SEPTEMBER 2018 PGS NEWSLETTER VOL LXXI NO 1 September 12, 2018 Tectonics of the Social hour 6:00 PM Midcontinent: Looking Dinner 7:00 PM West (Geologically) Program 8:00 PM Dinner costs from Pittsburgh $30.00 per person $10.00 student member Across the Craton Reservations Email your name and number of attendees in your party to: pgsreservations @gmail.com You can also reserve and pay via PayPal at: https://www.pittsburgh geologicalsociety.org/ Dr. Stephen Marshak Location Foster’s Restaurant University of Illinois, Urbana-Champaign Foster Plaza Bldg. 10 Green Tree PA Deadline for reservations is noon on Monday, Sept. 10. Speaker Abstract Geologists have long held a fascination with and magnetotelluric arrays) that serve to mountain belts, because of their scenic beauty, characterize variations in crustal thickness, the and because they offer cross sections that intensity of faulting, and the relationship of provide access to rocks once deep in the crust. seismicity to structure; 2) structure-contour Datable igneous and metamorphic rocks in maps that help characterize the nature of mountain belts provide a basis for developing a displacement in fault-and-fold zones; 3) chronology of tectonism. The USA subsidence curves that constrain the timing of Midcontinent region doesn't display such basin subsidence; 4) a digital elevation model drama. These interior plains, which extend (DEM) of the Great Unconformity (the contact from Pittsburgh west to the Rockies, are part of between Precambrian and Paleozoic strata), North America's cratonic platform, a region in that gives a clearer image of structural relief which crust that formed over 1 billion years ago between basins and domes; 5) results from a lies buried beneath a veneer of nearly flat-lying thermochronologic study of the Great Phanerozoic sedimentary strata. This region Unconformity that reveals times during which has been relatively stable, tectonically, through exhumation (uplift and erosion) of North the Phanerozoic. But it has not been America took place. completely stable. Because of the lack of relief and the lack of outcrops, our direct knowledge Taken together, the above results emphasize of tectonic activity in the Midcontinent has that the cratonic platform holds the record of a remained limited. Fortunately, new data complex, though subtle, tectonic history. sources are providing glimpses into the Subsequent to Proterozoic rifting, which tectonic history of the Midcontinent (and the established a rectilinear network of rest of the cratonic platform), and are laying a permanently weak upper-crustal faults, stress foundation for understanding how such transmitted into the interior during Appalachian continental lithosphere behaves orogenic events caused transpressional and geodynamically. transtensional fault reactivation. Just prior to supercontinent breakup, delamination of the In this presentation, I will summarize the lithospheric mantle may have caused up to 6 tectonic features of the cratonic platform km of uplift across the entire continent. (epeirogenic basins, domes, and arches; Differential movements prior to the Mesozoic localized fault-and-fold zones), and will probably continue to affect subtle differential provide: 1) selected observations from the uplift, and therefore the distribution of EarthScope project (including seismic arrays intracratonic plateaus, today. About the Cover Image This illustration of cratonic structure comes from a 2017 paper in Geology by Steve Marshak and colleagues. The basement revealed: Tectonic insight from a digital elevation model of the Great Unconformity, USA cratonic platform and other research papers from Steve Marshak’s group can be downloaded from his ResearchGate page: https://www.researchgate.net/scientific-contributions/73572629_Stephen_Marshak 2 Speaker Biography Dr. Stephen Marshak served as a professor of structural geology and tectonics at the University of Illinois, Urbana- Champaign, for 35 years. He began his career at Illinois, in 1983, after receiving degrees from Cornell (A.B), the University of Arizona (M.S.), and Columbia University (Ph.D.). While at Illinois, he also served as the Head of the Department of Geology (for 8 years) and as the Director of the School of Earth, Society, & Environment (for 10 years). Steve continues to participate in research projects domestically and internationally, with a focus on tectonics of cratonic lithosphere, structure of fold-thrust belts, development of rock fabrics, and Precambrian tectonics. Most recently, he was involved in an EarthScope project (OIINK) focused on the Midwest. Steve served as Chair of the Division of Structural Geology and Tectonics of the Geological Society of America, sat on NSF panels for Structure and Tectonics and for Continental Dynamics, and was an associate editor for Geology and for Tectonophysics. Steve particularly enjoys teaching and has received college-level and campus-level instructional awards at the University of Illinois, as well as the Neil Miner Award of the National Association of Geoscience Teachers. He shares his passion for geoscience education in college textbooks that he authors or co-authors (including: Earth—Portrait of a Planet, Essentials of Geology, Earth Science, Earth Structure, Basic Methods of Structural Geology, and Laboratory Manual for Introductory Geology) and through a Massive Open Online Course (MOOC) called Planet Earth . and You. 3 PRESIDENT’S STATEMENT Speaking of the website, I would like to express my sincere gratitude to Karen Rose Cercone for upgrading the PGS website and producing, Welcome to the along with John Harper, our monthly newsletter. 