Geochemistry and origin of Pliocene and Pleistocene ash layers from the Iceland plateau, site 907

• Main Authors: Lacasse, Christian, Paterne, Martine, Werner, R., Wallrabe-Adams, H.-J., Sigurdsson, Haraldur, Carey, Steven, Pinte, Guy
• Other Authors: University of Rhode Island (URI), Centre des Faibles Radioactivités, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Helmholtz Centre for Ocean Research Kiel (GEOMAR), Laboratoire Pierre Süe (LPS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Ruth N. Riegel
• Format: Book Part
• Language: English
• Published: HAL CCSD 1996
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Iceland Plateau; Jan Mayen; Kolbeinsey; Iceland
• Online Access: https://hal.science/hal-03543747; https://hal.science/hal-03543747/document; https://hal.science/hal-03543747/file/sr151_17.pdf; https://doi.org/10.2973/odp.proc.sr.151.122.1996

Section 3: IGNEOUS PETROLOGY/GEOCHEMISTRYArticle number 17 International audience The upper 90 m of sediments from Ocean Drilling Program Leg 151 Site 907 on the Iceland Plateau contain numerous wellpreserved volcanic ash layers that provide an excellent record of the source and timing of major Pliocene and Pleistocene explosive eruptions that have occurred in this region. A total of 23 tephra layers and six ash zones were analyzed for major and trace element chemistry and grain size characteristics. Relative ages of the tephra layers were estimated based on paleomagnetic and oxygen isotope stratigraphy. Thicknesses of the ash layers range from less than 1 to 18 cm. It is inferred on the basis of their sorting coefficient and grain size that the majority of the tephra layers are the result of ash fallout from large explosive eruptions. Most of the tephra layers are crystal-poor, with less than 10% total crystal content. Colorless shards dominate over sideromelane (brown glass) and tachylite. Platy bubble wall shards represent the dominant morphological type of glass, with minor amounts of pumice and vesicular shards. The major element composition of glasses indicates four compositional groups: basalt, basaltic andesite, trachyte and rhyolite. All of the compositionally bimodal tephra layers and the rhyolitic layers have a tholeiitic affinity, compatible with a source from volcanoes in the Pliocene-Pleistocene and upper Pleistocene volcanic rift zones in Iceland. Tephra with alkaline and peralkaline rhyolitic (comendite) glass composition were likely erupted from the only two regions in Iceland having produced transitional and alkali rock series of similar composition: the Snaefellsnes Peninsula and the Eastern Volcanic Zone. Three tephra layers are found to have a trachytic composition, high total alkali concentration, and affinity with the trachy-basaltic rock series of Jan Mayen. All of the basaltic glasses show high potassium concentration (>0.2 wt%), which excludes their origin from the Kolbeinsey ...