Available Acreage for Sale near Garberville California Geology

Bear Buttes is located approximately 4 miles north of Redway at the headwaters of Butte Creek in Humboldt County, CA. The Bear Buttes elevation ranges from 2,400-2,800 feet.

Diorite bedrock near the Bear Buttes is described as a medium-grained, dark-gray intrusive rock (spittler, 1983). Diorite is the intrusive equivalent to basalt. Diabase is described as fine to coarse-grained material in dikes and sills that are part of the Coast Range ophiolite (McLaughlin et al., 2000).

The Coast Range ophiolite represents oceanic crust on which much of the sedimentary rock of the Great Valley sequence was deposited. A complete ophiolite sequence consists of serpentinized harzburgite tectonite at the base, overlain by cumulate ultramafic and gabbroic rocks, passing upward into noncumulate gabbroic and related plutonic rocks, then into diabase dikes, and finally into pillow lavas. The Coast Range ophiolite, however, generally is highly sheared, dismembered, thinned, and locally missing, presumably as a result of faulting, at many places along the fault contact between Franciscan and Great Valley rocks. Only in a few places is a nearly complete lithologic sequence of Coast Range ophiolite preserved, and there the total stratigraphic thickness of the ophiolite is about 3 to 5 km (Hopson and others, 1981). Isotopic ages ranging from about 165 to 153 Ma (Hopson and others, 1981) indicate that the Coast Range ophiolite is Middle and Late Jurassic in age. Paleontologic and paleomagnetic evidence suggests that the Coast Range ophiolite formed in an equatorial setting and was transported great distances northward before being accreted to North America and overlain by the Great Valley sequence (Pessagno and others, 1984; Hopson and others, 1986; McLaughlin and others, 1988).

Diorite is a plutonic igneous rock composed of coarse grains of plagioclase feldspar and less than 40 percent hornblende (see amphibole) and biotite (see mica), or, more rarely, pyroxene or olivine. Small amounts of potassium feldspar and quartz may also occur, along with traces of magnetite, apatite, sphene, and zircon. Diorite is the plutonic equivalent of the volcanic rock andesite and is intermediate between gabbro and granite. Diorite occurs around margins of granitic batholiths, in separate plutons, and in dikes. It forms by the melting of rocks in the lower crust, by the assimilation of crustal rocks in basaltic magma, or as by metamorphic processes.