Browse Map

Explore away

Explore Map Collection

Check out our basemaps

Print a Map Plus

Generate a high-quality PDF

Field Guide

Discover local flora, fauna, geology, and more

Local Flora & Fauna

Learn the ecology of your area

Local Geology

Learn the geologic formation at your feet

Get Started or Sign In

Welcome

Continue with Apple

Already have an account? Sign In

Measure

Topo

Ecoregions

Public Lands

...

BASEMAPS

Default Weather

Temperature

Smoke

...

WEATHER

Lacustrine and fluvial sedimentary rocks (ORQs;0)

Geologic Formation in OR, CA, WA

Print Map

Generate High-Quality PDF

Lithology

Silt

Sand

Clay

Other (11,559 mi²)

Geologic Age

Pleistocene (2.58 Ma – 11700 years ago)

Geologic Unit Label

Unconsolidated to semiconsolidated lacustrine clay, silt, sand, and gravel; in places includes mudflow and fluvial deposits and discontinuous layers of peat. Includes older alluvium and related deposits of Piper (1942), Willamette Silt (Allison, 1953; Wells and Peck, 1961), alluvial silt, sand, and gravel that form terrace deposits of Wells and others (1983), and Gresham and Estacada Formations of Trimble (1963). Includes deltaic gravel and sand and gravel bars, in pluvial lake basins in southeastern part of map area. In Rome Basin, includes discontinuous layers of poorly consolidated conglomerate characterized by well-rounded, commonly polished pebbles of chert and pebbles and cobbles of quartzite. In places contains mollusks or vertebrate fossils indicating Pleistocene age; mostly deposits of late Pleistocene age, but locally includes some deposits of early Holocene age. Includes Touchet Beds of Flint (1938), deposits of valley terraces of Newcomb (1965), and, in southeast Oregon, basin-filling deposits that incorporate Mazama ash deposits (Qma, Qmp) in the youngest layers

— USGS