2018-2019 PGS If you have not had the opportunity to visit the season! After a new PGS website, check it out at summer of field https://www.pittsburghgeologicalsociety.org/ work, traveling, and let us know what you think. vacationing and enjoying the warmer Lastly, I would like to thank Diane Miller, who temperatures, I has completed her term as Director-at-Large. hope you are ready Diane was instrumental in setting up our Twitter to engage and feed and assisted with other social media participate at our monthly meetings. These are initiatives. Please consider following us if you times to connect with our colleagues in an are a regular Twitter user. If you prefer informal setting, talk with each other while LinkedIn for your professional news and enjoying a meal and learning about some networking, consider joining the PGS Group on aspect of the local or regional geology. that site, moderated by board member Wendell Barner. And of course, our Facebook page is I want to start off the year expressing my kept current by board member Erica Love. sincere gratitude to all the board members for their continued commitment to PGS. Thank you One of my goals this year is to try to increase for your years of volunteer service and the time the participation of young professionals in our and effort involved in running a professional monthly meetings. We would love to have you society. PGS would not exist without your share your stories of employment successes or commitment. I would like to welcome our dilemmas and to speak with the many student recently elected Directors-at-Large: Brian members as they begin to plan their careers. I Dunst, returning for another 2-year term, Albert would like to encourage the young Kollar, and Ray Follador. The latter two both professionals to become mentors for the have served as Past Presidents and their numerous students looking for someone to combined knowledge and experience will be provide guidance as they transition from the invaluable. They join Wendell Barner, Erica world of academia to the workplace. Look for Love, and Mary Ann Gross, our continuing notices in future newsletters for specific events Directors-at-Large, and Counselors Chuck geared toward enticing young professionals to Shultz and John Harper on the PGS board. come back and be a part of the society. Kyle Fredrick and Ken LaSota will continue to I would like to remind you to renew your serve as Treasurer and Secretary. Dan Harris membership early. As you are renewing your has stepped in to serve as Vice President, in membership please consider donating an extra charge of organizing the speakers for the dollar or two to the Galey Fund to help support monthly meetings. Dan has worked hard to the student meals at our monthly meetings. arrange an excellent speaker lineup for the year, so I hope to see you at our monthly I am looking forward to working with the board meetings. If you have any ideas for future this year and the members of PGS. See you at speakers or wish to make a presentation, the meetings. please feel free to share with any board member or post a comment on our website. Tamra 4 IN MEMORIAM PGS Honorary Member TOM STURGES It is with great sadness that we announce that Tom Sturges PE, long-time PGS Honorary Member, former Corporate Member of the Society, and Chairman of the Board of Pennsylvania Drilling Company, passed away on June 6 of this year at age 73, from complications of a brain tumor. Tom grew up in Whitehall, PA, the son of Frank and Hazel Sturges, with his sister, Mary Lee Sturges Clark. He attended the Kiski School and graduated from Bucknell University with a degree in Civil Engineering. He worked for the Newport News Shipbuilding and Dry Dock Company, then moved back to Pittsburgh to join Pennsylvania Drilling Company, a family company founded in 1900, specializing in exploratory and environmental drilling. Tom eventually became Chairman, expanded PennDrill Manufacturing, and added another manufacturing facility in Winchester, VA. Tom was an active alumnus of both Kiski and Bucknell throughout his life and received “The Distinguished Alumni Award” for his service to Kiski. He was deeply involved in nonprofit boards, including the boards of The Early Learning Institute for 43 years and Conservation Consultants. He volunteered for the Carnegie Science Center, and was a member and leader of many professional organizations, including the National Drillers Association, American Society of Civil Engineers, and Association of Environmental and Engineering Geologists, in addition to his work with the Pittsburgh Geological Society.