In my business of geological education, I meet a lot of people in different geographic areas.  That is probably one of my most favorite things about doing what I do, you hear various stories related to the area’s geology, see new faces and share your interest with them.  Sometimes, during one of our visits to a town to do a program, we luck out and learn something very interesting about the area, probably something I never heard before and the folks have the evidence to proof what they are talking about.

One of those case recently arose.  I had met a gentleman who is very interested in local minerals and has indeed discovered some “cool” stuff on his expeditions in the YorkCounty.  One of his great pieces is petrified wood from Manchester.  Well preserved and rather large for a specimen, I must have looked like a dog waiting for my supper when you showed me that one!!  Certainly one of the best pieces of local petrified wood I have seen from YorkCounty.  Not to get off track, this person had a friend from the Newville, CumberlandCounty area who has done his own research of that area.  With his research he had some questions about items he recovered from the GreatValley region of central Pennsylvania.   So we made arrangements to meet on a Sunday afternoon since that was the only time I had available in the next few weeks and off we go to the Newville area.

I have done very little research in the GreatValley but had time to do some preliminary reading on maybe I should expect to find out there.  I studied the geologic maps since this person gave me an address to check out including Goggle Earth to get a picture of the lay of the land.  With hammer and camera in hand, we met at the designated location (thanks to the GPS) and he gives me some background of what he is doing and has found.  It turns out that much of his research is not geologically related but archaeologically based and certainly I still felt comfortable in that realm.

Float of limestone laying in the field close to the quartz crystals

During the preliminary discussion, I was told what my goal was for the day.  In the rolling hills of the western GreatValley area, this friend uncovered hundreds of small six-sided shaped quartz crystals almost resembling the famous Herkimer diamonds from upper New York state.  Wow, what I had to decide was if these crystals were really transported in from Herkimer for some sort of trading goods from previous residents of the valley or were rthey native to that area?

Again, I did not have much experience of mineral collecting from this portion of CumberlandCounty but I think I would have heard about these clear quartz crystals.  I should have seen some of these crystals for sale at a local rock and mineral show or even a rock swap, but I never did.  After he took me to an area where you has unearthed many of these crystals, I soon drew a conclusion that these crystals were native, weathering out of the limestone.  Wow, so cool and just walking through the freshly dug excavation, these crystals were abundant.  My guide and his friend even have perfected finding these at night using flaahlights at a low angle to the ground to detect their reflection.  Very creative!!!!

Quartz crystals recovered from the Newville area

I wanted to see more of the  immediate area to look at the available rock exposures and loose rocks in the fields.  Upon walking more of the property, I was shown a cave with a vertical entrance which apparently has been known by local cavers for many years.  I knew I was in sinkhole and cavern area knowing the rock formations for which laid under my feet.  Sure enough, with the topography, I located a solution valley that was created when two of more sinkholes combined to make one large sink and later became inactive, forming a narrow, elongated valley.  Other sinkholes were spotted around the edge of this property where residents brought their old metal and disposed of it in the sink.

Anoither sampling of the quartz crystals

Our last stop was at a small inactive quarry where the limestone was well exposed.  A great outcrop to see the structure of the limestone and maybe some more quartz crystals.  Although we didn’t find any of the clear quartz crystals, we did locate a cavity of white quartz crystals.  No other minerals were detected but seeing these clear quartz crystals native to the limestone and having great fellowship with my guides for the day was certainly worth the trip.

Limestone exposed in the abandoned quarry

After I got home and knowing exactly where I was on the trip, I went to my library again to find out if these fine quartz crystals were every reported by a geologist.  Sure enough, when I went to the classic book “Mineralogy of Pennsylvania” by Samuel Gordon in 1922 and I turned to CumberlandCounty, what did I see?  Not one listing of clear quartz crystals but two in the county.  After locating these locations on the CumberlandCounty map and referring to the geologic maps, both of those locations were in the same limestone formation as I visited earlier.  It is hard to believe that among my rockhounding friends that have explored CumberlandCounty, they never said a word about the quartz.

