The Valley Spring Domain (VSD) consists of 1288-1232 Ma plutonic and supercrustal rocks with an older crustal component (1366 + 3 Ma) interpreted as a continental margin arc and terrigenous clastics formed on Laurentia. See Mosher (1998).

Lithologies include microcline-quartz-(biotite/hornblende) gneisses and minor amounts of schist, amphibolite, metagabbro and marble.  Much of the VSD represents a highly attenuated felsic plutonic complex.  Elsewhere probable protoliths are ignimbrites and rhyolitic volcanic rocks interbedded with local mafic flows or sills, calcareous tuffs, limestones and volcanoclastic deposits. 

Ages and relationships to PSD & CCD in eastern uplift

Most of the VSD consists of pink felsic gneisses (above right), which in many locations preserve intrusive relationships between gneisses of different compositions (see Zumbro, 1999).  Elsewhere protoliths are difficult to discern but are most likely metavolcanic or metaplutonic. Rare cross beds in arkoses (upper left - folded with vertical axial plane) and sillimanite nodules (lower left) indicate some units are sedimentary in origin and represent terrigenous clastics.

Interlayered mafic and felsic gneisses (above left and upper right) represent metavolcanic rocks and sills and share a common deformational history.  Boudins of mafic sills (upper right) contain relict eclogitic assemblages indicating high P metamorphism; retrogression during boudinage occurred later under medium P amphibolite facies conditions. Minor marbles (lower right) are found within both the VSD and PSD, suggesting the two domains were proximal and a continental margin depositional environment.  These units provide excellent marker horizons for mapping large scale structures. See Zumbro (1999)