The remarkable early to middle Eocene volcanic sequence of the Crescent Formation exposed on the Olympic Peninsula consists predominantly of tholeiitic to minor transitional alkaline basalts with sparse sedimentary interbeds. A composite section measured in the vicinity of the Dosewallips River includes 8.4 km of pillowed to massive submarine basalts overlain by 7.8 km of subaerial flows. An upper limit of about 48 Ma on the age of the Crescent basalts is indicated by faunal assemblages in sediments interbedded with the uppermost flows in the sequence and a circa 50 Ma 40Ar/39Ar age on a leucogabbro from the presumably correlative Bremerton Igneous Complex. Stratigraphically controlled samples collected from throughout the Crescent basalt sequence show that two distinctly different chemical types exist. The lower part of the sequence originated from a relatively depleted mantle course resembling normal (N) to enriched (E)‐MORB. The upper flows have a chemistry resembling E‐MORB to oceanic island tholeiites. This difference could be due to either variable metasomatism of a single source domain, or influx of a separate enriched‐mantle source component during the extrusion of the upper part of the sequence. Paleomagnetic measurements indicate that the Crescent basalts have not been significantly rotated, nor translated northwards since their extrusion. Paleotectonic reconstructions show that formation of the Crescent basalts and the Coast Range volcanic province as a whole coincided with a marked increase in the velocity of oblique convergence of the Kula plate with North America at about 60 Ma. Other geologic, geochemical, and paleomagnetic data are consistent with the interpretation that extrusion occurred in a basin or series of basins formed by a rift system along the continental margin of North America. Rifting might have been initiated by the influence of a hotspot, an increase in the rate of oblique convergence, or the kinematic effects of the Kula‐Farallon ridge as it migrated along the margin. If extrusion is related to the passage of the triple junction, then the Coast Ranges can be considered to be an important tectonic marker for early to middle Eocene plate reconstructions.

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A paleomagnetic study of 14 sites in the baked sedimentary rocks of the Newark basin Passaic Formation in southeastern Pennsylvania reveals two types of magnetic behavior. Dark gray-colored, baked sedimentary rocks have peak unblocking temperatures of 640øC, high magnetic intensities, and shallow, normal polarity, northeasterly directions. Light gray-colored rocks have peak unblocking temperatures of less than 580øC, low magnetic intensities, and intermediate inclination, normal polarity, northwesterly directions. The low unblocking temperature magnetizations are secondary magnetizations which have declinations similar to but are shallower than the B remagnetization observed by Witte and Kent (1991) throughout the Newark basin. The discrepancy may be due to "underprinting" by an unresolved primary magnetization. The low unblocking temperature magnetization was probably acquired by growth of secondary magnetite during a hydrothermal event, as postulated by Sutter (1988), based on geochronologic data. The high unblocking temperature magnetization is significantly prefolding. Both the low-peak unblocking temperature magnetization and the high-peak unblocking temperature magnetization suggest a 15 ø counterclockwise block rotation of the Sassamansville syncline. If this rotation is removed from the high unblocking temperature sites collected around the fold, a stronger passage of the fold test results. Six sites were also collected from baked sediments and one site from diabase in northern Virginia's Culpeper basin, since Sutter's geochronological work indicated that the intrusives in the Culpeper basin are coeval to the Newark basin intrusives. Virtual geomagnetic poles (VGPs), based on the tilt-corrected, high-temperature Newark basin magnetizations, were compared with the VGPs calculated from the site means of a high-temperature magnetization isolated from baked sedimentary rocks in the Culpeper basin and to the magnetizations reported by Raymond (1982) from dikes and sills. In this comparison the in situ Culpeper poles agreed with the prefolding Newark poles significantly better than the prefolding Culpeper poles. This result indicates that Culpeper intrusives erupted into already tilted sedimentary rocks. The paleomagnetic pole determined from the combined Culpeper baked sediments, dikes, and sills (in situ coordinates) and the Newark basin baked sediments (tilt-corrected Paper number 94TC00294. 0278-7407/94/94TC-00294510.00 coordinates) lies at 60øN,69øE and is of 201 Ma age. This latest Triassic/earliest Jurassic pole, when combined with the Newark basin Carnian results (Witte and Kent, 1989) and Norian results (Witte et al., 1991) corrected for a counterclockwise block rotation (Kodama et al., 1994), provides a record of significant polar wander from eastern North America's Mesozoic basins for the Late Triassic. This is consistent with observations made for a similar time period from rocks on the Colorado Plateau (Bazard and Butler, 1991). Comparison of the Newark/Culpeper pole to similar age poles from the K...

Abstract. Dating magnetizations in Precambrian rocks is increasingly important in the attempt to unravel Precambrian plate configurations and supercontinent assemblages. We used lowtemperature demagnetization and modern thermochronometric methods to dissect a multicomponent magnetization of the Glamorgan Gabbro, Ontario, previously studied by Butban and Dunlop

The Nelson Field is located in Blocks 22/11, 22/6a, 22/7 and 22/