Lava deposition history in ODP Hole 1256D; insights from log-based volcanostratigraphy

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doi: 10.1029/2009GC002933
Author(s): Tominaga, Masako; Umino, Susumu
Author Affiliation(s): Primary:
Texas A&M University, Department of Oceanography, College Station, TX, United States
Other:
Kanazawa University, Japan
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 11(5). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 74 refs.; illus., incl. 2 tables, sketch map
Summary: A log-based volcanic stratigraphy of Ocean Drilling Program Hole 1256D provides a vertical cross-section view of in situ upper crust formed at the East Pacific Rise (EPR) with unprecedented resolution. This stratigraphy model comprises ten electrofacies, principally identified from formation microscanner images. In this study, we build a lava flow stratigraphy model for the extrusive section in Hole 1256D by correlating these electrofacies with observations of flow types from the modern EPR, such as sheet flows and breccias, and pillow lavas and their distribution. The resulting flow stratigraphy model for the Hole 1256D extrusive section represents the first realization of detailed in situ EPR upper oceanic crust construction processes that have been detected only indirectly from remote geophysical data. We correlated the flow stratigraphy model with surface geology observed from the southern EPR (14°S) by Shinkai 6500 dives in order to obtain the relationship between lava flow types and ridge axis-ridge slope morphology. This dive information was also used to give a spatial-time reference frame for modeling lava deposition history in Hole 1256D. In reconstructing the lava deposition history, we interpreted that the origins of the ∼100 m thick intervals with abundant pillow lavas in Hole 1256D are within the axial slope where pillow lavas were observed during the Shinkai 6500 dives and previous EPR surveys. This correlation could constrain the lava deposition history in Hole 1256D crust. Using the lateral scale of ridge axis-ridge slope topography from the Shinkai 6500 observations and assuming the paleospreading rate was constant, 50% of the extrusive rocks in Hole 1256D crust were formed within ∼2000 m of the ridge axis, whereas nearly all of the remaining extrusive section was formed within ∼3000 m of the ridge axis. These results are consistent with the upper crustal construction model previously suggested by seismic studies.
Year of Publication: 2010
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; 07 Marine Geology and Oceanography; Cocos Plate; East Pacific; East Pacific Rise; Electrical logging; Equatorial Pacific; Igneous rocks; Integrated Ocean Drilling Program; Lava; Leg 206; Lithostratigraphy; Nazca Plate; North Pacific; Northeast Pacific; ODP Site 1256; Ocean Drilling Program; Ocean floors; Pacific Ocean; Pillow lava; Plate tectonics; Submersibles; Tectonics; Volcanic rocks; Volcanism; Well logs; Well-logging
Coordinates: N064400 N064400 W0915600 W0915600
Record ID: 2011003727
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