THE UPPER PERMIAN (OCHOAN) CASTILE FORMATION: SIXTEEN OCTAVES OF PALEOCLIMATE VARIABILITY (Invited Presentation)

The continuous sequence of 210,000+ evaporitic varves in the Ochoan Castile Formation is a benchmark paleoclimate archive with no close contenders from any other geologic epoch. This remarkable ”geoclimatic record” was systematically and incrementally measured by Roger Y. Anderson starting in the late 1950’s together with Walter Dean and Doug Kirkland. In the ensuing decades the three scientists variously published their research on the significance of the Castile varves, establishing the foundational evidence for their annual origins. In his final years, Roger characterized the Castile varve time series as a broadband spectrum of paleoclimatic dynamics with “orbital”, “solar” and “chaos” domains. Here I review this characterization with a spectral analysis of the Castile varve time series that spans sixteen octaves of paleoclimatic variability. The results fully support Roger’s observations for Milankovitch cycles (the orbital domain), “quasi-bi-millennial” oscillations with 3000-year to 1500-year periods and a host of centennial oscillations with 200-year to 100-year periods (the solar domain). Decadal and inter-annual oscillations (the chaos domain) are analyzed across a high-resolution photo-scan of a 9.35-cm-long (240-year-long) segment from the varve series, supported by microprobe analysis, revealing strong, superimposed 21-year, 9.4-year and 4.3-year cycles. The statistical significance (99.6%) of the 9.4-year cycle as a spectral line is particularly high and distinguishes it as non-chaotic and a possible record of the Ochoan solar cycle. Spectral structure in the intra-annual band indicates variability within the annual cycle. Future interrogation of the Castile record might focus on the power differential between varves and lower-frequency oscillations, to solve the mystery of strong paleoclimate responses to the exceedingly weak Milankovitch forcing mechanism, and to link paleoclimate variability and direct solar forcing at decadal-millennial timescales.