Milky quartz crystals from the abandoned quarry.

STOP 1.  Hyde Heritage Rail Trail County Park Exposure

Harpers Formation phyllite and quartzite

Located between Hyde and INdian Rock Dam Rock, Spreing Garden Township

1. Harpers Formation derived from Harpers Ferry, WV
2. Southern 33% of YorkCounty is composed of metamorphic rocks
3. This ridge (Country Club Ridge) is just south of the dividing line between the Piedmont Lowlands Section (PLS) and the Piedmont Uplands Section (PUS).
4. Walk a portion of the exposure and notice what appears to be layering.  Actually this rock has undergone heat and pressure where bedding has become obscure.
5. What you believe is layering is known as foliation – a feature only found in metamorphic rocks where platy minerals in the rock align themselves to produce a flat plane.
6. Notice any folding in the exposure?
7. We are situated very close to a north-south fault.  Although most of the rocks in the PUS are folded, these rocks have been more tightly folded with the influence of the fault.
8. Find isolated beds of quartzite.  Quartztite is thicker “bedded” than the phyllite and more resistant to erosion.
9. There are small quartz veins also found here.
10. Notice how some of the tree roots anchor themselves into the bedrock and are accelerators in weathering of the rock.

Folding in the metamorphic rocks at Hyde

STOP 2.  Stoney Brook Diabase Dike

Diabase and Conestoga Formation limestone

Along the Railroad just west of the Pleasant Acres Road, Springettysbury Township

1. Diabase is an intrusive igneous rock giving the rock a coarse-grained appearance.
2. All diabase in Pennsylvania is Jurassic in age.
3. A dike is a narrow intrusion of magma in this case only measuring about 20 feet wide, but is about 35 miles in length
4. This magma was believed to be about 1100º C. and baked the surrounding rock into a metamorphic rock named as a hornfels.
5. Larger intrusions have formed mineral resources in southeastern Pennsylvania such as the Cornwall Iron Mines, LebanonCounty and Dillsburg magnetite deposit, York       County.
6. The magma intruded the Conestoga Formation composed of limestone.
7. Ripple marks have been found in this thinly-bedded limestone.
8. What is the direction and angle of dip of the limestone?
9. The Conestoga Formation is one of several limestone/dolomite units in the YorkValley, all forming on a continental shelf off the coast of ancient North America known as        Laurentia.
10. This limestone is now considered Cambro-Ordovician in age.

Stoney Brook Dike just west of Pleasant Acres Road

STOP 3.  Accomac Metabasalt

Catoctin Formation

Located along the south side of Accomac Road just west of the intersection with River Road, Hellam Township

1. Formed as a result of rifting of the supercontinent Rodinia about 620 mya.
2. Basalt forms on an oceanic crust (i.e. mid-oceanic ridge)
3. Look for quartz pods (filled-in gas bubbles) sometimes showing a trace of copper
4. Grass-green mineral is epidote and darker green mineral is chlorite
5. Notice crystal size – extrusive meaning it cooled quickly and is fine-grained
6. Fractures in the rock are known as joints (fractures where no movement has taken place)  Geologists can take measurements of joints and calculate direction of pressures
7. Notice one area where bedrock is missing with a small drainage ditch – a possible fault?
8. Across the road notice the erosion taking place as the stream crosses over the bedrock
9. The rock has gone at least one period of heat and pressure – metamorphism (meta)
10. Potholes are well developed in the metabasalt

Accomac road cut exposing the Catoctin metabasalt

STOP 4. Rocky RidgeCountyPark

Chickies Formation – Hellam Member

Located at the end of Deininger Road, Spring Gettysbury Township.  Proceed to the Oak Timbers North Overlook

