Presentation on theme: "Hinged Alleghanian Uplift of the Bronson Hill terrane in Connecticut and Massachusetts Elizabeth R. Goeke, Julie L. Boyd, and Robert P. Wintsch Indiana."— Presentation transcript:
Hinged Alleghanian Uplift of the Bronson Hill terrane in Connecticut and Massachusetts Elizabeth R. Goeke, Julie L. Boyd, and Robert P. Wintsch Indiana University, Bloomington, Indiana
Research support by: Geological Society of America Student Research grants awarded to Elizabeth R. Goeke and Julie L. Boyd National Science Foundation grants #EAR 91- 04495 (R. P. Wintsch) and #EAR99-09410 (R. P. Wintsch) Department of Geological Sciences, Indiana University
Goals: To evaluate the Alleghanian overprint on rocks previously metamorphosed in the Acadian Orogeny.
Why the Bronson Hill terrane? The entire terrane was metamorphosed during the Acadian Orogeny. The terrane extends from the Long Island Sound to the New Hampshire/Canadian border. Cooling ages from Connecticut in the Bronson Hill are indicative of cooling from Alleghanian events.
Julie’s horn ages on a map
Julie’s musc ages on a map
Ponder the Difference: Hornblende ages are cooling from Alleghanian heating in the south and the Acadian Orogeny in the north. Muscovite ages are fairly uniform the length of the terrane and indicative of cooling from Permian heating.
Map of ERG samples
Thermometers and Barometers: Holland and Blundy, 1994 hornblende-plagioclase thermometer Graham and Powell, 1984 garnet-hornblende thermometer Kohn and Spear, 1989 and 1990 garnet-hornblende-quartz-plagioclase barometer
Various P-T paths with gar-hb points, hb-pl points, and exhumation lines
Conclusions: The southern portions of the Bronson Hill were buried to greater depths during the Alleghanian Orogeny than those in northern Connecticut and Massachusetts. The Bronson Hill was exhumed quicker in the south than to the north.