November 2021 Outcrop by The Rocky Mountain Association of Geologists

OUTCROP Newsletter of the Rocky Mountain Association of Geologists

Volume 70 • No. 11 • November 2021

The Rocky Mountain Association of Geologists

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OUTCROP | November 2021

Vol. 70, No. 11 | www.rmag.org

OUTCROP The Rocky Mountain Association of Geologists

1999 Broadway • Suite 730 • Denver, CO 80202 • 720-672-9898 The Rocky Mountain Association of Geologists (RMAG) is a nonprofit organization whose purposes are to promote interest in geology and allied sciences and their practical application, to foster scientific research and to encourage fellowship and cooperation among its members. The Outcrop is a monthly publication of the RMAG.

2021 OFFICERS AND BOARD OF DIRECTORS PRESIDENT

2nd VICE PRESIDENT-ELECT

Cat Campbell ccampbell@caminoresources.com

Mark Millard millardm@gmail.com

PRESIDENT-ELECT

SECRETARY

Rob Diedrich rdiedrich75@gmail.com

Jessica Davey jessica@desertmountainenergy.com

1st VICE PRESIDENT

TREASURER

Nathan Rogers nathantrogers@gmail.com

Rebecca Johnson Scrable rebecca.johnson@bpx.com

1st VICE PRESIDENT-ELECT

TREASURER ELECT

Courtney Beck Antolik courtneyantolik14@gmail.com

Mike Tischer mtischer@gmail.com

2nd VICE PRESIDENT

COUNSELOR

Peter Kubik pkubik@mallardexploration.com

Jeff May jmay.kcrossen@gmail.com

RMAG STAFF DIRECTOR OF OPERATIONS

Kathy Mitchell-Garton kmitchellgarton@rmag.org CO-EDITORS

Courtney Beck Antolik courtneyantolik14@gmail.com Nate LaFontaine nlafontaine@sm-energy.com Wylie Walker wylie.walker@gmail.com CONTRIBUTING EDITORS

Elijah Adeniyi elijahadeniyi@montana.edu Danielle Robinson danielle.robinson@dvn.com

ADVERTISING INFORMATION

Rates and sizes can be found on page 37. Advertising rates apply to either black and white or color ads. Submit color ads in RGB color to be compatible with web format. Borders are recommended for advertisements that comprise less than one half page. Digital files must be PC compatible submitted in png, jpg, tif, pdf or eps formats at a minimum of 300 dpi. If you have any questions, please call the RMAG office at 720-672-9898. Ad copy, signed contract and payment must be received before advertising insertion. Contact the RMAG office for details. DEADLINES: Ad submissions are the 1st of every month for the following month’s publication. The Outcrop is a monthly publication of the Rocky Mountain Association of Geologists

Rex Stout rex.stout@gmail.com

WEDNESDAY NOON LUNCHEON RESERVATIONS

RMAG Office: 720-672-9898 Fax: 323-352-0046 staff@rmag.org or www.rmag.org

DESIGN/LAYOUT: Nate Silva | nate@nate-silva.com

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Outcrop | November 2021 OUTCROP

Webinar Series Members in Transition

2021

Visit Petroleum Pivoters for more resources!

Rockies Members in Transition (MiT) is a joint effort of members of AAPG, DERL, DIPS, DWLS, RMAG, SPE-Denver, WENCO, WGA, and WOGA in the Rocky Mountain region to help association members in the midst of a career transition.

Nov. 4 12pm-1pm (MST)

Webinars are free and open to all

“Reservoir Evaluation and CO2-Enhanced Oil Recovery Feasibility Study of the Kitty Field, Powder River Basin, Wyoming” Register at www.rmag.org

Presenter: Brian J. Black, MI3 Petroleum Engineering Corp

Rockies MiT Members in Transition

OUTCROP | November 2021

Vol. 70, No. 11 | www.rmag.org

OUTCROP Newsletter of the Rocky Mountain Association of Geologists

CONTENTS FEATURES

DEPARTMENTS

12 Lead Story: The Mowry Shale of the Powder River Basin— A Multiscale Evaluation of an Emerging Unconventional Play

6 RMAG October 2021 Board of Directors Meeting

28 RMAG On the Rocks: The Day After—The Rise of Mammals at Corral Bluffs

24 Online Lunch Talk: Bruce Trudgill

ASSOCIATION NEWS 2 RMAG Summit Sponsors 4 Members in Transition Nov. 4 Webinar

8 President’s Letter

26 Online Lunch Talk: Ali Jaffri 35 Welcome New RMAG Members! 37 In The Pipeline 37 Outcrop Advertising Rates 38 Advertiser Index

COVER PHOTO

38 Calendar

Old mining cart in the mountains near Breckenridge, CO. Photo by Bobby Schoen.

6 Publish with The Mountain Geologist 7 RMAG November Short Course 9 RMAG Board Election 36 RMAG Foundation News for 2021

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RMAG OCTOBER 2021 BOARD OF DIRECTORS MEETING By Jessica Davey, Secretary jessica@desertmountainenergy.com

semester (2022) and are working to compile a full list of schools with geo-based programs. The Publications Committee is still working diligently to pull together the 100-Year Anniversary special edition publication. The On the Rocks Committee has eight potential field trips in the works for next summer, I don’t know about you, but I’m excited to see what the options will be! The Educational Outreach Committee is seeking volunteers to help sort and identify the many donated collections of minerals, rocks, and fossils that are stacked in the storage facility. The Ad Hoc Committee on Diversity and Inclusion took a break in October and will resume discussions in November. I hope you are all enjoying the nice fall weather we have been experiencing lately, and getting out to see some lovely rocks in their natural habitats.

