Carboniferous tonsteins (kaolinized volcanic-ash beds) of wide geograp
hic distribution are known in both Europe and North America. Relict vo
lcanic minerals common in these Euramerican tonsteins are volcanic qua
rtz (including beta-quartz paramorphs), zircon and ilmenite; less comm
on are magnetite, fayalite, rutile, monazite, xenotime, apatite and sa
nidine. Data for two relatively thick (3-13 cm) and widespread (> 400
km) European tonsteins (Erda and Sub-Worsley Four-foot) indicate an in
crease in detrital quartz near the top of the beds which indicates mix
ing with normal clastic sediments, including the introduction of heavy
detrital minerals (e.g., tourmaline and garnet). These thick tonstein
s show multiple horizontal bedding, normal graded bedding, disturbed b
edding, and centimeter-scale scour surfaces. The Fire Clay tonstein in
North America represents from one to five separate volcanic air-fall
ash deposits as determined by normal graded bedding and mineralogical
analysis. These features indicate several episodes of volcanic-ash dep
osition and very localized subsequent erosion and bioturbation. Electr
on microprobe data from glass inclusions in volcanic quartz in Euramer
ican tonsteins indicate a rhyolitic origin for these tonsteins and rev
eal chemical ''fingerprints'' valuable for intra- and inter-basinal co
rrelations. However, the tectonic framework for European and North Ame
rican tonsteins was quite different. In Europe, volcanic-ash beds were
associated with Variscan collisional tectonics, whereas in North Amer
ica, volcanic ash was associated with Ouachita tectonic activity, expl
osive volcanism from the Yucatan block, collision between the South Am
erican and North American plates, and the formation of Pangea.