Llanvirnian

Llanvirnian

[lan′vir·nē·ən]
(geology)
Lower Middle Ordovician geologic time.
References in periodicals archive ?
Conodont faunas with Lenodus variabilis in the Upper Arenigian to Lower Llanvirnian of Sweden // Acta Palaeontol.
174), that "Two spectacular bursts in diversity took place [in the broad Ordovician context], one in the late Arenig and the other in the late Llanvirnian to early Caradocian.
Ten to 30 kilometres to the north and northeast of the Napadogan area of this paper, felsic and mafic volcanic rocks are more abundant (Poole 1963; Irrinki 1980, 1981), and some mafic volcanic rocks contain blocks of Llanvirnian slate and chert.
John Riva determined that they were Llanvirnian (written communication to Poole 2001).
The presence of early Ordovician (late Tremadocian to early Arenigian) graptolites in the underlying Bright Eye Brook Formation of the Woodstock Group (see above) and Late Ordovician (early Caradocian) graptolites in the overlying Belle Lake Formation of the Meductic Group (see below) restricts the depositional range of the volcanic components (Porten Road, Eel River, and Oak Mountain formations) of the Meductic Group to between early Arenigian and Llanvirnian time.