NEIGC 2008 Trip Summaries
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2008 New England Intercollegiate Geological Conference October 10-12, 2008 Westfield State College, Westfield, Massachusetts Preliminary list of trip descriptions updated 07/27/2008 Note: this list is incomplete and will be updated as more information becomes available. Conference registration materials will be available shortly. Friday, October 10 A1 Marble Karst of the Stockbridge Formation, Berkshire Region, Western Massachusetts. Trip leader Ernst H. Kastning, New Hampshire Geological Survey [email protected] Berkshire County, the far-western county of Massachusetts that extends from the Connecticut state line to the south to the Vermont state line to the north, contains nearly all of the major karst features in the Commonwealth. The county is nearly coincidental with the Berkshire Mountains that also have a physiographic extension into neighboring states. The karst of western New England is largely confined to the metamorphic Stockbridge Formation and its stratigraphic equivalents in Connecticut and Vermont. In places, the formation also extends into estern New York. The Stockbridge (Lower Cambrian to Lower Ordovician) consists of at least seven mapped members that are calcareous in whole or part. Collectively this formation is regarded as a marble that is largely calcitic in the upper part and dolomitic in the lower part. Some units contain interbedded quartzitic lamina and nodules. This fieldtrip is dedicated to the late Alan R. (“Sundance”) Plante who passed away last year. Most of the trip will visit localities of karst and caves in the Berkshires that Alan studied and mapped in considerable detail from the late 1960’s until his death. The trip includes some of the most noteworthy localities of karst in western Massachusetts. A highlight will be the lunch stop at Natural Bridge State Park in North Adams, with an opportunity to explore the Hudson Brook Chasm, including the historic Natural Bridge and abandoned Hoosac Quarry. Starting location: Commuter Parking Lot, Westfield State College. Starting time: 8:00 a.m. Bring sturdy boots, flashlight, camera (to poke into some caves), rain gear, bag lunch, and drinks. Rock hammers and collecting paraphernalia are welcome, but must not be used in caves or state parks. A2 Deep Crustal Partitioned Transpression and Ductile Extrusion of the Monson Orthogneiss, Bronson Hill-Central Maine Boundary Zone, South-Central Massachusetts. Trip leaders Matt Massey and David Moecher, University of Kentucky [email protected], [email protected] Middle to Late Paleozoic collision between Laurentia and Avalonia/Meguma is well documented in the northern Appalachians, and is invoked as the cause of the Acadian and Alleghanian orogenies in eastern New England and the Canadian Maritimes. Following initial sinistral oblique convergence between in the Late Silurian, dextral transcurrent tectonics dominated from the Devonian through the Carboniferous from southern Newfoundland through Nova Scotia, New Brunswick, and Maine. Dextral transpression is not confined to coastal terranes, but is documented in central and northern New Brunswick, central Maine, and as far northwest as the Gaspé peninsula. The extent to which Middle to Late Paleozoic dextral transcurrent motion was effective along strike of the orogen into southern New England (Massachusetts and Connecticut), remains to be fully assessed. This field trip will examine evidence for Late Paleozoic dextral transpression at mid-crustal levels in the southern Bronson Hill-Central Maine boundary zone in central Massachusetts. The largely dextral regime resulted in lateral and vertical extrusion of orthogneiss, which resulted in local occurrences of coeval sinistral and dextral displacement. Evidence supporting the transpressional/extrusion model was documented during 1:25000 to 1:1200 scale geologic mapping of the Palmer 7.5 minute quadrangle, south-central Massachusetts, with additional observations in adjoining quadrangles. The field trip will focus on structural and petrological evidence at various scales for sinistral ductile displacement within the Mount Dumplin high strain zone (MDHSZ), the western margin of the Monson orthogneiss. The MDHSZ is the focus of high non-coaxial strain resulting from northward displacement of the Monson orthogneiss relative to the Belchertown intrusion and Glastonbury orthogneiss. The trip will also examine the style of internal deformation of the Monson orthogneiss, an S to L-S tectonite, and revisit the dextral Conant Brook shear zone, the eastern margin of the Monson, which accommodated dextral displacement between the BHZ and CMZ. Starting location: Big Y/Ocean State Big Lots shopping center, Hwy. 32 in Palmer, MA (exit 8 of Mass Turnpike) Starting time: 8:00 a.m. Lunch will be available at delis in Ware, MA. Note: This trip will include four traverses of approx. 