Abstract: Sedimentological study of various Liassic sequences in the Pontides has revealed the outlines of thegeomorphological, depositional, and tectonic characteristics of their environment of deposition. At the beginning ofthe Lias, the Pontides were a positive region associated with the active continental margin of Paleo-Tethys alongthe northern border of Gondwana - land. On this wide area, formed mainly from various Paleozoic (? and Triassic}rocks, clastic platform sediments of dominantly fluvial, swamp, and shallow - marine environments were laid down.Rifting and associated block faulting began along the southern border of the Pontides related to the opening ofthe northern branch of Neo - Tethys at the beginning or just before the Sinemurian. This event affected large areasin the Pontides and generated seamounts and intervening basins corresponding with horsts and grabens respectively.This topography determined the tectonic characteristic of the northern margin of Neo-Tethys and controlled sedimentation during and after the Sinemurian. On top and along the flanks of the seamounts locally condensed seriesincluding, red-grey coloured biomicrite, bîosparite and pelmicrite, and shallow carbonate facies including oolitesand reefs were deposited, whereas mainly grey - coloured turbidites made up of shales, sandstones, conglomerateswith volcanic and crystalline clasts, and intercalations of tuffs and lavas characterized the basin deposition. Locally,into these turbidities, material was carried from the condensed sequences capping seamounts. In some areas (e.g.Amasya and Gümüşhane) deep-sea deposits directly overlie the seamount deposits as a result of the latter`s subsidence, perhaps owing to listric normal faulting and block rotation. Environmental analysis of the Liassic deposits inthe Pontides show that the Bilecik, Ankara and Alucra (Giresun) areas were generally located on seamounts, the Mudurnu and Niksar-Reşadiye areas were basins; and the Amasya, Havza, Gümüşhane and tspir - Yusuf eli regionswere rapidly subsiding seamounts. These data indicate that the northern branch of Neo - Tethys formed as a resultof the rifting of the Paleo-Tethyan magmatic arc from the Gondwana - land platform during the Lias and notearlier, during the Trias as claimed by some researchers.