The Ancestral Salt Flat Graben.
Alternative Paleozoic History of the
Sierra Diablo and Apache Mountains,
Trans Pecos, West Texas.
Robert C. Trentham
CEED/Univ. Texas of the Permian
Basin

P. B. King, 1942, p. 614

Acknowledgements
 University of Texas of the Permian Basin
 Bob Lindsay, Chevron – Consultant
 Bob Ward
 Al Smith
 Hughes Family – Apache Ranch

West Texas Physiographic Features
After King (1965)

Salt Flat Graben
After King (1965)

An Ancestral Salt Flat Graben
Can Explain:
 The location of the western boundary of the Tobosa Basin
 Wolfcampian and Leonardian shelf margins in the Sierra Diablo’s
 A lack of Siliciclastics in the upper
Guadalupian in the Apache Mountains
 The location of the Ochoan “Western
Marine Channel”
 The presence of a separate Apache
Platform

Issues
 The Salt Flat Graben is not solely a
Basin and Range Feature.
 The eastern boundary faults of the
Sierra Diablo, Beach, Carrizo and
Van Horn Mountains have had a complex history and were active periodically during the Paleozoic.
 The Ancestral Graben controlled regional deposition throughout the
Paleozoic.

Lack of Evidence
 The position of the Guadalupian
Shelf Margin between the
Guadalupe and Apache Mountains is unknown
 The exact location of the Ochoan age western channel connecting the Delaware Basin and the Marfa
Basin/Permian Ocean is unknown

Evidence
 Western margin of the Tobosa Basin is coincident with the eastern boundary fault of the Sierra Diablo Uplift.
 The eastern boundary fault of the Sierra Diablo Uplift was active during lower Hueco (l. Wolfcampian) as there is evidence of thick Powwow Conglomerate in the Basin
 The Wolfcampian in the Sierra Diablo Range appears to have been composed of a series of isolated platforms which shed debris in the Basin
 The location of the Leonardian shelf margins, at the north end of the Sierra Diablo Range, appears to have been controlled by the position of the Sierra Diablo Fault and
Babb Flexure

Evidence
 There is a lack of thick siliciclastics in the
Guadalupian section in the Apache
Mountains which needs to be explained.
 The presence of Super Mature sand in the upper Munn in the Apache Mountains indicates the presence of a local Ordovician source
 Fault trends in the Baylor Mountains are different than in the surrounding ranges

Lower Paleozoic of West Texas u. Mississippian l. Mississippian
Devonian u. Silurian l. Silurian u.Ordovician
m. Ordovician l. Ordovician
Cambro-Ord
Trans Pecos Delaware
Basin
Helms Fm.
Miss. Lime
Barnett Fm.
Miss Lime
Percha Shale
Siluro-Devonian
Woodford Shale
Thirtyone Fm.
Siluro-Devonian
Fusselman Fm.
Wristen Fm.
Fusselman Fm.
Montoya Fm.
Montoya Fm.
[ Simpson Group ] Simpson Group
El Paso Group Ellenburger Group
Bliss SS.
Wilberns SS.

Tobosa Basin
 Defined by the limits of
Simpson Group sediments
 125’ of Simpson Group sediments are present in the Baylor
Mountains.
 Simpson has been assumed to feather out between the Baylor and
Beach Mountains.
Galley (1956)

Tobosa Basin Margin
 The Simpson is missing in the Beach and Sierra
Diablo Mountains where
Montoya overlies El Paso
 There are facies changes in the Montoya from the
Beach to the Baylor
Mountains (King, 1965)
 Tobosa Basin margin could be controlled by the Sierra
Diablo Fault Zone.
BEG, 1983

Upper Paleozoic Stratigraphy
Apache / Sierra Diablo Delaware Basin
Ochoan Castile u. Guadalupian m. Guadalupian
Tansill
Yates
Seven Rivers
Goat Seep u. Munn (Queen) l. Munn (Grayburg) l. Guadalupian San Andres
Salado/Castile
Lamar Lime
Bell Canyon
Cherry Canyon
Brushy Canyon u. Leonardian Cutoff Fm.
Victorio Peak Fm.
m. Leonardian Clear Fork l. Leonardian Abo u. Wolfcamp u. Wolfcamp
Hueco
Powwow
Cutoff Fm.
Victorio Peak Fm.
Bone Springs
Bone Springs
Hueco
Powwow

