Deep-Water Sandstones, Brushy Canyon Formation, West Texas

AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS CONTINUING EDUCATION COURSE NOTE SERIES #40 Field Guide For AAPG Hedberg Field Research Conference - April 15-20,1999 Deep-Water Sandstones, Brushy Canyon Formation, West Texas

R.T. Beaubouef, C. Rossen, F.B. Zelt, M.D. Sullivan, D.C. Mohrig, G D.C. Jennette Exxon Production Research Co. with significant contributions from J.A. Bellian, S.J. Friedman, R.W. Lovell, D.S. Shannon and the rest of the EPRCo. Deep-Water Reservoirs Group

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Published by the Education Department of The American Association of Petroleum Geologists Copyright O 1999 by Field Guide For The American Association of Petroleum Geologists All Rights Reserved AAPG Hedberg Field Research Conference: Printed in the U.S.A.

DEEP-WATER SANDSTONES, BRUSHY CANYON FORMATION, ISBN: 0-89181-189-3 WEST TEXAS AAPG grants permission for a single photocopy of an item from this publication for personal use. Authorization for additional copies of items from this publication for personal or internal use is granted by AAPG provided that the base fee of $3.50 per copy and $.50 per page is paid directly to the Copyright April 15-20, 1999 Clearance Center, 222 Rosewood Drive, Danvers, Massachusetts, 01923 (Phone: (978) 750-8400). Fees are subject to change. Any form of electronic or digital scanning or other digital transformation of portions of this publication into computer-readable and/or transmittable form for personal or corporate use requires special permission from, and is subject to fee charges by, the AAPG.

Cover: Panoramic photograph of the western escarpment of the Guadalupe Mountains showing the northern 10 krn of the Brushy Canyon outcrop belt at the northwest margin of the Delaware Basin. The R.T. Beaubouef, C. Rossen, F.B. Zelt, M.D. Sullivan, basin margin area is to the left in this view, and the basin center is toward the right. In this setting, the D.C. Mohrig, and D.C. Jennette Brushy Canyon Formation is an onlapping wedge comprised of siltstone dominated slope facies with large, sandstone filled submarine canyons and slope channels. These channel complexes are oriented Exxon Production Research Company southeasterly and represent former point sources of siliciclastic sediment delivered to the Delaware Basin.

with significant contributions from J.S. Bellian, S.J. Friedman, R.W. Lovell, D.S. Shannon, and the rest of the EPRCo. THE AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS (AAPG) DOES NOT ENDORSE Deep-Water Reservoirs Group OR RECOMMEND ANY PRODUCTS OR SERVICES THAT MAY BE CITED, USED OR DISCUSSED IN AAPG PUBLICATIONS OR IN PRESENTATIONS AT EVENTS ASSOCIATED WITH THE AAPG. AAPG Continuing Education Course Note Series #40 This and other AAPG publication are available from:

The AAPG Bookstore Geological Society Publishing House P 0 Box 979 Unit 7, Brassmill Enterprise Centre Tulsa OK 74101-0979 Brassmill Lane, Bath, U.K. Phone: (918) 584-2555 or (800) 364-AAPG (USA) Phone: +44 1225 445 046 Fax: (918) 560-2652 or (800) 898-2274 (USA) Fax: +44 1225 442 836 www.aapg.org www.geolsoc.org.uk

Australian Mineral Foundation Affiliated East-West Press Private Ltd G-1/16 Ansari Road Darya Ganj Published by AMF Bookshop The American Association of Petroleum Geologists 63 Conyngham Street New Delhi 1 10 002 lhlsa, Oklahoma, U.S.A. Glenside, South Australia 5065 India Printed in the U.S.A. Australia Phone: +9l 11 327 9113 Phone: +61 8 8379 0444 Fax: +91 11 326 0538 Fax: +61 8 8379 4634 E-mail: [email protected] www.amf.com.au/amf

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Table of Contents Pages .. Introduction and Overview ...... 11- 12

Outcrop Localities ...... 1.1.5.3

Slope systems Upper slope canyons and channel complexes ...... 1 .1. 1.7

Middle slope channel complexes ...... 2 1.2.3

Base of slope channel complexes ...... 3.1. 3.9

Basin floor systems 4 . Basin floor channel complexes ...... 4.1.4.8

Proximal basin floor fan ...... 4.2.4.4

Medial basin floor fan ...... 4.5.4.8

Basin floor sheet complexes ...... 5.1.5.3

Extended Bibliography pages ...... 6.1. 6.2

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 - Introduction Reaional Bas Settina Exceptional oblique-dip exposures of submarine fan Slope-to-basin variations in channel sue, geometry and complexes of the Brushy Canyon Fm. allow reconstruc- fill are related to variations in the degree of bypass asso- tion of channel geometries and reservoir architecture ciated with channels and the timing of channel backfill. from the slope to the basin floor. The Brushy Canyon On the slope, major feeder channels are deeply incised conslsts of 1,500 ft. of basinally restricted sandstones into thick laminated siltstones, have simple margins, and and siltstones that onlap older carbonate slope deposits are vertically stacked due to proximity of fixed point at the NW margin of the Delaware Basin. This succes- sources. The channel fills are highly variable in charac- sion represents a lowstand qequence set comprised of ter, reflecting deposition from both lower and higher- lugher frequency sequences that were deposited in the energy flows during late-stage backfilling. At the toe of basin during subaerial exposure and bypass of the adja- slope, sandstones occur in nested, multi-story channel cent carbonate shelf. Progradational sequence stacking complexes not confined by single, master erosion sur- patterns reflect changing position and character of the faces. Channel bases are commonly marked by lenticu- slope as it evolved from a relict, carbonate margin, to a lar, coarse-grained lags deposited from high-energy constructional, siltstone-dominated slope. Lowstand fan bypassing flows. Channel fills are complex, and indicate systems tracts consist of sharp-based, laterally extensive, repeated episodes of erosion, bypass, and hackfii, with sand-prone basin floor deposits and large, sand-filled thick-bedded sandstones concentrated in channel axes channels encased in siltstones on the slope. The aban- and thin-bedded sandstones and siltstones preferentially donment phase of each sequence (lowstand wedge-trans- preserved along channel margins. In down-fan, more gressive systems tract) consists of basinward-thinning aggradational settings, lags are absent. Channels are siltstones that drape the basin floor fans. The slope-to- smaller, less complex, and simply filled with thick-bed- basin distnbution of lithofacies is attributed to a three ded amalgamated sandstones. These channels are rela- stage cycle of: 1) erosion, mass wasting, and sand tively short-lived features that were rapidly plugged by bypass on the slope with concurrent deposition from high-energy flows. In distal, predominantly nonchannel- sand-rich flows on the basin floor, 2) progressive back- ized areas of the basin floor, sandstones form laterally filling of feeder channels with variable fill during wan- extensive sheets that are broadly lenticular as a result of ing stages of deposition, and 3) cessation of sand deliv- minor erosion, depositional mounding, and compensa- ery to the basin and deposition of laterally-extensive silt- tional stacking patterns. stone wedges. Paleocurrents and channel distributions indicate SE-E sediment transport from the NW basin margin via closely spaced point sources.

