Application of channel-belt scaling relationship to Middle Jurassic source-to-sink system in the Saishiteng area of the northern Qaidam Basin, NW China

Palaeodrainage basin, as an important component of the source-to-sink system, contains critical information on provenance and palaeoenvironment. Previous studies indicate that the scaling relationships of source-to-sink system components generally follow power laws, and channel-belt thickness represents a reliable first-order proxy for the drainage area. In this study, a database of borehole cores and geophysical well logs of the Jurassic coal measures from Saishiteng area in the northern Qaidam Basin was used to reconstruct the palaeogeography, and to identify single-story channel-belts. Three palaeochannels, namely, River A, River B and River C, were identified which were persistent throughout the Dameigou and Shimengou Formations during the Middle Jurassic. The mean channel-belt thicknesses of River A, River B and River C in the Dameigou Formation were 9.8 m, 8.9 m and 7.9 m, respectively, and those in the Shimengou Formation were 7.4 m, 6.2 m and 5.4 m, respectively. We estimate the drainage area of three major rivers by using scaling relationships between drainage area and channel-belt thickness. The drainage areas of River A, River B and River C in the Dameigou Formation were 63.0 × 103 km2, 50.1 × 103 km2 and 37.7 × 103 km2, respectively, and those in the Shimengou Formation were 32.3 × 103 km2, 21.2 × 103 km2 and 15.3 × 103 km2, respectively. The drainage basin lengths of River A, River B and River C in the Dameigou Formation were 300.4 km, 239 km and 180.2 km, respectively, and those in the Shimengou Formation were 154.3 km, 101.3 km and 73.1 km, respectively. For both the Dameigou and Shimengou Formations, River A showed the largest scale, followed by River B and River C succeedingly, which was mainly determined by the stretch direction of provenance in the southern Qilian Mountains. The variations of channel-belt thickness, drainage area and drainage basin length between Dameigou and Shimengou Formations are the response of source-to-sink system to the transformation from extension to compression depression during the Middle Jurassic in the northern Qaidam Basin.