Escandorgue

Escandorgue
Escandorgue in the Massif Central
Highest peak	Plateau de l'Escandorgue ( 851  m )
location	Département Hérault (Southern France )
part of	Massif Central
Coordinates	43 ° 43 '  N , 3 ° 21'  E Coordinates: 43 ° 43 '  N , 3 ° 21'  E
rock	basalt
Age of the rock	Pliocene

The Escandorgue is a small, in the southern French department of Herault located volcanic massif of the Quaternary . It forms an approximately 30-kilometer-long, north-south trending, ridge-like ridge that is connected to the Causse du Larzac in the north .

geography

The Escandorgue separates the Lergue and Salagou basins in the east from the Orb basins in the west. It is also drained by the following rivers:

• Graveson
• Ruisseau du Mas de Mérou
• Ruisseau de Mélac
• Ruisseau de Sourian
• Ruisseau de Vasplongues
• Ruisseau de Nize
• Soulondre

The ridge forms a southern extension of the 800 to 900 meter high Causse du Larzac. It begins in the north not far northwest of the 785 meter high Col du Perthus (on the D 902), then exceeds an altitude of 850 meters and gradually drops to 400 meters to the south. It culminates in the northern section with the Plateau de l'Escandorgue at 851 meters, its second highest peak, the Pioch Lachiou , reaches 849 meters.

At the top of the Col de la Baraque de Bral (611 meters), the RD 35 crosses the ridge from Lunas to Lodève . From the Col, the D 142 branches off to the north in the direction of Le Caylar and follows the entire northern section of the Escandorgue. After cutting the Col de la Baraque , the Escandorgue gains altitude again in the south and reaches another 698 meters in Le Mourel . The topographical southern end of the Escandorgue in the true sense then forms the Col de la Merquière pass near Brenas with 372 meters.

There are no larger settlements on the Escandorgue, only smaller villages and hamlets. The high elevations are mainly used for livestock.

geology

The arrangement of volcanic deposits in the Hérault department. The Escandorgue in the north impresses with its straight north-south orientation

In terms of volume, the largest part of the Escandorgue ridge is built up by flat Jurassic sediments, which are covered by quaternary volcanic rocks with a basaltic composition. The Jura series is a southern continuation of the sequence of layers of the Causse du Larzac, consisting of marls from the Lias and dolomites and limestone from the middle and upper Jura. Volcanism began in the Gelasian about 2.5 million years ago BP and lasted until the Pleistocene (1.5 million years BP). During this approximately one million year period, several small volcanic centers released basaltic lavas by means of strombolic eruptions , which poured over the plateau and filled paleo valleys.

Brenas at the south end of the Escandorgue

The following volcanic centers can be distinguished from north to south up to the 372 meter high Col de la Merquière :

• Volcanic cone west of Campestre . It lies at an altitude of over 800 meters and is located on the Doggers Dolomites .
• Basal extrusion west of Villecun on the Col de Bellevue . Two necks have protruded above the hettangium and are connected by a passage . Ringdykes are placed around one of the support centers.
• Important volcano near Saint Amans .
• Large volcanic cone at the 635 meter high Signal de Brenas west of Brenas. The strombolic cone, composed of ashes, lapilli and cinder, is criss-crossed by basaltic corridors and rises above Triassic shell limestone .
• Lava flow at Col de la Merquière at an altitude of 440 meters.

South of the Col de la Merquière is the large basaltic Plateau de Cerlencas , which is already covered by the layers of the Saxonian ( Permian ). Strictly speaking, it no longer belongs to the Escandorgue, but it is genetically related to it. The magma intruded here at two significant, overlapping faults - the southeast trending Mas Blanc fault and the east northeast trending Naves fault . Two ridges with several necks extend from the Signal de Brenas to the Plateau de Cerlencas, such as Castelas de Malevielle , La Roque southeast of Campillergues at an altitude of 338 meters and Pioch-Aurous-Haut at an altitude of 361 meters, a massive basanite with development towards ankaramite and limburgite . All of these necks also overlay saxonium. The Courbezou volcanic cone (486 meters) east of Bédarieux can be regarded as the southernmost branch of the Escandorgue volcanoes. It lies over the Dolomites of the Bathonian and Bajocian and clays and gravels of the Lower Eocene . This is where the volcanoes of Escandorgue end, but volcanism continues further north (to Canals on the Larzac) and south (for example in basalts of the Monts de Faugères east of Faugères and in basalts of the Monts de Cabrières ) north of Lieuran-Cabrières to finally reach the Mediterranean Sea at the Cap d'Agde volcano .

Individual evidence

1. ↑ Nehlig, P. et al .: Les volcans du Massif Central . In: Revue Géologues . Numéro spécial Massif Central. BRGM, 2003, p. 1-41 .
2. ↑ geze, B .: Languedoc Méditerranéen Montagne Noire . In: Guides Géologiques Régionaux . Masson, Paris 1979, ISBN 2-225-64120-X .