Depositional Setting Basin Tectonics Deep-water sandstones and siltstones of the Brushy Development of the Permian Basin Complex was initiat- Canyon Formation were deposited in the Delaware Basin ed in Mississippian to Early Pennsylvanian time in a of the Permian Basin Complex (West Texas and New foreland basin setting located to the north of the Mexico) during early Guadalupian (Permian) time. Marathon Fold Belt. Loading and convergence resulted During the Guadalupian, the deep-water portion of the in uplift of shelfal areas along high-angle reverse faults basin (light gray area) had water depths on the order of and subsidence in the basin. Thrust-loading in the 400-600 m (King, 1948) and was surrounded by exten- Marathon Fold Belt peaked in the Late Pennsylvanian to sive shallow-water shelves (dark blue areas) of the Early Permian (early Wolfcamp) and was followed by Northwest Shelf (north), Diablo Platform (west) and isostatic adjustment that produced a wide-spread angular - Central Basin Platform (east). unconformity (mid Wolfcamp unconformity) along the I 5N Permian Paleolatitude basin margin (Ross, 1986). This unconformity locally - - - - cuts down into the Pre-Cambrian (King, 1965). modified from Wright, 1962; Fitchen, 1997 Following the mid-Wolfcamp unconformity (Late Wolfcampian, Leonardian and Guadalupian time), the Figure 1. Basin setting and outcrop belt of the Brushy Canyon Formation, early Guadalupian basin was characterized by tectonically stable shelf mar- (Permian). gins and gradually decreasing subsidence rates (from 3.7 cm/k.y. in the Wolfcampian to 0.8 cm/k.y. in the Guadalupian, Ye and Kerans, 1996).

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 I Primary Measured Sections I + Paleocurrent Orientation I Major Depositional Axis ECS - El Capitan South GC - Guadalupe Canyon BM - Brushy Mesa PCC - Plane Crash Canyon PC - Popo Channel DM - Delaware Mountain CC - Colleen Canyon

Figure 2b. Paleogeographlc Interpretation of Brushy Canyon Outcrop Belt (Modified From: Zelt and Rossen, 1995)

Figure 2% As shown on an insert from a geologic map of Firmre 2b. The Brushv Canvon outcrov belt is intemreted West Texas, the Brushy Canyon Fm. is exposed along the torepresent an oblique-transkt from thk slope to baiin floor western escarpments of the Guadalupe and Delaware at the NW margin of the Delaware Basin. Paleocurrent Mountains. These mountain ranges form a single structural indicators and channel distributions along the outcrop belt block that was tilted gently eastward (3-10 degrees) and indicate siliciclastic sediment supply from the NW-W, via uplifted relative to the Salt Flat Graben located to the east, numerous closely-spaced (1-2 km) point sources. In the as a result of Late Cenozoic basin and range normal-faulting northern part of the outcrop belt (southern Guadalupe and along NNW-trending normal faults (King, 1948). The northern Delaware mountains) the dominant direction of northern limit of the Brushy Canyon occurs in the southern sediment transport is toward the SE (basinward and approxi- Guadalupe Mountains and marks the pinchout of the Brushy mately normal to the interpreted trends of Leonardian-early Canyon against the northwestern basin margin. The south- Guadalupian carbonate shelf margins in this part of the ern outcrop limit is structurally controlled. In the graben basin). In the central part of the outcrop belt (central boundary zone, the outcrop belt is locally offset by NNW- Delaware Mountains), paleocurrent indicate sediment trans- trending normal faults with offsets of tens to several hun- port to the E-SE. This variability is interpreted to reflect dred meters. Structural complexity locally hampers lateral sediment input from both the northwest and western mar- correlation of stratigraphic units in the northern Delaware gins of the basin. As a result of variable flow directions, the Figure 2a. Geologic map of West Texas and Mountains (Guadalupe Pass area) and in the Delaware NW-trending Brushy Canyon outcrop belt provides an Brushy Canyon outcrop belt. From: Geologic Atlas Mountains southeast of Bitterwell Mountain. Field analysis oblique, dip-oriented profile into the basin in the north, and of Texas: Van Horn-El Paso Sheet, 1967. Texas by Exxon has been concentrated in the northern 35 lan of the a more oblique, strike-oriented profile to the south. Bureau of Economic Geology outcrop belt (Guadalupe Mountains National Park and 6 Bar atp- wens Pear and mespmng ~ormatNonr [ and LBonsidian mc*r undMde6 Ranch areas).