Happy Halloween to all you spooky fun geos! The 2021 RMAG Board of Directors once again met virtually at 4 pm on Wednesday, October 20. Everyone was present for the meeting except for Nathan Rogers and Courtney Beck Antolik. Treasurer Rebecca Johnson Scrable reported that the RMAG financials continue to look good for 2021; the investment account continues to perform well. A big portion of membership renewals have gone out, so make sure you renew on time! Kathy has continued to manage the RMAG operations remotely from her home, and RMAG has hired an Executive Director! The Continuing Education is planning to start hybrid in-person/online luncheons starting in January, so keep an eye on the website for updates. The Membership Committee is preparing to reinvigorate talks at universities beginning in the spring

Publish with… Why contribute? • Reach a broad industry and academic audience • Quarterly peer-reviewed journal • Permanent archiving includes AAPG Datapages • Quick turn-around time • Every subdiscipline in the geosciences Expanded geologic focus: • Entire greater Rocky Mountain area of North America • West Texas and New Mexico to northern British Columbia • Great Plains and Mid-Continent region

Email: mgeditor@rmag.org https://www.rmag.org/publications/the-mountain-geologist/

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RMAG SHORT COURSE

Kinematics and Structural Styles of Extension, Contraction, Strike-Slip, and Inversion with Dr. Molly Turko

11 / 10 & 11 / 2021

Online

This 2-module structural geology course will give participants the opportunity to understand the relationship between the kinematics of various folding and faulting styles related to stress and mechanical stratigraphy from the regional basin scale down to the outcrop. We will cover structural styles of extension, contraction, strike-slip, and inversion. Styles of contraction will include both thick-skin (basement involved deformation, i.e. Laramide Orogeny) and thin-skin (no basement involved, i.e. Sevier Orogeny). Concepts of transpression and transtension will be included in our discussions on strike-slip faulting, as well as how they can develop during structural inversion and/ or reactivation of pre-existing structures.

$150/RMAG members $185/Non-members $75/Students Register at rmag.org

email: | phone: 720.672.9898 Vol.staff@rmag.org 70, No. 11 | www.rmag.org 1999 Broadway, Suite 730, Denver CO 80202

fax: 323.352.0046 www.rmag.org OUTCROP| |web: November 2021 follow: @rmagdenver

PRESIDENT’S LETTER By Cat Campbell

The secret of change is to focus all of your energy not on fighting the old, but on building the new. —SOCRATES

The progression of time marked by the shifting of seasons, transitional colors in nature, lengthening nights and Christmas displays already appearing in stores has me pondering change this month. To start, we’ve had some big changes at RMAG. I am beyond excited to welcome our Executive Director Bridget Crowther. Bridget, a Colorado native, is joining us from the American Institute of Architects, an organization with more than 95,000 members, where she oversaw multiple awards programs for the institute. In this role, she managed the strategic directions of the programs, managed budgets, and oversaw events and meetings. Another major aspect of this role was building relationships, something that is essential to success at RMAG, especially as we look to the next 100 years. The American Institute of Architects is based in DC, and with the incredible remote possibilities opened by the COVID era, Bridget returned home and realized her next chapter would include staying in Colorado. And she has personal ties to RMAG already–her grandfather was a longtime member before he passed away in 2012 and had an impressive stash of old Outcrop issues in his home. Bridget’s degree from Beloit College is in Political Science, but she is excited and ready to tackle the geology that we will all force on her with our passion for our science! Welcome Bridget!

Our second big change at RMAG this year is one that only Winnie the Pooh can articulate for me.

How lucky I am to have something that makes saying goodbye so hard.

This summer we said goodbye to Debby Watkins, our director of Member Services. Debby’s incredible energy, creativity, commitment, and enthusiasm for geology is already dearly missed. I want to thank Debby for her years at RMAG and the impact she had on so many of our programs from Summit Sponsor to the GeoHike Challenge. I wish you all the best in your next chapter.

You are never too old to set another goal or to dream another dream. —CS LEWIS

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2022 Rocky Mountain association of GeoloGists

Board of directors election

VOTING NOW OPEN ElEction DatEs: OctOber 14, 2021 thrOugh NOvember 18, 2021 RMAG Members! You can now vote for the 2022 Board of Directors. Head over to www.rmag.org, login, and click on “Board of Directors Election” under Membership. There you’ll find information about all the candidates, as well as a paper ballot you can download if you want to mail it in.

CANDIDATES President-Elect

Need help or forgot your password? Contact the RMAG office at (720) 672-9898 or staff@ rmag.org. We’re here to help!

Ben Burke

First Vice President-Elect

Second Vice President-Elect

Jesse Melick

Matt Bauer

Ron Parker

Secretary

Sandra Labrum

email: staff@rmag.org

Treasurer-Elect

Kajal Nair

Andrew Keene

Holly Lindsey

phone: 720.672.9898

Vol. 70,1999 No.Broadway, 11 | www.rmag.org Suite 730, Denver, CO, 80202

fax: 323-352-0046

Anna Phelps

web: www.rmag.org

OUTCROP | November 2021 follow: @rmagdenver

PRESIDENT’S LETTER

Committee currently being chaired by Donna Anderson (shout out to Sarah Compton for her leadership prior to Donna). The committee just updated and organized sample boxes for teachers to use in their classrooms (see photo). Please check out their website to learn more about the many ways this committee is ensuring that earth sciences are being brought into schools and sign up to volunteer! Second, I want to recognize the work of Jeff May in creating the Diversity and Inclusivity ad hoc committee. This group of committed individuals is working to acknowledge the lack of diversity in the geosciences and make RMAG an organization that welcomes and honors diversity. Please check out our commitment here. Have a wonderful November and email staff@ rmag.org to be part of the change!

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While we are on the topic of change here, I want to acknowledge one of the biggest changes facing RMAG; turning 100. This organization has seen World Wars, a person walk on the moon, the discovery of DNA, and a few ups and downs in oil in gas and so much more. It’s unfathomable how the world changes on a constant basis. The exciting thing about RMAG is that we change with the times and will continue to do so. My goal this year as president of RMAG is to place RMAG in the best position possible for the next 100 years. That’s where Jack Welch’s comment comes into play.

Change before you have to. —JACK WELCH

We need to stay nimble and observe the world around us, determining how we best fit in. I want to highlight two programs that are helping RMAG stay essential and acknowledging the issues facing the geosciences today. First is the Educational Outreach OUTCROP | November 2021

Change is inevitable- except from a vending machine. —ROBERT C. GALLAGHER

Vol. 70, No. 11 | www.rmag.org

Mallard Exploration is a Denver-based upstream Oil & Gas Exploration and Production company focused on the DJ Basin of Colorado. We are building a successful business with strong ethics, hard work and industry-leading technology.

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LEAD STORY

The Mowry Shale of the Powder River Basin: A Multiscale Evaluation of an Emerging Unconventional Play

BY JEFFREY A. MAY1,2, ALEXA L. SOCIANU1,3, AND BRIAN T. HANKINS1,4 1. Department of Geological and Geophysical Engineering, Colorado School of Mines, Golden, CO 2. Geologic Consultant, Littleton, CO 3. PDC Energy, Denver, CO 4. Stratum Reservoir, Golden, CO

Shale is a prolific source rock, having yielded large volumes of oil and gas. In the Powder River Basin (PRB), cumulative Mowry-sourced production in all Cretaceous conventional reservoirs is estimated at ~1.2 BBO and 2.2 TCF, with over half a billion barrels of oil expulsed into the immediately underlying Muddy Sandstone alone (Anna and Cook, 2008). With an estimated undiscovered potential of 198 MMBO and 198 BCF (Anna and Cook, 2008), operators are now testing the Mowry Shale as a self-sourced reservoir.

INTRODUCTION The Mowry Shale is an organic-rich mudrock that accumulated in the Cretaceous Western Interior Seaway during the late Albian to Cenomanian. It occurs above the Shell Creek/Upper Thermopolis Shale and below the Belle Fourche Shale. During deposition, the Seaway was closed off to the south, preventing the influx of warm waters from the Tethys Ocean; cold, boreal waters prevailed. A hemipelagic mixture of radiolaria, marine kerogen, fish debris, and clay dominated sediment influx. Volcanism to the west provided sporadic inputs of silica-rich ash. High-energy events, including sediment-gravity flows and storm waves, frequently punctuated this fallout of detritus from suspension, delivering and reworking terrigenous silt and sand. During the Laramide Orogeny, the Seaway withdrew and basement-cored faulting and folding created the present-day configuration of numerous separate basins (e.g., Dickinson et al., 1998; Lawton, 2008). In many of these Laramide basins, the Mowry

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ROCK CHARACTER

The gross thickness of the Mowry in the PRB ranges from 130 to 250 feet, with a depositional thick to the west and northwest and thinning to the southeast (Figure 1A). The isochore pattern does not correspond to the present basin structural contours (Figure 1B). Seven cores that span this interval in the Wyoming portion of the basin, four of them proprietary, provide key data on facies, sequence stratigraphy, total organic carbon (TOC), maturity,

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FIGURE 1: Locations of seven cores used to characterize the Mowry Shale in the Wyoming portion of the PRB are overlain on (A)

gross thickness (contour interval is 12.5 feet) and (B) TVD structure (contour interval is 1000 feet). Note the dashed line representing the 8,000’ contour, below which the Mowry is in the continuous oil window (Anna, 2009). The orthogonal black lines on both maps are basement lineaments interpreted by Slack (1981). (C) Cores for this study are color coded and extend over a range of thermal maturity. The Nerd Oil Mountain 1-16 is the least mature, followed by the Cirque Resources Java State 16-1 and Cirque Resources Educated Guess 11-1H cores. Four proprietary cores, MWRY 1 through 4, yielded the most mature samples.

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there is an increase in the conversion of hydrocarbons relative to the potential. Production Index starts to drop off and oil saturations diminish around a Tmax of 460o C (Figure 2A). On a modified van Krevelen diagram of Hydrogen Index vs. Oxygen Index (Figure 2B), most data points fall along the sapropelic kerogen line indicating that Type II marine organic matter predominates, with some Type III. In

reservoir quality, and saturation. The cores extend from immature portions of the basin to those in peak oil generation (Figure 1C). Program pyrolysis of samples from six of the seven study cores provides information on Mowry kerogen type and source rock quality. The Mowry averages 2-3 weight percent TOC, with a maximum of around 8 percent. A Production Index vs. Tmax cross plot shows that with increasing depth and maturity

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LEAD STORY TVD, the approximate depth of active hydrocarbon generation (Anna, 2009) (Figure 1A). Six major Mowry Shale facies are recognized in the study cores; one bentonitic clay facies and five mudstone facies. Mudstone facies range from bioturbated sandy mudstone and thickly laminated silty mudstone to more and more siliceous facies with less and less detrital overprint (Figure 3A). The lighter gray units contain a greater detrital (extrabasinal) overprint, whereas darker gray intervals contain a preponderance of biogenic (intrabasinal) silica.

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a cross plot of Hydrogen Index vs. Tmax, the maturation pathway confirms the dominance of Type II kerogen (Figure 2C). Finally, a plot of S2 vs. TOC depicts the decrease of average Hydrogen Index with increasing depth and maturity (Figure 2D). Less mature samples from the Oil Mountain and Educated Guess cores plot as a Type II kerogen. The most mature Mowry 3 and 4 samples have entered a more gaseous phase, and are not truly dominated by Type III gas-prone terrestrial organic material. Given the Mowry Shale’s favorable source-rock properties, it is emerging as a self-sourced unconventional play in the PRB. However, fewer than 40 horizontal Mowry wells have been drilled to date, accounting for only ~2% of all horizontals in the basin. Most have targeted the formation below ~8,000’

SEQUENCE STRATIGRAPHY FRAMEWORK Silica in the Mowry Shale is predominantly biogenic in origin, formed by the recrystallization of

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FIGURE 2: Program pyrolysis results from samples collected from six of the seven study cores. (A) Production Index vs. Tmax

cross plot. (B) Modified van Krevelen diagram. (C) Hydrogen Index vs. Tmax cross plot. (D) S2 vs. TOC cross plot. Data points are color coded by core. OUTCROP | November 2021

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LEAD STORY

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FIGURE 3: (A) Six major facies are identified in the study cores, one bentonitic clay facies and five mudstone facies. Mudstones

range from light gray, bioturbated sandy mudstone and thickly laminated silty mudstone to more siliceous and darker gray facies with less detrital overprint. (B) A portion of the Educated Guess 11-1H core showing four interpreted parasequences, each capped by a flooding surface (FS). The complete succession represents a highstand systems tract topped by a flooding surface that corresponds to the correlative conformity of a sequence boundary (SB).

radiolaria (Milliken & Olson, 2017). However, an overprint of detrital clay and silt commonly produces repetitive 10- to 40-foot-thick, upward-coarsening cycles that are interpreted as parasequences (Figure 3B). Each parasequence is capped by a flooding surface. These surfaces represent periods of relative sediment starvation, when only amalgamated ash falls, now represented by bentonite, and/or the fallout of clay from suspension accumulated.

