Dox Formation
The entire Grand Canyon Supergroup overlies deeply eroded granites, gneisses, pegmatites, and schists that comprise Vishnu Basement Rocks.The lower member of the Dox Formation consists of silty-sandstone and sandstone, and some interbedded argillaceous beds, that form stair-stepped, cliff-slope topography.Elsewhere, within the central Grand Canyon, these Unkar strata (Bass, Hakatai, and Shinumo), occur in small, rotated, downfaulted blocks or slivers where they commonly are only partially exposed.The missing part of the Dox Formation and overlying Cardenas Basalt and Chuar Group are preserved in a prominent syncline and fault block that is exposed in the eastern Grand Canyon.[2] West of 75-mile Creek in the central Grand Canyon, the strata of the Dox Formation occurs in small, rotated, downfaulted blocks or slivers, and commonly are only partially exposed.The contacts between members of the Dox Formation are gradational and are based mainly on topographic expression, the sedimentary depositional environment, and color changes.Two intervals of convoluted bedding, which are the stratigraphically highest occurrence of fluid evulsion structures in the Unkar Group, occur within 30 m of the base of the Escalante Creek Member.The upper 67 m (220 ft) of the member consists primarily of maroon quartz sandstone that exhibits numerous channel features, and contains low-angle, tabular, and channel-like festoon cross beds.The strata of this member consist mainly of interbedded fine grained, slope-forming, argillaceous sandstone and sandy argillite, and subordinate claystone.Sedimentary structures found in this member include, salt crystal casts in the mudstone, and asymmetrical ripple marks and small-scale cross beds, in the sandstones.The Dox Formation that directly underlies the Cardenas Basalt consists of brick-red to vermilion well-bedded sandstone, with parallel bedding and shaly partings, forming smooth slopes.The basal 12 m (39 ft) of the Dox Formation directly overlying Shinumo Quartzite consists of predominantly dark green to black, fissile, slope-forming shale that contains thin sandstone beds.At the base of the Escalante Creek Member, the two intervals of convoluted bedding, which comprise the stratigraphically highest fluid evulsion structures in the Unkar Group, appear to represent the last of the series of earthshocks that began during deposition of the Shinumo Quartzite.The contact between the Solomon Temple and Comanche Point members of the Dox Formation marks a transition from fluvial and coastal environments to marine conditions.Interbedded purplish and red-brown strata of this member appear to reflect accumulation under alternately very shallow water marine and subaerial conditions.At the time that these tidal flats were covered by the initial eruption of the Cardenas Basalt, the eastern grand Canyon region was at or very near sea level.
(shows the ~15 degree dip)
(At left-(northwest), entering the Colorado River at a small 'deltaic' region-(alluvial fan).)
Stratigraphic rangeMesoproterozoicProterozoicArcheanTanner GrabenGeological formationUnkar GroupCardenas BasaltShinumo QuartzitesandstonemudstonedolomitebasaltGrand CanyonIsis TempleBright Angel CanyonColorado RiverUnited States of AmericaDox Castlerock formationCoconino County, ArizonaGrand Canyon SupergroupBass FormationHakatai ShaleNankoweap FormationgranitesgneissespegmatitesschistsVishnu Basement RocksbasalticVirginia Doxstratafaultsdownfaulted blocksTapeats Sandstonesynclinefault blocksedimentary depositional environmentquartzlithicarkosic sandstonecross-beddinggraded beddingconvoluted beddingsiltstoneSolomon Templeargilliteclaystonered bedsripple marksdesiccation cracksstromatoliticslope-formingmicaceouslava flowsoft sediment deformationconformableTonto Groupfoldedangular unconformityGreat Unconformitypeneplainmonadnocksmarine transgressionfossilsmarinecoastalestuarinefluvialdeltaicsedimentationnearshorefloodplainsbraided streamssheet flowtidal flatsubaerial40Ar/39ArpetrographicmicroprobedetritalzirconsGeology of the Grand Canyon areaWayback MachineBlack Suspension BridgeBridge Canyon DamGrand Canyon EscaladeGrand Canyon National ParkGrand Canyon SkywalkGrand Canyon Village, ArizonaKolb StudioMarble Canyon DamMaswik LodgePhantom RanchGeologyAgave phillipsianaApollo TempleBat Cave mineEricameria arizonicaEsplanade SandstoneGrand Canyon CavernsGrand Canyon Forest ReserveGrand Canyon–Parashant National MonumentChuar GroupSixtymile FormationGrand StaircaseFreya CastleHermit FormationHyaloclastite DamKanab PlateauNewton ButteOchoa PointProspect DamRedwall LimestoneTemple ButteBright Angel ShaleToroweap FaultUinkaret volcanic fieldVasey's ParadiseVenus TempleVishnu TempleVulcan's ThroneDeer CreekHavasu CreekHavasu Falls