SAMPLE TRANSECT AT DOMELAND: A POSSIBLE NEWLY FOUND IMPACT STRUCTURE IN CALIFORNIA
DEM data, satellite imagery, and geologic map overlays indicate three realms within the structure. At center, a possible central uplift ring is defined by a series of irregularly-raised granitic fins and exfoliation domes collectively forming a roughly circular rim ~6 km in diameter standing an average of 300 m above a shallow central basin within a broad region composed entirely of Upper Cretaceous granitoids. Ring dimensions are similar to complex impact structures. Beyond the north, east, and southwest flanks of the granitic ring sits what may be a partial annular trough composed of the same Upper Cretaceous granitoids extending out to a radius of ~8.2 km from the geographic center. Outlying units consist of Mesozoic and/or Paleozoic metasedimentary and metaigneous roof pendants as well as an Upper Jurassic diorite complex and sparsely distributed remnants of Neogene basalts and rare andesites. Together, the outlying units form a highland realm, which may define the outer limits of the possible annular trough. Aeromagnetic data indicate an anomaly of ~51,600-51,690 nT throughout the possible central uplift area. Bouguer gravity data indicate a low of –160 mGal coincident with hypothetical crater center, although this may be an extension of the Sierra batholith’s stronger gravitational low to the north.
In late June 2013, we collected rock samples from the hypothetical central uplift. Our literature review to date indicates we may possess the only lithologic samples ever collected from this realm. These samples are currently being examined for shock features and chemical signatures consistent with impact and we will report our progress.