Geologic and geophysical evidence for a clockwise rotation of shortening direction along the Appalachian front through the Late Paleozoic is accepted but details of the timing of this rotation are incomplete. To explore this hypothesis we examine structural, petrologic and thermochronologic data from southern New England to determine if evidence there supports this proposition.

Late Paleozoic dextral transpression toward ~240° is well documented in the Minas and Norumbega fault zones (Murphy et al, 2011; West and Hubbard, 1997). This was followed in southern New England by deformation event, D1, with NW shortening toward ~315° that wedged Avalon terrane rocks into Ganderian rocks producing foliations S1. A D2 event folded S1, producing the Lyme Dome, with shortening toward 315° that produced S2 trending to ~040°. Walsh et al. (2007) identified a third deformation D3, an overprinting foliation S3 in the Lyme Dome striking ~260°. A final deformation D4 refolded earlier structures with axial surfaces striking ~300° producing the Montville Dome and other folds east of the Lyme Dome (Goldsmith 1985) and a km-scale sheath fold in Westbrook Connecticut where fold axes and mineral lineations plunge ~60° toward 015 indicating NNE D4 vergence.

Geochronology including U-Pb ages of zircon, monazite, and sphene, and ⁴⁰Ar/³⁹Ar amphibole cooling ages (Wintsch et al. 2002; Aleinikoff et al. 2007; Walsh et al. 2007; Deasy and Wintsch 2019; 2020) show that S1 (parallel to the Honey Hill fault) was produced between ~315 and 290 Ma. In the Lyme Dome area S2 occurred between 288 and 280 Ma, and S3 occurred ~275 Ma (Walsh et al. 2007). The age of D4 is constrained to be older than regional amphibole cooling ages of ~260 Ma supported by the ages of recrystallized sphene separates from the D4 Falls River fault of ~261 Ma. Together these data from southern New England show a clockwise rotation of vergence from ~315° to 030° from ~ 290 to 260 Ma. Such rotation is supported locally by similar rotation of Foliation Intersection Axes in Rhode Island (Rich, 2006), and by regional structures that dome and deform Acadian structures and fold Permian ductile faults. This uniform pattern of regional rotation adds strong support to the rotation of Gondwana during its protracted approach to Laurentia that ultimately formed Pangea.