The invention relates to a method for the continuous obtention of synthesis gas by the direct gasification of carbon fractions contained in oil sands and/or oil shales in a vertical process chamber (2) having a calcination zone and an oxidation zone (6), in which the calcinated, fractions rich in carbon oxidize with oxygen-containing gas. The gaseous reaction products are withdrawn at the top of the vertical processing chamber (2) that has the shape of a vertical shaft furnace which is continuously flown through from the top to the bottom by a bulk material which itself is not oxidized. Oxygen-containing gas (10) is at least partially introduced beneath the oxidation zone, whereby the rising gas flow is facilitated. The bulk material is at least partially provided by the natural inert rock content in the oil sands and/or the oil shales. Added alkaline substances convert under reductive conditions the gaseous sulfur compounds, which were obtained at temperatures above 400 DEG C from the constituents of the oil sands and/or the oil shales, by chemical reaction into solid sulfur compounds which are at least partially discharged with the gaseous reaction products and are removed from the gas phase at temperatures above 300 DEG C by fine material separation (18).