PALEO-FLUID HISTORY OF THE NITTANY ANTICLINE, VALLEY AND RIDGE PROVINCE OF PENNSYLVANIA
Fluid inclusion microthermometry provides insight into trapping conditions, including pressure, temperature and fluid chemistry. Most inclusions are two-phase aqueous inclusions that have ice-melting temperatures of -24.2 to -9.5 °C (13.4 to 25.2 wt. % NaCl equiv. salinity). Eutectic values range from -47 to -39 °C and indicate CaCl2 - NaCl basinal brines. Homogenization values for the southern fold plunge-out range from 123 to 145 °C and reflect a trapping depth of 4.2 – 6.4 km at lithostatic conditions. In the western overturned limb, homogenization values have a very wide range (80 to 167 °C) and reflect multiple trapping events. Maximum trapping depth is 7.3 km. Based on the current preserved stratigraphic section through the Mississippian, little to no Pennsylvanian - Permian synorogenic sediment was deposited over the Nittany anticline.
Vein isotopic and fluid inclusion data indicate that there was moderate fluid connectivity during the formation of the Nittany Anticline. Samples from the southern plunge-out have δ18O vein isotope values that are 2-3 ‰ lower than the host rock, while δ13C values show little to no difference from the host. The veins in the western overturned limb have δ18O values ~1 ‰ greater than host rock and δ13C values 1-1.5 ‰ lower. Two samples from the Linden culmination, which have veins similar to each other (approx. δ18O 1.5 ‰ lower, δ13C 3.0 ‰ lower than the host rock).