Sequence stratigraphic analysis of marginal marine sabkha facies : Entrada Sandstone, Four Corners region

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Title: Sequence stratigraphic analysis of marginal marine sabkha facies : Entrada Sandstone, Four Corners region
Author: Makechnie, Glenn Kenneth
Abstract: The Middle Jurassic Entrada Sandstone of the Four Corners region , USA , is composed predominantly of very fine -grained , red , silty sandstone with poorly defined sedimentary structures . The origin of this facies is enigmatic , even though it is common both on the Colorado Plateau and globally , and is spatially situated between deposits recording unambiguous marine and aeolian environments . Eleven sections were measured along an 85 km transect from the Blanding Basin in southeastern Utah to the San Juan Basin in northwestern New Mexico . Outcrop and laboratory analyses distinguish eight facies : (1 ) silty shale , (2 ) shallow subaqueous reworked , fine - to medium -grained sandstone , (3 ) brecciated , very fine -grained sandstone , (4 ) crinkly laminated , very fine -grained sandstone with preserved wind ripples and abundant silty laminae , (5 ) weakly laminated , fine -grained sandstone with occasional silty laminae , (6 ) planar -laminated , fine -grained , wind -rippled sandstone , (7 ) cross -stratified , fine - to medium -grained aeolian cross -stratified sandstone , and (8 ) micritic limestone . Lateral and vertical relationships of these facies show a proximal to distal transition from cross -bedded wind -lain facies to loess -dominated sabkha facies with increasing abundance of water -lain facies basinward . The well known Todilto Limestone (facies 8 ) is situated stratigraphically below loess -dominated sabkha facies (facies 4 and 5 ) within the Entrada Sandstone , reinforcing previous interpretations that the unit represents a catastrophic flooding event and not a local groundwater flux .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -08 -1678
Date: 2010-12-23

Citation

Sequence stratigraphic analysis of marginal marine sabkha facies : Entrada Sandstone, Four Corners region. Master's thesis, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -08 -1678 .

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