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The Mowry parasequences stack into three major successions that display a larger scale, overall upward increase in silt content. Each parasequence within an individual succession is slightly coarser grained than the one immediately below. A silt-poor and biogenic silica-rich parasequence then terminates each succession, thus beginning the next cycle of upward-coarsening parasequences. Each of the three parasequence sets is interpreted as the

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LEAD STORY chronostratigraphic framework. Lab analyses demonstrate that, regardless of each core’s thermal maturity, the middle Mowry highstand systems tract always contains the highest average weight percent TOC (Figure 6A). In addition, the same section always exhibits the lowest average water saturation and, hence, highest hydrocarbon saturation in each core (Figure 6B). The best horizontal drilling target within the middle Mowry then can be identified based on an examination of the individual facies. The siltier extrabasinal facies tend to show lower average total organic carbon content, highest water saturation, somewhat higher porosity, and distinctly higher permeability (Figures 7A-7D). The highest oil saturations, conversely, occur in the more biosiliceous facies rather than in the coarser grained facies. Although the biosiliceous facies do not have the best permeability and porosity, they do have the greater hydrocarbon pore volume. Permeability within the most biosiliceous facies increases 25-fold in the condensate thermal maturity window as compared to the earliest oil window. Porosity within the Mowry is a mixture of interparticle pores and those associated with organo-minerallic aggregates of clay and organic matter (Figure 8A). Regardless of maturity, low-pressure gas adsorption analyses of all core samples show a broad peak in pore widths from about 20-60 nm (Figure 8B). However, median pore sizes and, especially, pore volume increase with maturity.

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distal record of western shoreline progradation, i.e., a highstand systems tract. The non-erosive flooding surface at the top of each highstand package corresponds to the correlative conformity of a sequence boundary (Figure 3B). The three highstand Mowry intervals serve to subdivide the formation into a lower, middle, and upper member. Regional correlation of Mowry flooding surfaces shows thinning of the highstand systems tracts and individual parasequences to the southeast (Figure 4A). Of special note is a sandstone at the top of the middle Mowry highstand systems tract in the Bighorn Basin. In an outcrop near Cody, Wyoming, hummocky cross stratification and oscillation ripples occur within the sandstone. On the east side of the basin, where it is known as the Octh Louie Sand, the interval is productive on structures (Lupton, 1916; Long, 1997; Finn, 2010). This mid-Mowry sandstone apparently correlates distally to a very silty parasequence at the top of the middle Mowry in the PRB. Reconstruction of the approximate depositional dip shows the Mowry accumulated on a very low-gradient ramp, less than 0.01o, with no lowstand deposits. Using the chronostratigraphic framework for mapping, sequential progradation of the Mowry highstand packages into the PRB can be seen (Figures 4B-4D). Thickening occurs proximally in a northwest direction, with thinning distally to the southeast.

RESERVOIR QUALITY

WELL PERFORMANCE AND COMPLETIONS

Reservoir quality of the Mowry Shale is significantly enhanced in areas of higher thermal maturity. Three distinct thermal anomalies or “hot spots” occur within the PRB (Figure 5A). The highest maturity samples, collected from cores associated with the middle hotspot, exhibit the lowest mixed illite/smectite ratios, hence less bound water and greater brittleness due to clay transformation with temperature (Figure 5B). There also are trends of lower water saturation, somewhat higher porosity (except for the very shallowest core), and distinct increased permeability with increasing maturity (Figures 5C-E). The optimal reservoir interval within the total Mowry section can be identified using the OUTCROP | November 2021

In addition to storage and deliverability being controlled by sweet spots (i.e., location) and rock properties, well performance also is related to completion techniques. The newest wells typically display the best performance overall, with higher cumulative production often over fewer months. The evolution to better wells, in part, can be attributed to increased proppant and fluid loads per perforated foot of lateral. It also appears that operators have recognized the importance of the hot spots, as oil gravities and GORs have generally increased in the newer wells, thus enhancing reservoir drive. Other metrics show systematic changes in

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subdivide the Mowry into a lower, middle, and upper member. (B) Lower Mowry gross thickness (contour interval is 5 feet). (C). Middle Mowry gross thickness (contour interval is 2 feet; note the color bar change vs. the scale used for B and D). (D) Upper Mowry gross thickness (contour interval is 5 feet).

FIGURE 4: (A) Regional correlation of the Mowry Shale flooding surfaces. The parasequences stack into three highstand systems tracts (red triangles) that

LEAD STORY

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LEAD STORY

FIGURE 5: (A) Mowry Tmax map based on publicly available USGS data from cores and cuttings (contour interval is 1o C). Three

distinct thermal anomalies or “hot spots” are indicated. Reservoir properties relative to thermal maturities of core samples include (B) illite/smectite clay content, (C) water saturation, (D) porosity, and (E) permeability. Data are color coded by core; refer back to Figure 1 for Ro values of each core.

FIGURE 6: (A) Total organic

carbon content and (B) average water saturation analyzed within the chronostratigraphic framework (lwr= lower Mowry, mid = middle Mowry, upr = upper Mowry). Data are color coded by core.

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LEAD STORY

FIGURE 7: Facies (color coded) relative to reservoir properties. (A) Total organic carbon content. (B) Water

saturation. (C) Porosity. (D) Permeability.

FIGURE 8: (A) Argon-ion milled scanning electron photomicrograph showing pores associated with aggregates of

clay and organic matter. Sizes shown in nanometers (nm) are approximate pore widths. (B) Pore volume vs. pore width (lines on the cross plot are color coded to the cores).

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LEAD STORY

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CONCLUSIONS

drilling and completion design with time, resulting in better economics. Lateral lengths of Mowry wellbores have increased over the past two decades, helping yield better initial and cumulative production (Figure 9A). Furthermore, operators have continually increased fluid and proppant concentrations during this period (Figures 9B and 9C). Along with these trends, completions have steadily incorporated more stages per well concomitant with decreasing stage lengths (Figures 9D and 9E). Because the Mowry Shale play in the PRB is still in its early stages, all horizontals drilled to date are essentially parent-type wells.

