In the coastal area of Surinam four series of sediments can be distinguished (cf. fig. 2 and Schols en Cohen, 1953): the Niokerie series (with a. o. clays in several colours and some shales), only known in a few borings in the neighbourhood of Paramaribo and Nickerie; the Zanderij series (with white sands an kaolinic clays); part of those sediments (especially in the outcrop region) seem to represent detritus from the nearby hilly country, washed out and supplied by small rivers; Zanderij series outcrops in the “savannah-belt” (“savannah-gordel” in fig. 1); the Coropina series (with fine sands and clays) is found at the surface in the “older coastal plain” (“oude kustvlakte” in fig. 1); in this region its sediments have the character of tidal flat deposits; the Demerara series comprising the youngest sediments is mainly found in the “younger coastal plain” (“jonge kustvlakte” in fig. 1). During and shortly after the formation of the Zanderij series the region has been tilted towards the north. After the formation of the tidal sediments of the Coropina series a rather important lowering of the sea-level caused valley intrenchment down to a depth of about 6—8 m below the surface of the ""older coastal plain"". During the following rise of the sealevel the sediments of the Demerara series were deposited and the valleys were partly drowned and silted up. Up till now it was not possible to establish the exact geological age of these series and phenomena. Fig. 4 shows the palaeogeographical evolution of a part of the Surinam coastal area.