|Northeastern Section - 47th Annual Meeting (18–20 March 2012)|
|Paper No. 12-2|
|Presentation Time: 1:50 PM-2:10 PM|
CORRELATION OF EXTRUSIVE UNITS OF NORTH MOUNTAIN BASALT AND CENTRAL HIGH ATLAS CAMP LAVAS USING GEOMAGNETIC PALEOSECULAR VARIATION
KENT, Dennis V.1, WANG, Huapei1, and OLSEN, Paul E.2, (1) Earth and Planetary Sciences, Rutgers University, Wright-Rieman Labs, 610 Taylor Road, Piscataway, NJ 08854, email@example.com, (2) Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-1000|
In the Newark basin , the level marking the end-Triassic extinction event occurs one Van Houten cycle (~20 kyr) before the first CAMP basalt and is preceded within less than another Van Houten cycle by reverse polarity Chron E23r, one of the shortest (~25 kyr) polarity intervals recognized in the Newark astronomically-tuned geomagnetic polarity time scale. This same tight chronostratigraphic sequence of events is recorded in the Fundy basin of Nova Scotia , where the initial CAMP extrusive unit (North Mountain Basalt) has a precise U-Pb zircon date of 201.27± 0.03 Ma . In the Central High Atlas Mountains of Morocco, two magnetic excursions were found within the Intermediate Basalt (39Ar/40Ar date of 199.9± 0.5 Ma) and somehow might correlate to E23r [4, 5]; this would imply that the underlying Lower Basalt was erupted prior to the end-Triassic extinction event but the reliability of the excursion data seems doubtful . Paleomagnetic study of the Moroccan basalts also revealed systematic groupings of magnetic directions, which were interpreted as a record of secular variation . We sampled most if not all of the lava flows in the Fundy basin that comprise the ~300 m-thick North Mountain Basalt in outcrop (30 sites) as well as in several industry cores drilled near Margaretsville, Nova Scotia (e.g., GAV-77-3). We find only two directional groupings for the entire North Mountain Basalt, a finding that basically confirms the results of Carmichael and Palmer  and suggests very rapid extrusion. The progression of VGP clusters corresponding to the directional groups for the North Mountain Basalt resemble the VGP clusters corresponding to directional groupings reported  for the upper Lower and lower Intermediate lavas from Morocco. We speculate that the episodic volcanicity associated with initial phases of CAMP can be correlated over (predrift) distances of ~1000 km on submillennial time-scales of paleosecular variation.
References: 1, Olsen, P.E. et al., 2002, GSA Spec. Paper 356:505–522; 2, Deenen, M.H.L. et al., 2011, CJES 48:1282-1291; 3, Schoene, B. et al., 2006, GCA 70:426–445; 4, Marzoli, A. et al., 2004, Geology 32:973–976; 5, Knight, A.B. et al., 2004, EPSL 228:143–160; 6, Font, E.N. et al., 2011, EPSL 309:302-317; 7, Carmichael, C.M. & Palmer, H. C., 1968, JGR 73:2811-2822.
Northeastern Section - 47th Annual Meeting (18–20 March 2012)
General Information for this Meeting
|Session No. 12|
The CAMP Province: Compositional Variation, Sources, and Environmental Effects
Hartford Marriott Downtown: Ballroom D
1:30 PM-3:30 PM, Sunday, 18 March 2012
Geological Society of America Abstracts with Programs, Vol. 44, No. 2, p. 56
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