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Shelf-Basin Relationships Showing Position of 3rd-Order Senll~nceBoundaries oc ) Rustler - salad01

I 0 5km 1Okm

Delaware Mountains Figure 3. This figure illustrates a summary of the sequence stratigraphic framework for Upper Leonardian-Guadalupian strata of the Northwest Permian Basin

A sequence stratigraphic framework has been developed TST deposits. These sandstones typically overlie subaerial carbonate highstand systems show an evolution from low- Brushy Canyon thins to pinchout by onlap onto a basin- for the Permian Basin strata based on the work of Silver exposure sufaces, and are gradational upwards into overly- angle carbonate banks in the Early-Middle Guadalupian, to ward-sloping submarine erosion surface (Harms and Pray, and Todd (1969), Meissner (1972), Sarg and Lehmann ing carbonate shelf deposits. TST and HST are dominated high angle reef margins in the Middle-Late Guadalupian 1974) interpreted as a sequence boundary. Farther updip, (1986), Kerans and others (1992), Kerans and Fitchen by shelf and shelf-margin carbonates that exhibit, respec- (Kerans and Fitchen, 1996). The Brushy Canyon in a shelf top setting, the base Brushy Canyon sequence (1995). In this diagram major, 3rd order sequence bound- tively, retrogradational, and aggradational to progradation- Formation and overlying Cheny Canyon Sandstone Tongue boundary is correlated to a karsted subaerial exposure sur- aries (composite sequence boundaries) are shown in red. a1 vertical stacking patterns. Overall sequence stacking are interpreted, respectively, as the LSF and LSW systems face at the top of the Lower San Andres carbonate bank Basinally-restricted deep-water siliciclastics (LST) were patterns of 3rd order sequences suggest that sequences con- tract for the basal Guadalupian third order (composite) (Kerans and Fitchen, 1995). The transgressive-highstand deposited during lowstands of relative sea level (LST) tained within the Delaware Mountain Group formed within sequence. The Brushy Canyon consists of up to 360 m of systems tract for this sequence is represented by mixed when shelfal areas were subaerially-exposed. Thin, lateral- a 2nd order cycle composed of LST, TST, and HST domi- basinally-restricted sandstones and siltstones deposited in clastic-carbonate, aggradational to progradational clino- ly extensive sandstones on the shelf are interpreted as early nated sequence sets. Within this second order cycle, the basin-floor and slope settings. At the basin margin, the forms of the Upper San Andres Formation.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 GUADALUPE MTS. DELAWARE MTS. NW+ -30 Miles SE SHELF SLOPE BASIN FLOOR Figure 5 --Fig 6.t SC SFN EC GC 4t h 3rd Order Order 1Upper B.C.

Middle B.C.

Lower B.

Upper Cutoff ~iierCutoff 1 Bone Spring Limestone -I

I LEGEND Lowstand Sandstones Lowstand Slope Siltstones Carbonates (deep water) Lowstand Wedge Slope Siltstones SSB Sequence Set Boundary &channels --Sheets Condensed Intervals SB Sequence Boundary Conglomerates & Slumped Zone Sheit Sequence Stratigraphy from Korans and Fitchon, 19%

Figure 4. Schematic geologic cross section of the Brushy Canyon Fm. from the Guadalupe to Delaware Mountains illustrating the onlapping wedge-shaped geometry, the slope to basin floor variations in lithofacies and internal stratigraphy. Also shown are the general locations of photographs shown in figures 5 and 6.

Basinally-restricted, deep-water sandstones and siltstones related updip on the shelf to a subaerial exposure surface fan systems tract (LSF) of each sequence consists of sharp- Brushy Canyonmember. The overall progradational stack- of the Brushy Canyon Fm. are Early Guadalupian in age, developed at the top of the Lower San Andres carbonate based, laterally-persistent, sandstones on the basin floor, ing pattern of Brushy Canyon high frequency sequences and are interpreted as a third order, lowstand sequence set bank margin (Keraus and Fitchen, 1995). and of large, sand-tilled channels encased in siltstones on suggests evolutionof the slope from a relict, carbonate that was deposited in the Delaware Basin during subaerial the slope. The abandonment phase of each lowstand sys- slope that was primarily a site of sediment bypass in early exposure and bypass of the adjacent, carbonate shelf. On In basin floor areas, the Brushy Canyon can he subdivided tems tract (lowstand wedge-transgressive systems tract) Brushy Canyon time,to a more constructional, siltstone- the slope and basin floor, the base of the Brushy Canyon into three, laterally persistent sand-prone units separated by consists of basinward-thinning siltstones that drape the dominated slope in late Brushy Canyon time. Fm. is a basinward-sloping submarine erosion surface that thinner, laterally persistent siltstones which are interpreted basin floor fans. Basin floor deposits are best represented truncates older (Leonardian-early Guadalupian) carbonate as high frequency (4th order) sequences (informal lower, in the lower Brushy Canyon member, whereas the transi- rocks of shelf margin and slope facies. This surface is cor- middle, upper Brushy Canyon members). The lowstand tion from slope to basin floor is best expressed in the upper

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 DELAWARE MTS. 1

Figure 5. Oblique aerial view to NW showing slope to basin floor transition in Brushy Canyon outcrops of the Guadalupe and Delaware mountains.

