Event Name : Augustine Pleistocene Tephra
|Stop: 40440 || Years BP Tephrochronology || |
From Waitt and Beget (2009): "A section at 10 to 30 m altitude overlying the south-coastal landslide block (unit Pl) includes exotic-bearing out-wash of chiefly volcanic debris (unit Po) and an interbedded primary pumiceous fall deposit from Augustine Volcano. The pumiceous-gravel outwash dips as steeply as 38 degrees north and northeast, onshore dips implying glacier ice banked against Augustine Island. Adjacent or underlying glacier ice that had supported the deposits melted and caused the beds to settle and rotate to dips steeper than repose angle."
"At altitude about 290 m along Augustine Creek (west-most of the Pleistocene sections), one of the lowest beds of a section of alternating tephra and pumiceous pyroclastic-flow deposit is waterlaid pumice whose wood and charcoal fragments by two radiocarbon AMS dates precede 39,000 yr B.P. (table 2 [in original text]). This bed is overlain by several thin beds apparently of glacial outwash (containing exotic stones) intercalated with beds of waterlaid(?) pumice sand and gravel, beds overlain in turn by angular pumice gravel (Augustine fall) (fig. 15 [in original text]). Thus some Pleistocene glacial and volcanic materials may predate the late Wisconsin glaciation of Cook Inlet."
"In the lowest parts of the westmost inlier sections (azimuth south-southwest, altitude 280 m), pumiceous beds overlie and are interbedded with the top of glacial and glaciofluvial deposits that bear exotic stones and from whose base come the radiocarbon dates exceeding 39,000 yr B.P. (fig. 18 [in original text]). Overlying the glacial horizon is 17 m of sandy flow deposits punctuated by four major pumice-fall beds (unit PHfp; see just below [in original text])."