Table 1 shows biogeochemical data collected from five depths in the CSW1.1 well at the Coast Range Ophiolite Microbial Observatory, California, USA during a one-day sampling event in June 2016. Included are latitude and longitude of the CSW1.1 well, depth each sample was collected, oxygen level and other water quality parameters such as pH, temperature, and oxidation reduction potential. Hydrogen sulfide was measured via spectrophotometric methods, and anions were measured using ion chromatography. Dissolved gases were measured using a gas chromatograph with a flame ionization detector. Data was collected to understand the fluid chemistry in this well that is quite extreme relative to typical waters at Earth's surface and used to inform both Gibbs energy calculations and microbiological analyses.