Sularp Brook (), Lund Municipality, Skåne, Sweden, is the location of the

Global Boundary Stratotype Section and Point A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted b ...

(GSSP) which marks the boundary between the Middle and Late epochs of the

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

period on the

geologic time scale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...

. The

first appearance In American comic books and other stories with a long history, first appearance refers to the first issue to feature a fictional character. These issues are often highly valued by collectors due to their rarity and iconic status. Reader interes ...

of the

graptolite Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian ( Miaolingian, Wuliuan) through t ...

''Nemagraptus gracilis'' defines the boundary. The rock section consists primarily of dark-gray shale and mudstone, except for a phosphorite marker bed 1.4 m above the GSSP, and was probably deposited at a water depth exceeding 100 m. Drill cores have revealed almost identical stratigraphy across an area several km wide. Due to heating, possibly from an intrusive

dike Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes ...

, the stratotype is unfit for dating by magnetic analysis, but this lack is compensated by the diversity of chemostratigraphic and

biostratigraphic Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...

options.

References

* * Geology of Sweden Stratigraphy of Europe Ordovician Sweden Geography of Skåne County Scania {{paleo-site-stub