Hamilton Quarry is a Late Carboniferous (Virgilian) lagerstätte near Hamilton, Kansas, United States. It has a diverse assemblage of unusually well-preserved marine, euryhaline, freshwater, flying, and terrestrial fossils (invertebrates, vertebrates, and plants). This extraordinary mix of fossils suggests it was once an estuary. This type of Lagerstätte is considered a Konservat-Lagerstätte (or conservation lagerstätte), due to the quality the preservation of soft tissue (skin preservation).
The lagerstätte occurs within a paleovalley that was incised into the surrounding Carboniferous cyclothemic sequence during a time of low sea level, and was then filled in during a subsequent transgression. The channel has a capping series of interbedded laminated limestones and mudstones for which are designated the Lagerstätte beds or ‘vertebrate horizon’. This facies contains a well-preserved mixed assemblage of terrestrial (conifers, insects, myriapods, reptiles), freshwater (ostracods), aquatic (amphibians, reptile), brackish or euryhaline (ostracods, eurypterids, microconchids, fish), and marine (brachiopods, echinoderms) fossils.