Scientific Ocean Drilling Accomplishments and Challenges (2011) / Chapter Skim
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2 Scientific Accomplishments: Solid Earth Cycles
2 Scientific Accomplishments: Solid Earth Cycles
Pages 13-26
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From page 13... ...
, a lynchmagnetic field, the processes of continental rifting, the sub pin for establishing the paradigm of plate tectonics in the duction of oceanic lithosphere, and voluminous outpourings early 1970s. Scientific ocean drilling focused on obtaining of magma onto the crust, for example, are significant mani ages of the seafloor magnetic reversal stratigraphy and corfestations of solid Earth cycles and are recorded in rocks on responding biostratigraphic ages of sediments at successive the ocean floor.
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From page 14... ...
. ODP Leg 197 pro vided compelling paleomagnetic evidence that from about 76 to 45 myr the Hawaiian hotspot was rapidly migrating phy recovered from ocean sediments at ODP Sites 677 and southward to reach its present position, a finding that held 846, where benthic and planktonic foraminiferal dates were implications for reconstructing past Pacific plate motions and correlated with Earth's orbital variations (e.g., Shackleton also for the concepts of plume stability and mantle dynamics et al., 1990; also see Chapter 4)
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From page 15... ...
its composition, genesis, and structure, and the causes and consequences of different ridge spreading rates, is through STRUCTURE, COMPOSITION, AND the type of sampling enabled by scientific ocean drilling. FORMATION OF OCEANIC LITHOSPHERE Scientific Accomplishments and Significance Earth's lithosphere consists of the crust and the nonconvecting portion of the upper mantle, formed by repeated One motivation for early drilling into ocean crust was to magmatic activity at mid-ocean ridges.
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From page 16... ...
Although the during IODP legs and in the amount of recovered core. For total number of holes drilled into ocean crust between 1974 example, IODP Hole 1309D on the Atlantis Massif along the and the end of ODP in 2004 is about 50, these early efforts Mid-Atlantic Ridge penetrated to a depth of 1,415 m, and were hampered by technical difficulties in both penetrating Hole 1256D in the equatorial east Pacific penetrated to 1,507 the very dense crystalline rock and recovering samples.
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From page 17... ...
study of intact ocean crust and opholites exposed on land. Fields of Inquiry Enabled Goals Not Yet Accomplished Rocks recovered by DSDP, ODP, and IODP have Although considerably more is now known about fueled studies and advancements in geochronology, experi- oceanic lithosphere than before scientific ocean drilling mental petrology, geochemistry, geodynamics, seismology, began, major questions remain because so few holes have submersible-aided outcrop mapping and sampling, and struc- penetrated more than 500 m into the lithosphere.
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From page 18... ...
. of the lower ocean crust to determine its vertical stratigraphy Nearly coincident with the initial DSDP rifted-margin and composition with depth, the processes by which it forms, legs, dredging on the flank of the Galicia Bank recovered and how these shape the composition of mid-ocean ridge mantle peridotites and set the stage for ODP Leg 103, which basalt, the most abundant magma type on Earth.
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From page 19... ...
, Broken Ridge (ODP Leg mal fault thought to play a major role in the thinning of con120) , and Woodlark Basin (ODP Leg 180)
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From page 20... ...
of an iterative process that also required both onshore and offshore geophysical and geologic calibration and validation, and geodynamic modeling. Fields of Inquiry Enabled The formation of magma-rich margins and associated The discovery of exhumed mantle during drilling LIPs has also recently been linked to biotic events and dipole expeditions along the Iberian Margin prompted extensive reversal frequency, especially in the case of the North Atlanreinterpretation of existing seismic data and acquisition of tic and associated SDRs (Eldholm and Thomas, 1993)
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From page 21... ...
ODP Legs 125 and 195 proSUBDUCTION ZONE PROCESSES AND THE vided samples of unusual minerals and freshened pore fluids SEISMOGENIC ZONE derived from interaction of subducted sediments and crust Subduction zones, where one tectonic plate plunges with the overlying forearc mantle (Maekawa et al., 1993; beneath another, are the source of some of Earth's greatest Fryer et al., 1995, 1999)
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From page 22... ...
requires the riser drilling capability of the DSDP and ODP legs (e.g., ODP Legs 125 and 126) yield Chikyu and has been the major component of the Japanese a nearly complete 45 myr record of arc volcanism in the contribution to IODP in recent years.
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From page 23... ...
Only to test models of subduction zone processes and earthquake four submarine LIPs have been drilled thus far: the 55 Ma genesis. Installation of instruments to measure temperature, North Atlantic Volcanic Province on ODP Leg 104 (e.g., Stoseismic waves, strain, pressure, fluid flow, and pore water rey et al., 2007)
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From page 24... ...
24 SCIENTIFIC OCEAN DRILLING Box 2.4 NanTroSEIZE Eight NanTroSEIZE expeditions were completed between 2008 and 2010.1 Stage 1, completed in February 2008, was a transect of eight sites that targeted the shallow part of the accretionary complex, providing information on stresses, pore water geochemistry, and sediment age, lithology, and physical properties (see white paper by Casey Moore, Ap pendix C)
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From page 25... ...
LIPs may have also played an important role in The Shatsky Rise expedition (ODP Leg 198) recovered massive extinctions.
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