The Mowry Shale in the PRB is an organic-rich biosiliceous mudstone composed of recrystallized radiolaria with an overprint of detrital clay and silt. Systematic fluctuations in the influx of this extrabasinal material formed multiple thin basinal parasequences that are organized into three regressive packages or highstand systems tracts. The identification of thermally mature regions is key to developing an economic Mowry drilling program in the PRB. Three of these sweet spots are present and exhibit decreased mixed illite/smectite, lower water saturations, higher porosity, and

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FIGURE 9: Completion metrics over time for horizontal Mowry wells. (A) Lateral lengths. (B) Fluid concentration. (C)

Proppant concentration. (D) Number of stages. (E) Stage lengths. OUTCROP | November 2021

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2019.3.2 Available for Download Peter Batdorf

CONTACT YOUR ACCOUNT MANAGER

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Senior Account Manager (GeoGraphix by LMKR) C : + 1 724 919 2506 | P : + 1 412 795 1271 pbatdorf@lmkr.com

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LEAD STORY Geological Survey, Digital Data Series DDS-69-U, 93 pp. Anna, L.O., and Cook, T.A., 2008, Assessment of the Mowry Shale and Niobrara Formation as continuous hydrocarbon systems, Powder River Basin, Montana and Wyoming: U.S. Geological Survey, Open-File Report 2008–1367, 1 sheet. Dickinson et al., 1998; Paleogeographic and paleotectonic setting of Laramide sedimentary basins in the central Rocky Mountain region: Geological Society of America Bulletin, v. 100, p. 1023-1039. Finn, T.M., 2010, New source rock data for the Thermopolis and Mowry Shales in the Wyoming part of the Bighorn Basin, Chapter 4: US Geological Survey, Digital Data Series DDS-69-U, 16 pp. Lawton, T.F., 2008, Laramide Sedimentary Basins, Chapter 12, in A.D. Miall (editor), Sedimentary Basins of the World: The Sedimentary Basins of the United States and Canada, v. 5, p. 429-450. Long, M.S., 1997, Description and history of the Manderson Field: Montana Geological Survey, Wyoming Geological Survey, and Yellowstone-Bighorn Basin Research Association, Bighorn Basin Symposium Guidebook: 50 Years on the Frontier – Evolution of the Geology of the Bighorn Basin, p. 35. Lupton, C.T., 1916, Oil and gas near Basin, Big Horn County, Wyoming: U.S. Geological Survey Bulletin 621-L, Contributions to Economic Geology, Part II, p. 157-190 + one plate. Milliken, K.L., and Olson, T., 2017, Silica diagenesis, porosity evolution, and mechanical behavior in siliceous mudstones, Mowry Shale (Cretaceous), Rocky Mountains, U.S.A.: Journal of Sedimentary Research, v. 87, p. 366-387. Slack, P.B., 1981, Paleotectonics and hydrocarbon accumulation, Powder River Basin, Wyoming: American Association of Petroleum Geologists Bulletin, v. 65, p. 730–743.

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higher permeability. Within these hot spots, selection of a horizontal target should concentrate on the middle Mowry highstand interval. This section always shows the highest total organic carbon content and hydrocarbon saturations, regardless of thermal maturity. The best zone for landing a lateral wellbore within the middle Mowry then has to be identified. Although the biosiliceous facies has the maximum average hydrocarbon saturations, it is not necessarily the best target. The coarser grained facies, in contrast, have lower hydrocarbon saturations, but higher porosities and permeabilities. Thus, for fracability and deliverability, the optimum target likely is in the coarsest grained parasequence at the top of the middle Mowry highstand systems tract, where it occurs directly above the more biosiliceous lower portion with the maximum hydrocarbon storage. Improved Mowry well performance based on location, target selection, and completion techniques is now generating economics comparable to some of the best U.S. shale plays.

ACKNOWLEDGEMENTS

This research was completed with substantial support from the Mudrocks and Tight Oil Consortium (MUDTOC) at Colorado School of Mines, directed by Dr. Stephen Sonnenberg, and its industry sponsors. Additionally, the authors would like to acknowledge anonymous Wyoming operators for their donation of cores and data instrumental to this study.

REFERENCES

Anna, L.O., 2009, Geologic assessment of undiscovered oil and gas in the Powder River Basin Province, Wyoming and Montana, Chapter 1: US

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ONLINE LUNCH TALK Speaker: Bruce Trudgill Date: November 3 | 12:00 pm - 1:00 pm

Pre-Laramide Salt Tectonics in the Eagle Basin A New Paradigm for the Tectonic Evolution of Central Colorado By R. Wes Pearigen II, Savannah Rice, Haley Thorson, Bruce Trudgill, Thomas Hearon IV and Mary Carr Dept. of Geology and GE, Colorado School of Mines, Golden, CO, 80401

southern part of the basin. Previous work in this

Combined field mapping, measured stratigraphic sections, and balanced cross-sections of the Pennsylvanian-aged Eagle Valley Evaporite and overlying Late Pennsylvanian to Jurassic-aged strata indicate a long-lived phase of salt tectonics in the Eagle Basin, central Colorado. Diapiric salt structures exposed at the surface represent a series of formerly connected, polygonal salt walls flanked by deep, elongate minibasins in the

area interpreted these structures to be the result

of the Laramide Orogeny and younger tectonism; however, the proposed phase of salt-influenced

deformation in the Eagle Basin has a similar history to the Paradox Basin to the southwest and suggests a new paradigm for the tectonic and stratigraphic evolution of this region.

BRUCE TRUDGILL is a structural geologist in the Department of Geology and GE at the Colorado School of Mines, where he has taught undergraduate and graduate course for over 18 years. His research interests are focused on structural controls on depositional systems and he has been working on the salt structures in the Paradox Basin for over 20 years. More recently, fieldwork with graduate students and colleagues has led him to the mountain ranges of Central Colorado, mapping pre-Laramide salt structures across the region. In his spare time Bruce spends as many days as possible hiking in his local mountain ranges: the Indian Peaks and James Peaks Wilderness areas.

