Mastogloia Sea

[7] As a result, some sea (salt) water started to penetrate into the basin through the Danish straits, mixing into the vast freshwater body.

This phase of the body of water takes its name from the brackish water-dwelling diatom genus Mastogloia, the species of which are characteristic of the geological deposits of this stage.

[6][8][b] As fresh water lakes became part of the sea identification in the now marine deposits of Mastogloia smithii allow dating which is between 9.8 and 8.5 ka cal.

[2] Continuing sea level rise during this stage deepened the straits connecting the body with the ocean, thus increasing the influx of salt water.

[3] The marine microfossil record in today's deepest part of the Baltic Sea shows before 7.1 ka cal.

[12] In the Baltic Basin the Early Holocene rapid sea-level rise, well known from more southern European North Sea coasts was only after 8.5 ka cal.

[6][15] Even the fossil diatom content of the phase's sediments – cited by researchers as the key method of distinguishing deposits of different Baltic stages – is ambiguous, in many places showing no difference from that of Ancylus deposits, and at best including an admixture of Mastogloia diatoms in an otherwise typical Ancylus flora.

[8] Deposits of the Littorina Sea phase show a drastic change both in the visible characteristics of the sediment and its diatoms.