Abstract

Figures 1-1 – 1-5

Soft sediment structures

  Figures 2-1 – 2-3

  Microscale

  Mesoscale

Structural trends

  Figures 2-4 - 2-5

  Text

Evolution of MT C

Thickness

  Figures 3-1 – 3-3

Text

Conclusions

References

Future research

Figures 1-1 - 1-5

Soft-Sediment Structures 

Figures 2-1 – 2-3 

Figure 2-1. Contractional overprint of extensional microstructures.

Figure 2-2. Two views of a complex deformation zone (CDZ) that contains a ZAM block, looking north (left) and south (right) from canyon cut: Location: Rolling Rock Canyon.

Figure 2-3. CDZs and other structural features within MTE bodies: Location: Side canyon on south side of Rock Art Canyon, facing west.

Microscale (mms-cms) 

Zones of Abundant Microstructures (ZAMs) (Figure 2-1) 

A zone of abundant microstructures (ZAM) is a body of rock that contains up to four types of soft-sediment deformation features: 1) normal microfaults (NMF), 2) microboudins (MB), 3) reverse microfaults (RMF), and 4) microfolds (MF). Faults die out vertically within beds or sole into a hemipelagic layer. NMFs are generally listric. Fault length is limited by bed thickness (generally < 10 cm). Fold amplitudes are generally less than 1 cm. 

NMF and MB are usually overprinted by MF and/or RMF. This suggests that the slump was overprinted by contractional features when the downslope end of the body came to rest before the upslope end (Farrell, 1984). 

ZAMs are bounded on the top and bottom by truncation surfaces (TS) and may contain internal truncation surfaces as well. The vertical distance between bounding TS is no more than a few meters (the thickest ZAM observed is 6.5 m in height). 

ZAMs appear locally within Unit 7 and comprise most of the observed portion of Unit 9 in the Delaware Mountains. Bounding TS in Unit 9 are generally planar and have a shallow dip or are horizontal. Bounding TS within Unit 7 are often deformed themselves and may be part of larger mesoscopic folds or complex deformation zones (CDZ) that contain rocks without ZAMs. These relationships, and the relative thinness of Unit 9 and other ZAMs, suggest that: 1) ZAMs in Unit 7 were later transported piggyback style within larger slump bodies, and 2) Unit 9 represents a slump (or package of slumps) that was not later transported.

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Mesoscale (ms) 

Complex Deformation Zones (CDZs) (Figures 2-2 and 2-3) 

Complex deformation zones are local 3D regions within a slump body that are 1) characterized by a set of fold segments that have axial surfaces with similar strikes and differing dips, and 2) roughly cylindrical in shape with the long axis generally horizontal. They occur within Units 7 and 8. 

Field evidence suggests that CDZs are concentrated within locally thicker zones within an MTE body and may indicate a soft-sediment "pile-up."

Structural Trends (Figures 2-4 and 2-5) 

Figures 2-4 and 2-5 

Figure 2-4. Paleo-transport directions (PTD), Williams Ranch Member (excluding Correlation Unit 6) as suggested by fold axis and lineation trends. Dark blue arrows: Average PTD based on fold axes; Violet arrows: Average PTD based on contractional lineations; Light blue arrows: Average PTD based on extensional lineations.

Figure 2-5. Correlation units, Williams Ranch Member, Delaware Mountains study area. Left. Generalized stratigraphic column based on thicknesses at head of Rock Art Canyon. Yellow lines represent drapes (undeformed turbidites). Center. Lithologic and structural comparison of units. Right: Representative photographs of units.

Text 

The orientation of fold axes in an MTE body may be an indicator of transport direction (roughly perpendicular to the fold axis), although there may be local variation within the body, and fold axes may rotate from the transport direction at body margins (Hansen, 1971). Lineations resulting from the intersection of normal microfaults and microfolds with bedding planes may also indicate transport direction at the times that extension and contraction were taking place, respectively. 

Fold axis orientations in the Cutoff Formation show variation by location and by correlation unit. 

The primary trend is N-S with a secondary trend of ENE-WSW. These two trends may represent: 1) differences in transport vectors among separate MTE bodies, or 2) deflection by underlying topography. 

Fold asymmetry may indicate the transport direction; however, relatively few measurable asymmetric folds were observed. The primary inferred direction from these folds is north to south, although some folds indicate the reverse. 

