with marine infill
Fluvial channel sandstone with abundant waterescape structures
Gradational transition between calcarenite gritstoneand micritic limestone
Abundant shell debris: lags of crinoid and bivalvefragments
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
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UNCOMPAHGREUPLIFT
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MOAB
Circle Cliffs Trough Emery Arch
Cutler Foredeep
UndividedCutler Gp
LowerCutler Beds
Pre-Cambrian Rocks
Pennsylvanian &Mississippian Rocks
Triassic RocksOrgan Rock Fm
Cedar Mesa Sst
WhiteRim SstToroweap Fm
Kaibab Fm
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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 ColoradoPlateau. Not all the unit boundaries can be correlatedwith confidence over the distances shown, rather thediagram reflects a generalised stratigraphy. Numbers1, 3 and 4 refer to the regionally extensive sequencesof Blakey (1996), from which the figure is taken.
Four Corners
Utah
Arizona
Nerv
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1000 ft300 m
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100 miles
Cedar Mesa Sst
Halgaito FmLowerCutlerBeds
Organ Rock Fm
MonumentValley
Monument Valley
Canyonlands Canyonlands
UndividedCutler Gp
Organ Rock Fm
Cedar Mesa Sst
PakoonLst
Pakoon Lst
Hermit FmEsplanade Sst
Esplanade SstSupai FmSedona
Holbrook
Defia
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Pla
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Magollon
Rim
LowerCutler Beds
Elephant Canyon Fm
See insert in upperleft-hand corner.
Pavant Range
Virgin River
GrandWashCliffs
Grand Canyon
San Rafael Swell
UncompahgreUplift
Paradox
Basin
Grand
Canyon
Zuni - Defiance
Arch
Sedona
Arch
CircleCliffs
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 rocksvertical exaggeration 150x
Fence diagram showing thedistribution of major units withinPermian sequence 1 (Blakey(1996), as identified withinsouthern Utah & northernArizona (after Blakey, 1996).Note that the Lower Cutler Bedsare time equivalent to thePakoon Limestone ofArizona.
Uncompahgre Uplift
Arkosic sst and cong.
Mixed sst, mst, lst & cong.
Sst, mst & local lst.
Sst with large cross-beds
Evaporites
Limestone & dolomite
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100 miles
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EpicontinentalSea
Lower CutlerBeds
Pakoon Lst
EsplanadeSst
CedarMesaSst
HalgaitoFm
Coast
al s
abkh
a/tid
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lats
Arid coastallowlands
Dune field/erg
Alluvialfans
Alluvial Plain
Cutle
rG
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Esp
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SupaiFm
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Upper part of intervalremoved by pre-White
Rim Erosion
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aeolia
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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 Paradoxsalt in subsurface
Limit of Paradoxsalt in subsurface
Studylocalities
Studylocalities
The Lower Cutler beds exposed in the Paradox basin of southeastern Utah represent the preservedremnant of a large, shallow epicontinental sea that occupied a position across much of what is nowsouth-central Utah and north-centralArizona. The incised valley systems replete with nearshore andnon-marine facies, which represent the focus of this study, record the coastline of this sea insoutheast Utah. To the south and west of the Canyonlands region, strata composed of
the Lower Cutler Beds, are knownby a variety of names including the Elephant Canyon Formation and the Pakoon Limestone.
shallowmarine limestones and calcarenites, which are time-equivalent to
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Fluvial architectural elements, characterised by cross-bedded and planar-laminatedsandstones and sandy-siltstones, are arranged into multi-storey channel complexesthat commonly exhibit relief on both their basal and upper surfaces.Aeolian architecturalelements, characterised by homogeneous and large-scale cross-bedded sandstonefacies, are arranged into sharp-based units that usually infill topography at the top of theunderlying fluvial units. Shallow marine architectural elements are characterised by bothcalcarenite gritstone facies, arranged into erosively-based co-sets, and micriticlimestone facies, with abundant marine macro-fossils. The coarse-grained calcarenitegritstone facies occur most commonly as complex co-sets of strata, which form the fill ofdeeply-incised channelised elements that cut down into underlying aeolian and fluvialunits. These channels are interpreted to represent incised valleys that were cut by fluvialsystems during periods of relative sea-level lowstand and which were later infilled byshallow marine strata during subsequent transgression. A variety of onlap relationshipsare 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 LowerCutler Beds times and incised valley systems with marine stratal infills are associatedwith each of these flooding events, though only the uppermost three are recorded here.
Study area
Study area
studyarea
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