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Vol. 70, No. 11 | www.rmag.org

WE ARE GREAT WESTERN AND WE ARE COMMITTED TO:

PEOPLE

EXCELLENCE

TEAMWORK

GROWTH

STEWARDSHIP

RESILIENCE

WE ARE #CommittedtoColorado Vol. 70, No. 11 | www.rmag.org

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ONLINE LUNCH TALK Speaker: Ali Jaffri Date: December 1 | 12:00 pm - 1:00 pm

Beyond Red Beds What makes sandstone-hosted copper work? By Ali Jaffri, CEO - Applied Stratigraphix carry no depositional or climatic connotation. Furthermore, copper from classic “Redbed Type” mines is neither sourced nor hosted in redbeds. We propose a better predictor of copper occurrence is a combination of Cu-rich labile minerals, halite sourced brines to mobilize the minerals, and reductants that can be contained within sandstones of various depositional origins, not exclusively redbeds.

The “Redbed Type” model for sediment-hosted stratiform copper accumulations has been widely accepted for decades and serves as a template for greenfield copper exploration. The model assumes: 1) Redbeds are deposited in alluvial to fluvial environments, 2) Redbeds are associated with arid climates in rift basins, and 3) Redbeds are a primary source of Copper. Recent sedimentological work on redbeds challenges this paradigm. We now understand that redbeds

ALI JAFFRI, PH.D. is the CEO of US-based Applied Stratigraphix LLC and has twenty-two years of international experience. He has worked on projects in the US, Norway, Angola, Kazakhstan, New Zealand, UK, Mozambique, Madagascar, Pakistan, and Equatorial Guinea. He has a doctorate from Colorado State, Masters from Oklahoma State and Bachelor’s from University of Colorado. Specializing in sediment-hosted metals and Potash he has trained over five hundred geologists and engineers from fifty-six companies in ten countries. He is currently serving on the AAPG-Energy Mineral Division’s Uranium Committee.

Well Log Digitizing • Petrophysics Petra® Projects • Mud Log Evaluation Bill Donovan

Geologist • Petroleum Engineer • PE

(720) 351-7470 donovan@petroleum-eng.com OUTCROP | November 2021

Vol. 70, No. 11 | www.rmag.org

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RMAG ON THE ROCKS

The Day After: The Rise of Mammals at Corral Bluffs October 25, 2021

RMAG members and DMNS researchers enjoyed a glorious day looking at the Paleogene age, D1 Sequence of the Denver Formation at Corral Bluffs just east of Colorado Springs. appears as a topographic rise in an otherwise rolling landscape. About 140m (460 feet) of eroding cliffs of golden tan mudstones and sandstones are exposed. They are part of the unconformity bounded D1 Sequence of the Denver Formation, Cretaceous to Paleogene age. Although non-descript to the average motorist when seen from the road, the sedimentary layers at Corral Bluffs hold both evidence and great clues of ancient life - clues that shed light on how diverse fauna, especially mammals, and flora re-emerged after the end-Cretaceous extinction, best known for wiping out the dinosaurs. The exposure resembles an amphitheater carved by gullies and sprinkled with cactus, and other high desert vegetation. One must look closely at the geology to see what is preserved. Some things are obvious and others more subtle. The name Corral Bluffs, not “coral” like the reefs,

By Denise M Stone When Tyler Lyson was a youngster, he fell in love with fossils. Finding them gave him a thrill that would lead to a PhD in Vertebrate Paleontology and a Curator and Research position at the Denver Museum of Nature and Science (DMNS). Soon after he would go on to make one of the most astounding fossil discoveries in the world, right here in Colorado. Corral Bluffs is where it happened. On October 16, Dr. Lyson and his research colleagues guided a group of RMAG members through the outcrop rich with Earth history and told us his amazing story.

LOCATION

Corral Bluffs is in the southwestern corner of the Denver Basin just north of Highway 94, a few miles east of Colorado Springs. The area is considered a “restricted open space” in El Paso County and OUTCROP | November 2021

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Map of the Denver Basin and cross-section showing exposure of the D1 Sequence east of Colorado Springs where Corral Bluffs is located. The study area equivalent location is shown by the white dot. From Raynolds et al. (2007).

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RMAG ON THE ROCKS

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but corral, comes from the fact that this location was a stop along the Goodnight-Loving Cattle Trail. The bluffs served as a natural enclosure for the cattle that were driven from central Texas north to Wyoming in the 1860s. The group of 30 RMAG members and 9 DMNS researchers assembled at the Space Village Avenue Loaf-and-Jug and carpooled a short distance into the base of the bluffs. The property is gated, so permission to enter was required ahead of time. There, in 60-degree temperatures under beautiful blue skies we intently listened to Dr. Lyson tell the story of Corral Bluffs.

THE BACK STORY

A curious weathering texture, informally called “cigars,” was observed on the bedding planes of sandstones at Corral Bluffs. These structures are believed to be a signature of groundwater movement indicating a common flow direction; in the photo fluids would have moved from right to left. Petrographic work shows the “cigars” are more resistant to weathering due to zeolite cements.

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EARLY WORK

In 2016, on his first trip to this area, Dr. Lyson picked up a grapefruit-sized concretion, hit it with a hammer and staring back at him inside was a preserved vertebrate fossil! He was in shock. This single discovery at this locality was a game changing event in the study of the K/T boundary, now officially referred to as the K/Pg or Cretaceous/Paleogene boundary. But Dr. Lyson wasn’t the first one to find a skull in a concretion at Corral Bluffs. That honor belongs to Sharon Milito, an award-winning educator and research assistant with the Corral Bluffs Alliance, a nonprofit that is dedicated to preserving the area. Dr. Lyson’s initial idea to look for fossil-bearing concretions came from having done field work in an area of South Africa where fossil-bearing concretions were present. He thought the Corral Bluffs concretions could be fossiliferous as well. Where there’s one, why not more? And there were more. Once colleagues with Lyson that day knew what to look for, within minutes they found more. Since these initial discoveries, the location has received not only the attention of the global geoscience community but also the mainstream media.

