Introduction
This digital map database and the PDF derived from the database were
created from the analog geologic map: Wells, R.E. (1981), “Geologic map of the
eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington.”
The geodatabase replicates the geologic mapping of the 1981 report with minor
exceptions along water boundaries and also along the north and south map
boundaries. Slight adjustments to contacts along water boundaries were made to
correct differences between the topographic base map used in the 1981 compilation
(analog USGS 15-minute series quadrangle maps at 1:62,500 scale) and the
base map used for this digital compilation (scanned USGS 7.5-minute series
quadrangle maps at 1:24,000 scale). These minor adjustments, however, did not
materially alter the geologic map. No new field mapping was performed to
create this digital map database, and no attempt was made to fit geologic
contacts to the new 1:24,000 topographic base, except as noted above. We
corrected typographical errors, formatting errors, and attribution errors (for
example, the name change of Goble Volcanics to Grays River Volcanics following
current State of Washington usage; Walsh and others, 1987). We also
updated selected references, substituted published papers for abstracts, and cited
published radiometric ages for the volcanic and plutonic rocks. The reader is
referred to Magill and others (1982), Wells and Coe (1985), Walsh and others
(1987), Moothart (1993), Payne (1998), Kleibacker (2001), McCutcheon (2003),
Wells and others (2009), Chan and others (2012), and Wells and others (in press)
for subsequent interpretations of the Willapa Hills geology.
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First posted July 31, 2014
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