[Bill Menke’s Journal entry for June 5-9; 2015 Intern Workshop and Fieldtrip]. Mike Kaplan and I led a four day Workshop and Fieldtrip in Harriman State Park, New York. The morning workshops focused on continental evolution and the afternoon fieldtrips focused on the geologic history of the Hudson Highlands. Six Summer Interns, Camera Ford, Karina Galinskaya, Thomas Harper, Christy Jenkins, Peter Skryzalin and John (Jack) Wilding, participated.

[Friday, June 5, 2015]. We left Lamont-Doherty Earth Observatory (LDEO) in the late afternoon and drove up to Baker Camp. This camp is a collection of cabins and lodges on the northeastern shore of Lake Sebago, in Harriman State Park. It was built in the 1920’s by George Fisher Baker, a financier from Tuxedo NY, to benefit his workers. It is now owned by the Park but is privately operated. I had met its very pleasant and enthusiastic proprietor, Rae Hirsch, back when I was a volunteer kayak coach at the neighboring American Canoe Association camp. Rae assigned us to Cabins E and F, located at the northeast corner of the camp, on a hillside high above Lake Sebago.

We unpacked our mountain of gear and organized ourselves. I doled out assignments for both workshop and dinner. Since there were eight of us, I formed four two-person dinner teams to cook each of our four evening meals. Karina and I took on today’s menu of macaroni and cheese. We cooked the cheese sauce from scratch, combining cheddar and Romano cheese with heavy cream. We all sat on chairs on the deck of the Cabin F and had a relaxing dinner.

After dinner, the interns and I set up our seismometer, on a rock ledge adjacent to the cabin. I had brought it along as part of a data-collection demo; it included a RefTek 130 recorder and a Mark Products L22-D geophone, along with battery and GPS antenna. As always, the “stomp test”, where one kicks the rock and observes the resulting wiggles on a computer screen, generated some smiles. The interns then spent an hour doing their “homework”, preparing simple demos and reading short papers that we would discuss the next morning.

Some rain fell during the night.

[Saturday, June 6, 2015]. We ate breakfast in the Baker Camp Dining Hall, eating oatmeal, eggs and other food the staff had cooked. Vadim Levin, a seismologist from Rutger’s University, joined us for our morning workshop. We began with two five-minute demonstrations on important geological subjects, each given by one of the interns. Thomas’ demo was on differential erosion. He demonstrated the importance of this process in creating the landforms that we would see later in the day by brushing a sand and plaster model, removing the softer sand and leaving the stronger plaster. Jack’s demo was on the uranium-lead dating system. He used piles of pennies to illustrate the decay of a parent radioactive element into its daughter product and to explain the concordia diagram. Vadim then gave an introduction on the geology of eastern North America, likening the zone of different ages in our geological map to the layers of an onion – each zone formed by a different orogeny. He then explained the challenges of extending our knowledge of the earth from the surface, where the rocks can be directly samples, to the deep lithosphere, which can be accessed only more remotely. He led us through a discussion of the deep lithospheric root beneath the craton, showing us seismic images from:

Van der Lee, S., and A. Frederiksen, Surface Wave tomography applied to the North American upper mantle, in Seismic Earth: Array Analysis of Broadband Seismograms, AGU Monograph 2005.

We then worked through two papers on the geology of cratons. The first addressed the age of the rocks:

Bowring, Williams & Compston, 3.96 Ga gneisses from the Slave province, Northwest Territories, Canada, Geology 2013.

And the second the temperature of the cratonic lithosphere:

Boyd, Gurney & Richardson, Evidence for a 150-200-km thick Archean lithosphere from diamond inclusion thermobarometry, Nature 1985.

We then prepared for our afternoon fieldtrip, preparing a lunch and applying sunscreen and bug repellant. Today’s fieldtrip was a traverse of the region, to examine the two main lithologies and to understand the boundary between the metamorphic rocks of the Hudson Highlands and the topographically much lower sedimentary rocks of the Newark Basin, to the south. Vadim joined us for the first of our five stops:

A rock cliff behind Baker Camp, to examine the gneiss exposed there;

The overlook along the Mountain Trail (blazed in orange) in Kakiat County Park, to examine leucogranite exposed there and to view the Newark Basin below us;

A stream gulley in Monsey Glen County Park, to examine sandstones (and where we spotted a Garder Snake);

A road-cut at the Route 202 – Old Route 202 in Montebello NY, to view conglomerates;

A road cut along Pavilion Road in Suffern Ny to view slickensides; and

Bear Mountain Summit, to view the leucograntites there and to view the Hudson River as it cuts through the Highlands.

Back at Baker Camp, Camera and Peter prepared a dinner of vegetable curry, while the rest of us relaxed. I walked down to Lake Sebago and watched flotilla of Canada Geese and goslings paddle along the lake shore. After dinner, we met briefly, so I could dole out tomorrow’s readings.

[Sunday, June 7, 2015]. We ate breakfast again at the Baker Camp Dining Hall. Dallas Abbott, an LDEO geologist, joined us today and participated in both workshop and fieldtrip. Camera presented a demo on isostacy, using boards floating in water to explain how the addition of rock to the earth’s surface can lead to metamorphism of deeper rocks and how erosion can bring once deeply buried rocks to the surface. Christy presented a demo on hypsometry, using clay models to emphasize the unusualness of our planet with its two-topographic-level division into continents and oceans. We worked through two papers on continental evolution. The first concerned the evidence for modern-day-like plate tectonics in the ancient earth:

Calvert, Sawyer, Davis & Ludden, Archean subduction inferred from seismic images of a mantle suture in the Superior Province, Nature, 1995.

and the second argued for distinctly different styles of crustal formation during those times:

Zegers & van Keken, Middle Archean continent formation by crustal delamination, Geology, 2001.

