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. They occur at 6:30 PM on the second Thursday of the month, except summer months.


Kent Littlefield


Bill Bruck


Mike Meyer


Amy Randolph


The Geology Along the Northwest Lancaster County River Trail


Presented by:  Jeri Jones, Jones Geological Services   


Meeting Date:  Thursday, March 11, 2021

Meeting Time:  6:30 p.m.

Meeting Location:  Zoom

RSVP:  Email the HAGS secretary by noonish on the day of the meeting to RSVP and for Zoom meeting details. 

Presentation Summary:  The Northwest Lancaster County River Trail (NWLCRT) runs from Columbia, PA northward 23 miles to Falmouth, PA. The trail, now almost totally paved, parallels the Susquehanna River and lies within its floodplain for much of that distance.  The trail passes through Cambro-Ordovician carbonates, Cambrian metamorphics and Mesozoic sedimentary and igneous rocks.  Historic sites along the NWLCRT include St. Charles Furnace, the first documented archaeological site in Lancaster County; the Marietta Furnace Complex, Marietta Borough; Shock Mill Bridge; the village of Billmeyer; and the Conewago Canal.  Outstanding geologic locations include Point Rock Tunnel, Chickies Rock, Haldeman Island, White Cliffs of Conoy and the famous diabase potholes.  The NWLCRT provides great opportunities to illustrate key geologic fundamentals.  Although carbonate exposures are rare along the trail, large examples of some of these rocks have been used to line parking areas.  Also, evidence of gravel terraces can be seen north of Marietta and south of Falmouth.   An educational geologic guidebook has been published that includes 28 stops and points of interest along the trail.  Grab your bike tonight and let’s go for a rock ride!  

Speaker Bio:  Jeri Jones received his B.S. in Geoarchaeology from Catawba College where he specialized in studying the Carolina slate Belt in North Carolina.  Jeri Jones was employed by the County of York for 38 years where he provided educational programs, field trips and designed interpretation panels.  He operates Jones Geological Services in Spring Grove, PA where he studies the geology of southeastern Pennsylvania, and has traveled throughout the country conducting field trips and programs for all ages.  He previously taught at HACC-Gettysburg and York College of Pennsylvania and presently is teaching at Messiah University.  He received the Digman Award for Geologic Excellence from the Eastern Chapter of the National Association of Geoscience Teachers. He has authored five books, narrated a geologic education video series and written numerous articles.  Jeri also is a guest columnist for the York Daily Record/York Sunday News where he writes about local earth science, and he’s also started the “Zoom Rock Room” held every Tuesday evening where various aspects of earth science are discussed. Jeri also serves as a clay consultant at Lincoln, Williams Grove, BAPS, Selinsgrove and Big Diamond speedways.

Spring 2021 HAGS/AEG meeting dates and topics:


April 8, 2021 – Jacalyn Wittmer Malinowski, Assistant Professor of Geological Sciences, SUNY Geneseo - Conservation Paleobiology in the Finger Lakes Region of NY State

May 13, 2021 - Rose-Anna Behr, P.G., PA Geological Survey - Over, Under and Through: Three-pronged approach to field mapping a karst terrain of western Virginia

HAGS Guidebooks, available for purchase, $5 each, plus $2 S&H. Multiple books may have discounted shipping.

1st Annual Field Trip‐Geology 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. $5.00 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. $5.00 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. $5.00 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, $5.00 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, $5.00 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., $5.00 plus $2.00 S&H.

21st Field Trip‐ Shermans Creek from Dellville to Duncannon, Perry County, Pennsylvania, William Roman, May 12, 2012, 48 pages, color, $5.00 plus $2.00 S&H.

22nd Field Trip‐ Some geological aspects of the north side of the Cumebrland Valley in Cumberland County, PA, Bill Sevon, May 4, 2013, 33 pages, large font, color photos, $5.00 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.

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