Determining the Sediment Source Area Through Petrographic Analysis of the Hermosa Formation, Silverton, Southwestern CO

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Eastern Illinois University The Keep

Undergraduate Honors Theses Honors College

2013

Kristina P. Pourtabib

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Part of the Geology Commons, and the Sedimentology Commons Determining the Sediment Source Area Through Petrographic Analysis of the Hermosa Formation, Silverton, Southwestern CO

(TITLE)

BY Kristina P. Pourtabib

UNDERGRADUATE THESIS

Submitted in partial fulfillment of the requirement forobtaining

UNDERGRADUATE DEPARTMENTAL HONORS

Department of Geology and Geography along with the Honors College at EASTERN ILLINOIS UNIVERSITY Charleston, Illinois

2013 YEAR

I hereby recommend this thesis to be accepted as fulfilling the thesis requirement for obtaining Undergraduate Departmental Honors

Date

Date HONORS COORDINATOR

Date ,DEPARTMENT CHAIR Pourtabib -Senior Thesis KP

Deter01ining the Sediment Source Area through Petrographic Analysis of the Hermosa Formation, Silverton, Southwestern, CO

Kristina Pourtabib

Dr. Diane Burns

Department of Geology/Geography

Senior Thesis

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I. Abstract

The Pennsylvanian/Permian Hermosa Formation in southwestern Colorado is composed of arkosic sandstone, marine limestone, and shale that formed at a time when the region consisted of open-marine carbonate shelves and coastal plains. During the time of deposition, there were many tectonically active highlands in the region, including the Ancestral Rocky Mountains, San Luis Highlands, and the Uncompahgre, Emery, Zuni-Defiance-Kaibab Uplifts. Previous studies have attributed the source of the main sediment supply of the Hermosa Formation to the Uncompahgre branch of the Ancestral Rocky Mountains with smaller amounts of elastics from the Defiance-Zuni uplifts (Wengerd and Matheny, 1958; Wengerd and Strickland, 1954; Baars and Stevenson, 1981). None of these studies, however, specifically investigated source areas and provided no evidence fortheir claim of provenance. Because the area around the Hermosa Formation consisted of many dynamic regional uplifts, it is possible that there was more than one sediment source area. By analyzing the sediment from the Hermosa Formation and determining the provenance, it will provide a better understanding of the paleogeographic evolution of this region.

This provenance study utilized Gazzi-Dickinson point counts in conjunction with optical mineralogy techniques to better constrain the source location. The results indicated that sediment was derived from a continental block provenance, contained moderately mature grains, and had a plagioclase compositional range near the pure albite endmember. Based on these findings, the Hermosa samples most likely were derived primarily from the Ancestral Rocky Mountains, substantiating the claims of provenance from previous studies in the area.

II. Introduction

During the Pennsylvanian/Permian, the area now known as the Western United States was inundated by a shallow, warm, shelf-type sea (Wengerd and Matheny, 1958). The Hermosa Formation was formed from subaerial and subaqueous environments along the shoreline of this transgressing and regressing sea. This Formation is found throughout the four comer's region of the United States and is subdivided into three distinct members, including the lower Pinkerton Trail; middle Paradox, and upper Honaker Trail. The Pinkerton Trail member is composed of roughly 800 ft. of limestone and shale sequences deposited at a time (Atokan - Desmoinesian) when the region was covered in a shallow sea (Prommel, 1923; Wengerd and Matheny, 1958). The Paradox member (Desmoinesian), was deposited in a complex marine sedimentary environment and consists of evaporates (gypsum, anhydrite, salt), interbedded with shale, sandstone, and limestone (Baker, et al., 1933; Wengerd and Matheny, 1958). The Honaker Trail member (Desmoinesian - Virgilian) includes fine to coarsely-grained limestone, chert and calcareous sandy siltstone, deposited as a complex shelf assemblage (Wengerd and Matheny, 1958).