This photo provides a vlew toward the basin margin from of laminated siltstones that are interpreted as slope photo. The 4th order LST intervah can be further subdx- units. Based on our correlations, the Lower Brushy the palm basin-floor. The base of the Brushy Canyon deposits. In the Delaware Mountains (right) the Brushy vided into higher order units as is evident within the Lower Member onlaps the SSB (or facies changes into slope silt- (heavy red line) consists of a basin margin submarine ero- Canyon is dominated by 3 laterally-extensive sandstone Member in this photo. Four or five resistive sandstone stones) in the area below El Capitan. The top of the sion surface and correlative conformity on the basin floor packages (informal Lower, Middle and Upper Brushy bodies capped by sandstone-poor intemals can be traced Middle Member extends farther updip and is correlated that is interpreted as a LST sequence set boundary (SSB). Canyon members) that are interpreted as basin floor for several kilometers from south to north. Although not into Bone Canyon of the western escarpment, Guadalupe The blue line, near the top of the Delaware Mountains, deposits (4th order LSF). Thinning of the Brushy Canyon obvious from this view, the Upper Member can be subdi- Mountains. The hulk of the Brushy Canyon Fm. present on marks the approximate position of the Brushy Canyon toward the basin margin (from 370 m on the right side of vided into a similar number of 5th order units. Tracing the Western Escarpment is interpreted to be stratigraphical- "genetic top" (CSM Top Brushy Canyon) of Gardner and the photo to 100 m on the left side) occurs by progressive higher order units in the Middle Member is more difficult ly equivalent to the Upper Brushy Member of the Delaware Sonnenfeld (1996). In the basin margin area (Guadalupe onlap onto the basal SSB, and the Brushy pinches out because of a lack of prominent, laterally extensive siltstone Mountains. Mountains), the Brushy Canyon is dominantly composed entirely a few km to the north of the area shown in this intemals and a high degree of amalgamation of sandstone

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 I Basin-Floor Expression of Brushy

ary (SB), 4th Order rface, 3rd Order urface, 4th Order -mi Figure 6. Stratigraphic succession of Brushy Canyon in basin-floor position (view to NE from Lookout Knob)

Stratigraphic Hierarchy: On the basin floor, the base area to Guadalupe Canyon, located some 20 km to the Vertical Stacking Patterns: In this position, the three Although not well exposed in this view, the Upper Member Brushy Canyon sequence set boundary is a relatively con- north. The 4th order LST intervals can be further divided Brushy Canyon Members show a distinct vertical progres- is characterized by very large, deeply incised, multi-story formable surface underlain by the Pipeline Shale and into higher order units that are important for local correla- sion in sand body geometry, channel abundance, and chan- channel complexes with amalgamated sandstone fills up to Upper Cutoff Formation. The Lower, Middle and Upper tion and potentially for analysis of vertical stacking pat- nel geometry. The Lower Brushy Member is dominated 1 km wide (e.g. Buena Vista locality indicated on photo). Brushy Canyon Members, interpreted as 4th order terns. Higher order units are most apparent within the by sheet-like, tabular sandstone bodies or packets, that These channel complexes are quite complex and record sequences within the Brushy, form three distinctive, topo- Lower Member which can be subdivided into five laterally locally contain small-scale sand-filled channels with simple multiple episodes of channel cutting, bypass and back-fill- graphic mesa or benches that are laterally persistent across persistent sandstone ledges that can be traced for several erosional margins. In the Middle Brushy Member, simple ing. The Brushy Canyon stratigraphic hierarchy and verti- the outcrop belt. Each member contains a lower sand- kilometers laterally. Although not obvious from this view, sand-filled channels are larger and more abundant. cal stacking patterns are reviewed schematically in figure 7. prone unit (100-150 m thick) interpreted as a LSF that is the Upper Member can be subdivided into a similar num- capped by a thinner (up to 15 m thick) laterally extensive ber of units. Higher order subdivision of the the Middle siltstone internal (interpreted as a LSW). The "40 ft. Member is more diicult due to the high degree of chan- Siltstone" that separates the Middle and Upper Brushy nelization and local lack of laterally persistent siltstones. Canyon Members can be traced with confidence from this

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 8 a,SQL t SEQUENCE STRATIGRAPHY Zelt & ??g Sa 4e King (1948) Rossen(1995) m, pk o HIGHER ORDER SURFACES, DEPOSITS iRRY CANY :ORMAT Channel Fill Assemblages \

BRUSHY , CANYON Beds I Bedsets

Y V Abandonment, Drape Surfaces I Intervals IPlPLELlNE SHALE I A Erosional Surfaces, Sequence Boundaries ? LSF I LST (Lowstand Fan, Lowstand Sytems Tract) * the number and stratigraphic position of 5th order packages shown is only a schematic and not meant to depict the actual internal stratigraphy of any LSW - TST (Lowstand Wedge, Lowstand Sytems Tract member of the Brushy Canyon Formation and Transaressive- Svstems Tracts undifferentiated) Figure 7. This diagram relates the lithostratigraphy and sequence stratigraphy of the lower Delaware Mountain Group, emphasizing a hierarchy of bounding surfaces and schematically depicts the large scale, apparently progradational stacking patterns discussed on previous pages.

Stratigraphic Subdivisions of the Brushy Canyon tions of these units contain a number of 5th order units that 3rd Order Stacking Patterns. The stacking patterns, In general, the channel types and lithofacies are consistent Formation. The Brushy Canyon Fm. represents a 3rd are also bound by erosional surfaces, contain internal aban- lithofacies and channel types are distinct between the LSF with proximal-medial fan depositional environments. By order LST sequence set that is bound above and below by donment surfaces, and can be correlated for distances up to intervals of the 4th order units and the diagram depicts the contrast, the Upper Member is characterized by very large, major unconformities or their correlative conformities, and 20 km within the outcrop belt. The 5th order packages are large scale, apparently progradational stacking of 4th order deeply incised, multi-story channel complexes up to lkm can be correlated throughout the Delaware Basin. In the built of higher order depositional units that include channel units seen in the Delaware Mountains. In general, the wide separated mainly by unrelated, inter-channel strata. outcrop belt, this sequence set consists of three 4th order fill assemblages, bed sets and beds that generally do not Lower Brushy Canyon is dominated by sheet-like, tabular The fill of these complexes record multiple episodes of stratigraphic packages that are bound by sharp, locally ero- have long correlation lengths, but can be subdivided in the sandstone bodies. Channels occur within extensive sand- channel cutting and filling and evidence for prolonged peri- sional contacts and can be correlated throughout most of same manner. stone "packets" and are often genetically associated with ods of bypass. The channel types and lithofacies are con- the Delaware Mountains and a portion of the Guadalupe adjacent sandstone sheets. Channel types and lithofacies sistent with middle-lower slope depositional environments. Mountains (30-40 km). Surfaces of abandonment separate are consistent with medial-outer fan depositional environ- These stacking patterns may indicate: a) changes in the ori- LST fan (LSF) dominated intervals from LST wedge ments. The Middle Member is seen as primarily a mix of entation or position of depositional axes of systems through (LSW) - TST dominated intervals. The sandstone-rich por- laterally extensive sandstones and relatively large channels time, b) progradation of systems through time, c) a change filled with massive sandstones. The channels have relative- in the style and character of depositional systems through ly simple, erosional margins and genetic associations time, or d) some combination of these processes. between channel and inter-channel strata are not obvious.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Down-Slope Trends in the Erosion, Transmission and 1 Deposition of S1 " mt ' Ti ' idity Currents 'hrbidites, > 90 % of the Brushy supercritical climb of both types of bedforms constrains L Canyon Fm. the bedload-transport distance to less than one bedform Bedload Deposits length, a distance of less than 3 m. Median grain size: Many of the fusulinids within the sandy turbidites can be INITIATION OF - > Coarse Sand TURBIDITY CURREh . interpreted to have been moved into sites of deposition BY FAILURE OR Stratification: UNDERFLOW 1. plane parallel beds and laminae; as bedload. The intermingling of this bedload with the 2. tabular cross beddmg; suspended load requires that it travelled to the site with 3. trough cross beddmg; approximately the same velocity. This suggests that the 4. isolated (starved) bedfonns. fusulinids fell out of suspension a relatively short dis- Key Points: tance up dip from the site. Otherwise, the slower mov- These deposits are defined here to primarily consist of ing bedload would not arrive at the site of deposition particles that travelled as bedload some minimum dis- until after most of the sand bed had already accumulated. FLOW DECELERATIONI LEADS TO tance before deposition that was at least equal to the CURRENTS THAT ARE "OVERCHARGED" Silty turbidites. Progradation of the submarine slope to WlTH SUSPENDED SEDIMENT, DRMNG FLOWS CONTINUE TO DECELERATE DUE thickness of the transporting turbidity current. Since DEPOSITION TO DROPS IN THEIR EXCESS DENSITY maximum bedload velocities are only about 114 of the the Delaware Basin throughout deposition of the Brushy THAT ARE PARTIALLY ASSOCIATED Canyon Fm. is primarily the result of the deposition of WlTH THE DEPOSITION OF PREVIOUSLY average current velocity, with time this coarser-grained SUSPENDED SEDIMENT material separates from the suspended sediment and the thick, wedge-shaped packages of silty turbidites. These current itself. These relatively thin deposits, interpreted thin-bedded turbidites came from slow-moving currents DEPOSIT TENDENCY: as lags, are up dip equivalents to thicker sandstones that that began depositing sediment at the time of their initia- were deposited from suspension from relatively long- tion. These currents are different than those that acceler- lived turbidity currents. ated down some portion of the slope, cutting channels and transporting sand all the way to the basin floor. Suspension Deposits Erosion by + Median grain size: Debrites < 5 % of the Brushy Head < Medium Sand Canyon hm. of Current - - Shurtfication: Fabrics of these deposits range from frameworks of 1. structureless beds (may be graded); gravel with sand-filled pore spaces to sandstones with a 2. climbing dune stratification (trough cross bedding); small number of out-sized clasts. Pebbles, cobbles and 3. ripple stratification; boulders in these deposits are either limestones from 4. plane parallel laminae. underlying formations or intraformational rip-up clasts. Erosion (L Deposrt~on + , Key Points: by Body . Sandy turbidites. Climbing dunes and ripples document Hemipela ites, < 5 % of the Brushy of Current the movement of sediment as bedload after it has settled Canyon 8m. out of a turbidity current from suspension. These These mudstones are made up of particles from either a deposits are still considered suspension deposits because hypopycnal plume or a wind-blown source. The the distance the sediment moves as bedload is very small deposits are typically enriched in total organic carbon. Bypass 8 Deposition + relative to its length of transport as suspended load. The Centimeter-thick volcanic ashes are present. b Tail - of Zurrent Figure 8b. Sediment is constantly being exchanged between the bed and an overriding turbidity current so any modification of the surface by the current is always equal to the sum of a depositional and erosional component.

A turbidity current can be divided into three parts, a the bed, the only possible suspension deposit at that head, a body and a tail. Differences in properties of the point would come from the tail. Packages of thinly flow from the head to the tail of a current set the pat- bedded, relatively fine-grained turbidites can be seen terns of erosion and deposition associated with its pas- directly on top of many significant erosional surfaces. sage over any particular point on the bed. The heads of These deposits can be interpreted either as sedimenta- turbidity currents always have a tendency to erode the tion associated with a relative shutdown of the sediment substrate, because the arrival of the head is always asso- delivery system or as the deposits of the tails of bypass- ciated with an acceleration. The bodies of turbidity cur- ing turbidity currents. The two interpretations forecast rents carry most of the suspended sediment in the flow. a very different location for the time-equivalent sands. Therefore, conditions in the body determine whether at In the shut-down scenario any sand is expected to be a point the current primarily is eroding the bed, deposit- trapped up dip of these positions, while in the case of ing sediment on the bed, or carrying it further down dip. bypass, sand is expected further out into the basin. If sediment carried in the body is bypassing a section of

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Generic Turbidite Profile --.I--- I----- : I:: 11:: 111 I I IV '

Complete Sediment BypaswTransmission: Ineamplete Sediment Bypass, Type 1: Thin, Incomplete Sediment Bypass, Type 2: Thin, with no additional erosion lenticular, coarse-grained beds, interpreted as onlapping, fine-grained beds, interpreted as lags of bedload material. deposits of turbidity-current tails. Relative Downslope Distance

Figure 9b. A channel complex records a history of cutting and filling associated with a succession of turbidity currents. The changes through time observed in any vertical section through a channel complex are the consequence of spa- tial changes in the position of that channel cross-section relative to the runout of the characteristic turbidity current. During Phase I this turbidity current is eroding the substrate in this position and depositing all of its sediment load further down dip. During Phase 11, this channel cross-section is located where currents are just beginning to deposit sediment. During Phase III the cross-section and the "sweet spot" of turbidity-current deposition are coincident. During Phase N the cross-section is located down dip of almost all turhidity current deposition. Deposition of thielS, laterally persistent beds that dapthe margins ofthe heerosional containec Variable degrees of emdon can be associated with the bases of these beds. Approximate envelopes for each of these phases are drawn above on the profile for the generic turbidite. Changes through time in the character of the runout of the effective turhidity current are primarily controlled by variation in the amount of sediment available, in the caliber of this sediment and in the long profile of the system.