1. Rock containing rounded pebbles is known as a conglomerate
2. Rock fragments of mostly quartz with occasionally darker fragment of metarhyolite
3. Can you detect any bedding?
4. Notice how the fragments are more resistant to erosion – standing higher than rock
5. Any theories on how this rock formed (include a continental shelf, IapetusOcean and other bodies of water in your thinking)
6. York, Lancaster, Lebanon and Berks counties can be seen from the overlook
7. Can you recognize any familiar landmarks?
8. Harder rocks underlie ridges and softer rocks underlie the valleys, i.e. sandstone and quartzite ridges; limestone and shales in the valleys)
9. We are at an elevation of about 940 feet above sea level
10. We can see a distance of 52 miles to the northeast on a clear day

Hellam Conglomerate exposed at Rocky Ridge County Park.

STOP 5. Sheep Bridge Road

Gettysburg Formation shale and sandstone

Located on the west side of Sheep Rock Road just north of the Conowego Creek, Newberry Township

1. Sandstone has thick bedding and shale has thin bedding. Grain size also varies.
2. Which of the two rocks is more resistant to erosion?
3. These rocks were laid down in an “Everglades” environment as Pangaea was rifting apart
4. Fossils in the area include petrified wood, ferns, dinosaur footprints and reptilian remains
5. The thickness of the New Oxford and Gettysburg formations are at least 25,000 feet thick
6. Can you detect the angle of dip and direction?
7. These rocks are undeformed and positioned nearly the same as when they were deposited
8. The red color of the rock was created when the sediment was above water level and exposed to the atmosphere
9. Clam shrimp found in this formation in DauphinCounty indicates fresh water environment
10. Which layer in this road cut is the oldest?

Sheep Bridge road cut exposing Triassic sedimentary rocks

STOP 6. Pinchot State Park Toboggan Run Area

Diabase Exposure

Warrington Township

1. This is one of the best exposures of diabase in YorkCounty
2. Compare this diabase with that seen at Stoney Brook
3. This diabase formed in a sill (a lenticular body of magma) formed at least one mile beneath the surface
4. In a sill, the magma closest to the outside will cool quicker than the middle
5. This event was the last stage of the rifting of Pangaea
6. Igneous rocks weather in a characteristic rounded shape boulders (spheroidal weathering)
7. Notice the cracks on the rocks – these are believed to be cooling cracks as the magma cooled now magnified by weathering
8. One could have fun here recreating how the boulders were all connected at one time
9. The rock develops a reddish-brown weathering rind
10. How do you think this rock would be for having a good groundwater supply?

Diabase exposed at Toboggan Run at Pinchot State Park

STOP 7.  Rossville   Road Cut

Diabase and Gettysburg Formation hornfels

Located on the east side of Old York Road, 0.50 and 0.75 miles north of Rossville, Warrington Township

1. Check the diabase at the lower road cut for grain size – positioned in the middle or on the edge of the sill?
2. White veins in the diabase of composed of a mineral group known as zeolites.  Heulandite and stilbite are present here in crystals
3. In the upper road cut, this rock was originally rocks similar to what we saw at Sheep Rock Road but these have been heated by the magma now known as hornfels
4. Can you detect the direction of the bedding?
5. A chemical reaction here formed a small amount of native copper to form in the rock
6. Upon weathering of the rock, native copper will adjust to the new conditions forming azurite (blue and malachite (green)
7. This rock has no economic value and only occurs on the joint surfaces
8. Other minerals formed in this method include garnets and opal
9. Gold is found in area streams, mostly washing out of the diabase
10. Collect your pieces of samples for the coffee table!

Azurite and malachite exposed in the upper road cut along Old York Road

March is usually a busy month for my wife and myself.  With Lou Ann as a minister, Lent occurs in March with Wednesday services and other Holy Week activities.  The Geological Society of America Northeastern Section holds their annual gathering also in March.  Not that Lou Ann travels with me, but I was hoping she would have made the trip north to where this blog is being written.  What would you answer if I would ask where is the highest elevation in New England and is the second highest point east of the Mississippi River?  The peak is in the Presidential Range of the White Mountains in New Hampshire and also has a cog railroad that many of you traveled up on a vacation.  The answer is Mount Washington.

