Data report: petrography of volcaniclastic intervals in IODP Expedition 385 cores from Guaymas Basin, Gulf of California

The Guaymas Basin is a 6 Ma transtensional ocean basin located in the central Gulf of California characterized by active seafloor spreading, off-axis magmatism, and high biogenic and terrigenous sedimentation rates. Sparse volcaniclastic intervals were identified by shipboard scientists in Quaternary sedimentary cores recovered during International Ocean Discovery Program (IODP) Expedition 385. Shipboard visual core descriptions and smear slide analyses were used to identify 57 volcaniclastic intervals, which were then sampled and analyzed macroscopically and microscopically. Petrographic modal analyses were conducted on a subset of 36 thin sections with a total of 300 points counted per thin section. A grain classification scheme was developed from published literature to characterize the compositional and textural variability of volcanic grains in cores from across the basin. Point count percentages reveal that vitric volcanic lithic fragments, particularly brown glass shards, are the dominant clast type observed at all drill sites, whereas crystal-bearing volcanic lithic fragments and mineral grains comprise a minor percentage of the total points counted. The vitric fragments also exhibit a wide range of shard vesicularity and morphologies. This data report presents a petrographic analysis of volcaniclastic deposits recovered during Expedition 385 to elucidate on the modal and spatial distribution of volcanic material in the Guaymas Basin.