Abstract

The Middle Triassic Latemar Limestone in the Dolomites region, northern Italy, consists of hundreds of vertically stacked, meter scale, platform carbonate cycles. Each cycle is composed of a shallow marine subtidal carbonate unit with a thin (centimeter scale) vadose diagenetic dolomite cap. These "Latemar couplets" are the products of repeated episodes of submergence/emergence with durations estimated at nearly equal 20,000 yr. The couplets are arranged in upward thinning bundles of five, indicating the presence of a nearly equal 100,000 year modulating component. We examined this high frequency cycling in the platform buildup using a variety of classical and advanced spectral analysis techniques. We found significant evidence for the presence of a Milankovitch forcing signal in this cycling. We also present evidence that the adjacent coeval basinal facies, the Livinallongo Formation, exhibits a similar bundling pattern in its cm-scale hemipelagic carbonate/shale alternations. We conclude that Milankovitch-forced, small amplitude sea-level oscillations were the most likely cause of these Middle Triassic carbonate rhythms.

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