Structure, Stratigraphy, and Climate of the Mesozoic Chignecto Subbasin, Bay of Fundy, Canada
WITHJACK, MARTHA O., and MARTIN H. LINK, Mobil Research and Development Corporation, Dallas, TX, and PAUL E. OLSEN, Lamont Doherty Geological Observatory, Palisades, NY
The Chignecto subbasin is one of three Triassic/Jurassic subbasins in the Bay of Fundy rift system of southeastern Canada. Although no wells have been drilled in the subbasin, offshore seismic data and onshore outcrop data show that the basin contains typical rift structures and stratigraphy.
The Chignecto subbasin is an asymmetric rift basin bounded on the west by a series of gently to moderately dipping normal faults. The seismic data show that the total heave on these boundary faults locally exceeds 10 km. Most strata within the basin dip gently to the west toward the boundary faults. Field data show that a divergent wrench fault zone composed of numerous strike-slip, oblique-slip, and normal faults bounds the Chignecto subbasin on the south. The normal faults bounding the basin on the west and the divergent wrench fault zone on the south are reactivated Paleozoic compressional structures.
Major stratigraphic features in the Chignecto subbasin include an unconformity that subdivides the basin strata into pre- and syn-rift sequences and an asymmetric arrangement of sedimentary and seismic facies and corresponding lithologies. The Triassic/Jurassic syn-rift strata within the basin thicken toward the western boundary faults. Coarser-grained strata of alluvial-fan and fluvial origin interfinger with finer-grained strata of fluvial and lacustrine origin near the boundary faults. Eolian deposits and evaporites in adjacent Mesozoic rift basins indicate an arid climate for the Late Triassic/Early Jurassic. Large-amplitude reflections observed within the western half of the basin probably represent high-velocity evaporites or carbonates deposited within the deepest part of the C ignecto subbasin.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)