4- siltstone --+ drape

Substantial reduction in the quantity and caliber of the sediment moving down a channel associated with change in updip conditions (e.g., relative sea-level rise or channel avulsion).

Figure 9a. Conceptual model for construction of a channel complex.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Slope to Basin Variations in Channel and Sandbody 1 Archib--b. .re, Brushy Canyon Formatin-, Delaware Basin nShelf

Basin Floor =\

Figure 10. Schematic illustration of slope to basin transect planned for conference. Slope to basin variations in channel size, geometry and fill are interpreted primarily to be related to system- atic, down-fan changes in the degree of erosion, the degree of sediment bypass, and the timing of Day 3 channel filling.

Day 4 Proximal Basin Floor Day 4"4g+@s$$~:!s*&*e:~y~&; ,,-:-.. 1 &&&* res 4.2-4.4' Medial Basin Floo (Figures 4.F * 8) Distal Basin Floor (Figures 5.1-5.3)

Submarine canyons consist of erosional features, up to At the toe-of-slope, the decrease in depositional gradient On the basin floor, channels are less deeply incised, and The distal basin floor is predominantly composed of later- 100 m deep and 1 km wide, incised into older shelf margin leads to development of broad, multi-story channel com- typically have simple margins. Coarse-grained lag deposits ally-extensive sandstone sheets composed of medium- to carbonates. Fills are locally conglomeratic and predomi- plexes that are not confined by master erosion surfaces. are less common, and channels typically stack in compen- thick-bedded, amalgamated to non-amalgamated massive nantly composed of amalgamated, channelized, thick-hed- Major channel surfaces are marked by lenticular, coarse- sational, or laterally-offset stacking patterns. In proximal turbidites. Beds are typically broadly lenticular and stack ded sandstones. On the middle to lower slope, 10-50 m grained lag deposits that were deposited by bedload deposi- basin floor areas, channels are moderate in size and are compensationally. Channels exhibiting obvious erosional deep, vertically-stacked slope channels are incised into tion from by-passing, high-concentration flows. Axes of typically filled from axis to margin by thick-bedded, amal- confinement are rare and axes of deposition in this setting thick, basinward-thinning wedges of laminated siltstones. channels are dominated by amalgamated, thick-bedded tur- gamated turbidites. These channels are interpreted as rela- are represented by zones of vertically-stacked, amalgamat- These channels are characterized by simple to compound bidites, whereas thin-bedded sandstones and siltstones are tively short-lived features plugged by rapid deposition from ed thick-bedded turbidites that are flanked laterally by channel margins, and by variable fills that range from preferentially preserved along the channel margins. Multiple high-concentration flows. In medial basin floor areas, medium-bedded, semi-amalgamated turbidites. These fea- thick-bedded, amalgamated sandstones, to thin-bedded, erosion surfaces separate the channel axis facies from the channels are less incised and channel fills consist of highly tures reflect rapid suspension deposition in an unconfined non-amalgamated sandstones. Channel fill variability is thin-bedded channel margins. Complex patterns of channel aggradational successions of massive or dune cross-strati- setting from predominantly high-concentration flows. attributed to long histories of sediment bypass followed by fill record overall channel aggradation through repeated fied sandstones. At the transition from confined to uncon- relatively late-stage filling compared to channels on the episodes of erosion, sediment bypass and channel filling. fined portions of the fan, channels consist of basin floor. Vertically-stacking of channels is locally con- vertically-stacked, low-relief erosion surfaces that pass lat- trolled by slump-scar topography and reflects proxi~tyto erally (away from the channel axis) into medium- to thick- up-dip feeder canyons. bedded, amalgamated to non-amalgamated, massive sandstones that form laterally extensive, but broadly lenticular sheets.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 ieneralized Three Stage Evolution of Lowstand Systems Tracts, Brushy Can- -- n Formation

I. MAIN PHASE LOWSTAND FAN

I II. LATE-STAGE LOWSTAND FAN

TIME INCREASING

Figure 11. Interpreted evolution of Brushy Canyon lowstand systems during 4th order lowstand of relative sea level. An understanding of the relative timing of sand-prone deposition on the basin floor versus slope during a cycle of sea level change explains many of the variations from slope to basin floor in channel architecture that were described in the previous figure.