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III. Methods

Point-Counting Methods

In order to analyze the source area(s) for the Hermosa, samples were obtained near Molas Pass outside of Silverton, Colorado in the summer of 2011. Thin sections were dyed with cobaltinitrite and amaranth. The cobaltinitrite stained the potassium feldspars green/yellow while the amaranth stained the plagioclase red/pink in order to aid in the feldspar identification. Gazzi-Dickinson point counts were performed systematically on thin sections at 1 mm increments on a mechanical stage affixed to a petrologic microscope to determine grain populations. These grain populations were categorized according to the method outlined in Dickinson and Suczek (1 979) and plotted on QFL and QPK diagrams.

Monocrystalline quartz grains (Q) and polycrystalline quartzose lithic fragments (Qm) comprised the category designated Q. Plagioclase (P) and K-Feldspar (K) were combined into the category monocrystalline feldspar grains (F). Lithic fragments of volcanic and metavolcanic origin (Lv) along with sedimentary and metasedimentary grains (Ls) comprised the category entitled unstable polycrystalline lithic fragments (L). As heavy minerals and calcareous grains were disregarded in Dickinson's and Suczek's model, the same was done for this study (1979). Results will be plotted as QFL diagrams for both individual sample data as well as a single data point for combined information for the entire formation.

Optical Methods

In addition to the Gazzi-Dickinson analysis, optical mineralogy techniques such as the Michel-Levy (thin section), Carlsbad-Albite (thin section), Schuster (grain mount), and Tsuboi (grain mount) Methods were utilized to obtain a compositional range of plagioclase grains (Burri, et al., 1967; Morse, 1968; Tobi and Kroll, 1975). The first three methods use the extinction angles on plagioclase grains to determine the composition, while the last

method measures the index of refraction of the fast ray ( n 'a) . These optical methods were employed because of the difficultyin finding usable interference figures on the grains from extensive sample alteration, difficulty in distinguishing untwinned plagioclase from k feldspar and quartz grains in grain mounts, and the preferential orientation of the plagioclase grains fromcleavage. All twelve samples were used, but only samples HB3, HO.SI, Hl, H3, and H2 gave compositional ranges from all four of the optical methods. The remaining samples were only used for select methods because they contained much altered plagioclase grains, making certain optical determination difficult. The results fromthese four optical methods were averaged for each sample to obtain an overall compositional range for the plagioclase grains, and these results were correlated with known albite/anorthite compositions.

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IV. Data

Point-Counting Data

Q Increasing Maturity or Stability from Continental Continental _..- Block Block Provenances Provenances

and Qfldia1rams above for Hermo sa samplesplott illl int� continental block provenance QmPK- cateeorvwith moderate 1r1in maturity. (Dickinson and Suczek. 1979)

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite Opaque 2 14 18 0 0 0 0 27 3 3 100 33 65 8 33 28 0 0 6 0 7 3 200 so 92 18 46 36 0 6 11 0 75 11 5 300 % 33.0% 2.0% 14.0% 18.0% 0.0% 0.0% 0.0% 0.0% 27.0% 3.0% 3.0% 100 33.0% 4.0% 17.0% 14.0% 0.0% 0.0% 3.0% 0.0% 25.0% 4.0% 2.0% 200 31.0% 6.0% 15.0% 12.0% 0.0% 2.0% 3.6% 0.0% 25.0% 4.0% 2.0% 300

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Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 28 1 19 17 0 0 0 0 29 7 100 63 6 36 33 0 0 0 0 47 15 200 9 57 45 0 5 0 0 65 27 300 92 % 28.0% 1.0% 19.0% 17.0% 0.0% 0.0% 0.0% 0.0% 29.0% 7.0% 100 32.0% 3.0% 18.0% 17.0% 0.0% 0.0% 0.0% 0.0% 24.0% 8.0% 200 31.0% 3.0% 19.0% 15.0% 0.0% 2.0% 0.0% 0.0% 22.0% 9.0% 300

HB2

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 33 1 14 13 0 0 10 0 14 15 100 23 0 13 28 31 200 72 4 29 0 0 105 45 35 20 37 300 7 0 9 0 42 % 1.0% 14.0% 13.0% 0.0% 10.0% 100 33.0% 0.0% 0.0% 14.0% 15.0% 37.0% 2.0% 15.0% 12.0% 0.0% 0.0% 7.0% 0.0% 200 14.0% 16.0% 15.0% 12.0% 300 35.0% 2.0% 0.0% 3.0% 7.0% 0.0% 12.0% 14.0%

