Abstract The Appalachian peri-Gondwanan realm (APGR) is an extensive tract of exotic Neoproterozoic-early Palaeozoic crustal blocks that occupies the eastern flank of the orogen. Traditionally, southern APGR elements have been correlated with those of the northern Appalachians on the basis of gross geological similarities. Most palaeogeographical reconstructions of the APGR are based on data from the northern Appalachians; consequently in these reconstructions, southern APGR elements are viewed commonly either as being affiliated spatially with those of the north or ignored. However, emerging data from two southern Appalachian crustal blocks give new insights into the palaeo- geography of the APGR. The Smith River allochthon may be a part of the APGR on the basis of recently obtained U-Pb monazite and staurolite ages that are apparently incompatible with a Laurentian origin. The allochthon and possibly adjacent terranes, appear to have followed a palaeogeographical track independent of other APGR elements. The Carolina zone is recognized as peri-Gondwanan in origin on the basis of its (i) gross geological evolution, (ii) fossil fauna and (iii) tectonic history. Mid-Palaeozoic regional kinematic patterns suggest that Carolina and its commonly held northern counterpart, the Avalon zone, travelled together on the same lithospheric plate, but their contrasting tectonic histories suggest that they formed along different margins of this plate. These interpretations lead to a new model for middle Palaeozoic interactions of the APGR with Laurentia.

Location The Cortlandt Complex is located in northern Westchester County, New York, just south and east of the city of Peekskill onthe east bank of the Hudson (Fig. 1). The site is about a one-hourdrive north of New York City; principal access routes from thesouth are U.S. 9 and the Taconic State Parkway. The complexcomprises about 25 mi2 (65 km2) of exposure (Fig. 2) and has aroughly elliptical shape, elongated east-west. Individual localitieswithin the overall site are indicated in Figures 1 and 2, and willbe described in detail below. Stop 1 is in the Popolopen Lake 7½-minute Quadrangle and is located some miles west of Peekstill. It may be reached bytaking U.S. 6 west from Peekskill to Cranberry Hill, about 2 mi (3.2 km) east of the intersection of U.S. 6 and I-84. As a startingpoint of the trip, it may also be reached by taking the U.S. 6 (east) exit on I-84. Stop 2, in the Peekskill Quadrangle, is reached by taking Welcher Avenue (U.S. 9A) south from Peekskill to the town of Buchanan. Turn right onto Tate Street, then bear right at a smalltraffic circle onto Westchester Avenue. Turn right at Buchanan Town Hall and park. Stop 3 is in the Ossining Quadrangle take New York 129 east from U.S. 9 in Croton-on-Hudson for about 2.5 mi (4 km), then turn north (left) on Croton Avenue before crossingthe bridge over the Croton Reservoir. About 0.3 mi (0.5 km) north on Croton Avenue, stop at an abandoned quarry on theleft.