Maintrapp

from Wikipedia, the free encyclopedia

Volcanic relics are summarized as Maintrapp , Untermaintrapp , Trapp von Frankfurt or Main basalt formation , which are found in the southwestern foreland of the Vogelsberg in the area of ​​the Wetterau and the Ronneburg hill country , which is roughly defined by the connecting lines between Frankfurt am Main , Bad Homburg vor der Höhe , Friedberg , Ranstadt , Büdingen , Gelnhausen , Langenselbold and Hanau is limited. The Main line is only crossed by the deposits near Mühlheim-Dietesheim and the Hanau districts of Steinheim and Klein-Auheim or near Frankfurt-Louisa train station and west of Neu-Isenburg . The two last mentioned, very small-scale occurrences are supposed to be part of a larger cover that was proven by drilling in the subsoil of the western part of the Frankfurt city forest. In a similar way, the aboveground deposits of Mühlheim-Dietesheim and Hanau-Wilhelmsbad form parts of a coherent ceiling that extends underground into the Kahl am Main area.

Status as an independent volcanic complex

At the beginning of the 20th century, the volcanic phenomena in this area were assigned to the Vogelsberg volcanism. The demarcation against the volcanism of the Vogelsberg goes back essentially to the Hessian state geologist Wilhelm Schottler , who on the one hand based the independence on the relative petrographic uniformity of these rocks, on the other hand assumed that these basalts could be differentiated on the basis of their age: on the basis of stratigraphic terrain findings of the Basalt he assumed that the volcanic rocks were formed in the lower Pliocene (and thus were significantly younger than the Vogelsberg volcanism). More recent radiometric dates show that this assumption was incorrect and that the formation of the rocks took place in the Miocene (see section "Age of volcanism"); However, since then no uniform assessment has been able to establish itself in the literature: Partly the view of two separate volcanic areas is advocated, partly the affiliation of volcanism to the Vogelsberg is insisted.

Appearances in the terrain

In contrast to the closed occurrence of volcanic rocks, as it is known from the Vogelsberg to the northeast, the volcanic deposits of the Maintrapps consist essentially of isolated, larger and smaller remnants of the ceiling on the mountain ranges, which mostly extend in a NE-SW direction, between those in the Valleys, the rocks of the Tertiary (Wetterau) or Permian (Ronneburg Hügelland) come to the fore in large areas. Regarding the occurrence of volcanic production chimneys, there is again disagreement in the literature: While older works confirm the existence of such structures, their absence is found in the more recent literature. The volcanic rocks in the southern part of the deposit are mainly tholeiitic basalts ; Alkali basalts, limburgites and tuffs occur less often and mostly in small areas.

Age of volcanism

The age of the rocks is given as 16.3 million years. Other dates vary between 13 and 16 million years (cited from).

Economical meaning

Abandoned basalt quarry in tholeiitic basalt of the Ronneburg Forest (near Altwiedermus )

In the Steinheim-Dietesheim area, rocks from the Maintrapps were mined on a large scale. The quarries are no longer in operation and are partially used as recreational areas. Mining was carried out on a smaller scale in numerous other places; the traces are then not particularly noticeable in the landscape.

Individual evidence

  1. ↑ a b c Gottfried Hofbauer: Volcanoes in Germany. Scientific Book Society, Darmstadt, 2016, p. 157
  2. ^ Wilhelm Wenz: The Mainz basin and its peripheral areas. Ehrig Verlag, Heidelberg, 1921, pp. 208-221
  3. ^ A b Lars-Oliver Renftel: Explanations of the Geological Map of Hesse 1: 25000, sheet 5819 Hanau . Ed .: Hessian State Office for Soil Research. 2nd Edition. Wiesbaden 1998, p. 50-57 .
  4. ↑ a b c Hans Pfisterer: The basalts of the southwestern foothills of the Vogelsberg on the right bank of the Main. In: New yearbook for mineralogy, geology and paleontology, supplement volume. Volume 40, 1916, pp. 1-50
  5. ^ Wilhelm Wenz: The Mainz basin and its peripheral areas. Ehrig Verlag, Heidelberg, 1921, p. 24
  6. ↑ William Schottler: The Vogelsberg. In: Notblatt der Hessische Geologische Landesanstalt zu Darmstadt, 5th episode , issue 18, Darmstadt 1937, pp. 3–86
  7. ↑ Maurice Krafft: Guide to the volcanoes of Europe. Volume 2: Germany - France. Ferdinand Enke Verlag, Stuttgart, 1984, pp. 1-2
  8. ↑ Theodor Ernst, Gerd Schorer: The pyroxenes of the "Maintrapps", a group of tholeiitic basalts from the Vogelsberg. In: New yearbook for mineralogy, monthly books. 1969, pp. 108-130.
  9. ↑ A. von Reinach: Explanations of the special geological map of Prussia, sheet Hüttengesäß (5720 Büdingen, reprint) . Ed .: Hessian State Office for Soil Research. Wiesbaden 1996, p. 42-49 .