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Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 40 2 9 19 0 0 20 0 2 8 100 31 32 0 0 3S 0 11 200 81 s s 12S 7 42 48 0 SS 0 6 12 300 s % 40.0% 2.0% 9.0% 19.0% 0.0% 20.0% 0.0% 2.0% 8.0% 100 0.0% 3.0% 16.0% 16.0% 0.0% 17.S% 0.0% 3.0% 6.0% 200 41.0% 0.0% 42.0% 2.0% 14.0% 16.0% 0.0% 2.0% 18.0% 0.0% 2.0% 4.0% 300

HB4

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite Sl 2 29 0 0 1 100 s s s 2 3 10 0 0 200 9S S7 18 s 8 4 130 18 92 0 3 28 14 300 s s s % Sl.0% S.0% 100 2.0% 29.0% 0.0% 0.0% S.0% 1.0% S.0% 2.0% 200 48.0% 2.0% S.0% 29.0% 0.0% 0.0% 9.0% 3.0% 4.0% 2.0% 43.0% 31.0% 300 2.0% 6.0% 0.0% 1.0% 9.0% 2.0% S.0% 2.0%

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Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 36 2 15 18 0 0 12 0 15 2 100 7 23 44 0 0 0 5 200 75 21 25 108 13 36 63 33 30 10 300 0 7 0 % 36.0% 2.0% 15.0% 18.0% 100 0.0% 0.0% 12.0% 0.0% 15.0% 2.0% 38.0% 4.0% 12.0% 3.0% 200 22.0% 0.0% 0.0% 11.0% 0.0% 13.0% 4.0% 12.0% 3.0% 300 36.0% 21.0% 0.0% 2.0% 11.0% 0.0% 10.0%

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 46 16 100 4 9 0 0 6 4 8 7 81 8 34 23 0 0 20 200 6 12 16 116 12 48 0 26 300 35 7 10 23 23 % 16.0% 100 46.0% 4.0% 9.0% 0.0% 0.0% 6.0% 4.0% 8.0% 7.0% 3.0% 200 41.0% 4.0% 17.0% 12.0% 0.0% 0.0% 10.0% 6.0% 8.0% 39.0% 4.0% 16.0% 12.0% 300 0.0% 2.0% 9.0% 3.0% 8.0% 8.0%

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Counts Qm Qp p K Lv Ls weathered/ altered plucked Matrix Muscovite Opaque 25 0 34 17 0 0 6 4 2 12 0 100 53 11 52 33 0 0 13 6 8 23 1 200 78 18 73 51 0 12 19 9 11 28 1 300 %

25.0% 0.0% 34.0% 17.0% 0.0% 0.0% 6.0% 4.0% 2.0% 12.0% 0.0% 100 27.0% 6.0% 26.0% 17.0% 0.0% 0.0% 7.0% 3.0% 4.0% 12.0% 0.5% 200 26.0% 6.0% 24.0% 17.0% 0.0% 4.0% 6.3% 3.0% 4.0% 9.0% 0.3% 300

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 35 5 21 22 0 0 8 1 0 8 100 73 9 46 40 0 0 12 2 0 18 200 104 15 70 50 0 8 24 2 0 27 300 %

5.0% 21.0% 22.0% 0.0% 0.0% 8.0% 1.0% 0.0% 8.0% 100 35.0% 37.0% 5.0% 23.0% 20.0% 0.0% 0.0% 6.0% 1.0% 0.0% 9.0% 200 35.0% 5.0% 23.0% 17.0% 0.0% 3.0% 8.0% 0.7% 0.0% 9.0% 300

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Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 16 8 28 10 0 0 10 5 16 7 100 35 18 25 0 0 25 7 29 11 200 so 28 71 32 0 4 37 12 48 21 300 47 % 16.0% 8.0% 28.0% 10.0% 0.0% 10.0% 5.0% 16.0% 7.0% 100 0.0% 18.0% 9.0% 25.0% 13.0% 0.0% 0.0% 12.5% 4.0% 15.0% 6.0% 200 16.0% 9.0% 24.0% 11.0% 0.0% 1.3% 12.3% 4.0% 16.0% 7.0% 300