Prior to this discovery, in the early 1900s, the area had been studied by others in search of fossils, but few, mainly fragments had been found. Early researchers saw concretions but may not have appreciated their potential to form around a fossil fragment or skull nucleus. As Dr. Lyson points out, their fossil-search approach was rather standard: look for bones either laying on the ground or in-situ sticking out of the sedimentary layers. They recognized the presence of concretions but not their significance. If you’ve ever had the idea that an area or outcrop has been fully studied and there is nothing more to learn about it, think again. New eyes and new ways of thinking can lead to new discoveries. As Dr. James Hagadorn, DMNS geologist, pointed out, “We’re all earth scientists but have seen different rocks in our careers. We all bring a different wealth of knowledge to the outcrop.” Another thing to consider is that the meteorite

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RMAG ON THE ROCKS

RIGHT: First view of the Corral Bluffs outcrop, east of Colorado Springs as our convoy of vehicles drove to stop 1. The section has 140 m (460 feet) of vertical D1 section of the Denver Formation, Paleogene, exposed over 1.4 km (0.9 miles).

LEFT: Cast of a crocodilian skull from (closeup of what Dr Lyson was holding in the prior photo) Corral Bluffs study area that has been encased in clear acrylic for study and display purposes. BELOW: Stratigrapher Dr. Ken Weissenburger and Corral Bluffs Alliance geoscientist Sharon Milito, hold up a true-to-scale “long section” of the Corral Bluffs outcropping section. The area has 140 m (460 feet) of vertical D1 Sequence exposed over 1.4 km (0.9 miles).

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RMAG ON THE ROCKS

RIGHT: Representative sample of plant fossil fragments from the Corral Bluffs study area east of Colorado Springs.

section exposed over 1.4 km (0.9 miles). The depositional environment that produced the D1 Sequence at Corral Bluffs is interpreted as a low relief savanna. Dr. Weissenburger described it as a freshwater terrestrial flood plain dominated by mud with pulses of sand channel development. The channels in outcrop are up to 5 m (16 ft) thick and best seen at the base of the cliff. The stacked sand channels have a braided geometry. Paleocurrent measurements reveal an ENE flow direction. The floodplain was a pathway for the runoff and synorogenic sediment eroded and transported west to east from the Rocky Mountains. No doubt deposition was rhythmic and seasonal with long periods of quiescence and short pulses of flood induced sand deposition. Corral Bluffs is about 24 km (15mi) from the present-day foothills of the Rockies.

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impact explanation for the end-Cretaceous global mass extinctions was introduced in the 1970s and became widely accepted only in the early 1990s. This subsequently gave the current generation of geoscientists a new way of thinking about the earliest Paleogene sediments. They hold the evidence for understanding the post-impact re-emergence of life; a mindset the early researchers didn’t have. Unlike the K/Pg boundary in other areas of the world, at Corral Bluffs there is no evidence for the usual tell-tale signs of the impact – no iridium, no fused quartz and no tektites. The K/Pg boundary here is gradational in the shallow subsurface. It is not a contact you can put your foot on because the section is reworked. The contact with the overlying D2 Sequence is not exposed here either, as it has been removed by erosion.

THE TREASURES

Where before there were only fragments of teeth and bones known as CPD or Comminuted Plant Debris, now complete skulls have been found! What’s amazing is the diversity of species of mammals, turtles, crocodilians and plants. A whole ecosystem has been

STRATIGRAPHY

The scope and scale of the outcrop under study was clearly shown in the “long section” rolled out by stratigrapher Dr. Ken Weissenburger, who joined our trip. The area has 140 m (460 feet) of vertical D1 OUTCROP | November 2021

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RMAG ON THE ROCKS

ABOVE: Plant leaf fossil found at Corral Bluffs in the D1 Sequence of the Paleogene age Denver Formation. It was found on a bedding plane. Its organic material was replaced by iron. The central stem of the leaf is well-preserved.

ABOVE: Representative samples of vertebrate fossils (mammals, turtles and crocodilians) from the Corral Bluffs study area east of Colorado Springs. What makes the area unique are the array of complete skulls that have been found as well as the diversity of species. RIGHT: Pear-shaped concretion containing carbonaceous plant material with a weathered outer rim, from the D1 Sequence of the Denver Formation at Corral Bluffs.

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RMAG ON THE ROCKS

The team of DMNS researchers working on the Corral Bluffs study area that guided us through the outcrop; from left to right they are: Dr. Tyler Lyson, Vertebrate Paleontologist DMNS and Project Director; Dr. Mike Lewan, Geochemist; Dr. James Hagadorn, Lead Geoscientist, DMNS; Dr. Matthew Butrin, Paleobotanist; Dr. Gussie MacCracken, Paleobotanist; Sharon Milito, Corral Bluffs Alliance Geoscientist; Dr. Ken Weissenburger, Stratigrapher; Dr. Luke Weaver, Vertebrate Paleontologist, Mammals; Dr. Dave Krause, Vertebrate Paleontologist, Mammals; Dr. Holger Peterman, Vertebrate Paleontologist (not shown in photo).

uncovered. A lot of the fossils found at Corral Bluffs are showcased at the DMNS Corral Bluffs exhibit. Corral Bluffs is a treasure trove. Most notably, vertebrate fossils are preserved in phosphatic concretions ranging from pebbles to basketballs in size. The chemical composition of the concretions is variable. Calcification, pyritization, silicification, phosphatization and the formation of zeolites are all documented. It’s clear there were multiple phases of diagenesis working on these rocks. Many questions exist. Unraveling the paragenesis or sequence of alteration is a huge challenge. What is the source of the phosphate or how can it be that a silicified fossil is formed inside an ironstone concretion? One of the sandstone channel outcrops at Corral Bluffs may hold a clue as it shows a curious weathering texture, informally called “cigars,” developed on bedding planes. These structures are believed to be a signature of ground water movement, their parallel

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geometry indicating a common flow direction. The cigars appear to be more resistant to weathering as a result of less soluble zeolite cements. The sandstones with their complex diagenesis and cigars were a paleo fluid pathway. Was ground water flow responsible for the abundance of fossil-bearing concretions at Corral Bluffs? Can it also explain the high abundance of pyrite, usually not found at that time, and carbonate, usually not present in this fluvial-dominated environment? We will have to wait and see what the researchers come up with. Ultimately, whatever Dr. Lyson and his group find out will contribute to the key questions everybody is asking. Why did some softshell life and some mammals survive the extinction, and others not? How did Earth’s ecosystem rebound from this devastating blow? Dr. Lyson answered, “Life is resilient, life finds a way.”

