Late Quaternary history and paleoecology of a small oxbow wetland on glaciated terrain were investigated using sediment lithology (cores, bulk samples, backhoedug trenches), ground-penetrating radar, vascular plant and moss macrofossil stratigraphies, and accelerator mass spectrometric radiocarbon dating. A nearly complete mastodon skeleton was recovered from late Pleistocene detrital peat and peaty marl near the top of the sediment sequence. Sedimentation in the basin began with silt and clay over dense cobble outwash transported southward from the nearby Hyde Park Moraine. Overbank sediment deposition occurred between ∼13,000 and 12,220 yr B.P. during a period of tundra vegetation, which ended with a sharp rise in spruce needle abundance and a shift to autochthonous marl and finally peat deposition. Fossils of aquatic and wetland plants began to accumulate before the tundra-spruce transition and increased after it. Rich fen wetland began to infill the pond with peat, while the upland supported open white spruce and later white spruce–balsam fir–tamarack forest. The mastodon, 11,480 ± 40 radiocarbon years old, was contemporaneous with spruce–balsam fir–tamarack forest and rich fen wetland. Many mastodon bones were articulated or nearly so, indicating that the animal died in the basin and that postmortem bone dispersal was slight.

Abstract The Hudson Valley fold-thrust belt of eastern New York State involves a relatively thin sequence of shallow-marine Silurian and Lower Devonian strata. Because of the thinness of this sequence, structures of the belt are relatively small. Thus, first-order ramps and flats, and fault-related folds can be seen in their entirety at a single roadcut. A field trip in the southern half of the Hudson Valley fold-thrust belt, from the latitude of Catskill to the latitude of Rosendale, provides an opportunity to see many examples of these structures, and to discuss the three-dimensional architecture of fold-thrust belts in an orocline. In particular, we will see how along-strike changes in stratigraphy affect fold wavelength and the depth of detachment horizons. The trip also provides the opportunity to examine the relationship between mesoscopic structures (e.g., solution cleavage and veining) and first-order structures.

The Taconic melanges of eastern New York developed through the progressive deformation of a synorogenic flysch sequence deposited within a N-S elongate foreland basin. This basin formed in front of the Taconic Allochthon as it was emplaced onto the North American continental shelf during the medial Ordovician Taconic Orogeny. The flysch was derived from, and was subsequently overridden by the allochthon, resulting in the formation of belts of tectonic melange. An east to west decrease in deformation intensity allows interpretation of the structural history of the melange and study of the flysch-melange transition. The formation of the melange involved: isoclinal folding, boudinage and disruption of graywacke-shale sequences due to ductility contrasts; sub-aqueous slumping and deposition of olistoliths which were subsequently tectonized and incorporated into the melange; and imbrication of the overthrust and underthrust sedimentary sections into the melange. The characteristic microstructure of the melange is a phacoidal conjugate-shear cleavage, which is intimately associated with high strains and bedding disruption. Rootless isoclines within the melange have apparently been rotated into an east-west shear direction, consistent with fault, fold, and cleavage orientations within the flysch. The melange zones are best modeled as zones of high shear strain developed during the emplacement of the Taconic Allochthon. Total displacement across these melange zones is estimated to be in excess of 60 kilometers.