Preliminary Interpretation on the Role of Sub-Ice Topography on the Emplacement of Basaltic Pillow Lavas at Tennana Cone, Mount Edziza Volcanic Complex, British Columbia, Canada
Abstract
The Mount Edziza Volcanic Complex (MEVC) is a northeast trending, 75km long volcanic edifice in Northern British Columbia. Erupting cyclically over the last 7.5 ma, volcanic centers along the complex have erupted alkalic basalts to rhyolites and a range of intermediate alkalic lavas. Several episodes of sub-ice or ice- contact volcanism are recorded since 2Ma (Souther, 1992), including a basaltic volcaniclastic ridge and associated lava flows at Tennena Cone on the western side of the MEVC. Tennena Cone (TC) is a 200m high sequence, dominated by pillow-fragment breccias, that overlies trachytic lava flows of the approximately 1Ma-old Ice Peak Formation (IPF). The IPF flows vary from 3 to 7 meters in thickness and form a cliff-forming stepped topography. Underlying the IPF lavas are glaciogenic sediments, of dominantly glaciofluvial origin. A widespread area of pillow and subaqueous lobate lava flows that originated from TC were emplaced on its western margin. These lavas overlie both the steep topography of the IPF, and distally, the glaciogenic sediments. The geomorphology and structures of the TC lava flows suggest that were initially emplaced as sheet-like pillow lavas with local ponding on a dissected plateau of underlying IPF lavas, but as they approached the steep sub-ice cliffs of IPF lavas (and thicker ice), the growth of pillow mounds at the flow termini occurred. However, at one locality the pillow lavas spilled over a gap in the sub-ice cliffs, and were then focused downstream within sub-ice sinuous drainage tunnels. We intend to conduct volatile analyses on samples of glass rinds of pillow lavas in both pillow mounds and sheets to constrain the thickness of overlying ice. Knowing ice thickness and reconstructing the paleo- topography, we can begin to interpret how ice flow dynamics may control the emplacement of sub-ice basaltic lavas.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.V53C1756H
- Keywords:
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- 8408 Volcano/climate interactions (1605;
- 3309);
- 8414 Eruption mechanisms and flow emplacement;
- 8425 Effusive volcanism;
- 8427 Subaqueous volcanism;
- 8429 Lava rheology and morphology