Open AccessA compaction correction for the paleomagnetism of the Nanaimo Group sedimentary rocks: Implications for the Baja British Columbia hypothesis
Author(s) -
Kim BangYeon,
Kodama Kenneth P.
Publication year - 2004
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003jb002696
Subject(s) - geology , paleomagnetism , cretaceous , sedimentary depositional environment , sedimentary rock , bedding , paleontology , concretion , continental margin , bed , apparent polar wander , remanence , magnetic dip , geomorphology , anisotropy , geophysics , magnetization , structural basin , tectonics , physics , quantum mechanics , magnetic field , horticulture , biology
A paleomagnetic and magnetic anisotropy study of the Late Cretaceous Northumberland formation on Hornby Island, British Columbia, was conducted to determine if burial compaction could have caused its anomalously shallow inclinations. The shallow Nanaimo Group inclinations have been used to support the Baja British Columbia (Baja BC) model of continental dynamics in which superterranes were transported thousands of kilometers northward along the active North American continental margin in the Cretaceous. A mean of the site means from the Northumberland formation is D = 5.8°, I = 50.9°, α 95 = 7.9° ( N = 8). Anisotropy of magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence (AAR) were measured to identify and correct for any inclination shallowing caused by depositional/compactional processes. Both concretion and fine‐grained rock samples had typical depositional/compactional AMS and AAR fabrics with bedding perpendicular minimum principal axes. A revised correction equation was used to account for the effects of either triaxial magnetic fabrics or small angular deviations of principal axes from the bedding plane. The average inclination was increased by 9.6° after the compaction correction ( D = 6.1°, I = 60.5°, α 95 = 7.1°, N = 8), and the mean inclination of concretion and fine‐grained rock sites was significantly steeper than Ward et al. 's [1997] result ( I = 42.5°) placing Hornby Island and the Insular superterrane at a paleolatitude of 41°N in the Late Cretaceous. This paleolatitude indicates that Baja BC did translate northward since the Late Cretaceous by about 1600 km but not by the 3500 km previously indicated.