Analysis of the northern Sierra accreted terrane, California, with airborne thermal infrared multispectral scanner data

Abstract

Sedimentary and igneous rocks of the northern Sierra accreted terrane and the Sierra Nevada batholith have been distinguished and mapped with the help of data from the airborne thermal infrared multispectral scanner (TIMS). TIMS acquires radiant spectral emittance data in the 8.2 to 12.2 μm (thermal infrared) part of the electromagnetic spectrum, where diagnostic spectral emission features of rocks and minerals occur. These features allow the discrimination of major rock types, because a distinct relation exists between the emissivities of the types of silicate minerals in rocks and the colors in the TIMS false-color imagery. Using a computer-enhanced TIMS image, we have been able to separate silica-rich metasedimentary and felsic igneous rocks from intermediate and mafic igneous rocks. In addition, several previously unmapped phases within the Mesozoic batholith were identified and mapped. These rocks are inseparable on conventional color aerial photography, but they are distinguishable on TIMS imagery. These results suggest that TIMS data should have widespread applicability to geologic mapping in many tectonic settings, including well-exposed batholithic belts, accreted terranes, and Precambrian shield areas.