Tuffaceous Mud is a Volumetrically Important Volcaniclastic Facies of Submarine Arc Volcanism and Record of Climate Change

Abstract

The inorganic portion of tuffaceous mud and mudstone in an oceanic island arc can be mostly volcanic in origin. Consequently, a large volume of submarine volcaniclastic material is as extremely fine‐grained as products of subaerial eruptions (<100 µm). Using results of IODP Expedition 350 in the Izu rear arc, we show that such material can accumulate at high rates (12–20 cm/k.y.) within 13 km of the nearest seamount summit and scores of km behind the volcanic front. The geochemistry of bulk, acid‐leached mud, and its discrete vitriclasts, shows that >75% of the mud is volcanic, and that most of it was derived from proximal rear arc volcanic sources. It faithfully preserves integrated igneous geochemical information about arc evolution in much the same way that terrigenous shales track the evolution of continental crust. In addition, their high sedimentation rate enables high resolution study of climate cycles, including the effects of Pleistocene glaciation on the behavior of the Kuroshio Current in the Shikoku Basin south of Japan.

Across‐Arc Diversity in Rhyolites From an Intra‐oceanic Arc: Evidence From IODP Site U1437, Izu‐Bonin Rear Arc, and Surrounding Area

“…Many drilling cruises have focused on the Izu-Bonin forearc and volcanic front (e.g., Fryer & Pearce, 1992;Reagan et al, 2017;Taylor et al, 1992), but Site U1437 represents the first drilling within the rear-arc region (Figure 1). In three consecutive cored holes, the JOIDES Resolution ultimately drilled down to 1,806.4 meters below seafloor (mbsf), through at least 15 Myr of volcaniclastic stratigraphy, with tephra and other volcano-derived materials alternating with thick successions of tuffaceous mud (Figure 2; Tamura et al, 2015;Gill et al, 2018;Schmitt et al, 2017). The core was subdivided into seven lithostratigraphic units, based on the relative proportion of mud to discrete ash or tephra.…”

The First 10 Million Years of Rear‐Arc Magmas Following Backarc Basin Formation Behind the Izu Arc

“…Age data with arrows are U-Pb zircon ages from Schmitt et al (2018). The depth of samples of this study (including the samples of Sato et al 2020), and the mud samples of Gill et al, (2018) are shown on the left side of the figure. The samples with Nb/Yb ratio of <0.2, 0.2-0.7, and >0.7 are classified as VF-type, Rift-type, and RASC-type.…”

Progressive and Punctuated Magnetic Mineral Diagenesis: The Rock Magnetic Record of Multiple Fluid Inputs and Progressive Pyritization in a Volcano‐Bounded Basin, IODP Site U1437, Izu Rear Arc

“…Tuffaceous mud and mudstone with intercalated ashes and volcaniclastics characterize the uppermost 1,320 m, comprising Lithological Units I through V, with only two comparatively short intervals (Units II and IV) in which fine volcaniclastics dominate. Locally derived volcanic components generally make up 70–100% of the mud fraction, although this drops to 20–50% in intervals deposited during Pleistocene glacials in the upper part of Unit I, where continentally derived hemipelagic muds dominate (Gill et al, ; Kars et al, ). Unit VI, from 1,320 to 1,460 mbsf, exhibits a coarser volcaniclastic input and a reduced mudstone component than the overlying mud‐dominated lithology of Units I through V. Mudstone is absent from the underlying Unit VII, which extends to the bottom of hole.…”