49. THE GEOLOGY AND FORMATION OF THE KING'S TROUGH COMPLEX IN THE LIGHT OF DEEP SEA DRILLING PROJECT SITE 608 DRILLING1

• Main Author: Robert B. Kidd
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Mid-Atlantic Ridge; Sion; Northeast Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.498.8315; http://www.deepseadrilling.org/94/volume/dsdp94pt2_49.pdf

The continuously cored record from Deep Sea Drilling Project Site 608 has been used as a reference stratigraphy with which to compare the results of all previous dredge and rock core sampling of the King's Trough tectonic complex. Some dredge hauls from the axis of King's Trough and Palmer Ridge contain lithologic and stratigraphic units that are absent at Site 608 either because they predate basement formation at the drill site or because they fall within the range of the major upper Eocene-lower Oligocene hiatus that drilling penetrated. Combining the data sets confirms and refines previous models of formation for the complex that involve rifting of an aseismic ridge or hot-spot trace that began its development at the Mid-Atlantic Ridge in the early Eocene (about 56 Ma). Two major intraplate tectonic events subsequently affected this ridge: (1) in the late Eocene (about 32 Ma), intru-sion of trachytic rocks along fault planes, uplift, and explosive volcanicity near sea level; and (2) in the early middle Mi-ocene (about 20 Ma), extensional rifting and subsidence of the basins and deeps of the complex through step-faulting. Palmer Ridge became isolated as a sliver of exposed deep ocean crust during this subsidence. We refrain from discussing new plate kinematic models for the Northeast Atlantic and western Europe, but point out that, whereas the ridge uplift and intraplate volcanism was coeval with the main phase of the Pyrenean orogeny, the extension and rifting of the King's Trough complex was independent of events on the European margin. The complex does not appear to have been a plate boundary at any time.