Preliminary reconnaissance geologic map of the Juneau, Taku River, Atlin, and part of the Skagway 1:250,000 quadrangles, southeastern Alaska

The Cannery Formation: Devonian to Early Permian arc-marginal deposits within the Alexander Terrane, southeastern Alaska

“…The rocks at Point Retreat on Admiralty Island, the type locality for the Retreat Group, include greenschist and quartzite intruded by quartz diorite that yielded concordant Neoproterozoic U-Pb ages of 545-547 Ma (Karl and others, 2006). The chert in Hawk Inlet, which contains Late Devonian fossils, does not resemble the rocks at Point Retreat, so it should not be included in the Retreat Group or the Mesozoic unit of Brew and Ford (1985). Black chert with limestone lenses is absent in Cannery Cove: the chert in Hawk Inlet does not correlate with the rocks in Cannery Cove in either age or lithology, nor in degree of deformation or metamorphic grade.…”

“…As described above, the chert in Hawk Inlet was originally assigned to the Retreat Group by Lathram and others (1965) and later by Brew and Ford (1985) to their unit Mzps. The rocks at Point Retreat on Admiralty Island, the type locality for the Retreat Group, include greenschist and quartzite intruded by quartz diorite that yielded concordant Neoproterozoic U-Pb ages of 545-547 Ma (Karl and others, 2006).…”

“…12). This black metachert on Admiralty Island was assigned to the Retreat Group by Lathram and others (1965) and later assigned by Brew and Ford (1985) to their map unit Mzps, which corresponds exactly in area to the unit formerly mapped as the Retreat Group. The Hawk Inlet metachert was never assigned to the Cannery Formation although it is mapped near rocks assigned to the Cannery Formation ( fig.…”

Geologic map of Alaska

“…Csejtey and others (1992) did not assign either this unit or the basalt to known packages or assemblages because of the discontinuous and fault-bounded nature of their occurrence ^gsl Glenn Shale, lower unit (Triassic)-Grayish and brownish-black carbonaceous and calcareous shale (Van Kooten and others, 1996) and thin-bedded fossiliferous limestone in lower part of unit; rare thin oil shale (Brabb and Churkin, 1969) (Brabb, 1969). A similar and possibly equivalent unit of calcareous phosphatic shale, limestone, and minor calcareous sandstone and granule conglomerate was mapped in the Livengood quadrangle (Weber and others, 1992 (Lathram and others, 1965;Brew and Ford, 1985). Volcanic flows are interbedded with, but mostly overlie, gray to black limestone, graywacke, slate or argillite, black chert, and conglomerate (Lathram and others, 1965).…”

“…The upper limestone and chert varies along strike from an interbedded sequence to apparent limestone-chert conglomerate, which is, in turn, overlain by dark-gray slate, interbedded with very fine-grained and silty calcareous graywacke (Brew and Ford, 1985). On generalized map, included as part of unit Plss Ph Halleck Formation and similar sedimentary rock units (Permian)-Consists of calcareous siltstone and sandstone, silty limestone, and polymictic pebble and cobble conglomerate (Muffler, 1967;Brew and others, 1984) in the Petersburg and Port Alexander quadrangles.…”