Joe Gonzales (2017 CNYAPG Student Scholarship recipient), "Pressure-temperature-time histories across the Burgess Branch Fault Zone, northern Vermont"
Metamorphic rocks in the Tillotson Peak Complex, northern Vermont, provide evidence for subduction processes during the Taconic Orogeny (470-450 Ma). Previously documented metamorphic fabrics and 40Ar/39Ar data were interpreted to record deformation from multiple orogenies. A glaucophane total fusion 40Ar/39Ar age constrains the timing of Taconic high-pressure (HP) metamorphism as 468 ± 6.4 Ma (Laird et al., 1984). The Burgess Branch Fault Zone (BBFZ), a polydeformed steep eastward dipping normal fault (present day), separates Tillotson Peak (footwall) blueschists and metapelites from Ottauquechee Formation metapelites (hanging wall). P-T-t histories were derived from samples collected along a transect across the Tillotson Peak Complex and into the BBFZ. Total fusion 40Ar/39Ar geochronology on phengite and K white mica-chlorite thermobarometry were used to constrain P-T-t. Chemically homogeneous phengites in garnet mica schist from the Hazen’s Notch Formation within the Tillotson Peak Complex yielded pressures of 16-20 kbar assuming 450oC and an 40Ar/39Ar age 480 ± 1.3 Ma (1). Another garnet mica schist yielded an age of 468 ± 1.8 Ma. A Hazen’s Notch Formation mica schist farther east yielded pressures of 9-12 kbar at 450oC and an age of 478 ± 1.3 Ma. Within the BBFZ, petrographic observations reveal chemical zoning and intergrowth of different composition phengites suggesting partial to complete recrystallization. A BBFZ Hazen’s Notch Formation phengite yielded recrystallization P-T as 6-8.5 kbar at 370oC and an age of 407 ± 1.3 Ma. BBFZ Ottauquechee Formation phengites yielded ages of 417 ± 1.2 Ma and 415 ± 1.8 Ma. A Stowe Formation phengite yielded an age of 436.7 ± 1.2 Ma. P-T data indicate that Hazen’s Notch schists may have formed at greater depths than previously known. The 40Ar/39Ar total fusion ages are concordant with those of previous studies, and 468-480 Ma ages in Hazen’s Notch schist are possibly related to exhumation of HP metamorphic rocks. In contrast, 407-417 Ma recrystallized BBFZ phengites appear to be unrelated to exhumation of HP lithologies, instead they are possibly related to the late-reactivation deformation.
Mariana Rhoades will introduce her new book "HISTORIC QUARRIES & THE STONE INDUSTRY ERIE COUNTY, NY, 1820-1930"
Liz Moran of EcoLogic LLC will discuss the major findings of the Cayuga Lake Modeling Project (CLMP), a detailed evaluation of the sources and fate of phosphorus loading to Cayuga Lake from point and nonpoint sources. The NYSDEC required Cornell University to fund the CLMP as a permit requirement for continued operation of the Lake Source Cooling facility. The university and NYSDEC designed the CLMP to provide knowledge and tools for a rational, science-based approach to managing Cayuga Lake and other regional waters. EcoLogic managed communications among the many researchers, modelers, and institutional partners on behalf of Cornell’s Facilities and Energy Management Division.
The investment of four years and three million dollars resulted in a deeper understanding of three issues central to managing Cayuga Lake and other regional waters: phosphorus sources, phosphorus bioavailability (i.e., potency for supporting phytoplankton growth), and the impact of water motion on distribution of phosphorus and phytoplankton.
USGS will present results of a unique project in the Genesee River valley, in relation to the former Retsof/AKZO-Nobel salt mine. All remedial operations have shut down at the flooded mine, but brine is slowly being forced up through two collapse chimneys between the mine and the buried bedrock surface in the Genesee River valley. This brine is slowly being assimilated into the basal glacial aquifer and the New York State Department of Environmental Conservation wants to know where this brine is moving and its fate into the future. All monitoring wells related to the mine collapse and closure, and short-lived brine remediation project were sealed several years ago.
The USGS is using Time Domain Electromagnetics (TEM) - a non-invasive surface geophysical approach to determine where the high conductivity brine is moving. Data collected in the fall of 2016 indicated that the higher conductivity water can be seen to depths of 1,000 ft, and results of 39 TEM soundings across and along a section of the Genesee valley show that the brine is flowing to the thalweg of the valley and apparently slowly dispersing in the basal aquifer as the brine mixes with natural (fresher) groundwater.
Field trip date is tentative.