Regenerative growth in fossil horsetails following burial by alluvium.
Under backwater conditions, fine-grained alluvium of 15 m thickness was deposited in the reach upstream from the lava dam.
On average, surface soil nutrient content is highest in the alluvium, lowest in granite and intermediate in sedimentary soils.
This recent alluvium is topped by welldrained soils that remain moist through seepage and capillarity during the dry season; they are prime agricultural land.
These losses cannot be compensated by weathering of the parent material, since the old alluvium on which these soils have evolved has been thoroughly weathered before sedimentation.
Both plutons seem to represent a single entity as they are contiguous, and the intervening area between them of about 1000 m is concealed under alluvium and sand dunes.
The river valley consists of porous alluvium that constitutes a huge aquifer that is recharged mostly from the river while providing late season flow back into the river.
The road crosses alternating layers of sandstone, shale and mudstones which are overlain by variable depths of glacial clays, sands and gravels, alluvium and industrial fill.
