Back to the Jurassic: Architecture of eolian, wadi, microbialite, and disturbed facies, Carmel Formation and Navajo Sandstone, Kane County, south-central Utah

Abstract

ABSTRACT Two sites in Kane County, south-central Utah, were selected for this two-day field trip. Stunning outcrop examples of the internal structure of eolian, wadi, and microbialite beds are accessible in the Middle Jurassic Carmel Formation at White House camp along the Paria River, and outcrop details of deformed bedding are accessible in the Lower Jurassic Navajo Sandstone on Wire Pass/Coyote Wash trail. Respective facies are described and interpreted within a theme of “back to basics in sedimentology” and within a landscape framework of the Grand Staircase and the East Kaibab monocline. A tan, cross-bedded facies of coastal eolian origin and a red lenticular facies of wadi origin in the Thousand Pockets Member, Carmel Formation, were coeval with a wavy laminated facies of organo-sedimentary origin in the Judd Hollow Tongue of the Carmel Formation. Grainflow, wind-ripple, and grainfall processes conspired on Jurassic dunes to deposit a cross-bed array of eolian sandflow, wind-ripple, and grainfall foreset strata, and wind-ripple and possibly grainfall toeset strata in the tan cross-bedded facies. Episodes of wadi flooding are preserved in the red lenticular facies as cyclical, upward-fining sandstones-mudstones punctuated by exposure and mudcrack fills. They locally and temporarily interrupted eolian sedimentation before being overrun and buried by eolian dunes. Ripples and microbes built up the wavy laminated facies at a supratidal marine shoreline of the Middle Jurassic seaway. Ground-shaking from an earthquake or extraterrestrial impact triggered severe deformation of eolian dune sand in the disturbed facies of the Navajo Sandstone.