Harrisburg Area Geological Society


The purpose of the Harrisburg Area Geological Society (HAGS) is to stimulate geologic thought, advance and disseminate geologic knowledge, and provide fellowship amongst area individuals interested in earth sciences. Monthly meetings (at GTS Technologies at 441 Friendship Road in Harrisburg) present a realm of geologic topics, ranging from tectonics, coal, carbonate groundwater geochemistry, Martian geomorphology, engineering geophysics, nuclear waste repositories, and ore mineralogy. Field trips allowed members to visit geologic sites within and beyond Pennsylvania. All events are open to the public and free unless otherwise stated. Meetings are at GTS Technologies, 441 Friendship Rd, Harrisburg, PA 17111



President- Kent Littlefield-

Vice-president- Bill Bruck-

Treasurer- Jeb Baxter-

Secretary- Amy Randolph-

 Up coming events :April 13, 2017 – Dr. Walter Cressler, West Chester University – Seeing the Forest for the Fossil Trees: Uncovering a 365 million-year-old Landscape in Pennsylvania, or, Rendezvous at Red Hill: Encounters in the Late Devonian

4-13-17 HAGS AEG mtg Cressler Devonian forest

Abstract: Red Hill is a kilometer-long road cut in Clinton County, north-central Pennsylvania. Its layers of siltstone and sandstone are part of the Duncannon Member of the Late Devonian Catskill Formation. They were laid down as river deposits 365-million-years ago. Buried in the deposits are the remains of an ancient forest of spore-bearing Archaeopteris trees and associated vegetation that was growing in the floodplain landscape. These include some of the earliest seed-bearing plants, strange ferns from now-extinct groups, and small swamp trees that were ancestral to the coal-forming species of the subsequent Carboniferous Period. Charcoal was found at Red Hill, and represents evidence of some of the earliest known forest fires. Red Hill provides the most vivid picture of the type of landscape into which vertebrates first emerged from the water. It is the locality where Ted Daeschler discovered the earliest tetrapod from North America. Numerous fish species and terrestrial invertebrates have also been identified there. Red Hill is the fossil locality that provides the most thorough information for reconstructing a terrestrial ecosystem from the critical transition period of the Late Devonian.

Speaker Bio: Walt Cressler is a paleobotanist and science librarian based at West Chester University of Pennsylvania. He received his Ph.D. in geology from the University of Pennsylvania. As a librarian and geologist, he likes to read the landscape like a book and tell the stories that he finds there. His own family story is deeply rooted in the Pennsylvania landscape. While doing research at Red Hill on Late Devonian forests, he discovered that one of his great-great-grandfathers operated a sawmill just a few miles away during the great lumber boom of the late nineteenth century.

2017 HAGS/AEG meeting dates and topics:

May 11, 2017– Dr. Alyson Thibodeau, Dickinson College– Using Isotopes to Trace the Source of Turquoise in the Aztec Empire

May 20, (Rain date June 3) A float through the Devonian, A guided kayak trip from Milesburg to Dowdy’s Hole, Centre County, PA. BYOBoat, or rent one from Tussy Mt Outfitters.

Contact Rose-Anna at to sign-up. No fee, unless you rent a boat (includes paddle, life vest, launch permit, and shuttle back to your car for $45). Families and non-members welcome.

The free guide can be downloaded from

September 14, 2017  – Dr. Marcus Key, Jr., Dickinson College – Using stable isotopes in bryozoans to constrain the timing of the formation of the Isthmus of Panama relative to the onset of the Gulf Stream and Northern Hemisphere Glaciation

October 12, 2017Dr. William Stein, SUNY Binghamton – a presentation on the Earth’s earliest forests – research into the Middle to Late Devonian fossil forest record in the Catskill Mountain area of New York State.

November 9, 2017 – Sharon Hill, P.G., Chief – Permitting & Technical Section, PA DEP, Bureau of Mining Programs – Spooky Geology

HAGS Guidebooks, available for purchase

1st Annual Field TripGeology in the South Mountain area, Pennsylvania, Noel Potter, Jr., editor, April 24, 1982, Reprinted 1992. 37 p. $5.00 plus $2.00 S&H.