H0.51

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 33 6 20 14 0 0 17 1 6 3 100 67 13 42 26 0 0 35 4 9 4 200 95 18 55 45 0 4 51 8 18 6 300 % 33.0% 6.0% 20.0% 14.0% 0.0% 0.0% 17.0% 1.0% 6.0% 3.0% 100 34.0% 7.0% 21.0% 13.0% 0.0% 0.0% 17.5% 2.0% 5.0% 2.0% 200 32.0% 6.0% 18.0% 15.0% 0.0% 1.3% 17.0% 3.0% 300 6.0% 2.0%

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H0.52

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 36 5 14 23 0 0 8 1 11 2 100 75 13 26 38 0 0 20 1 21 6 200 23 43 52 0 2 12 300 108 6 32 22 % 36.0% 5.0% 14.0% 23.0% 100 0.0% 0.0% 8.0% 1.0% 11.0% 2.0% 13.0% 3.0% 200 38.0% 7.0% 19.0% 0.0% 0.0% 10.0% 0.5% 11.0% 36.0% 300 8.0% 14.0% 17.0% 0.0% 2.0% 11.0% 0.7% 7.0% 4.0%

Counts Qm Qp p K Lv Ls weathered/altered plucked Matrix Muscovite 24 11 0 0 0 15 1 10 5 100 34 0 0 30 200 53 19 64 0 1 18 15 22 89 2 0 2 1 300 76 55 29 24 % 24.0% 11.0% 34.0% 0.0% 100 0.0% 0.0% 5.0% 1.0% 10.0% 5.0% 200 27.0% 9.5% 32.0% 0.0% 0.0% 0.0% 5.0% 0.5% 9.0% 7.5% 25.0% 30.0% 0.6% 0.0% 300 7.3% 0.6% 18.0% 0.3% 10.0% 8.0%

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Optical Data

Michel-Levy (An10)

Plag. CW extinction CCW extinction Grain angle angle Average angle 0 0 1 6 5 5.5° 0 0 2 13 10 11.5°

3 go 12° 10.5°

4 14° 12° ** 13°

5 11° 12° 11.5° 0 0 6 10° 10 10

7 12° 11° 11.5°

Carlsbad-Albite (An5)

RHCCW RHCCW rain# LH CWangle LH CCWangle Avg. angle angle angle Avg. angle

1 17 16 16.5 15 12 ** 13.5

2 16 15 15.5 13 11 12

3 15 14 14.5 14 12 13

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Schuster (An12)

CCWangle avg. angle

20 ** 20

Tsuboi (An3)

oil relief B.L.T. 0.1.T. line out-crystal low 1.54 low/moderate (-) shaddow far-crystal low(-) line out-crystal low brown fringe-crystal low 1.53 low (-) (-) line in-crystal high 1.526 very low (+) orange fringe-match line in-crystal high 1.528 very low (+) orange fringe-match

ABBE Avg. Final final oils reading oil 1.528 1.5286 1.5296

1.53 1.5306

V. Data Interpretation

Point-Counting Interpretation

The overall mineralogy of the Hermosa Samples consisted of major amounts of monocrystalline quartz, plagioclase, and potassium feldspar. Minor mineralogy consisted of muscovite, sericite, biotite and other feldspar altered clays. The plagioclase grains were generally euhedral to subeuhedral and the grain sizes ranged from sample to sample. Albite twinning was primary on the quartz grains and the potassium feldspar exhibited characteristic tartan twinning which is indicative of microcline. Strained quartz and polycrystalline quartz

12 KP Pourtabib - Senior Thesis textures were visible which gave indication that the grains were derived from a nearby metamorphic core like the Ancestral Rocky Mountains (Basu et al., 1975: Blatt and Christie, 1963). Thin sections and hand samples were moderate grain sorting with predominantly subangular to subrounded grains. Thin section minerals were generally low 1st order to low 2nd order interference colors while the altered clays and muscovite ranged from moderate 2nd order to high 3rd order interferencecolors. Based on whole sample mineralogy, the primary rock lithology is an arkose.

