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


A Look at the Pennsylvanian Subperiod of the Carboniferous Period


Presented by:  Larry Smith, P.G. – PA Dept. of Environmental Protection


Meeting Date:  Thursday, March 12, 2020

Meeting Time:  6:30 p.m.

RSVP: Noonish, March 10, 2020. Please specify if you will be attending the meeting only, or both the meeting and optional, pay-on-your-own dinner before the meeting.


Meeting Location: AEG Offices 441 Friendship Road (near Bass Pro Shop)

Dinner Location:  Fiesta Mexico 3957 Paxton Street, Harrisburg 

Dinner Time: beginning at 4:45 or whenever you get there 

Presentation Summary:  The Carboniferous Period ranged from 358.9 to 298.9 million years ago and included our Mississippian and Pennsylvanian Subperiods, with the Pennsylvanian lasting approximately 24 million years.
In general terms, the Carboniferous was like today - with tropical through arctic environments, orogenic activities, fresh water and marine life in abundance, glaciers, profuse amounts of plants, and a relatively low CO2 atmospheric concentration. However, a detailed look shows a significant contrast with the landmasses forming into one continent (Pangea), mammals were absent, insect families were significantly less diversified, many insects and other arthropods were giant in size, angiosperms were nonexistent, and vast tracts of tropical wetland vegetation were present. Profuse plant growth in ideal environmental conditions was set to form the large worldwide bituminous and anthracite coal beds of today.

This presentation will focus on the Pennsylvanian Subperiod and what it was like during that time regarding the fauna and flora, conditions allowing for the preservation of the plants, and southern glacial fluctuations with associated climatic changes and sea level variations, that exposed or inundated lowland areas.

Speaker Bio:  Larry Smith is a P.G. who attended Bloomsburg University where he received a BS degree in Geology. He worked as an environmental geologist for over 20 years before accepting a position with DEP’s Hazardous Sites Cleanup program in 2012, as a geologist and regional project officer. His work involves groundwater remediation projects associated with state and federal Superfund site. He’s had an interest in fossils since childhood, and gave a talk to HAGS in April 2019 on fossils in amber. 

Spring 2020 HAGS/AEG meeting dates and topics:


March 12, 2020 – Larry Smith, P.G., PA DEP - Pennsylvanian Subperiod plant fossils

April 9, 2020 – Steven Jasinski, PhD, Paleontologist, PA State Museum - topic to be announced

May 14, 2020 - Professor Marcus M. Key, Jr., PhD, P.G., Dickinson College - An historical geoarchaeological approach to sourcing an 18th century building stone: Use of Aquia Creek Sandstone in Christ Church, Lancaster County, Virginia.

Fall 2020 HAGS/AEG meeting dates and topics:


September 10, 2020 – Steve Clark, P.G. - Marcellus Shale Gas Drilling and Wellsite Geology

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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