Gowganda Formation, Ontario Early Proterozoic Varve Thickness Data Hughes, G.B.; Giegengack, R.; Kritikos, H.N. Hughes, G.B. Giegengack, R. Kritikos, H.N. earth science/paleoclimate/paleolimnology (notes,null,null,count,null,paleolimnology,null,null,N,varve number) earth science/paleoclimate/paleolimnology (varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (Wharncliffe>LATITUDE 46.4338>LONGITUDE -83.3329) Rhythmically deposited argillites of the Gowganda Formation (ca. 2.0-2.5 Ga) probably formed in a glacial setting. Drop stones and layered sedimentary couplets in the rock presumably indicate formation in a lacustrine environment with repeating freeze-thaw cycles. It is plausible that temporal variations in the thickness of sedimentary layers are related to interannual climatic variability, e.g. average seasonal temperature could have influenced melting and the amount of sediment source material carried to the lake. A sequence of layer couplet thickness measurements was made from high-resolution digitized photographs taken at an outcrop in southern Ontario, Canada. The frequency spectrum of thickness measurements displays patterns that resemble some aspects of modern climate. Coherent periodic modes in the thickness spectrum appear at 9.9-10.7 layer couplets and at 14.3 layer couplets. It is unlikely that these coherent modes result from random processes. Modern instrument records of regional temperature and rainfall display similar spectral patterns, with some datasets showing significant modes near 14 yr in both parameters. Rainfall and temperature could have affected sedimentary layering in the Gowganda argillite sequence, and climate modulation of couplet thickness emerges as the most likely explanation of the observed layering pattern. If this interpretation is correct, the layer couplets represent predominantly annual accumulations of sediment (i.e. they are varves), and the thickness spectrum provides a glimpse of Early Proterozoic climatic variability. The presence of interannual climate patterns is not unanticipated, but field evidence presented here may be of some value in developing a climate theory for the Early Proterozoic. STUDY NOTES: Varve thickness data from the Gowganda Formation, southern Ontario, measured on an argillite outcrop located in the Mississagi River Valley near Wharncliffe, Ontario, Canada (at the intersection of highway 554 and highway 129). Sediments are early Proterozoic age, ca. 2.0-2.5 billion years before present. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Hughes, G.B. Investigator : Giegengack, R. Investigator : Kritikos, H.N. 2015-03-11 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/18216 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/on/gowganda2003varve.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/on/gowganda2003varve.txt English https://www.ncdc.noaa.gov/paleo/study/18216 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/on/gowganda2003varve.txt Gary B. Hughes, Robert Giegengack, Haralambos N. Kritikos2003Modern spectral climate patterns in rhythmically deposited argillites of the Gowganda Formation (Early Proterozoic), southern Ontario, CanadaEarth and Planetary Science Letters2071-413-2210.1016/S0012-821X(02)01155-Xhttp://www.sciencedirect.com/science/article/pii/S0012821X0201155X START YEAR: 2250000000 cal yr BP * END YEAR: 2224999744 cal yr BP -83.3329 46.4338 -83.3329 46.4338