Pennsylvanian-age plant macrofossil biostratigraphy in tropical Pangaea: uniformitarianism, catastrophes and the ‘Cantabrian’ problem

Abstract

Abstract Upper Carboniferous stages in terrestrial strata are consistently recognizable throughout the Euramerican Realm based on the ranges of plant macrofossils rather than named biozones. Uniformitarianism is an invaluable principle used to understand much of Earth's history. However, it has been recognized that relatively short time intervals exist when major changes occurred in the biota and sedimentation style at a non-uniformitarian time scale. Many well-defined Upper Carboniferous stage boundaries are located at such events. The Cantabrian Stage was proposed in 1969 based on the assumption that the ‘Florensprung’ (‘floral jump’) of Gothan, a dramatic change in terrestrial floras at the traditional Westphalian–Stephanian boundary, indicated that strata were missing, and the postulated ‘gap’ had to be closed by finding strata representing this ‘missing’ time elsewhere. The suggestion of a ‘gap’ or hiatus at this level reflects uniformitarian thinking, but is incorrect. As recent work has shown that a drastic climatic change reached a threshold in the tropical palaeoequatorial parts of Pangaea at the Westphalian–Stephanian (approximately the Moscovian–Kasimovian) boundary as a consequence of a drying trend, floras changed rapidly, and the traditional Westphalian–Stephanian boundary is thus one of the most easily recognizable biostratigraphic boundaries in Pennsylvanian terrestrial beds. The Cantabrian Stage, proposed to fill the non-existent gap, does not exist and cannot be recognized, either in its type area or elsewhere.