Powwow Conglomerate Thickness
OPERATOR
McBay
WELL POWWOW SUBCROP
#1 Strasser 2280 PCMB
Davis, Armour & West #1 Davis
Gulf #1 Grisham
570 to >2450
742
???
BARNETT
LaGloria
Humble*
#1 Stansberry 40
#1-B Reynolds 50
MONTOYA
SIMPSON
Gulf
Sunray*
#1-C Foster 160'
#1 J.B.Foster
210'
Continental #1 Foster
Canter, Hamm & O'Brien #1 Foster
230'
230'
Cosden
Outcrop
#1 Cockrell 280'
0 - 300'
WRISTEN
MONTOYA
MONTOYA
WOODFORD
PCMB
VARIOUS
In outcrop and subsurface, the Powwow Conglomerate (lower Hueco) is nowhere thicker than 300’

Powwow Conglomerate
 Except in the three wells which penetrate the
Hueco in the Graben:
McBay #1 Strasser
Davis, Armour & West
#1 Davis
Gulf #1 Grisham in these wells, there are from 742 to >2450’ of debris.
 Conclusion: The only three wells in the Graben indicate Permo-Penn movement on the Graben
Margin

Wolfcampian – Leonardian
Carbonate shelves
 Recent work by the BEG has concluded that the Sierra
Diablo's were a series of isolated platforms capped by carbonate banks shedding debris into an Ancestral Salt Flat
Graben during Wolfcampian. The Kriz Lens is now believed to be composed of a series of carbonate debris flows.
 Conclusion: The
Graben existed during the lower Permian
Wilde, 1995

Wolfcampian – Leonardian
Carbonate shelves
 The location of the Leonardian shelf margin, at the north end of the
Sierra Diablo Range, appears to have been controlled by the position of the Sierra Diablo Fault and Babb Flexure
Fitchen 2000

Sierra Diablo –
A Low Relief Highland
 There is evidence of a Sierra Diablo positive/Salt Flat Graben negative during middle and upper Ordovician, Wolfcampian and Leonardian
 During the Guadalupian where was the shelf margin? The only Guadalupian in the range is “back reef” Goat Seep north of the
Babb Flexure (King,1965). Was there ever any Guadalupian present in the Sierra
Diablo's?
 and Ochoan…

Guadalupian Siliciclastics
 The thick sections of
Grayburg and Queen siliciclastics, present in the
Guadalupe Mountains, are missing in the Apache
Mountains
 Sands are assumed to be brought into the basin thru channels in the Guadalupe
Mountains, the Salt flat area
 It appears that some was deflected into the basin north of the Babb Flexure – Brushy
Canyon channel directions
 “Back Reef” Goat Seep is present north of Babb Flexure
Beaubouef et. al. 1999

Simpson age sand grains in the lower Munn/Grayburg
(upper Guadalupian)

Ochoan Evaporites
 There was a western channel between the
Delaware Basin and the Marfa Basin /
Permian Ocean. However,
 The location of the channel is conjectural
Adams (1967) Hill
(1999)

Western Ochoan Channel
 If the Salt Flat graben system was active during Ochoan, the egress would most logically be to the south thru the Van Horn area with the Sierra Diablo –
Beach – Van Horn
Ranges as low relief highlands to the west and the Apache and
Wylie Mountains to the east

A Separate Apache Platform
 The lack of siliciclastics in Apache Mountains
 Periodic rejuvenation of the eastern boundary faults of the Sierra
Diablo – Beach – Van
Horn Mountains and subsequent graben development
 Ochoan outlet to Marfa
Basin

Summary
 Evidence of an Ancestral Salt Flat
Graben is found throughout the
Paleozoic in:
 Simpson and Montoya age Tobosa
Basin margin
 Powwow Conglomerate
 Wolfcamp and Leonard shelf margins
 Guadalupian siliciclastics
 Ochoan Channel