HR: 09:50h
AN: A51F-12    [Abstracts]
TI: Implications of the Cyclostratigraphy of Jurassic Lacustrine Strata of the Hartford Rift Basin (CT and MA, USA) for the Time Scale of the Early Mesozoic
AU: * Olsen, P E
EM: polsen@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964-1000, United States
AU: Kent, D V
EM: dvk@rci.rutgers.edu
AF: Department of Geological Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, United States
AU: Whiteside, J H
EM: Jessica_Whiteside@Brown.edu
AF: Geological Sciences, Brown University, 324 Brook Street, Box 1846, Providence, RI 02912, United States
AB: The Hartford basin of CT and MA contains at least 7 km of continental deposits formed during the Late Triassic and Early Jurassic. About 3 km of the middle part of the section beginning at the oldest flood basalt sequence of Jurassic age, part of the CAMP LIP, are characterized by fine-grained lacustrine strata that based on fourier analysis exhibit a hierarchy of sedimentary cycles characteristic of Milankovitch climate forcing. Cycles with periods of ~20, ~100, and 405 ky are present and a larger scale cyclicity with a period of 1.75 m.y. carries on from the Triassic pattern seen in continuous core from the 100-km distant cyclical Newark basin sequence. Six virtually complete 405 ky cycles are present, with the oldest one beginning close to the Triassic-Jurassic boundary. Based on paleomagnetic polarity stratigraphic correlation with the Moncornet core of the marine Paris basin (Yang et al., 1996 J.G.R. 101:8025), the youngest of these 400 ky cycles is of early Sinemurian or very latest Hettangian age, giving a duration for the Hettangian of approximately 2 m.y. Assuming an age of approximately 201.3 Ma for the basal lava flow (from Schoene et al, 2006, Geochem. Cosmochim. Acta 70:426), this gives a Hettangian-Sinemurian boundary age of about 199 Ma, with the precision limited by the biostratigraphy in the Moncornet core. This age is in agreement with the new high-precision U-Pb dates from marine sections (Pálfy & Mudil, 2007, Volumina Jurassica, IV:294), providing independent confirmation of the orbital forcing interpretation.
DE: 0399 General or miscellaneous
DE: 1165 Sedimentary geochronology
DE: 1520 Magnetostratigraphy
DE: 3205 Fourier analysis (3255)
DE: 9611 Jurassic
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting