Shoreline displacement data from the Trondheimsfjord area have been collected and a synthesis of the Late Weichselian and Holocene relative uplift is presented. The isobase direction is N 30–35°E during the whole period. The gradients of the shorelines are 1.7? m/km at 11,800 years B.P., 1.3 m/km at 10,000 years B.P., gradually decreasing towards the present with a value of 0.2 m/km at 5,000 years B.P. Some irregularities in the shoreline gradient curve in the Late Weichselian and Preboreal chronozones may be ascribed to crustal readjustments by faults. An interpolation of the 9,500 years B.P. shoreline to the Ångermanland and Baltic area shows a relative uplift at 11,800 years B.P. of 400–450 m in the central area of glaciation. The island of Hitra was probably deglaciated at about 12,000 years B.P. and Ørlandet/Bjugn somewhat later. The Younger Dryas ice marginal deposits at Tautra have been deposited early in this chronozone, and deposits proximal to this at Hoklingen and Levanger were probably deposited in the late part of the same chronozone.

Diatoms in lower sediments from eight basins of the Frosta peninsula, Nord‐Trødelag, Norway, have been analysed. All the basins have been isolated from the sea, and a succession from a flora influenced by marine and brackish water to a freshwater flora is always found. An attempt is made to establish a relative salinity range for the fjord basin around the investigated area, from the Younger Dryas chronozone to the end of the Atlantic chronozone. These changes seem to be controlled by the accumulation and ablation of the ice shield and also by major climatic changes in the early and middle Holocene. It is not possible to make a general list of lagoon taxa, because of great variation from basin to basin. The isolation contact (marine/brackish boundary) must be established at the end of the brackish water flora in the absence of lagoon types. The first period after isolation is characterized by a maximum in productivity with dominance of alkaliphilous types among the diatoms. A pioneer flora with dominance of Fragilaria taxa can be traced in the uppermost basins which were isolated just after the deglaciation of the area

The Sognefjord Formation in the Troll Field area was deposited during a general rise in sea-level during the Late Callovian to Early Volgian. A detailed study including palynology, sedimentology, response modelling and petrography of carbonate cement has been performed on 15 wells primarily from the western part of the field. All wells have been extensively cored through the reservoir enabling detailed palynological and sedimentological study of the depositional sequences in the wells. The Sognefjord Formation is interpreted, in this study, as a shoreline-attached tidally-influenced shelf complex. The study is based on the general consistency found between the eustatic sea-level curve published by Haq et al. in 1987 and the biostratigraphical zonation for the Troll Field described here. The response to sea-level fluctuations in a shallow marine environment is discussed and a response model is established. A theoretical assessment of the criteria for recognizing important events is presented. The maximum flooding surfaces (mfs) and sequence boundaries (sb) are easiest to recognize. Theoretically there is a higher probability of forming carbonate cements in connection with maximum flooding surfaces. The stratigraphically important dinocysts on Troll are classified according to their relation to sea-level fluctuations. Most of the palynozone boundaries are related to maximum flooding surfaces, except for a few which coincide with sequence boundaries. A stratigraphical subdivision of the Troll Field reservoir is presented based on a comprehensive palynological study. Lithofacies analysis in conjunction with palynofacies interpretation have been applied to delineate the depositional environment. As an aid to the interpretation a theoretical model was established. The predicted succession and variability of sequences and facies types outlined by the theoretical model could be recognized in all wells. Petrographical analysis shows that early diagenetic, near-surface cementation has occurred in connection with maximum flooding surfaces and sequence boundaries on Troll. With the help of the stratigraphical framework the presence or absence of sequence boundaries, transgressive systems tracts, maximum flooding surfaces, and highstand systems tracts in each cycle has been defined in each well. This has given the detailed geometry of the reservoir sands of the field, and also allowed correlation of carbonate cemented horizons which are associated with bounding surfaces of the systems tracts. Knowledge of the distribution and extent of these cemented horizons has considerable significance for oil production strategy, particularly the siting of horizontal wells.