1 km length in wooded areas in moderately steep and vegetated terrain, and a short hike along an abandoned railroad grade that is now heavily overgrown, rocky, and damp. Sturdy, waterproof footwear is recommended. All other stops are easily accessible roadcuts. A3 Paleoecology and Paleontology of the Jura-Trias in the northern Hartford basin, CT and MA, Part I. Trip leaders Paul Olsen [email protected] and Nick Macdonald, Columbia University. This two-day field trip (see also trip B3) will explore the paleoecology and paleontology of the Triassic-Jurassic Hartford rift basin of Massachusetts and northern Connecticut. Rich assemblages of plants, crustaceans, insects, fishes, and tetrapods, especially dinosaurs will be examined in their field context in light of recent advances in our understanding of the geological time scale, mass extinctions, climate change, and giant volcanic eruptions. In addition to the field sites, we will visit the Pratt Museum, the premier repository for classical Triassic-Jurassic fossils. Starting location: Commuter Parking Lot, Westfield State College. Starting time: 8:30 a.m. Bring a bag lunch. A4 Field Evidence for Flow of Basaltic Magma through Fractures and Porous Media. Trip leaders Anthony R. Philpotts and Doreen E. Philpotts, Yale University [email protected] Basaltic magma is formed in the upper mantle and has to flow to reach Earth’s surface. Igneous rocks formed in the crust retain little evidence of magmatic flow, and consequently, considerable debate has arisen over the ascent of basaltic magma. For example, does basaltic magma in large regional dikes rise vertically, or does it spread laterally from a central feeder? This trip will examine field evidence for the flow of basaltic magma, first, in a 50-m-wide diabase dike that fed the first of the flood-basalt flows in the Hartford basin, second, in a 1.5-m-wide vesicular camptonite dike, and thirdly, through crystal mush in the thick Holyoke flood-basalt flow. The first two stops show that an initial period of upward flow of magma in the dikes was followed by a long period of downward flow before solidification occurred. If this is true of many other dikes, flow directions determined by such techniques as the anisotropy of magnetic susceptibility (AMS) may be recording only the final stages of flow. The AMS results from the camptonite dike show that the flow direction is at right angles to what has been commonly assumed in previous AMS studies. At the third stop, the flow of magma through a thick pile of crystal mush is of particular interest because it demonstrates how basaltic magma can differentiate to produce andesite and rhyolite. Flow through a porous medium, of course, is important in the source region of basaltic magmas, where partial melt along grain boundaries must rise slowly through a porous crystal mush and eventually segregate into larger channels of liquid that can rise more rapidly. These same processes were operating in the thick Holyoke flood-basalt flow as it solidified on the surface. The redistribution of residual liquid through porous flow and eventual formation of segregation sheets of liquid that cut the crystal mush provide an analogous situation to what must be taking place in the source region of basaltic magmas in the upper mantle. Warning: Although stops 1 and 3 are beside the road, the second stop involves a 30-45 minute strenuous hike, after which you are rewarded by a spectacular view of the southern part of the Hartford Basin (this will be our lunch stop, so bring food and drink). The best exposures of the camptonite dike are then found at the bottom of a very steep talus slope (not everyone may want to make this descent). Starting location: Exit 9, on Route 9, 8.2 miles south of Middletown, CT. Starting time: 9:00 a.m. Bring a bag lunch. Saturday, October 11 B1 Classic Helderberg and Onondaga Sections in Eastern New York: Birthplace of American Geology and Early Karst Studies. Trip leader Ernst H. Kastning, New Hampshire Geological Survey [email protected] The Helderberg Mountains and valleys of the Hudson and Mohawk rivers in east-central New York state are considered by many to be the birthplace of modern geology in North America during the middle of the nineteenth century. Early participants of the New York Geological Survey and founders of several state geological surveys studied under Amos Eaton and Ebenezer Emmons within the natural science programs of the Rensselaer School (now Rensselaer Polytechnic Institute) in Troy, New York. Extensive paleontologic and stratigraphic studies of the Helderberg and Onondaga groups (Silurian and Devonian) in Albany and Schoharie counties were among the first in the United States. The Helderberg and Onondaga sections extend well beyond this area, into western New York and south through the greater Appalachian region. This same area was one of the first regions in North America in which speleological studies began. Most of the units within the Helderberg and Onondaga groups are calcareous, consisting of dense limestone and dolostone. Karst is well developed, despite modification of the surface during Pleistocene glaciation. The longest and largest caves in the northeastern U.S. are located in Albany and Schoharie counties.