Comment on ‘A Miocene age for the Molo Formation, Norwegian Sea shelf off Vestfjorden, based on marine palynology’

First, I thank Grøsfjeld et al., (2019) for a well-organised paper that provides new insight on the age of the Molo Formation penetrated in exploration well 6610/3–1 off Vestfjorden/Lofoten, Norway. The stratigraphic position of the Molo Formation is well established above the Mid Miocene Unconformity (MMU) and below the Quaternary Naust Formation (Rise et al., 2005). Historically, recognition of in situ vs. resedimented forms has been a challenge and therefore the age assignments vary from Oligocene to Pliocene (Rokoengen et al., 1995; Henriksen & Weimer, 1996; Eidvin et al., 2007; 2014; Eidvin &Riis, 2013; Grøsfjeld et al., 2019). The aim of this comment is to discuss if some of the marine palynomorphs that Grøsfjeld et al. (2019) interpreted as in situ are instead resedimented as this may re-date the Molo Formation to the Early Pliocene. Grøsfjeld et al. (2019) clearly state that the assemblages are strongly dominated by reworked taxa, Paleogene taxa being particularly abundant. They discussed two age hypotheses for the Molo Formation, a Mid–Late-Tortonian, which they preferred, and a Messinian. They also gave a maximum age of Middle Miocene (Serravallian) and a minimum age of Lower Pliocene (Zanclean). My age suggestion corresponds with their minimum age and is slightly younger than their second hypothesis. The small shift in age is significant and of regional importance because it shifts the Molo Formation from a syn- to post- Mid Miocene compressional phase (Løseth & Henriksen, 2005). Hence, the Molo Formation will be younger than the syn-tectonic Kai Formation which was deposited during the global Mid to Late Miocene event (Potter & Szatmari, 2009).