Major-oxide and trace-element geochemical data from rocks collected in 2015 in lower Cook Inlet, Iniskin - Tuxedni region, Alaska

The Iniskin-Tuxedni Bay area contains excellent exposures of nearly all of the lower Cook Inlet Mesozoic succession, including most of the stratigraphic sections that define the interval and the petroleum source rocks that comprise the basin. An underdeveloped understanding of the Mesozoic petroleum system has led the Alaska Department of Natural Resources' Division of Geological & Geophysical Surveys and Division of Oil and Gas, and the U.S. Geological Survey to collaborate on a multi-year project that includes two major mapping campaigns. Geologic mapping between Chinitna Bay and the Johnson River during the 2015 field season encompassed volcanic arc rocks northwest of the Bruin Bay fault system, and Mesozoic forearc basin stratigraphy extending to the Cook Inlet coast. To understand and represent the complexity of the volcanic arc systems in the region, we analyzed ten samples of volcanic rocks, two samples of gabbro sill, and one mafic dike sample for major and minor oxides and trace elements. Although mineralization was not noted in the samples collected for major oxide analysis, findings of interest include: one sample with weak Cr and Ni enrichment, three samples with lightly elevated As, and slight S anomalies (0.37 wt percent and 0.25 wt percent) in samples described as Talkeetna Formation. The Talkeetna Formation sample with 0.37 wt percent S also had elevated Cu (321 ppm) and As (58 ppm). The analytical data tables associated with this report are available in digital format as comma-separated values (CSV) file.