Marshosztályozás

Marshosztályozás, also known as Marsh classification, is a method used in paleontology and stratigraphy to subdivide geological time, particularly in the Mesozoic Era. It is based on the study of fossilized remains, specifically the ammonites and belemnites that were abundant during that period. These marine cephalopods evolved rapidly and had distinct forms that changed over relatively short geological spans, making them excellent index fossils.

The classification system was developed by the German paleontologist Heinrich Georg Bronn and later refined by others. It divides the Mesozoic into distinct stages, each named after a specific rock formation where characteristic fossils were found. For instance, the Jurassic period, a major part of the Mesozoic, is broken down into numerous stages such as the Hettangian, Sinemurian, Pliensbachian, Toarcian, Aalenian, Bajocian, Bathonian, Callovian, Oxfordian, Kimmeridgian, Tithonian, and others. Each of these stages represents millions of years of Earth's history.

The Marshosztályozás provides a chronological framework for understanding the evolution of life and the geological events that occurred during the Mesozoic. It allows geologists and paleontologists to correlate rock layers across different geographical locations, even continents, by comparing their fossil content. This is crucial for dating rocks, reconstructing ancient environments, and understanding the distribution of prehistoric life. While newer dating methods exist, the Marshosztályozás remains a fundamental tool in historical geology.