Site 385: Volcanism at Vogel Seamount in the Central New England Seamount Chain

'Brian E. Tucholke (Co-Chief Scientist), Lamont-Doherty Geological Observatory, Palisades, New York; Peter R. Vogt (CoChief Scientist), Naval Research Laboratory, Washington, D.C.; Kenneth R. Demars, University of Rhode Island, Kingston, Rhode Island (now at: University of Delaware, Newark, Delaware); Jon S. Galehouse, San Francisco State University, San Francisco, California; Robert L. Houghton, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts (now at: University of Alberta, Edmonton, Alberta, Canada); Ansis Kaneps, Deep Sea Drilling Project, Scripps Institution of Oceanography, La Jolla, California; John W. Kendrick, Shell Development Company, Houston, Texas; I. N. McCave, University of East Anglia, Norwich, England; Charles L. McNulty, University of Texas, Arlington, Texas; Ivar O. Murdmaa, P. P. Shirshov Institute of Oceanology, Moscow, USSR; Hisatake Okada, Lamont-Doherty Geological Observatory, Palisades, New York (now at: Yamagata University, Yamagata, Japan); and Peter Rothe, Mineralogisch Petrografisches Institut der Universitàt Heidelberg, Heidelberg, Federal Republic of Germany (now at: Geographisches Institut der Universitàt Mannheim, Mannheim, Federal Republic of Germany). site, where it occurs 0.2 sec sub-bottom and 0.17 sec above the volcaniclastic apron. A total of 24 cores (227.6 m) was taken; the low overall recovery (63.4 m) reflects poor coring performance in cherts and uncemented volcaniclastic sands and gravels. Formations encountered are as follows: A discontinuously cored section of Pleistocene to upper Oligocene clays (0-138 m) overlies continuously cored upper lower Eocene clays and chert (138-165 m sub-bottom) containing a rich and well-preserved radiolarian fauna. Horizon A correlates with an alternating chert and radiolarian ooze in¬ terval approximately 153-165 meters sub-bottom. The sec¬ tion from 165 to 206 meters consists of zeolitic silty clay containing poorly preserved and unidentified radiolarian assemblages. Lowermost Danian to middle Maestrichtian marly ooze (206-251 m) overlies volcanogenic sediments older than middle Maestrichtian that continue to 393 meters. A thin (18 cm) layer of aphanitic basalt was cored at 283 meters; this could be either a sill, a flow, or a dis¬ placed boulder; however, its young radiometric age (21 ±3 m.y.) suggests it is a sill intruded during a period of minor volcanic rejuvenation during the early Miocene. The deepest volcanic material penetrated is a volcaniclastic breccia very similar to that recovered at Site 382 at Nashville Seamount. As at Nashville, breccia was recovered at two levels and episodic volcanism is suggested. The relatively inactive period is nevertheless represented by volcanogenic sedi¬ ments, and both episodes of breccia emplacement probably occurred within a few million years or less. Basalt fragments extracted from the breccia are highly alkalic, vesicular, and relatively enriched in light rare earths. The fragments were derived from various eruptive events, at least some of which occurred at depth of less than 0.5 to 1 km below sea level. Unfortunately, the volcanic unit is unfossiliferous ex¬ cept for a few long-ranging benthic foraminifers of possible. Coniacian-Santonian age, and the deepest reliable dates in the hole are for the Maestrichtian marly ooze above the unit. However, the two most reliable radiometric dates on the lower breccia (82.1 ± 8 and 91.2 ± 3 m.y.), in combination with other data, suggest the main constructional volcanism on Vogel Seamount may have occurred about 87 to 92 m.y.B.P. Although this makes Vogel Seamount slightly older than Nashville and would be consistent with plate mo¬ tion over a stationary hot spot at ~ 4 cm/yr, the age dif¬ ference may not be significant. Thus, simultaneous volcanism cannot be excluded.