Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 2. Implications for magma production rates and subduction erosion

Abstract

We studied the tephra inventory of 18 deep-sea drill sites from six DSDP/ODP legs (Legs 84, 138, 170,202, 205, and 206) and two IODP legs (Legs 334 and 344) offshore the southern Central American Volcanic Arc (CAVA). Eight drill sites are located on the incoming Cocos plate and 10 drill sites on the continental slope of the Caribbean plate. In total, we examined 840 ash-bearing horizons and identified 650 of these as primary ash beds of which 430 originated from the CAVA. Correlations of ash beds were established between marine cores and with terrestrial tephra deposits, using major and trace element glass compositions with respect to relative stratigraphic order. As a prerequisite for marine-terrestrial correlations, we present a new geochemical data set for significant Neogene and Quaternary Costa Rican tephras. Moreover, new Ar/Ar ages for marine tephras have been determined and marine ash beds are also dated using the pelagic sedimentation rates. The resulting correlations and provenance analyses build a tephrochronostratigraphic framework for Costa Rica and Nicaragua that covers the last <15 Myr. We define 39 correlations of marine ash beds to specific tephra formations in Costa Rica and Nicaragua; from the 4.15 Ma Lower Sandillal Ignimbrite to the 3.5 ka Rinc on de la Vieja Tephra from Costa Rica, as well as another 32 widely distributed tephra layers for which their specific region of origin along Costa Rica and Nicaragua can be constrained.

One Million Years tephra record at IODP Sites U1436 and U1437: Insights into explosive volcanism from the Japan and Izu arcs

“…For large explosive eruptions, the tephra volume that is deposited on the seafloor is often underestimated, but represents a major fraction of the total volume (e.g. Kutterolf, Freundt, & Peréz, ; Kutterolf et al, ; Schindlbeck et al, ). Temporal variations in these volumes and the eruptive frequency can serve as a first‐order proxy for quantitative time‐variations of the erupted volcanic flux at the arc.…”

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

“…Ash layers represent excellent stratigraphic marker beds in marine sediment sequences owing to their widespread distribution, potentially variable facies, near‐instantaneous emplacement, distinctive and correlative chemical signatures, and the presence of phenocrysts suitable for radiometric dating (e.g., Kutterolf et al, ). Such sediments can also provide constraints on the temporal evolution of both the volcanic source region and the ash‐bearing sediment facies (Schindlbeck et al, ; Scudder et al, ). In the forearc setting investigated here, tephra layers and intercalated volcaniclastic sediments are compositionally variable and so can provide important temporal and spatial information concerning volcanism in several geographically separate arc systems.…”

Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 1. Tephra ages and provenance

“…Using all these age constraints and the timelines provided by directly dated tephras, we converted the intercalated thicknesses of marine sediment to age‐depending (hemi‐)pelagic sedimentation rates as will be further discussed in Part 2 [ Schindlbeck et al ., ]. These sedimentation rates allow us to calculate the ages of single ash beds and tephra layers that were not captured by the dating approaches above.…”