Unit 6 is excluded from this analysis as its nature in the Delaware Mountains is unclear.

Vertical Evolution of MTC 

The vertical succession of MTE bodies in the Williams Ranch Member underwent an evolution over time. This evolution, from oldest to youngest, is as follows: 

• Large, semi-rigid slump bodies with a high degree of internal mesoscopic deformation (Units 7 and 8).

• Small, semi-rigid slump bodies with a higher degree of mesoscopic deformation (top of Unit 8, Unit 9).

• A return to sediment gravity flows as the primary form of deposition with localized slumping on local topography (Unit 10).

This pattern of waning size and/or deformation of MTE bodies occurs as the basin lowers its gradient through time (unit 6 is not considered as its nature in the Delaware Mountains is unclear).

Thickness Relationships 

Figures 3-1 – 3-3 

Figure 3-1. Isopach maps of correlation units, Williams Ranch Member, Delaware Mountains study area. Note: Units 7 and 8 have been mapped as a combined unit due to uncertain unit boundaries in Rock Art and Vertigo Canyons

Figure 3-2. Geologic map, Delaware Mountains study area. Blue line: Location of study area cross section. Red line: Location of cross section projection

Figure 3-3. Cross section X-X' from Panorama North Canyon to Colleen Canyon. Brushy Canyon Formation section after Slope and Basin Consortium (2004). Cross section assumptions:

• Thickness change is constant within all correlation units between measured sections.

• Underlying structure is a control on MTE body geometries with possible basement influence.

• Topography at the surface of the Cutoff Formation is a control on Brushy Canyon Formation deposition.

• Thickness changes within the five correlation units may be a result of folding or of thrust sheet stacking within those units.

Text 

Isopach maps of the five correlation units suggest that: 

• Unit 6 may be a drape or a rigid slide body.

• Units 7 and 8 had the largest amount of mesoscale deformation and had the greatest effect on overall thickness.

• Unit 9 is a local (less far-traveled) MTE body that may have slumped from a locally steep gradient immediately to the north.

• Unit 10 is a drape (with local slumping at its top).

• CDZs are concentrated in thicks.

• Cutoff topography affects Brushy Canyon geometry, but units underlying the Williams Ranch Member must also be a control. Basement control remains a possibility.

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Conclusions 

1) Deformed basinward Cutoff units were correlated with previously published undeformed shelfward units. Five basinward-stepping units were identified atop correlation unit 5 as part of the Williams Ranch Member (WRM).

2) A tentative second- and third-order sequence stratigraphic framework was established for the Cutoff that correlates to previous work on shelfal equivalents.

3) In the Delaware Mountains, at least 8 MTEs are represented in the WRM, not including earlier phases of multi-phase events. In the Guadalupe Mountains, MTEs were likely numerous, but their number is less well constrained.

4) Transport direction was primarily NNW to SSE with a secondary NE to SW component.

5) The three uppermost MTE bodies appear to be locally derived; the remainder may have been margin- or- slope-sourced, based on calculations using a power law relating runout and volume developed by Legros (2002).

6) MTE bodies within the WRM exhibit a pattern of waning volume and degree of deformation through time.

7) The dominant structural style is contractional, except north of Italy Canyon in the Guadalupe Mountains, where extensional evacuation scars coexist with scattered contractional features north of Italy Canyon.

8) CDZs and drape intervals are concentrated in areas of increased MTC thickness. ZAMs appear to result from local extension with later contractional overprinting. Some ZAMs appear to have been subjected to more than one phase of transport.

9) The WRM generally thickens basinward across the study areas through progradation and mass transport, with local variance resulting from preexisting topography and contractional “pile-ups.”

10) The WRM influenced development of paleo-bathymetry below the Brushy Canyon Formation (BCF) by filling preexisting larger-scale lows and creating smaller highs above them. Progradation and small-scale mass transport of the Cutoff shifted the toe of slope basinward from the inherited Victorio Peak toe of slope. The pinchout of the lower BCF coincides with the basinward limit of significant WRM mass transport deposits.

