Lake Pavin History, geology, biogeochemistry, and sedimentology of a deep meromictic maar lake

86

1500 1000 1500 1500 1500 1500

NNO

0,25 Ma - Sancy volcano: late stage1 Ma - Sancy volcano: initial stage2 Ma - Northern volcanoes (Banne d’Ordanche and Aiguiller)2,5 Ma - Intra-caldera volcanism3,2 Ma - Pre-caldera alkaline series

Basement

Phonolites

Basalts

Rhyolites

Evolved pyroclastites(mostly ‘Grande Nappe’ ignimbrite)Pyroclastic rocks of trachyteand trachyandesite composition

Sediment

Ordanchites

Trachytes and trachyandesites

0

4 km

Haute Dordogne

caldera

Sancycaldera

SSE

E D C B A

Fig. 4.2

Evolution of the growth and destruction of the Monts Dore massif (After Cantagrel and Baubron

1983

, modifi

ed). Ordanchite is tephrite related to the undersaturated series. A to E cor-

responds to the fi

ve main cycles of activity

A. Gourgaud