Micropaleontological evidence of a submarine fan in the lower Coaledo Formation, Southwestern Oregon, USA
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Abstract
The middle Eocene lower Coaledo Formation was interpreted as ten shoaling upward delta-margin cycles based on sediments and macrofauna. The strata, however, contains deep-water foraminifers. Explanations to resolve this anomaly included reworking, bathymetric range extension, or upward migration of water masses. Paleoecology analysis of foraminifers indicates that the few shelf species are poorly preserved whereas the well-preserved lower bathyal species dominate, and planktic organisms are present. Evidence for reworking, bathymetric range extension, or upward migration of water masses was not found in any of the cycles. The paleoecologic utility of hummocky cross-bedded sandstones is questioned as these features are controversial. In addition, there is no evidence of sea-level changes or tectonic activity to accommodate the bathymetric changes needed. Deposition of the lower Coaledo Formation on a submarine fan at lower bathyal depths eliminates the need to explain bathymetric anomalies or lack of tectonic movement.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Micropaleontological evidence of a submarine fan in the lower Coaledo Formation, Southwestern Oregon, USA |
| Series title | Journal of Foraminiferal Research |
| DOI | 10.2113/gsjfr.53.4.311 |
| Volume | 53 |
| Issue | 4 |
| Publication Date | November 30, 2023 |
| Year Published | 2023 |
| Language | English |
| Publisher | Cushman Foundation for Foraminiferal Research |
| Contributing office(s) | Geology, Minerals, Energy, and Geophysics Science Center |
| Description | 27 p. |
| First page | 311 |
| Last page | 337 |
| Country | United States |
| State | Oregon |