Eltville Tuff

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The Eltville Tuff is a volcanic ash layer that was deposited in Central Europe during the Last Ice Age maximum . The time of the eruption is estimated to be around 18,000 to 19,000 years BC. Estimated .

Naming and type locality

The Eltville Tuff, also known as Eltville Tephra , was named in 1967 by Arno Semmel after its eponymous type locality Eltville am Rhein .

Geographical distribution

The distribution area of ​​the Eltville Tuff stretches from Limburg in the Netherlands and eastern Belgium around Liège over the Eifel , north-eastern Luxembourg , to Karlsruhe and further east to near Nuremberg . The northern border passes about 50 kilometers north of Cologne and reaches its northeasternmost point near Göttingen . Meszner (2008) suspects a possible eastern extension of the Eltville Tuff distribution area as far as the Meißen area ( Zehren profile ).

Dating

The luminescence ages for the Eltville Tuff vary between 17,200 and 18,600 years BC. For the loess layer immediately above the tuff horizon, Zöller and Semmel (2001) use thermoluminescence dating to give 19,000 years BC. They date the underlying loess to 23,000 years BC. Chr. Lang et al. (2003) found OSL ages from 17,500 to 17,000 years BC. For the Eltville Tuff, Frechen and Preusser managed it in 1996 with 17,800 ± 700 BC. Limit (also OSL). Ludwig Zöller (1989) with 18,600 years BC gave somewhat higher thermoluminescence ages. And Zöller et al. (1988) with 19,100 BC. Chr.

Description and chemical composition

The dark to black-gray, only several millimeters to centimeters thick Eltville Tufflage consists of pyroclastics and mineral fragments . When exposed to frost, it often appears wavy or wrinkled and can locally split into two or more (up to a maximum of 6 in the Bockeroth II profile ) individual layers. The poorly sorted pyroclastics include fragments with blistered partitions and slightly rounded pumice fragments in the micro range. The grain sizes of the partly severely broken rock fragments range from 0.3 to 0.5 millimeters in the medium to coarse ash range. The microbeads show a bubble content of up to 70%, whereby the tiny bubbles (<0.001 millimeters) are arranged in an irregular and partly open structure. They come from a high-temperature lava with low viscosity . All these features indicate the origin of the Eltville Tuff to the ash ejection of a strong Strombolian eruption .

Due to the feldspar-rich composition of the surrounding loess, only mafic mineral fragments could be reliably assigned to the Eltville tuff. They have the following composition:

The clinopyroxen phenocrystals are very rich in calcium and magnesium and show a diopside to Fassaitic character. They can be divided into two groups with different depths of crystallization . A deep-seated group crystallized at a pressure of 6 kilobars, while the flat- seated group only crystallized near the surface at pressures of 2 to 0 kilobars. Xenocrystals included in the delivery are likely to be rare. Overall, the composition of the clinopyroxenes points to the multiphase crystallization from an alkali basalt magma .

The olivines show a forsterite content of Fo 86 to Fo 91 and are therefore compatible with a basaltic magma .

The brown horn blends are titanium-rich pargasites and kaersutites . They are also typical of alkalibasaltic magmas. Some of them possibly originate from accumulations and vein-like accumulations at the earth's crust / mantle boundary .

Since the volcanic glass contained in the pumice has meanwhile completely transformed into clay minerals ( illites ), a further rock analysis is unfortunately no longer possible. The signature of the mineral fragments found, however, clearly indicates an alkaline basaltic magma.

stratigraphy

The Eltville tuff was embedded in the succession of the Oberwürmlösses during the Lascaux-Interstadial . He is generally in the footwall of the heritage Heimer Naßbodenhorizont E 3 below and in the hanging wall of the E 4 superimposed. The Rambacher Tuff (26,000 BC) and the Lohner Boden (28,000 to 32,000 BC ) can be found even deeper in the lying area .

Emission center

The emission center of the Eltville Tuff has still not been clearly identified. However, the total thickness of the tufflage reaches a maximum of 2 centimeters south of Bonn (near Ringen ), so that the focus of the eruption is to be found in the Eastern Eifel.

See also

Individual evidence

  1. ↑ A. Semmel: New sites of volcanic material in Hessian Loessen . In: Notbl. Hess. L.-Office Soil Research. tape 95 , 1967, pp. 104-108 .
  2. ^ S. Meszner: Loosen in Saxony. New investigations into the stratigraphy of the Weichsel ice age looseness in the region around Lommatzsch . 2008 (diploma thesis at the Technical University of Dresden).
  3. ↑ P. Antoine, inter alia: Rapid and cyclic eolian deposition during the Last Glacial in European loess: a high-resolution record from Nussloch, Germany . In: Quaternary Science Reviews . tape 28 , 2009, p. 2955-2973 .
  4. ^ L. Zöller, A. Semmel: 175 years of loess research in Germany - long records and “uncon-formities” " . In: Earth Science Reviews . Volume 54 , 2001, p. 19-28 , doi : 10.1016 / S0012-8252 (01) 00039-3 .
  5. ↑ A. Lang, u. a .: High-resolution chronologies for loess: comparing AMS 14 C and optical dating results . In: Quaternary Science Reviews . tape 22 . Oxford 2003, p. 953-959 .
  6. ↑ M. Frechen, F. Preusser: Combined luminescence dating using the example of the loess profile Mainz-Weisenau . In: Frankfurter geoscientific work, series D . tape 20 . Frankfurt a. Main 1996, p. 53-66 .
  7. ↑ L. Zöller: Geomorphological and geological interpretation of thermoluminescence data . In: Bayreuth Geowiss. Work band 14 , 1989, pp. 103-112 .
  8. ↑ L. Zöller, HE Stremme, GA Wagner: Thermoluminescence dating on loess-palaeoboil sequences from the Lower, Middle and Upper Rhine . In: Chemical Geology (Isot. Geosc. Sect.) . tape 73 , 1988, pp. 39-62 .
  9. ↑ B. Smykatz-Kloss: The loess deposits of the Pleiser hill country near Bonn and Neustadt / Wied as well as Picardy: Mineralogical-geochemical and geomorphological characterization, influence of weathering and origin of the loess . In: Dissertation at the Rheinische Friedrich-Wilhelms-Universität Bonn . 2003.
  10. ↑ P. Nimis, P. Ulmer: Clinopyroxene geobarometry of magmatic rocks Part 1: An expanded structural geobarometer for anhydrous and hydrous, basic and ultrabasic systems . In: Contributions to Mineralogy and Petrology . tape 133 , 1998, pp. 122-135 .
  11. ^ BE Leake and the members of the Subcommittee on amphiboles of the International Mineralogical Association Commission on new minerals and mineral names: Nomenclature of amphiboles . In: European Journal of Mineralogy . tape 9 , 1997, pp. 623-651 .
  12. ↑ Ludwig Zöller: Würm and Rißlöß stratigraphy and thermoluminescence dating in southern Germany and neighboring areas . In: Habilitation thesis . Ruprechts-Karl University, Heidelberg 1995.
  13. ↑ L. Zöller, among others: Last interglacial, Lower and Middle Weichselian - a comparative study from the Upper Rhine and Thuringian loess areas . In: Journal of Geomorphology . tape 48 (1) , 2004, pp. 1-24 .
  14. ^ E. Juvigné, A. Semmel: Un tuf volcanique semblable à 1'Eltviller Tuff dans lcs loess de Hesbaye (Belgique) et du Limbourg neerlandais . In: Ice Age and the Present . tape 81 , 1981, pp. 83-90 .