Derivation of name. The name refers to the stratotype locality.
Stratotype.The Parautochthon river section at Brennsætersaga (Fig. 10) is designated as the stratotype. Here the new member is 4 m thick and rests unconformably on the Ringsaker Member of the Vangsås Formation. It is overlain by the Tømten Member of the Ringstrand Formation.
Lithology. The lower part of the member is dominated by siltstone with thin interbeds of sandstone whereas the upper part consists of medium- to coarse-grained quartz sandstone (the 'Bråstad sandstone' of previous literature).
Boundaries. In the Lower Allochthon and Parautochthon the Brennsætersag Member rests unconformably on the Vangsås Formation and there is a thin basal conglomerate, locally with boulders up to 0.3 m in diameter of Ringsaker Quartzite (Skjeseth 1963, p. 47). Small-scale channels have been observed in the top of the Ringsaker Member at Sollerud (new data). In the Autochthon the Brennsætersag Member rests on weathered crystalline basement, also with a conglomerate at the base. The boundary towards the overlying mud- and siltstones of the Tømten and Redalen members is sharp.
Distribution and thickness. The member is most typically developed in the Parautochthon of the Mjøsa District, where it is 1.5-4 m thick (Sollerud and Brennsætersaga sections, respectively). It is suggested attributing the lower sandy part of the Ring-strand Formation in the Autochthon to the Brennsætersag Member as well. In the Lauselva section this unit is 1.25 m thick and includes a conglomerate in the middle (a log is shown by Ebbestad et al. 2003, fig. 3). A very thin Brennsætersag Member is present in the higher trust slices of the Lower Allochthon, e.g. in the Bråstad River, where it is only 0.6 m thick (see Vogt 1924). Skjeseth (1963) reported a slightly greater thickness, but minor faulting has repeated the basal part of the succession. Here it is directly overlain by the Tømten Member. At Strandbergsodden (also Lower Allochthon) the Brennsætersag Member is c. 2.5 m thick and is overlain by the Redalen Member (see Vogt 1924). Both of these successions display a coarsening-upward trend, but no 'Bråstad sandstone' unit (sensu Vidal & Nystuen 1991) is developed. Elsewhere in the Lower Allochthon, e.g. north of Redalen and at Steinsodden, no Brennsætersag Member is developed.
Age. The Brennsætersag Member of the Parautochthon contains acritarchs of the Heliosphaeridium dissimilare-Skiagia ciliosa Zone (Vidal & Nystuen 1991). Holmia cf. mobergi has been reported from the unit at Brennsætersaga (Skjeseth 1963; Bergström 1980, 1981), but the single trilobite specimen most likely derives from the sandstone bed in the top of the Tømten Member in this section (M. Høyberget personal communication 2004). The Brennsætersag Member of the Lower Allochthon is inferred to be older than the Brennsætersag Member of the Parautochthon and Autochthon (Fig. 8).
Remarks. The member has previously been referred to as 'Basalavdeling med Discinella holsti' (Vogt 1924), Brennsæter Limestone, 1?1 (Skjeseth 1963), Brennsæter shale (Vidal & Nystuen 1991) and Bråstad sandstone (1?2) (Skjeseth 1963; Vidal & Nystuen 1991). The so-called Brennsæter shale and Bråstad sandstone of the Parautochthon cannot be correlated to sections within the Autochthon and Lower Allochthon in a consistent way and we suggest combination of them into just one coarsening-upward member.
From: A.T. Nielsen & N.H. Schovsbo, 2007