Bedding measurements
293,477 bedding measurements from published US geologic maps, recorded as strike and dip and cited to the map each came from — 36% of the Atlas.
What it is
Bedding is the depositional layering in sedimentary rock — the boundary between one bed and the next. It is measured as a plane: a strike and a dip, or equivalently a dip azimuth and a dip angle.
Its value to structural geology comes from a single assumption: beds are deposited close to horizontal. Any attitude other than horizontal is therefore a record of what happened to the rock afterwards, which makes bedding the most direct field measurement of deformation there is. Plotted as poles on a stereonet, bedding from a folded terrain scatters along a great circle whose pole is the fold axis — the standard construction for recovering a fold axis from scattered field data.
Bedding is the largest class in this compilation and the one most consistently recorded across every source, because it is the measurement a geologic map is largely made of.
How the Atlas records it
Every bedding row carries an azimuth and an inclination in one convention
(right-hand-rule strike and dip), a position in WGS 84 with the publisher's
own location confidence, the raw type term as the source published it, and the citation of the source map.
Selections export as CSV with a companion sources.csv of citations.
Which sources have it
| Source | Measurements | Share |
|---|---|---|
| NGMDB legacy quads | 79,090 | 27% |
| NPS GRI parks | 55,188 | 19% |
| Washington Geol. Survey | 35,349 | 12% |
| USGS NGMDB GeMS | 34,489 | 12% |
| Oregon DOGAMI (OGDC-8) | 27,911 | 10% |
| South Dakota SDGS | 19,147 | 7% |
| Virginia DGMR | 17,003 | 6% |
| Montana MBMG | 12,252 | 4% |
| Pennsylvania Geol. Survey | 3,227 | 1% |
| Alaska DGGS | 2,503 | <1% |
| Wyoming WSGS | 1,902 | <1% |
| Maine Geol. Survey | 1,654 | <1% |
| Oklahoma Geol. Survey | 1,387 | <1% |
| Wisconsin WGNHS | 861 | <1% |
| USGS data releases · MRDS | 837 | <1% |
| USGS SIM quads (NE) | 341 | <1% |
| Connecticut Geol. Survey | 175 | <1% |
| Vermont Geol. Survey | 161 | <1% |
Where it is
| State | Measurements | Share |
|---|---|---|
| California | 47,653 | 16% |
| Washington | 41,843 | 14% |
| Oregon | 36,927 | 13% |
| Virginia | 26,313 | 9% |
| South Dakota | 20,541 | 7% |
| Montana | 19,924 | 7% |
| Pennsylvania | 11,561 | 4% |
| Idaho | 10,742 | 4% |
| Arizona | 9,342 | 3% |
| Maine | 6,334 | 2% |
| Colorado | 6,182 | 2% |
| Wyoming | 6,127 | 2% |
| Tennessee | 5,290 | 2% |
| Nevada | 5,115 | 2% |
| Utah | 4,902 | 2% |
| Arkansas | 4,717 | 2% |
| Alaska | 4,332 | 1% |
| New Jersey | 3,166 | 1% |
| Maryland | 2,344 | <1% |
| Texas | 2,225 | <1% |
| New Mexico | 1,811 | <1% |
| Alabama | 1,594 | <1% |
| Oklahoma | 1,513 | <1% |
| Missouri | 1,328 | <1% |
| North Carolina | 1,240 | <1% |
| Wisconsin | 862 | <1% |
| Kentucky | 837 | <1% |
| Georgia | 765 | <1% |
| Minnesota | 610 | <1% |
| Vermont | 525 | <1% |
| New Hampshire | 522 | <1% |
| West Virginia | 499 | <1% |
| Connecticut | 362 | <1% |
| New York | 325 | <1% |
| Michigan | 321 | <1% |
| Nebraska | 30 | <1% |
| North Dakota | 19 | <1% |
| Massachusetts | 13 | <1% |
| Iowa | 6 | <1% |
| South Carolina | 5 | <1% |
| Kansas | 3 | <1% |