Rock magnetic studies on marine volcaniclastic sediments off Martinique, Lesser Antilles volcanic arc, IODP Expedition 340

Author(s): Saito, T.; Kataoka, K.
Author Affiliation(s): Primary:
Shinshu University, Nagano, Japan
Niigata University, Japan
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Large numbers of marine volcaniclastic sediments with various origins were recovered from the sites U1397 and U1398 during IODP Expedition 340. They were most likely derived from volcanoes on Martinique and possibly from Dominica, Lesser Antilles volcanic arc. Some volcaniclastic units were transported and deposited as turbidites, some were as thin tephra fall deposits and others show both characteristics. They contain various amounts of bioclastic component, pumice and lithic fragments and hemipelagic mud clasts. Therefore, these volcaniclastic sediments are suitable for investigating transport and emplacement mechanisms of volcanic materials and the resultant sedimentary and petro-facies in marine settings. In this study, we focused on magnetic minerals in the marine volcaniclastic sediments and carried out rock magnetic measurements. Thermomagnetic measurements showed almost reversible curves and induced magnetization decayed to almost zero below 580°C, suggesting little contribution of maghemite or hematite. Two Curie temperatures (Tc) with 350-400°C and 500-550°C indicate that the main magnetic carriers are Ti-rich titanomagnetite and Ti-poor titanomagnetite. The proportion of low-Tc titanomagnetite in central and bottom part of turbidite units was larger than that in hemipelagic sediments and in the topmost part of turbidite units, suggesting Ti-rich titanomagnetite is derived from volcanic events. Magnetic susceptibility and hysteresis measurements showed that heavy and large magnetic minerals in most turbidite units were concentrated at the lower part of the unit. Samples from the topmost and bottom part of turbidites showed higher degrees of anisotropy than those from the central part, indicating strong influence of suspension settling at the topmost part and shearing at the bottom part. However, in some turbidite units such features cannot be observed and hysteresis parameters and susceptibility values were almost concentrated. Probably the units suggest that the sediments did not experience segregation of specific particles during transportation and settling under the relatively calm condition. These preliminary results suggest that rock magnetic approaches can identify various types of depositional processes of marine volcaniclastic sediments with magnetic minerals as they are often related with volcanic events.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Antilles; Atlantic Ocean; Caribbean Sea; Caribbean region; Expedition 340; Geophysical methods; Geophysical surveys; IODP Site U1397; IODP Site U1398; Integrated Ocean Drilling Program; Lesser Antilles; Magnetic methods; Magnetic properties; Marine sediments; Martinique; North Atlantic; Sediments; Surveys; Volcaniclastics; West Indies; Windward Islands
Coordinates: N141642 N141642 W0615320 W0615321
N145425 N145425 W0612521 W0612521
Record ID: 2015006424
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