2nd Annual Field Trip‐ Geology along the Susquehanna River, south‐central Pennsylvania, J. Ronald Mowery, editor, April 16, 1983, 55 p. $5.00 plus $2.00 S8H.

3rd Annual Field Trip‐ Stratigraphy, structural style, and economic geology of the York‐Hanover Valley, G. Robert Ganis and David Hopkins, April 28,1984, 51 p. $5.00 plus $2.00 S&H.

4th Annual Field Trip‐ Pennsylvania’s polygenetic landscape, William D. Sevon, April 27, 1985, Reprinted 1992, 55 p. $5.00 plus $2.00 S&H.

5th Annual Field Trip‐ Selected geology of Dauphin and Northumberland Counties, Pennsylvania, by W. D. Sevon, W. E. Edmunds, G. R. Ganis, and J. P. Wilshusen, May 17, 1986, 22 p. $5.00 plus $2.00 S&H.

6th Annual Field Trip‐ Lower Jurassic diabase and the Battle of Gettysburg, D. T. Hoff, J. R. Mowery, and G. R. Ganis, April 25, 1987,17 p. plus appendices. $5.00 plus $2.00 S&H.

7th Annual Field Trip‐ The geology of the Lower Susquehanna River area, a new look at some old answers, Glenn H. Thompson, Jr., editor, May 7,1988, 56 p. $5.00 plus $2.00 S&H.

8th Annual Field Trip‐ Karst development and environmental geology in the carbonate rocks of the Lehigh and Lebanon Valleys, William E. Kochanov, April 29, 1989, 33 p. $5.00 plus $2.00 S&H.

In cooperation with the 20th annual Binghamton Geomorphology Symposium at Dickinson College‐The rivers and valleys of Pennsylvania, then and now, by William D. Sevon, October 20, 1989, 59 p. $5.00 plus $2.00 S&H.

10th Annual Field Trip‐ The Ridge and Valley Physiographic Province and the East Broad Top Railroad, William D. Sevon, June 1, 1991, 24 p. $5.00 plus $2.00 S&H.

11th Annual Field Trip‐ Paleozoic geology of the Paw Paw‐Hancock area of Maryland and West Virginia, Marcus M. Key and Noel Potter, Jr., May 9,1992, 25 p. $5.00 plus $2.00 S&H.

12th Annual Field Trip‐ South Mountain and the Triassic in Adams County, Pennsylvania, Raymond Britcher, editor, May 22, 1993, 41 p. $5.00 plus $2.00 S&H.

13th Annual Field Trip‐ Geology of the Lebanon Valley and western end of the Reading Prong, Charles Scharnberger, editor, April 23. 1994, 68 p. $7.00 plus $2.00 S&H.

15th Annual Field Trip‐ Pseudo‐Morainic Topography of the Allentown Area of Eastern Pennsylvania, Duane D. Braun and William E. Kochanov, May 4, 1996, 28 p. $7.00 plus $2.00 S&H.

16th Annual Field Trip‐ Notes on the Hamburg Klippe: biostratigraphy, ash layers, olistostromes, and “exotics,” G. Robert Ganis, April 26, 1997, 52 p. $15.00 plus $2.00 S&H

17th Annual Field Trip‐ Geomorphology in the Northern Cumberland Valley, PA, including the Carlisle Deluge of 1779, Noel Potter, Jr., Donald Hartman, and Helen Delano, April 18, 1998, 49 p, $7.00 plus $2.00 S&H.

18th Annual Field Trip‐ The Cove Syncline by canoe, William M. Roman and Michael A. Knight, May 15, 1999, 16 p. plus maps, Out of Print

19th Annual Field Trip‐ Geology of the Kishacoquillas Valley and vicinity, Mifflin County, Pennsylvania, Michael A. Knight and William M. Roman, May 20, 2000, 18 p. plus maps and sections, $7.00 plus $2.00 S&H.

20th Field Trip‐ Geology and Geomorphology of the South Mountain Area, Cumberland and Franklin Counties, Pennsylvania, Noel Potter, Jr., and William D. Sevon, May 14, 2011, 64 p., $10.00 plus $2.00 S&H.

No formal guidebooks were prepared for the 9th (1990) and 14th (1995) Field Trips. The 2001 trip was a repeat of the 2000 trip.