ABSTRACT: Spectral analyses of apparent cyclicity of Triassic-Jurassic strata in the Newark Basin (New Jersey, USA) have been used to generate peak recurrence intervals within the sequence. When calibrated to sedimentation rates derived from varve counts in lacustrine mudstones, these recurrence intervals yield cycles inferred to correspond to orbital forcing at basic precession, eccentricity and long eccentricity frequencies. Consequently, the Newark basin cyclostratigraphy has been proposed as a floating astrochronology capable of providing a continuous high resolution geochronometry for most of the Late Triassic and part of the Early Jurassic. Indeed, orbitally-forced cyclicity does appear to be the dominant control of some portions of the Newark Basin section, particularly in the Lockatong and lower Passaic formations. But the application of the Newark Basin cyclostratigraphy as chronostratigraphy requires that the stratigraphic record is complete, i.e. no substantial erosional or depositional gaps exist, and cyclical throughout. Several lines of evidence indicate that these requirements are not met. Outcrop and core data demonstrate that portions of the Newark Basin stratigraphic section are non-cyclic, particularly in the fluvial-dominated strata of the upper Passaic Formation and the Stockton Formation. Correlation of available biostratigraphic data, including both pollen and conchostracan zones between the Newark Supergroup and the Germanic Triassic, indicates that most of Rhaetian and a portion of late Norian time is not represented by sediment in the Newark Basin and elsewhere in the Newark Supergroup. This suggests that at least 3 Myr of Late Triassic time is not recorded by strata in the Newark Basin. The inability of the Newark cyclostratigraphy to unambiguously locate and date the base of the Rhaetian or to produce a numerical age for the base of the Norian compatible with independently derived constraints demonstrate that the Newark Basin cyclostratigraphy is not a valid “floating astrochronology.” At best, only the middle late Carnian through early late Norian interval, about 10 Myr in duration, may be sufficiently complete to be useful for astrochronological purposes. In great part, the problems with utilizing the Newark Basin record as the basis for an astrochronology result from an inability to make unambiguous correlations to the marine record. Resolution of these issues and discrepancies could potentially be achieved through the collection of additional data, such as magnetostratigraphic data from continuous Upper Triassic marine sections.
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