During Time I (Main Phase of Lowstand Fan), falling channel bypass followed by back-filling from high concen- channels that previously served as bypass corridors to the shelf result in cessation of sand delivery to the basin and base level and a lack of accommodation on the shelf result tration flows result in a predominance on the basin floor of basin. Channel fills may reflect deposition from a variety abandonment of both lowstand fan and slope channel sys- in high rates of sediment supply to the basin floor via suh- shallowly incised channels that are simply filled with thick- of flow types (both high and low concentration flows) tems. Deposition at the basin margin from dilute, low-den- marine canyons. Slope channels are primarily zones of bedded, amalgamated turbidites. depending on the "caliber" or importance of the point sity tubidity currents results in development of thick bypass and the basin floor is the main site of deposition for source as a sediment contributor, and the character of flows wedges of laminated siltstone that thin basinward. This high-energy, high-concentration, sediment gravity flows. During TieII (Late Stage of Lowstand Fan), a slow delivered to the slope at the time of back-filling. stage represents the constmction, or out-building of the As a result of rapid fan aggradation, the time duration relative sea level rise results in increased accommodation slope during Bmshy Canyon time. Thin, organic-rich silt- between channel cutting on the basin floor and channel fill- on the upper slope and outer shelf. Sediment flux to the During Tie111 (Lowstand Wedge), higher rates of rela- stones containing volcanic ashheds represent deposition ing is interpreted to be relatively short. Short phases of basin floor is reduced and deposition is focused in slope tive sea level rise and increased accommodation on the during times of condensed sedimentation.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Comparison of Interpreted Paleogeography for Lower and Upper Brushy Canyon Members- ~

Schematic Paleogeographic Map Lower Brushy Canyon Formation Schematic Paleogeographic Map Upper Brushy Canyon Formation

PROXIMAL CHANNELIZED FA BRUSHY MESA (EM)

CHANNELTO SHEET TRANSITION: COLLEEN CANYON (CC)

I SHEET COMPLEXES: CORDONIZ CANYON ma

SCuEt

APPROXIMATE LOCATION , OF OUTCROP I--'- Figure 12. Comparison of interpreted paleogeography for Lower and Upper Members of the Brushy Canyon Formation illustrating the progradation of depostional systems. For each member the positions of slope and basin floor environments are interpreted to have shifted progressively basinward through time. The approximate locations of the outcrop belts are shown as red dashed lines.

The position of the paleo-slope is interpreted to have pro- The siltstone slope facies that dominates the basin margin nated by channel types and lithofacies consistent with lower members of the Brushy Canyon Formation and are gressively built basinward during deposition of the Brushy area extends further southward into the Delaware medial-outer fan depositional environments. The middle shown above. However, the limited depositional dip per- Canyon sequence set. The position of the slope for the Mountains for the upper Brushy member than for that of member is dominated by channel types and lithofacies con- spectiveof the outcrop belt, and a lack of understanding of Lower Brushy Canyon Member was inherited from the the middle member reflecting this overall slope prograda- sistent with proximal-medial fan depositional environ- how and where these 4th order LST terminate within the relict CutoffBone Springs carbonate slope seen in the tion. Additionally, the stacking patterns, lithofacies and ments. By contrast, channel types and lithofacies within the basin hampers the interpretationof the stacking patterns. Guadalupe and Diablo Mountains. During the remainder channel types are distinct between the sandstone-rich, LSF upper member are consistent with middle-lower slope depo- of Brushy Canyon deposition the slope was "construction- intervals of the 4th order units seen in the Delaware sitional environments. Based on these observations general al" and dominated by basinward tapering, siltstone wedges. Mountains. In general, the Lower Brushy Canyon is domi- paleogeographic maps have been drawn for the upper and

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Figure 1.1. Topographic map showing an approximate outline of the Brushy Canyon outcrop belt, and locations of sites that will be visited on this trip. Upper Brushy Canyon sites are shown in green, Lower Brushy Canyon sites are shown in orange. Also shown are general paleocurrent directions and the approximate position of the toe-of-slope for each member of the Brushy Canyon Formation.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 mlles Paleageography 0- i5 This palwgwgraphic reconstruction for the Upper Brushy Canyon shows that North the noahem 20 lan of the outcrop belt was deposited in a slope to roe-of-slope jubmarine Canyon North Shumar setring. This slope was approximately 15 km wide, and had basin-ward dips of 2 degrees (assuming water dept!s of 4.50-600 m). Much of the slope was siltstone-prom and composed of thick basinward-thinning wedges of laminated siltstones interpreted as the deposits of dilute, fine-grained turbidity currents* Sediment Transport Sands were transported across this cofistructional siltstone slope, from the NW basin main towards the SE-E, via numerous closely-spaced point sources or sediment transport pathways The outcrop belt intersects these point sources in up-dip positions to the nath and progressively mare down-dip positians to the south. Charmel Architecture Thee main archtectural styles are recognized from up-dip to down-dip positions along these sediment transport pathways:

1) Upper slope areas are characterized by submarine canyons, incised into older, shelf-margin carbonates. These canyons are filled with a mix of siltstones, and large, sand-filled channels. The canyons typiedly broaden, and shallow out down-slope into more aggradational slope ssttings. 2) Middle to lower slope areas, down-dip of canyons, are characterized by sand-filled slope channels incised into thick laminated siltstones. These slope channels are typically vertically-stacked due to the focusing effect of up-dip feeder canyons.

3) In toeof-slope areas, the decrease in gradient and loss of channel confinement results in a transition from vertically-stacked slope channels, to bmad, nested multi-story channel complexes. These toe-of-slope channel complexes contain common caarse-grained lags and exhibit complex fill patterns that indicate repeated episbdes of erosion, sedimedt bypass, and channel back-filling.

Figure 1.2. Schematic paleogeographic map of Upper Brushy Canyon Formation. This paleogeographic map highlights the main slope environments (submarine canyons, slope channel complexes, and toe-of-slope channel complexes) that will be the focus of the first three days of the field conference. Day 1 will focus on submarine canyon fills and slope channel complexes in middle to upper slope settings. Day 2 (Guadalupe Canyon) will focus on vertically-stacked, slope channel complexes deposited in a middle slope environment. Day 3 (Buena Vista) will be spent investigating characteristics of channel complexes deposited in lower slope (toe-of-slope) environments.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Day I . Basin Margin Onlap Area: Su -

- Figure 1.3. Panoramic photograph and sketch of western escarpment, Guadalupe Mountains showing the northern 10 km of Brushy Canyon outcrop belt in the most proximal area near the NW margin of Delaware Basin. Detailed photographs of the area shown on following pages are referenced with white circles. A geologic map of the area is shown on the next page.

