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The McKenzie Watershed geology map is organized in a time/rock form
matrix. The oldest rocks in the watershed are from the Tertiary (66
to 1.8 million years before present), and the youngest are from the
Quaternary (1.8 mybp to the present). The rock forms are classified
into two main groups, volcanic and sedimentary. The volcanic rocks are
represented on the map in purple with dark purple being the youngest and
light purple the oldest. The sedimentary rocks from the
Quaternary/Tertiary and Tertiary time period are represented in browns and
the sedimentary deposits in the Quaternary are represented in
greens. A complete listing of rocks types in each category are
listed below.
Quaternary
(1.8 mybp to present)
Volcanic: andesite
of major stratovolcanoes (Qa), basaltic andesite and basalt (Qba),
youngest basalt and basaltic andesite (Qyb), rhyolite and dacite (Qrd)
Alluvial and Glacial Deposits: alluvial deposits (Qal),
glacial deposits (Qg), glaciofluvial deposits (Qgf), lacustrine and
fluvial sediments (Qs), terrace, pediment, and lag gravels (Qt)
Landslides and Debris-flow Deposits (Qls)
Quaternary/Tertiary
(66 mybp to present)
Volcanic:
basalt (QTb), basaltic andesite (QTba), mafic vent complexes (QTmv),
basaltic and andesitic ejecta (QTp)
Sedimentary: sedimentary rocks, mostly tuffaceous (QTs)
Tertiary (1.8
to 66 mybp)
Volcanic:
basaltic andesite (Tba), basaltic and andesitic rocks (Tbaa), hypabyssal
intrusive rocks (Thi), basalt and andesite intrusions (Tib), mafic vent
complexes (Tmv), ridge-capping basalt and basaltic andesite (Trb),
silicic vent complexes (Tsv), basaltic lava flows (Tub), mafic vent
& intrusive rocks (Tvi)
Sedimentary: undifferentiated tuffaceous sedimentary rocks (Tu),
sedimentary and volcaniclastic rocks (Tus), flows and clastic rocks,
undifferentiated (Tfc), undifferentiated tuff (Tut)
Eugene Formation (Tfee)
For more
information on the geology data set can be found at the Oregon Geospatial Data Clearinghouse.
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