The floristic relationship between the upland and lowland Carboniferous wetlands of Variscan Euramerica \u2014 Evidence from some medullosalean pteridosperm fronds

Christopher J Cleal,Borja Cascales-Miñana

doi:10.1186/s42501-019-0029-3

Abstract

Alethopteris grandinii represents remains of fronds of a medullosalean pteridosperm (probably a small tree) that rapidly migrated across the lowland wetland habitats of Variscan Euramerica in middle Asturian (late Moscovian) times. This was probably caused by changing drainage patterns within the lowland coal swamps, in response to climate and landscape changes. However, these medullosaleans had first appeared rather earlier, in early Bolsovian (early Moscovian) times, in upland wetland habitats. These upland habitats may have pre-adapted these plants to the changed condition in the lowland coal swamps.

Highlights

During Pennsylvanian times, large parts of palaeotropical Euramerica were covered by wetlands, often referred to as coal swamps because of the extensive coal deposits that were formed from their peats
7 Conclusions The medullosan pteridosperms that bore Alethopteris grandinii (= A. ambigua auct.) and possibly Alethopteris pseudograndinioides fronds occurred in the upland wetland basins of Variscan Euramerica in early Bolsovian times, and only migrated into the lowland wetlands in middle Asturian times, some 4 million years later
The vegetation change represented by the base of the Crenulopteris acadica Zone has been linked with landscape and climatic changes possibly resulting in better-drained substrates (e.g. Cleal et al 2010a), the continued development of coal deposits indicates we are still dealing with wetland habitats

Summary

Introduction

During Pennsylvanian (late Carboniferous) times, large parts of palaeotropical Euramerica were covered by wetlands, often referred to as coal swamps because of the extensive coal deposits that were formed from their peats. This is accompanied by a plot of the sizes of the types of A. grandinii, A. friedelii and A. ambigua ( of Alethopteris lesquereuxii Wagner) on the same dimension space. Wagner (1968) had previously stated that the slender pinnule form, which he called A. ambigua, could range down into the Bolsovian Substage Lower “Assise” Flambants: Pit V, Merlebach (Veine 5 and 16; Bertrand 1932), Borehole Chasseurs (depths 656.5 m, 794.0 m, 825.6 m and 910.4 m), Borehole Créhange 1 (depths 1799.4 m and 1799.6 m), Borehole Fockloch (depth 535.4 m), Borehole Folschviller 23 (depth 15.8 m), Borehole Hallering (depth 1341.5 m), Borehole Merbette (depths 1007.9 m and 1007.9 m), Borehole Merlebach (depth 278.6 m), Borehole Oratoire (depth 808.9 m), Borehole Simon 21 (depth 297.1 m), Borehole St Fontaine 1 (depths 709.8 m, 781.8 m, 933.5 m, 940.9 m, 956.7 m and 1051.4 m), Borehole St Fontaine 2 (depths 509.8 m, 1038.4 m and 1049.6 m), Borehole St Fontaine 4 (depths 942.4 m, 976.9 m, 1086.1 m, 1086.1 m and 1098.4 m), Borehole St Fontaine 6 (depth 1103.5 m) and Borehole Tritteling (depths 1044.8 m, 1079.5 m, 1102.0 m, 1102.2 m and 1102.3 m)

Discussion

Conclusions