The Brushy Canyon Sequence Set Boundary Depositional Setting

In the basin margin area, the Brushy Canyon thins towaru submarine erosion surface, that is correlative on the shelt In this area, the Brushy Canyon is largely siltstone-prone, the Victoria Peak carbonate bank. Downdip, on the mid- the north (from 400 m beneath El Capitan to ultimate pin- with a karsted, subaerial exposure surface. To the south, reflecting deposition in a slope setting. Sandstones are dle to lower slope, these canyons open up and feed sand- chout just north of Sbumard Peak) by onlap onto a relict in basin floor areas, it is a sharp, but relatively conforma- confined within large erosional channels (10-50 m deep) stone-filled slope channels that are incised into thick lami- carbonate shelf margin complex of Leonardian-Early ble contact with the Pipeline Shale. that are vertically-stacked to form laterally distinct "fair- nated siltstones. The vertical stacking of these slope chan- Guadalupian age (Victoria Peak, Bone Spring and Cutoff ways" or point sources into the basin. On the upper nels reflects the focusing effect of the updip feeder formations). The onlap surface is a basinward-sloping slope, these sand-filled channels are confined within sub- canyons. marine canyons up to 1 km in width that are incised into

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Geologic Map of the Bone Springs El Area of the Western Escarpment Capitan X 8078 Guadalupe of the Guadalupe ~ountains , Peak Modified from King (19i8)with information from Rossen (1 985), Harris (1 982), Franseen (1 989), Fitchen and Kerans (1995), Gardner et al. (1 W6), Rossen et al. (1 998) 0 0

North 4 0 1000 2000 1...... 1...... I

Bell Canyon Formation

A Brushy Canyon S base U.Cutoff SI base South Wells Member U.Vic.Pk. SI Lower Victorio Peak Fm.

youngest- I4 Shumard Canyon System - 3rd Order Sequence Boundary Brushy Canyon Formation - - El Capitan North System Paleo-current - lndlcators --- 3rd Order Sequence Boundary Siltstones (-org. rich] Figure 1.4. Geologic Map of the West Face of the LZ' El Capitan South System Rossen et al. 1998 Approx~mate Guadalupe Mountains adapted from King (1948) CSM Brushy Canyon Sandstones, emphasizing stratigraphy of Brushy Canyon oldest - Bone Canyon System --- Genetlc Top Approx~mate Conglomerates Formation upper slope systems.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021 Figure 1.5a. Basal, conglomeratic fill of the "Bone" paleo submarine canyon, Lower-Middle (?) Brushy Canyon Fm., Bone Canyon, Guadalupe Mountains. The "Bone" submarine canyon is approximately 75 m deep and 650- Figure 1.5b. Cabonate clast conglomerates, basal Brushy 900 m wide (see Fiaure 1.4). and is cut into the underlvina Cutoff and Bone S~rinaformations. The canvon Canyon, Bone Canyon. The Brushy Canyon conglomerates trends SE and is exposed ii'an interpreted slope posiion: The basal 25 m of'canyon fill consists if &&ate- in Bone Canyon consist of framework-supported pebble to clast conglomerates (0.5-7.5 m thick) and interbedded, thinner, stratified sandstones. The conglomerates contain boulder-sized clasts in a matrix of very fine-grained, silty sand- pebble to boulder-sized clasts (up to 4 m in length) and are interpreted as debris-flow deposits. Clasts within the stone. The conglomerates are interpreted as debrites based conglomerates were locally derived from carbonate shelf-margin and slope deposits of the underlying Cutoff, on: 1) chaotic clast orientations or weak alignment of clasts Victorio Peak and Bone Spring formations. parallel to bedding, 2) massive ungraded character, 3) overall non-erosional basal contacts, and 4) local protrusion of clasts above the tops of beds. The conglomerates reflect successive failures of the lithified carbonate basin margin that represent headward erosion of the "Bone" submarine canyon. Base of Brushy Figure 1.5~.Measured section of basal 75m of Bmshy Canyon Fm. Unit 2 has a channelized base and consists of medium to thick-bed- As shown on Figure 1.4, the NE canyon margin occurs 300 m (1000 Canyon that fills the "Bone" submarine canyon (from Rossen, 1985). Fill of ded, sandy, peloidal-skeletal grainstones that commonly exhibit ft) to the north of Bone Canyon where the entire, 75 m thick, basal the "Bone" submarine canyon is variable, and is subdivided into 3 Bouma turbidite subdivisions (i.e., graded Ta, Tab, and Tbc beds). Bmshy Canyon succession pinches out by onlap (sidelap) onto the channel fill associations (units 1-3) originally mapped by King in This unit reflects basinward transport of carbonate material derived base Brushy Canyon sequence boundary. The SW canyon margin is 1948 (see Figure 1.4). The overall variability of canyon fill is inter- from contemporaneous, shallow-marine environments existing at the not as well defined; however, thickness patterns suggest that the Cufoff Fm. preted to reflect variable flow types during late-stage canyon filling. heads of canyons. canyon margin occurs just SW of Bone Canyon. In a SE direction - (toward the basin), the breakup of the amalgamated Bone Canyon Unit 1 consists of carbonate-clast con.domerates and interbedded Unit 3 consists of channelized, medium- to thick-bedded, massive channel fills (units #1-3) into channelized lenses, separated by silt- Conglomerate sandstones. Successive conglomerateinits exhibit an overall thin- sandstones (interpreted channel axis facies) that interfinger laterally stones, is interpreted to reflect broadening and shallowing of the ning and fining-upward stacking pattern. Sedimentary structures in with thick intervals of rippled sandstones (interpreted channel margin Bone submarine canyon, and deposition in an increasingly aggrada- Limestone turbidites intervening sandstone units (upper plane-bed laminations, planar facies). tional slope environment. cross-bedding, small-scale channelization, and thin-bedded classical Siltstone turbidites) suggest deposition by both high-concentration, and low- concentration turbidity currents.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3816100/9781629810157_frontmatter.pdf by guest on 01 October 2021