Stop 27 HAZ Geotour 2020

Location ID: Stop27_Haz_GeoTour2020

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The first part of the outcrop here is medium to thick bedded quartzo-feldspathic sandstone, siltstone and granule conglomerate that may correlate with the Albian to Cenomanian Kitsuns Creek member of the Bulkley Canyon Formation of the Skeena Group as defined by Bassett and Kleinsphen (1996). As seen at the start of outcrop, the strata dip moderately to the south with trends varying from 074 to 115 degrees. As we walk south and up stratigraphic section the rocks become coarser grained with increasing number and thickness of pebble and boulder conglomerate beds.

Clasts are a mix of chert, quartz, feldspar phyric volcanics, rhyolite and siltstone with the percentage and angularity of rhyolite clasts increasing up section. Several white weathering, argillic altered beds with an abundance of rhyolite clasts occur in a faulted interval. South of the fault zone are chloritic mafic volcanics that are probably correlative with the alkali basaltic rocks of the Rocky Ridge succession. The upward coarsening of sedimentary beds and increasing abundance of rhyolite clasts in the Skeena succession suggests a period of active tectonism and explosive rhyolitic volcanism occurred prior to the main episode of Rocky Ridge volcanism. In the Babine Lake area rhyolite domes occur in this part of the Skeena succession and have given 104-107 Ma U-Pb isotopic dates (MacIntyre, D.G., Webster, I.C.L and Villeneuve, M. 1997). There may be potential for volcanogenic massive sulphide deposits associated with felsic volcanic centers.

Bassett and Kleinsphen (1996) suggest the Rocky Ridge volcanics represent an early stage continental arc that formed during a period of intra arc extension in the Intermontane belt. The lack of evidence for a western provenance for detritus, progression to deeper water sedimentary facies westward and current paleomagnetic reconstructions for the Insular terrane suggest the Rocky Ridge arc was open to the ocean along its western margin. Using facies interpretations, paleocurrent indicators and major and trace element geochemistry they propose a model where the Rocky Ridge volcanics erupted on the forearc side of the southern Omenica Belt and Idaho Batholith and were subsequently moved 1100 kilometers north to their present latitude. For a more detailed discussion see Bassett and Kleinsphen (1996).


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Location Data

Longitude: -127.3946
Latitude: 55.1852