Description: From Fierstein (2007): "The oldest flows from East Mageik (unit "meo" of Hildreth and Fierstein 2003) have more degraded surfaces than their younger counterparts, although they are not obviously ice-scoured...Tephra deposits possibly associated with this eruptive episode are three older ash layers identified in the Angle Creek key section: the bluish-grey ash (just below K-2500G: ∼6,000-6,700 14C years B.P.), the thick gritty salmon ash (K-2500E: underlying peat is 8430+/-115 14C years B.P.) and the thick orange-tan ash (K-2500B: ∼9,260 14C years B.P.). Glass shards from the thick gritty salmon ash span a wider SiO2 range (74-78 wt.%) than those from the bluish-grey and the thick orange-tan (74-76 wt.%) ashes, while oxide data for all three ash layers overlap (Fig. 23 [in original text]). Microprobe data for these ash layers are so similar to those from younger East Mageik tephra that I am fairly confident they, too, are from East Mageik. The total eruptive volume of the East Mageik lavas is 5-6 km3, to which the dacitic falls and one small andesitic pyroclastic-flow deposit preserved locally atop "meo" add no more than 0.1 km3 (Hildreth and Fierstein 2000). Thus, over a period of ∼7,000 years, the preserved tephra record suggests there may have been at least six eruptive episodes from East Mageik plus one phreatic event, each separated by as little as 100 years to as much as 2,700 years."
"Between the two mafic tephras just described [at the Angle Creek section] are two ash layers. One is a very thin (0.1-0.5-cm) pinkish-tan fine to very fine ash just a few centimeters above the mafic crystal ash. Though its light color stands out in the enveloping black peaty soil, this unit is so thin that it was not collected, and a correlative ash elsewhere has not been identified. The second tephra-a tan to salmon-colored fine to very fine ash-is ∼9 cm thick in Angle Creek (K-2500E, Fig. 3 [in original text]) and is, in turn, a few centimeters above the pinktan ash and 24 cm beneath the mafic orange fine ash. Because it is slightly gritty to the touch (but still very fine; Md<0.6 mm) it is here called the "thick gritty salmon ash". Despite its thickness, however, no other correlative ash has yet been identified in any of the other measured sections. Peat directly beneath the tephra yields a radiocarbon age of 8,430+/-115 14C years B.P. (Table 2, Fig. 3 [in original text]). A source at Mount Martin would seem likely, especially one associated with eruption of the Martin lava coulees just upstream, since radiocarbon dates of twigs in soil atop the coulees show the lavas must be older than ∼6,200 14C years B.P. (Fig. 3, Table 2 [in original text]; K-2661A-sx). However, microprobe analyses of Fe-Ti oxides in the tephra are unlike those of the coulees (Fig. 13 [in original text]). Although the youngest stubby lavas high up near the Martin cone do have glass and oxide compositions similar to the tephra, they are too young to correlate with it (since they are younger than the coulees). Thus, because the source was apparently not at Mount Martin, and because the source is inferred to be relatively local (this ash has gritty components and is not all ultra-fine), a source at Mount Mageik is considered most likely. Microprobe data (glass and Fe-Ti oxides) plot similarly to other tephras from Mageik (upper pale tan, lower grey, and ODLF ash layers; Fig. 13 [in original text]) and are, at least, consistent with this tentative conclusion."