Two different versions of the QFL plot were used in this study. Because the two plots had similar data distributions, the results will be discussed together. QFL grain populations, plotted in the continental block provenance range with decreasing grain maturity/stability, because the Hermosa samples contained abundant amounts of K-feldspar and plagioclase; the QmPK plot was also employed (Qm-monocrystalline quartz grains, P-plagioclase, K feldspar). The QmPK samples again plotted near the continental block provenance range with a moderate amount of grain maturity/stability which can indicate a shorter sediment transport distance. Continental block provenance source areas represent either sediment derived from positive, stable cratons, or fromlocal fault-bounded basement blocks (Dickinson and Suczek, 1979). The high amounts of quartz, plagioclase, and K-feldspar indicate extensive cratonic weathering over low-relief and long cross-continental transport distances (Dickinson and Suczek, 1979). Since the main continental block provenance in the Colorado region during the Pennsylvanian/Permian was the Ancestral Rocky Mountains (including the Uncompahgre Upliftbranch), our sediments were most likely derived from this uplift.

Optical Interpretation

The results from the Michel-Levy, Carlsbad-Albite, Schuster, and Tsuboi Methods of the samples were averaged for each sample individually. Only the results from samples in which all four optical methods were employed will be stated as follows: HB3 (An5), HO.SI (Ans), Hl (An10), H3 (An10), and H2 (An10). These results indicated an overall compositional range closer to the pure albite endmember (NaAlShOs). Looking at the Michel-Levy Method, there appears to be a steady compositional change going upsection from Ans, An10, An12, and back to Ans which could indicate slight shiftsin the predominant topographic high contributing sediment, but these results will have to be explored further. The simple albite twinning in these samples indicates authigenic albite in sedimentary rocks (mostly albite twinning or no twinning at all and no compositional zoning), and the low anorthite composition combined with the geology of our study area indicates the plagioclase was derived from the nearby granitic core of a topographic highland. The high sodium composition of the albite grains show the grains could not have come from a volcanic source area because neither albite nor anorthites are common in volcanic rocks. Most likely the albite is from sedimentary rocks which often contain detrital fragments or more-or-less altered plagioclase, sodic varieties being the most stable. The results of both methods point to

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a granitic cored continental block provenance source area. Since the Ancestral Rocky Mountain continental block uplift dominated the four-comers region throughout the Pennsylvanian-Permian this was most likely the main source of sediment supply.

Crystallography of the predominant plagioclase composition grain in our Hermosa samples. Grain is triclinic and predominant twinning lay on the 001 face and showed 010 twin planes.

I �

VI. Paleocurrent Analysis

Hermosa Formation, Silverton, CO

200 300

Paleocurrent Data modified from Hoy et al. (2003): Baars et al. (1981): Saperstone et al. (1984): Myrow et al. (2008): Johnson et al. (1988): Barbeau (2003): Mallory (1958): Johnson et al. (1992).

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The Pennsylvanian/Permian Ancestral Rocky Mountains formed as a result of the interactions of two massive converging plates (Gondwana and Laurussia) to form a continental-continental boundary in the late Paleozoic (about 300 m.y.a) (Baars and See, 1968: Baars and Stevenson, 1981: Barbeau, 2003). Paleocurrent data for the Hermosa Formation west of the Uncompahgre uplift and east of the Paradox Basin was scarce, so local paleoflow patterns could not be determined without the aid of field data. Pennsylvanian/Permianpaleoflow activity was the most dynamic in the Central Colorado Trough area located between the Uncompahgre Uplift and Front Range Uplift. The entire four-corners region experienced different episodes of transgression and regression which would have had a large impact on sediment dispersal patterns (Baars et al., 1981: Barbeau, 2003: Hoy et al., 2003: Johnson et al., 1988: Johnson et al., 1992: Mallory, 1958: Myrow et al., 2008: Saperstone et al., 1984). During the Pennsylvanian/Permian there were many aeolian dune deposits in northwestern Colorado, northeastern Utah, and southern Wyoming (Atchley and Loope, 1993). Sand from these deposits could easily have been incorporated into shallow seas and transported longer distances during storm surges. In areas of uplift there is subsequent erosion, and there were many alluvial fan features located along the boundaries of uplifts like the Uncompahgre and Front Range Uplift. Because the Hermosa is consistent primarily of arkosic sediment (indicative of being derived from a nearby uplift) the majority of the mineralogy could be attributed primarily to the Uncompahgre branch of the Ancestral Rocky Mountains with minor amounts from the Defiance and Zuni Uplifts to the southeast (Wengerd and Matheny, 1958; Wengerd and Strickland, 1954; Baars and

Stevenson, 1981 ) .

