Tephrostratigraphy and Provenance From IODP Expedition 352, Izu‐Bonin Arc: Tracing Tephra Sources and Volumes From the Oligocene to Recent

Abstract

Provenance studies of widely distributed tephras, integrated within a well‐defined temporal framework, are important to deduce systematic changes in the source, scale, distribution, and changes in regional explosive volcanism. Here, we establish a robust tephrochronostratigraphy for a total of 157 marine tephra layers collected during IODP Expedition 352. We infer at least three major phases of highly explosive volcanism during Oligocene to Pleistocene time. Provenance analysis based on glass composition assigns 56 of the tephras to a Japan source, including correlations with 12 major and widespread tephra layers resulting from individual eruptions in Kyushu, Central Japan, and North Japan between 115 ka and 3.5 Ma. The remaining 101 tephras are assigned to four source regions along the Izu‐Bonin arc. One, exclusively assigned to the Oligocene age, is proximal to the Bonin Ridge islands; two reflect eruptions within the volcanic front and back‐arc of the central Izu‐Bonin arc, and a fourth region corresponds to the Northern Izu‐Bonin arc source. First‐order volume estimates imply eruptive magnitudes ranging from 6.3 to 7.6 for Japan‐related eruptions and between 5.5 and 6.5 for IBM eruptions. Our results suggest tephras between 30 and 22 Ma reflect a subtly different Izu‐Bonin chemical signature compared to the recent arc. After a ∼9 Ma gap in eruption, tephra supply from the Izu‐Bonin arc predominated from 15 to 5 Ma, and finally a subequal mixture of tephra sources from the (palaeo)Honshu and Izu‐Bonin arcs occured within the last ∼5 Ma.

Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

“…This unit correlates directly with Unit 1 of Hole U1440B, but only the uppermost portion of this unit was penetrated in Hole U1440A. The overlying sedimentary sections are discussed by Robertson et al () and Kutterolf et al ().…”

“…The stratigraphy of Hole U1441A is relatively simple (Figure b; Reagan et al, ), consisting of four igneous chemostratigraphic units defined by the Expedition 352 science party (Reagan et al, ), based on chemical proxies determined by pXRF analyses (Ryan et al, ) and on the physical attributes of the units inferred from core: (1) a homolithic breccia of aphyric basalt derived from pillow lava; (2) pillow lava that is chemically and petrographically distinct from Unit 1; (3) a massive sheet flow of highly depleted, augite‐phyric basalt (referred to as depleted FAB or D‐FAB by Reagan et al, ); and (4) pillow lava that is chemically distinct from the overlying units. The overlying sedimentary sections are discussed by Robertson et al () and Kutterolf et al ().…”

Postmagmatic Tectonic Evolution of the Outer Izu‐Bonin Forearc Revealed by Sediment Basin Structure and Vein Microstructure Analysis: Implications for a 15 Ma Hiatus Between Pacific Plate Subduction Initiation and Forearc Extension

“…Biostratigraphic constraints from calcareous nannofossils reveal initial sedimentation at ~35 Ma (Robertson et al, ). Tephra layers higher in deep‐sea successions indicate that explosive dacitic IBM volcanism started around 28.6 Ma (Kutterolf et al, ). Since the IBM igneous basement formed at 52–50 Ma (Reagan et al, ), a ~15 Ma depositional hiatus must therefore exist prior to the oldest known sediment deposits.…”

Miocene to Holocene Marine Tephrostratigraphy Offshore Northern Central America and Southern Mexico: Pulsed Activity of Known Volcanic Complexes

“…All major and trace element data are given in supporting information Tables S1–S6; for standard analyses, see supplement of Schindlbeck, Kutterolf, Freundt, Alvarado et al () and Kutterolf et al (). Sampling and analytical methods concord with the methods applied in Kutterolf, Freundt, Peréz, et al (), Kutterolf et al (, , ), Schindlbeck et al (), Schindlbeck, Kutterolf, Freundt, Alvarado, et al (), and Schindlbeck et al ().…”

“…Geochemical fingerprinting of glass shards has been proved to be a reliable tool for tephra correlations (e.g., Kutterolf, Freundt, Peréz, et al, ; Kutterolf et al, ; Ponomareva et al, , ; Lowe, ; Schindlbeck, Kutterolf, Freundt, Alvarado, et al, ). Correlations of ash beds to terrestrial deposits as well as between different marine sites are based on major and trace element concentrations and ratios (Kutterolf, Freundt, Peréz, et al, ; Kutterolf et al, , ; Neugebauer et al, ; Schindlbeck et al, ; Schindlbeck, Kutterolf, Freundt, Alvarado, et al, ; Schindlbeck et al, ; Wulf et al, ) as well as the relative stratigraphic positions and age constraints. For each marine ash bed, we carried out 15–20 EMP analyses, and the majority of marine ash beds were analyzed additionally for their trace element composition by LA‐ICP‐MS.…”