Pg. 112. Marble Creek Orthogneiss. Included in Skagit Metamorphic Suite. In contrast to Shuksan Suite, the Skagit Metamorphic Suite contains a variety of metamorphosed intrusives. Metamorphosed acidic intrusives comprise predominantly trondhjemitic orthogneiss (including a larger elongate stock, Marble Creek Orthogneiss), small bodies of leucotrondhjemitic orthogneiss, and thin sills or dikes of usually gneissose, trondhjemitic metaporphyries. A larger elongate stock of leucotrondhjemitic gneiss, Haystack Creek Gneiss (new), was intruded in a crystalline state during a fairly late stage of metamorphism. Another larger semiconcordant leucotrondhjemite body (Alma Creek Leucotrondhjemite) was intruded near the end of the metamorphism; it is igneous but shows incipient adjustment to the facies of the surrounding schist. Age is Paleozoic(?).
Type locality and origin of name not stated. Occurs in northern Cascades, northwestern WA.

Source: US geologic names lexicon (USGS Bull. 1350, p. 468); supplemental information from GNU records (USGS DDS-6; Menlo GNULEX).