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.
Geologic Evidence for Rate of Plate Convergence during the Taconic Arc-Continent Collision
The rate of plate convergence during arc-continent collision can be estimated from the rate at which the secondary effects of subduction move across the underriding plate in advance of the plate boundary. The following sequence of events is typical: (1) shoaling and/or emergence of the continental shelf, presumably caused by lithospheric flexure; (2) rapid subsidence, by a combination of normal faulting and trenchward tilting; and (3) a change from platformal to flysch sedimentation. Such a sequence has been recognized in the Taconic foreland basin in eastern New York and interpreted as being the result of collision between the ancient passive margin of North America and an island arc terrane at an east-dipping subduction zone during Medial Ordovician times. A plot of age versus distance across strike shows that the diachronous migration of these phenomena across the foreland proceeded at rates of 2 to 3 cm/yr; we regard this as the plate convergence rate during the latter part of the Taconic Orogeny. Our result is comparable with modern rates of plate motion and also agrees with an earlier estimate for the Taconic, which was based on the rate at which a series of locations on the outer trench slope passed through fossil-defined isobaths.
An Essay on the Nature and Significance of the Normative Nature of Economics
It is conventional in economics to distinguish between the normative and the positive. The normative has to do with goodness and badness, and with what ought and ought not to be done;1 and the positive has to do with objective description and/or explanation, with what is and with what is necessary given some normative end. The normative has to do with desirability; the positive has to do with truth (in the sense of either descriptive accuracy or serviceability of a means to a given end).2