Anantecedent stream is a stream that maintains its original course and pattern despite the changes in underlying rock topography. A stream with adendritic drainage pattern, for example, can be subject to slow tectonic uplift. However, as the uplift occurs, the stream erodes through the rising ridge to form a steep-walledgorge. The stream thus keeps its dendritic pattern even though it flows over a landscape that will normally produce atrellis drainage pattern.[1]
Asuperimposed stream is astream that forms over horizontal beds that overlie folded and faulted rock with varying resistance. Having cut down through the horizontal beds, the stream retains its course and pattern as it proceeds to erode the underlying rocks despite their different character. The stream erodes a gorge in the resistant bed and continues its flow as before.[1]