11) Internal Cutoff structure could potentially be used to predict paleo-bathymetry below the BCF. The highest percentage of CDZs and drape intervals is found within WRM thicks, filling preexisting lows and creating smaller local highs. The lowest percentage

References 

Farrell, S.G., 1984, A dislocation model applied to slump structures, Ainsa Basin, South Central Pyrenees: Journal of Structural Geology, v. 6, p. 727-736.

Fitchen, W.M., 1993, Sequence stratigraphic framework of the upper San Andres Formation and equivalent basinal strata in the Brokeoff Mountains, Otero County, New Mexico, in D.W. Love, J.W. Hawley, B.S. Kues, J.W. Adams, G.S. Austin, and J.M. Barker, eds., Carlsbad region,New Mexico and West Texas, New Mexico Geological Society forty-fourth field conference, v. 44: Socorro, New Mexico, New Mexico Geological Society.

Gardner, M.H., 2002, Slope and basin regional cross section, Brushy Canyon Formation, Delaware Mountains, west Texas: Unpublished.

Hansen, E., 1971, Strain facies: New York, Springer-Verlag.

Harris, M.T., 1982, Sedimentology of the Cutoff Formation (Permian), western Guadalupe Mountains, West Texas and New Mexico: Master‘s thesis, University of Wisconsin, Madison, Wisconsin, 186 p.

Harris, M.T., 1987, Sedimentology of the Cutoff Formation (Permian), western Guadalupe Mountains, West Texas: New Mexico Geology, v. 9, p. 74-79.

Harris, M.T., 1988a, Postscript on the Cutoff Formation: The regional perspective and some suggestions for nomenclature, in S.T. Reid, R.O. Bass, and P. Welch, eds., Guadalupe Mountains revisited; Texas and New Mexico, West Texas Geological Society Publication 88-84: Midland, Texas, West Texas Geological Society, p. 141-142.

Harris, M.T., 1988b, Sedimentology of the Cutoff Formation (Permian), western Guadalupe Mountains, West Texas, in S.T. Reid, R.O. Bass, and P. Welch, eds., Guadalupe Mountains revisited; Texas and New Mexico, West Texas Geological Society Publication 88-84: Midland, TX, West Texas Geological Society, p. 133-140.

Harris, M.T., 2000, Members for the Cutoff Formation, western escarpment of the Guadalupe Mountains, West Texas, in B.R. Wardlaw, R.E. Grant, and D.M. Rohr, eds., The Guadalupian symposium, Smithsonian contributions to the Earth sciences, 32: Washington, Smithsonian Institution Press, p. 101-120.

Kerans, C., and W.M. Fitchen, 1995, Sequence hierarchy and facies architecture of a carbonate-ramp system: San Andres Formation of Algerita Escarpment and Western Guadalupe Mountains, West Texas and New Mexico, Report of Investigations No. 235, Bureau of Economic Geology, 86 p.

Kerans, C., W.M. Fitchen, M.H. Gardner, M.D. Sonnenfeld, S.W. Tinker, and B.R. Wardlaw, 1992, Styles of sequence development within uppermost Leonardian through Guadalupian strata of the Guadalupe Mountains, Texas and New Mexico, in D. H. Mruk, and B. C. Curran, eds., Permian Basin exploration and production strategies: Applications of sequence stratigraphic and reservoir characterization concepts: West Texas Geological Society Publication 92-91: Midland, Texas, West Texas Geological Society, p. 1-6.

Kerans, C., W.M. Fitchen, M.H. Gardner, and B.R. Wardlaw, 1993, A contribution to the evolving stratigraphic framework of Middle Permian strata of the Delaware Basin, Texas and New Mexico, in D. W. Love, J. W. Hawley, B. S. Kues, J. W. Adams, G. S. Austin, and J. M. Barker, eds., Carlsbad region, New Mexico and West Texas, New Mexico Geological Society forty-fourth annual field conference: Socorro, New Mexico, New Mexico Geological Society, p. 175-184.

Kullman, A.J., 1999, Fracture networks and fault zone features in a deep water sandstone, Brushy Canyon Formation, West Texas: Master’s thesis, Colorado School of Mines, Golden, Colorado, 256 p.

Lambert, L.L., 2000, The Guadalupian GSSP-The world standard Middle Permian series-Guadalupe Mountains National Park, in C.J. Crow, and G.L.J. Bell, eds., Field trip guidebook: Guadalupian deposition in sabkha, shelf, reef, and basin environments, Guadalupe Mountains, Texas and New Mexico, p. 57-70.

