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.
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...." One gets the impression of conflict within the Ordovician establishment.
Arenigian and Llanvirnian conodonts from Jamtland, northern Sweden.
Conodonts from the Guniutan Formation (Llanvirnian) in Hubei and Hunan Provinces, south-central China.
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.
(3), and interpreted the age as "may range from early Middle Arenigian to earliest Llanvirnian", thus supporting the Arenigian brachiopod age interpretation of Neuman (1968).
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.
The red chert and mudstone unit at the base of the Belle Lake Formation is likely Llanvirnian in age, as its contact with the early Caradocian wacke and shale is conformable.