VII. Conclusion

These results were compared to the study done by Dye and Burns (2010) on the contemporaneous Casper Formation of southeastern Wyoming. Their results indicated that sediments of the Casper Formation were derived frommore than one source area, both the Ancestral Rockies as well as a northeastern topographic highland. Since the samples of the Hermosa Formation near Malas Pass are located closer to the Ancestral Rocky Mountains than the Casper Formation, the sediment should be derived from a single source area. As shown by the Gazzi-Dickinson Method and the utilization of various optical mineralogy techniques our samples were derived from a common continental block provenance. Due to the fact that the region was so dynamically active during the Pennsylvanian-Permian it is possible that sediment from other, smaller topographic highs in the region also contributed sediment to the Hermosa.

VIII. Further Research

Future work on the Pennsylvanian/Permian Hermosa Formation would be greatly aided by being able to do some field work in the area. If more samples are taken from surrounding prominent Pennsylvanian uplifts then the mineralogy can be compared to the Hermosa to determine what other topographic highs possibly contributed sediment. Obtaining actual paleocurrent data would also aid this study as paleocurrent data from the literature for the Hermosa was scarce. Another aspect of this project to develop in the future would be to look

15 KP Pourtabib - Senior Thesis closer at the regional and local tectonics in order to get a clearer picture of what tectonic highs were prominent when and how much uplift and subsequent subsidence (erosion) took place. It would also be good to continue looking at the plagioclase compositions through optical means in order to map out a pattern of compositions (closer to or further from certain source areas). Provenance studies are a large task to undertake with many different facets to analyzing the proposed problem.

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IX. References

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Juan Mountains, southwestern Colorado. Geological Society Of America Bulletin, 79(3), 333-349.

Baars, D. L., & Stevenson, G. M. (1981 ). Tectonic evolution of the Paradox Basin, Utah and

Colorado. Field Conference - Rocky Mountain Association O.fGeolog ists, I 98, 123-31.

Baars, D. L. (1987). Paleozoic rocks of Canyonlands country. Field Symposium - Guidebook Of

The Four Corners Geological Society, JO, 11-16.

Baker, A. A., Dane, C., & Reeside, J. r. (1933). Paradox formation of eastern Utah and western

Colorado. Bulletin Of The American Association O.fPetroleum Geologists, I 7 (8), 963- 980.

Barbeau, D. L. (2003). A flexural model for the Paradox Basin; implications for the tectonics of

the ancestral Rocky Mountains. Basin Research, I 5 (1 ), 97-115.

Basu, A. A., Young, S. W., Suttner, L. J., James, W. C., & Mack, G. H. (1 975). Re-evaluation of the use of undulatory extinction and polycrystallinity in detrital quartz for provenance

interpretation. Journal ()_[SedimentaryPetrology, 45 (4), 873-882.

Blakey, R. C. (1980). Pennsylvanian and Early Permian paleogeography, southern Colorado Plateau and vicinity. In (pp. 239-257). United States: Soc. Econ. Paleontol. Mineral., Rocky Mount. Sect. : Denver, CO, United States.

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De Voto, R. H. (1965). Pennsylvanian and Permian stratigraphy of central Colorado. Mountain

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river-delta deposystems, Pennsylvanian Minturn Formation, Colorado. AAPG Bulletin, 87 (7), 1169-1191.

Jentgen, R. W. (1977). Pennsylvanian rocks in the San Juan Basin, New Mexico and Colorado. Guidebook - New Mexico Geological Society, (28), 129-132.

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region, northwestern Colorado and northeastern Utah. U. S. Geological Survey Bulletin, FF1 -ff38.

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northeastern Utah. U. S. Geological Survey Bulletin, CC1- cc3 5.

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Society, 10, 75-79.

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Loope, D. B., & Haverland, Z. E. (1988). Giant desiccation fissures filled with calcareous eolian

sand, Hermosa Formation (Pennsylvanian), southeastern Utah. Sedimentary Geology, 56 (1-4), 403-413.

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