Abstract

Paleomagnetic measurements and a dated tephra from outcrops of Davis Creek silt overlying ancient geomorphic surfaces in the East Block of the Cypress Hills, Saskatchewan, indicate that these sediments were deposited during several polarity intervals of the Late Miocene C4 polarity chron. Polarity and tephra data reported in this study provide minimum ages for the formation of underlying depositional and erosional surfaces, while previous studies provide maximum ages based on fossils and tephra underlying the oldest depositional surfaces. Collectively, these suggest that most of the Davis Creek silt was deposited over about a 1 Ma time span from about 9.3 to 8.3 Ma, confirming that the Cypress Hills region acquired most of its topographic relief and preglacial surficial deposits during the first half of the Late Miocene. Based on polarity and tephra studies, as well as magnetostratigraphic correlation of the two study sites, we conclude that rates of loess accumulation in the Cypress Hills were apparently very low during the Late Miocene.

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