Blackberry Hill is a Konservat-Lagerstätte of Cambrian age located within the Elk Mound Group in Marathon County, Wisconsin. It is found in a series of quarries and outcrops that are notable for their large concentration of exceptionally preserved trace fossils in Cambrian tidal flats. One quarry in particular also has the distinction of preserving some of the first land animals. These are preserved as three-dimensional casts, which is unusual for Cambrian animals that are only lightly biomineralized. Additionally, Blackberry Hill is the first occurrence recognized to include Cambrian mass strandings of scyphozoans (jellyfish).
Age and stratigraphic placement
The strata at Blackberry Hill are known to belong to the Elk Mound Group; however, the lack of good stratigraphic markers (i.e., index fossils) in some Blackberry Hill localities, coupled with uncertainties about the age range of the Elk Mound Group itself, make it difficult to assign a precise age to these strata. Many researchers consider these rocks to be Late Cambrian, which is the age to which the Elk Mound Group was originally assigned; however, some recent authors now believe the Elk Mound Group and the fossils of Blackberry Hill could date back to the Middle Cambrian, based on certain fossils obtained from other areas.
Geological and environmental setting
Most of the strata are composed of well bedded quartz sandstone and orthoquartzite. They were deposited mainly on intertidal and supratidal zones of tidal flats of an inland sea of the supercontinent Laurentia. Ripple marks and numerous other sedimentary structures identical to those found on modern beaches abound on the strata surfaces. One of the most conspicuous features is extensive areas of specific structures not unlike those associated with modern biofilms and microbial mats. There is evidence suggesting that the feeding potential of this presumed microbial material was one of the forces that lured the first animals out of the sea. It is also believed that the same material aided in the exceptional preservation of many of Blackberry Hill's trace fossils.
Significance
Among the many paleontological discoveries thus far made at Blackberry Hill are the following: The first body fossils, and therefore the identity, of one of the first animals to walk on land. The only fossils that link those animals with their trackways. Body fossils of what may be the first phyllocarid with well preserved legs. Identification of the maker of Protichnites trackways after over 150 years of speculation. The largest concentrations of fossilized, stranded scyphozoans (i.e., jellyfish). What may be the first mating behavior in the fossil record.
The largest, most productive quarry is still in operation, thereby revealing fresh surfaces and the potential for new discoveries on a continuing basis.