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RMAG ON THE ROCKS valid data, great global collaboration among specialists and future publications to be written. You can read more about the discoveries at Corral Bluffs at the website of the Corral Bluffs Alliance (www.corralbluffs.org). There, newspaper articles, video of the NOVA television documentary and other sources are available. Also at the website, if you would like to see Corral Bluffs for yourself, you can sign up for a guided tour of the area with trained geoscientists. At the close of the day, trip coordinator Mike Tischer acknowledged to the group that this was the final trip, “the awesome one” of RMAG’s “On the Rocks” 2021 field season. It was great to get back to the rocks after the cancellation of all field trips in 2020. If you haven’t been on an RMAG field trip lately, you are really missing out! Make it a priority next season.

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BIGGER PICTURE So now that this exposure at Corral Bluffs is yielding so much information about the reemergence of life in the Paleogene, what about finding look-a-likes elsewhere in the USA or elsewhere in the world? The immediate goal of researchers is to understand and document the finds at Corral Bluffs. Long term, the goal is to find more localities like this and compare their environments.

A BIG THANK YOU

Many thanks to the many folks, researchers and post-docs, from the DMNS that guided our RMAG group in the field at Corral Bluffs. Each has a role in building an understanding of the history of the area from biostratigraphy to vertebrate paleontology, from paleobotany to chrono-stratigraphy, many specialists and researchers have a piece of this extraordinary pie. Together they are enthusiastically building an understanding of the re-emergence of life after the end Cretaceous global extinction. There is tedious field work necessary to gain statistically

Mike Tischer and Rob Diedrich of the RMAG On the Rocks Committee contributed to this article. Regretfully, Dr. Ian Miller a researcher and co-discoverer of the fossil bearing concretions at Corral Bluffs was unable to attend the field trip.

WELCOME NEW RMAG MEMBERS!

Kim Allen

Nicholas Ferry

is a student and lives in Fort Worth, Texas.

is a student and lives in Lawrence, Kansas.

works at Angelloz Energy Consulting LLC and lives in Lake Jackson, Texas.

works at Front Range Paleontological Services and lives in Gunnison, Colorado.

Jensen Angelloz Lee Cassin

is a retired and lives in De Beque, Colorado.

Josh Cooper

lives in Littleton, Colorado. Vol. 70, No. 11 | www.rmag.org

Michael King

Chioma Onwumelu

is a Research Assistant at University of North Dakota and lives in Grand Forks, North Dakota.

Chris Pacher

is a Geosolutions Sales Representative at Schlumberger and lives in Denver, Colorado.

Rob Tonnsen

is V.P. Reservoir Engineering at Tap Rock Resources and lives in Golden, Colorado.

David Williamson

is a Senior Geologist at Bedrock Geology and lives in Spring, Texas.

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RMAG Foundation News for 2021 BY DONNA ANDERSON | RMAG Foundation Secretary

This year, the RMAG Foundation has distributed $41,018 in funds and materials as follows: • $36,000 for 12 scholarships, which includes $1500 for 3 first-time Elmo and Kathy Brown Field Camp Scholarships for western Colorado universities and colleges. • $1000 to the Colorado State Science Fair • $3000 for Earth Science Teacher of the Year (ES TOTY) awardee, Tricia Kearns, which includes $1500 for professional development and $1500 to Webber Middle School, Fort Collins, for Earth Science activities. • $535 for one-year RMAG memberships, including ES TOTY Award applicants and all scholarship and Pick awardees. • $483 for Neil Harr Pick Awards: 8 seniors in 8 colleges/universities across Colorado received engraved rock hammers. The Foundation thanks its many donors who have helped fund this year’s awards. We are proud to support our geoscience community. The Foundation welcomes two new Trustees who will join the Board in January, 2022: Danielle Ebnother and Nathan (Nate) Rogers. They are replacing John Robinson and Mitchell Reynolds, who are both thanked for their long-time service to the Foundation. We thank ad hoc Trustee, Rob Diedrich, OUTCROP | November 2021

RMAG liaison to the Foundation, for his service as he assumes the role of RMAG President. He will be replaced by the incoming RMAG President-Elect. The liaison role helps the Foundation maintain strong relationships with the RMAG. In another move, Trustee Bob Tucker will become Foundation co-chair, sharing that responsibility with Laura Wray. Grant requests from outside organizations, including the RMAG, are down this year, perhaps due to pandemic “hangover.” The Board of Trustees is working to rectify this situation over the next months. Unfortunately, donations are also down this year. On a positive note, our low annual administrative costs are less than 10% of our outflows, reflecting our strong volunteer Board. Also, scholarship and award amounts are up from last year, reflecting a strong endowment. We welcome donations of any size by check/mail to the RMAG Foundation at 1550 Larimer Street, Suite 900, Denver, CO, 80202, and at our website. Your restricted and unrestricted donations provide organizational and scholarship support. In addition, because the RMAG Foundation is tax-exempt (Federal Tax ID 84-0730294), donations are eligible for corporate match. Vol. 70, No. 11 | www.rmag.org

IN THE PIPELINE NOVEMBER 3, 2021

and Inversion.” Online via RingCentral Meetings only.

RMAG Online Luncheon. Speaker: Bruce Trudgill. “Pre-Laramide Salt Tectonics in the Eagle Basin: A New Paradigm for the Tectonic Evolution of Central Colorado.” Online via RingCentral Meetings only. 12:00 PM-1:00 PM.

NOVEMBER 16, 2021 DWLS Luncheon. “Complications in Core Based OIP Determination When Evaluating Tight/ Unconventional Reservoirs.”

NOVEMBER 10, 2021

NOVEMBER 16, 2021

COGA 37th Annual Meeting. Hilton Denver City Center. 12:30-2:00 PM.

RMS-SEPM Webinar. Speaker: Bob Raynolds. “Stratigraphy of the Morrison Formation and Dakota Group on Dinosaur Ridge: A New Look at Our Backyard.” Email questions to information@rmssepm.org

NOVEMBER 10-11, 2021 RMAG Short Course. “Kinematics and Structural Styles of Extension, Contraction, Strike-Slip,

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CALENDAR – NOVEMBER 2021 SUNDAY

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RMAG Online Luncheon

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16 DWLS Luncheon. RMS-SEPM Webinar.

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Vol. 70, No. 11 | www.rmag.org

November 2021 Outcrop

Articles inside

President's Letter, November 2021