We managed to fit in an hour of kayaking before the fieldtrip, renting three canoes and two kayaks from Baker Camp and paddling a very pleasant loop around part of Lake Sebago. I was in the stern of one of the canoes, with Camera in the bow.

Our fieldtrip today was to Claudius Smith Den, a small cave on the western side of Harriman State Park, at the foot of a prominent scarp. My hiking map says that it was the refuge of Claudius Smith, a notorious Revolutionary Era outlaw who stole from the Continental Army and who was eventually captured and hanged in 1779. The site is one of the few in the park were the structural relationship between the gneiss and leucogranite is apparent. We parked at the Ramapo River Boat Launch in Tuxedo and spent about all afternoon hiking to and from the den. We visited the following sites:

A road-cut along East Village Road, to view folded gneiss;

An overlook along the Tuxedo – Mount Ivy Trail (blazed in red on white), to examine gneiss exposed there and to view the valley of the Ramapo River;

Claudius Smith Den, where we had lunch; and

The Black Ash Mine, along the Ramapo – Dunderburg Trail (also blazed in red on white), to examine iron ore.

We were fortunate to have sunny weather on this hike. The day was hot and humid, so we stopped at Bentley’s Deli / Café, on Route 17 in Tuxedo New York, for ice cream on the way back.

Mike and Thomas cooked a dinner of fried chicken, poached salmon and corn-on-the-cob. Afterwards, we lit a fire in the big stone fireplace in Cabin E, roasted marshmallows and made S’Mores.

[Monday, June 8, 2015]. Our morning workshop was devoted to deformation and volcanism. Karina presented a demo in which she sliced clay models of deformed strata to illustrate the patterns of folds and domes seen in cross-section. I led a discussion of two papers. The first:

Crouch, Mesozoic hotspot epeirogeny in eastern North America, Geology 1981.

presented evidence that the passage of the Monteregian hotspot across eastern North America during the Cretaceous period has led to uplift and erosion. The second:

Holbrook & Kelemen, Large igneous province on the US Atlantic margin and implicatiobs for magmatism during continental breakup, Nature 1993.

used seismic reflection images to argue that the rifting of Gondwana was associated with extremely large outpouring of magma (whose source remains mysterious to this day).

Todays fieldtrip also focused on deformation and volcanism, and included the following stops:

A road-cut along Seven Lakes Drive just south of Lake Sebago to examine a shear zone and a fault;

A road-cut along Route 106 just west of Kanawauke Circle to examine a pegmatite dike;

A rock ledge on the shore of Little Long Pond, to view a boudin in a shear zone (though to be a continuation of the one we examined on our first stop);

A road-cut along Route 106 near the Long Path (blazed in blue) crossing, to view a fold;

A road-cut along Seven Lakes Drive opposite Lake Tiorati to examine a diorite pluton;

The scarp called the Rock House; to discuss the origin of this and many other scarps in the park; and

A small iron mine along the Baker Camp access road, to view the zone of alteration associated with the pod of ore there.

After returning to Camp, Christy and Jack prepared our taco and burrito dinner. Afterward, we made S’Mores by the fireplace in Cabin E.

[Tuesday, June 9, 2015]. I chased a raccoon away from out deck at 4AM; it was raiding the garbage. We woke to light rain, but the forecast is for clearer weather in the afternoon.

We had breakfast in the dining hall and then began our final workshop. Peter, who had been assigned the duty of recording strikes and dips at all of our stops, showed us how they plotted up on a topographic relief map of the region and interpreted the patterns in terms of large-scale folds. Mike gave us an overview on dating techniques applicable to Pleistocene time scales problems and then led a discussion of two papers that focused on the timing of the end of the Pleisticene glaciation:

Caldwell and Muller, New York glacial geology, U.S.A., Quaternary Glaciations – Extent and Chronology, Part II, Elsevier 2004.

Balco & Schaefer, Cosmogenic Nucleide and vave chronologies for the deglaciation of southern New England, Quaternary Geochronology 2006.

At the very end, we managed to fit in a very brief discussion of the Snowball Earth Hypothesis, using:

Hoffman, Kaufman, Halverson and Schrag, A Neoproterozoic Snowball Earth, Science 1998.

We then packed up all our gear, left Baker Camp and began our last fieldtrip, to view the volcanic rocks of the Palisades intrusion. We drove to the Long Path (blazed in blue) trailhead along South Central Highway in Haverstraw NY and walked the ridge of the Palisades to High Tor, a high point that offers a great view of the Hudson River and the Highlands to the north. Mike pointed out many glacial striae on outcrops of diabase outcrops along the trail. We measured their direction and discussed whether the inferred glacial motion was consistent with the types of erratic boulders in the area. The hike is a long one – about 5 km each way – but the weather cooperated. The sky, which was been overcast with intermittent light rain in the morning was now partly sunny, with towering cumulous clouds. We climbed up onto the Tor (from the Dutch toren, meaning tower) and had our lunch sitting on the hexagonal joints of the Palisades diabase gazing out across the river. I discussed the rocks, which are part of the volcanic outpouring we had discussed in the Holbrook & Kelemen paper. Mike discussed how the river had been damned during the final retreat of the Pleistocene glaciers, by a moraine at Croton Point. We then headed back.

We stopped for ice cream at the Courtesy Mart in Mt Ivy New York before heading back to New York. We arrived about 3PM; our Fieldtrip and Workshop had lasted almost exactly four days.