Legros, F., 2002, The mobility of long-runout landslides: Engineering Geology, v. 63, p. 301-331.

Rossen, C., P.J. Lehmann, and J.F. Sarg, 1988, Trail guide for Day 1: Shumard to Bone Canyon traverse, in J.F. Sarg, C. Rossen, P.J. Lehmann, and L.C. Pray, eds., Geologic guide to the western escarpment, Guadalupe Mountains, Texas: Permian Basin Section, SEPM publication 88-30: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists, p. 17-60.

Sarg, J.F., 1986, Second day: Facies and stratigraphy of upper San Andres basin margin and lower Grayburg inner shelf, in G.E. Moore, and G.L. Wilde, eds., Lower and Middle Guadalupian facies, stratigraphy, and reservoir geometries: San Andres/Grayburg formations, Guadalupe Mountains, New Mexico and Texas: Permian Basin Section, SEPM Publication 86-25: Tulsa, Oklahoma, Permian Basin Section: Society of Economic Paleontologists & Mineralogists, p. 83-93.

Sarg, J.F., and P.J. Lehmann, 1986a, First day: Facies and stratigraphy of lower-upper San Andres shelf crest and outer shelf and lower Grayburg inner shelf, in G.E. Moore, and G.L. Wilde, eds., Lower and Middle Guadalupian facies, stratigraphy, and reservoir geometries: San Andres/Grayburg formations, Guadalupe Mountains, New Mexico and Texas: Permian Basin Section SEPM Publication 86-25: Tulsa, Oklahoma, Permian Basin Section: Society of Economic Paleontologists & Mineralogists, p. 9-35.

Sarg, J.F., and P.J. Lehmann, 1986b, Lower-middle Guadalupian facies and stratigraphy: San Andres/Grayburg formations, Permian Basin, Guadalupe Mountains, New Mexico, in G.E. Moore, and G.L. Wilde, eds., Lower and Middle Guadalupian facies, stratigraphy, and reservoir geometries: San Andres/Grayburg formations, Guadalupe Mountains, New Mexico and Texas: Permian Basin Section, SEPM Publication 86-25: Tulsa, Oklahoma, Permian Basin Section: Society of Economic Paleontologists & Mineralogists, p. 1-8.

Slope and Basin Consortium, 2003, Geologic map of Permian strata in the Delaware Mountains, west Texas: Unpublished.

Slope and Basin Consortium, 2004, Photograph of western escarpment of the Guadalupe Mountains, west Texas: Unpublished.

Sonnenfeld, M.D., 1993, Anatomy of offlap: Upper San Andres Formation (Permian, Guadalupian), Last Chance Canyon, Guadalupe Mountains, New Mexico, in D.W. Love, J.W. Hawley, B.S. Kues, J.W. Adams, G.S. Austin, and J.M. Barker, eds., Carlsbad region, New Mexico and West Texas, New Mexico Geological Society forty-fourth annual field conference: Socorro, New Mexico, New Mexico Geological Society, p. 195-203.

Sonnenfeld, M.D., and T.A. Cross, 1993, Volumetric partitioning and facies differentiation within the Permian upper San Andres Formation of Last Chance Canyon, Guadalupe Mountains, New Mexico, in R.G. Loucks, and J.F. Sarg, eds., Carbonate sequence stratigraphy-Recent developments and applications: American Association of Petroleum Geologists Memoir 57, p. 435-474.

Ongoing Research 

Immediate research goals include:

• Completion of mapping and measured sections in southernmost Guadalupe Mountains.

• Correlation with six fourth-order stratigraphic cycles of Kerans and Fitchen (1995).

• Creation of synthetic dipmeter log from data collected along five measured sections in the Delaware Mountains study area to determine if the identified outcrop relationships can be predicted from subsurface data.

• Field research of mass transport deposits (Eocene Hecho Group, Spain; Cretaceous Gosau Group, Austria) in other contractional basins with comparison to Cutoff Formation.

Land access issues have prevented continuing work in the Delaware Mountains, but planned future research there includes completion of mapping and collection of additional structural and thickness data, as well as extension of the study to include outcrops to the north and south and the Cutoff units below the Williams Ranch.

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