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Early geological maps: Mapa geognostico del Tirol (1808), a first approach to map the Alps

Considering geology, the Alps are today one of the best studied mountain region of the world. This circumstance can be explained by the geographic location, in the middle of a densely inhabited continent the Alps were never considered a hinderniss, travellers had to pass trough, and these travellers were the first to report on the natural wonders hidden between the mountain peaks.

Beginning with the 18th century local naturalists began to explore more systematically the region.
Surprisingly one of the first geological maps depicting a part of the Alps was drawn by a Spanish naturalist. The Catalan Carlos de Gimbernat (1768-1834) in 1808 produced on behalf of the Spanish King Karl IV the first geological map entitled "Mapa geognostico del Tirol".

Fig.1. Carlos de Gimbernat´s geological map (picture taken from BAUMGARTEN 2007).

Today only two copies are known, both treasured in the Bavarian State Library (Munich, Germany), a much greater project, planed by Gimbernat to map and describe the geology of the entire Alps, was never finished.
Gimbernat visited the eastern Alps between August and October 1803. His geological map was based on the cover sheet of one of the most exact maps available at the time for the region of Tyrol, the "Atlas Tyrolensis" of Peter Anich and Blasius Hueber published in 1774.
The hand-coloured map of Gimbernat depicts like modern geological maps the different lithologies (16 signatures) with different colours, also mines and quarries (9 signatures) are recorded, the map was intended to serve an economic cause. The quality of the map is very approximate (but we also must consider he did the field work and collection of rock descriptions in just three months), Gimbernat discerned only schist as a metamorphic rock, the broad rosé coloured area (Granit) is a misidentification of single and local intrusions in the predominant metamorphic unit.

Fig.2. Legend of rock types used by Gimbernat: Graniticas: Granite; Pizassas: Quartz schist; Calcareo-lamelar: stratified limestone; Calcareo-granulento: solid limestone; Dolomita: dolomite; Magnesiana: magnesite and serpentinite; Grauvaka: sandstones and conglomerates; Porfido: Rhyolite and ignimbrite; Grunstein: amphibole bearing rocks; Basalto: basalt; Arcilla lamelar: argillite; Piedra arenosa: sandstones s.s.; Hieso (Yeso): gypsum

For resources worth mining he distincts Oro (gold), Plata (silver), Cobre (copper), Plomo (lead), Zinc (Zinc), Hierro (Iron), Kobalto (Cobalt), Hulla (Coal) and Sal (Salt).
Tierra verde (seladonite) and Guijarrat (Quartz bearing rocks).

The colour schema adopted by Gimbernat is influenced by the suggestions of the German geologist Abraham Gottlob Werner (1749-1817) and the poet Johann Wolfgang von Goethe (1749-1832):

Colours after Gimbernat 1808*
Colours after Werner 1790**
Schist (Paragneisses and micaschists)
*light green
** grey-blue
Granit (Metamorphic rocks of mainly granitic origin)
*light red
** light red
Quartz porphyries (Acidic lavas, rhyolite and resulting effusive products - ignimbrites)
*light orange
**orange-brown
Sandstone
*light yellow
** yellow
Limestone
*light blue
** blue
Basalt
*light grey
**dark brown-dark green

Gimbernat shared also the Neptunian vision of Werner; all lithologies were deposited in a primordial ocean, and exposed subsequently by regression of the ocean.
This position is enforced by a letter send in 1808, describing the geology of the mapped area he declares:


"All the rocks were formed by crystallization in situ. Their horizontal position is the proof. It is erroneous to believe that so-called "terrestrial revolutions" have deformed the rocks."

References:


BAUMGARTEN, B. (2007): Carlos de Gimbernat and the first geological map of Tyrol (1808). Geo.Alps, Sonderband: 1-10

VOLKMAR, S. & VOLKMAR, M. (2005): Introduction to the geology of South Tyrol. Ufficio geologia e prove materiali - Provincia Autonoma di Bolzano-Alto Adige: 80

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