New York State Geological Association
The Chazy, Black River and Trenton Groups are a well studied sequence of fossiliferous limestones, dolostones and sandstones in the Champlain Valley of New York, Vermont and southern Quebec. These rocks record shallow water cyclic sedimentation in the foreland basin of Laurentia prior to and during the initial stages of the Taconic Orogeny. This field trip reviews the stratigraphy of these units, as well as the evidence for reconstructing depositional environments and cyclic sea level changes.
Comparison of Foreland Basin Sequences: The Trenton Group in Southern Quebec and Central New York: Chapter 10
Numerous high-angle faults that were active during deposition are recognizable within the autochthonous, Upper Ordovician, Trenton Group ramp sequence in southern Quebec. The facies of the Trenton Group in southern Quebec can be compared to those in New York and can be shown to be controlled by proximity to, or position within, the Taconic foreland basin.
Some new evidence on lithospheric bulges close to island arcs
Abstract The wavelength and position of the crest of the bulge in a lithospheric plate being subducted at a trench is difficult to determine from bathymetric profiles because of topographic irregularities. It is therefore proposed that Bouguer anomaly profiles and the position of the outer gravity maxima be used to determine these parameters as there is a close correspondence between the flexed lithosphere and the gravity profiles. A gravity profile across the New Hebrides Trench has been used in conjunction with observations on the level of raised atolls of the Loyalty Islands to determine the crest—trench distance and the wavelength of the lithosphere in this region. These give values which agree well with theoretical predictions. However, it has not yet been possible to determine the rate of elevation of the Loyalty atolls. On Niue Island of the Cook Archipelago, the rate of elevation is known from radiometric soil methods and in the absence of a gravity profile, a bathymetric profile has been used to determine the parameters of this bulǵe at the Tonga Trench. This yields a rate of convergence of 9 cm/year. However, the results do not have sufficient accuracy to resolve whether ancillary basinal growth is presently taking place in the Lau-Havre Trough, which could otherwise be ascertained by comparing the rate of convergence at the trench with the rate of spreading at associated mid-ocean ridges.