Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 1. Tephra ages and provenance
Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 1. Tephra ages and provenance
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DOI：
10.1002/2016gc006503
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发表时间：
2016-11
期刊：
影响因子：
3.7
通讯作者：
J. Schindlbeck;S. Kutterolf;A. Freundt;G. Alvarado;K.‐L. Wang;S. Straub;S. Hemming;M. Frische;J. Woodhead
中科院分区：
文献类型：
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作者：
J. Schindlbeck;S. Kutterolf;A. Freundt;G. Alvarado;K.‐L. Wang;S. Straub;S. Hemming;M. Frische;J. Woodhead
我们研究了18个深海钻探点的火山灰清单，这些钻探点来自中美洲火山弧（CAVA）南部近海的6个DSDP/ODP腿（腿84，138，170，202，205和206）和2个IODP腿（腿334和344）。8个钻探点位于即将到来的科科斯板块，10个钻探点位于加勒比板块的大陆坡。总的来说，我们检查了10840个含灰层，并确定了其中10650个为原生灰层，其中430个来自CAVA。灰层的相关性之间建立了海洋岩心和陆地火山灰矿床，使用主要和微量元素玻璃组合物相对于地层顺序。作为海洋-陆地相关性的先决条件，我们提出了一个新的地球化学数据集的重要新近纪和第四纪哥斯达黎加火山岩。此外，还确定了海相火山岩的新Ar/Ar年龄，并利用远洋沉积速率测定了海相火山灰层的年龄。由此产生的相关性和物源分析建立了哥斯达黎加和尼加拉瓜的火山灰年代地层框架，涵盖了过去的<1500万年。我们定义了39个相关的海洋火山灰床，以特定的火山灰形成在哥斯达黎加和尼加拉瓜，从4.15马下Sandillal火山灰灰岩的3.5万年林孔德拉Vieja火山灰从哥斯达黎加，以及另外32个广泛分布的火山灰层，其特定的原产地沿着哥斯达黎加和尼加拉瓜可以受到限制。
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 Rincón 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.