Offshore Gas Field, Cuarta Offshore Oil Field, Molino Gas Field, and others. Paleontology Microfossils are common in the Rincon, and have been helpful in dating the unit. Formaniferal remains in particular are abundant, and the various types have allowed staging of the layers into Upper Zemorrian and Lower and Upper Saucesian. Within Santa Barbara County, two significant fossil finds (aside from microfossils) have been made in the Rincon Formation. In Ventura County, the exposure of the formation along Los Sauces Creek has yielded ten different species of ostracoda; a detailed study suggested that the sea bottom they inhabited was around 2,000 meters deep, very near to the edge of the continental shelf. Radon Naturally high in uranium, the Rincon Formation is a notorious source of radon gas emissions in Santa Barbara and Ventura Counties, making them the counties with the greatest radon hazard in California. Radon is a byproduct of radioactive decay of uranium, which is present in the Rincon at around 20 to 30 parts per million (ppm). A 1993 study found that approximately 74% of homes built on the Rincon Formation, or on alluvium or soils derived from the Rincon Formation, showed interior radon concentrations in excess of 4 picocuries per liter (pCi/L), the U.S. EPA action level, and 26% had measured levels of radon over 20 pCi/L. According to the U.S. EPA, non-smokers exposed to radon at the 20 pCi/L level over a lifetime had a risk of dying from lung cancer at 36 in 1000, as opposed to 7 in 1000 at the 4 pCi/L level, and 2 per 1000 at the average indoor radon level in the United States of 1.3 pCi/L. Smokers were at a much greater risk, with fully 260 out of 1,000 expected to die of lung cancer with a lifetime exposure of 20 pCi/L of radon. Radon migrates upwards from its source, entering buildings wherever the bottom is imperfectly sealed, for example through cracks in a concrete slab. If a structure is poorly ventilated – such as when the windows remain shut during the cool season – radon can accumulate to a hazardous level. Some of the mitigation measures employed in houses on the Rincon Formation since the discovery of the problem in the 1990s include building ventilation systems for the air space beneath the structure, performing "soil suction" in which the gas is pulled directly from the soil under the