Get Dggs.alaska.govpubskeywordPublications - CoalAlaska Division Of Geological ...

The northern Alaska Peninsula is a region of transition from the classic magmatic arc geology of the Alaska Peninsula to a Proterozoic and early Paleozoic carbonate platform and then to the poorly understood, tectonically complex sedimentary basins of southwestern Alaska.

It is marked by metamorphosed andesite, rhyolite and basalt with small amounts of limestone, marble and conglomerate. On top of the Coast Range batholith are remnant metamorphic rocks from the gneiss, schist and marble dominant Tracy Arm terrane.

Fundamentally, Alaska is a collage of terranes2 pieced together about 65 to 100 million years ago, but the process of their formation and assembly contin- ues today. As these terranes were tectonically assembled, their rocks were deformed and metamorphosed.

(2) Metamorphosed marine and marginal sedimentary rocks, carbonate platform, oceanic igneous (ocean crust) rocks, and volcanic rocks comprise western and northern Alaska, north of the Tintina fault system.

Common metamorphic rocks include phyllite, schist, gneiss, quartzite and marble. Foliated Metamorphic Rocks: Some kinds of metamorphic rocks -- granite gneiss and biotite schist are two examples -- are strongly banded or foliated.

The coastal geology of Alaska is incredibly complex, having been shaped by fault tectonics, volcanism, glaciation, fluvial processes, sea level changes and annual sea ice. The southeast portion of the coast is characterized by rugged, rocky coastal areas with sheltered fjords. It remains mostly ice-free.

Amethyst, a variety of quartz, has been found sporadically for years in the granitic uplands near Tok and Northway, Alaska. Other rocks and minerals found include Rhodonite, Fluorite, Garnet, Cinnabar, and Rutilated Quartz. Alaska designated Jade as its official state gem in 1968.

Alaska doesn't have a state rock, but it does have a state gem, jade. A gem is a precious or semiprecious rock or mineral that looks pretty when it is cut and polished. Jade is usually green, and it is hard but easily carved. Most of the jade in Alaska is found on the Seward Peninsula.