Northeastern Section - 47th Annual Meeting (1820 March 2012)
Paper No. 40-10
Presentation Time: 1:30 PM-5:30 PM


SMITH, Mark R.1, CRESPI, Jean M.1, and STEINEN, Randolph P.2, (1) Center for Integrative Geosciences, University of Connecticut, Storrs, CT 06269,, (2) Connecticut Geological Survey, Department of Energy and Environmental Protection, 79 Elm Street, Hartford, CT 06106

New construction in Lisbon, CT, has exposed large and conveniently accessible roadcuts with a dense and heterogeneous collection of faults. The roadcuts, which are just west of the Tatnic fault, are well-layered gneiss of the Tatnic Hill Formation in the Putnam-Nashoba terrane. Fault-slip data from 90 faults were collected in order to understand the post-Alleghanian brittle deformation.

Fault-slip data were separated into phases using the program T-Tecto and arranged chronologically based upon age relations identified from fault surfaces in the field. Phase 1 consists of a conjugate set of ~NW-SE-striking normal faults coupled with a conjugate set of ~N-S-striking sinistral strike-slip faults and ~E-W-striking dextral strike-slip faults. Phase 2 consists of ~NW-SE-striking strike-slip faults, interpreted as reactivated surfaces from the normal faults of phase 1. Phase 3 lacks a conjugate set and consists of faults that are most likely reactivated surfaces. Each conjugate set from phase 1 was evaluated separately because drag folds observed in the field suggest the strike-slip faults (renamed phase 1b) postdate the normal faults (renamed phase 1a). Phase 1a displays a ~NE-SW σ3, phase 1b displays a ~NW-SE σ1, phase 2 displays a ~N-S σ1, and phase 3 displays a ~ENE-WSW σ1.

The stress orientations are interpreted as related to Mesozoic rifting and subsequent development of the passive margin. Phase 1 stress orientations indicate a change from NE-SW (phase 1a) extension to NW-SE (phase 1b) compression. Phase 1b possibly developed synchronously with structural inversion of the rift basins. Main-phase rifting with NW-SE extension is not seen, suggesting that phase 1a is the transition from rifting to structural inversion. Phase 2 stress orientations indicate N-S compression and are consistent with other observations in New England. Phase 3 stress orientations indicate ENE-WSW compression possibly characterized by the present-day state of stress. Previous work has seen structural inversion in synrift strata in the Fundy rift basin and southeastern United States characterized by NE-striking reverse faults; however, we see structural inversion in basement characterized by conjugate strike-slip faults.

Northeastern Section - 47th Annual Meeting (1820 March 2012)
General Information for this Meeting


Session No. 40--Booth# 27
Structural Geology (Posters)
Hartford Marriott Downtown: Ballrooms A & C and Ballroom Pre-function Area
1:30 PM-5:30 PM, Monday, 19 March 2012

Geological Society of America Abstracts with Programs, Vol. 44, No. 2, p. 97

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