Geologic Map of Alaska: Rocks of Hammond River shear zone of Till and others (2008a)

Rocks of Hammond River shear zone of Till and others (2008a)

Unit symbol:	Khs
Age range	Cretaceous (145 to 66 Ma)
Lithology:	Metamorphic
Group name:	Rocks of Hammond River shear zone of Till and others (2008a)

Heterogeneous mix of finely laminated, mostly mylonitic lithologies derived, in part, from adjacent units exposed in the eastern Wiseman and western Chandalar quadrangles. Unit is recessive, poorly exposed, and includes large (up to 0.5 km across) bodies of black quartzite and smaller exposures of quartz-rich schist, metagabbro, dark-brown marble, and relatively undeformed metasandstone and metasiltstone (Moore and others, 1997b; A.B. Till, unpub. data). In thin section, minerals are strained and broken. Protolith rocks may range in age from Proterozoic to Paleozoic; no age control is available. Age of unit is based on likely age of tectonic event that created the shear zone, which encompasses a zone of deformation between the Schist belt and Central belt of Till and others (2008a). Equivalent to the Hammond River phyllonite of Moore and others (1997b); westernmost extent of the unit is approximately located

Source map information

Source map	Till, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, 2008, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Open-File Report 2008-1149, 88 p., 2 sheets, scale 1:500,000.
Symbol	Khs
Unit name	Rocks of the Hammond River shear zone
Description	Heterogeneous mix of finely laminated, mostly mylonitic lithologies derived in part from adjacent units exposed in the eastern Wiseman and western Chandalar quadrangles. Unit is recessive, poorly exposed, and includes large (up to 0.5 km across) bodies of black quartzite and smaller exposures of quartz-rich schist, metagabbro, dark brown marble, and relatively undeformed metasandstone and metasiltstone. In thin section, minerals are strained and broken. No age control available. The unit encompasses a zone of deformation between the Schist and Central belts. This unit is part of the Central belt.
Lithology	Metamorphic

Correlated geologic units

Label	Khs
Description	Rocks of Hammond River shear zone
Geologic age	Cretaceous
Geologic setting	Melange

Lithology	Form	Importance
Metamorphic		Indeterminate, major
Clastic < Sedimentary	Bed	Indeterminate, major