7-11 Taphonomy and geochemistry of the Miocene Ortok bone bed, Kyrgyzstan

Session: Earth Life Sciences across the Cordillera (Posters)

Presenting Author:

Authors:

Abstract:

On the north side of the Kochkor Basin, Kyrgyzstan, near the small town of Ortok is a small outcropping of Late Miocene syntectonic basin-filling sediments. While unpresuming in size or appearance, it has produced hundreds of mammal fossils. After initial collections in the 1960 were used to provide rough geochronology for constraining the timing of tectonic uplift in the basin no collections occurred for the following 50 years. Since 2012 however the bone bed has produced both extensive surface collections every few years and incredibly dense quarries. All fossils thus far collected are mammals, predominantly ungulates. A high diversity of ungulates, ranging in size tiny bovids to giant rhinos, suggests that the ecosystem could support large numbers of both browsers and grazers, possibly indicating a mixed semi-open habitat. While limited in number, the carnivores also suggest a thriving diverse ecosystem, with both giant cats and hyenas. With this diversity of mammals indicating a rich and productive ecosystem, the question arise of what could cause such a high density of bone to accumulate in one place?

We believe this site records a chilling story of how local and regional tectonics drive rapid changes in climate resulting in major turn overs in faunas. Today Kyrgyzstan still has rich riparian zones, but most of the country is dominated by high steppe lands and montane regions. Biostratigraphy and paleomagnetostratigraphy of Ortok place the bone bed between 5-7 million years old, a time period that corresponds well with major uplift of the Tien Shan and Pamirs. We suggest this uplift blocked the Indian monsoon from reaching Central Asia, resulting in huge droughts. An over representation of juvenile herbivores and rough “last supper” wear confirm this. As dead ungulates accumulated, carnivores were less impacted. When the rains finally returned, at least temporarily, carcasses were pushed across the valley to pile up into a rich bone bed. We are now adding geochemical analyses to the statistical analyses of the fauna to better investigate signs of drought and the impact this could have on increasing aridity.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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