No, I am not really on top of the mountain (but I would love to spend a night up there), but the conference is being held at the Mountain Washington Omni Hotel in Bretton Woods.  When they said the resort is at the base of Mount Washington, they weren’t lying.  What a view from the back porch of the hotel!!  Yes, although there wasn’t much snow laying on the ground when we arrived, it is snowing now with several inches expected.  Attending these annual meetings is educational as presenters provide updates on research, talking about the science theories of years past and new technologies.  You get to also see fellow geologists that you only see at these gatherings.

What made me think about writing a blog like this one?  Actually when a fellow geologist friend and myself left the area to head north, I asked him, “If we were to travel in the old days by horse and buggy, I would how long it would have taken to go 545 miles to Bretton Woods?  Yes, alittle exaggerated, but just think about traveling in those days.  One of the papers I heard from a Pennsylvania geologist here was about the first geologic investigation of the Keystone state.  The geologist started in Philadelphia, traveled to Harrisburg, then to Philipsburg and ending in Erie.  Imagine, not only taking a horse and buggy that distance but locating rock exposures, drawing the exposures and staying overnight.  Wow, quite impressive and I don’t think that is for me.

By attending such a meeting as this, you have a chance to compare the field practices of those early explorers to what we use today.  In the early days, they didn’t have topographical maps.  They may have had very crude map showing the mountains, but not much else.  Today we have the use of GPS, 3-D relief maps, highways with a 65 mph speed limit including nice rock exposures and cars.  These pioneering geologists did not have the regional view to correlate rocks, did not really know where the rich coal deposits were nor the important mineral resources or Marcellus gas.

From the 38 themed sessions scheduled at the conference, a lot of information is made available.  Each session lasts up to 3 hours and has presenters every 15 minutes.  Yes, this is what I said!  You have 15 minutes to deliver your information, maybe answer a question.  This meeting occurring in New Hampshire means that many of the papers are centered on New England geology, but you may be able to take some information  back home to use in Pennsylvania.  Finally, the Geological Society is celebrating its 125 years so the conference is running with that theme.  The good news about this annual meeting is that the 2014 meeting will be held in Lancaster, so maybe I will take a horse there to make it feel like old times.

Before I came to New Hampshire, I had several programs to present.  The first program was on the world-famous Peach Bottom Slate for the Harrisburg Area Geological Society.  About 45 geologists attended the program.  You know how they say presenting a program in front of your peers is always the hardest to do.  I find that true also, since everyone has a common interest.  However, you realize shortly into the program that you are in control and let the script roll.  Have fun with the audience as I do.  I judge my audience on how much they laugh at my jokes because science is truly boring unless you spice it up.  The program went well, but during the question period afterwards, I got intimidated.  There was a retired state geologic survey employee in the audience who I knew, but never really talked to him.  He said he had a question and a statement.  I got myself propped thinking that he was going to question something I said.  His question was one about the Susquehanna River which I did not really have a answer for, but told him that.  His statement was that I need a great job presenting the program, so I was relieved.

My other program was a PointPoint program on the Susquehanna River for “Date Night” at Shank’s Mare Outfitters in Long Level.  I have done other programs for this special night over the years and Liz Winand always attracts an interesting group of people for across the region.  This night wasn’t any exception.  There were couples from Lancaster and YorkCounty, some having an interest in geology and others just enjoying the night along the river.  A great group as always with good questions and yes, they laughed at my jokes.

Finally, let me know if there are any topics you would like for me to write about.  I usually write a blog as an educational piece, giving either historic or geologic information for the readers to enjoy.  I have received comments back on numerous blogs with stories of your own or complimentary comments about the blog.  Thank you for those, but do not hesitate to let me know what you would like to see on this page.