Overstep Explained

An overstep is a geological form that has a deposition of a stratum across inclined, progressively older rocks.^[1]

The Indira Gandhi National Open University syllabus definition is: "The term overstep is used to describe the relationship of beds in an unconformable sequence where the younger series rests upon progressively older members of the underlying series."^[2]

An onlap is a more general term than overstep, in which the younger beds overlap onto successively older beds.

Notes and References

1. Alistair F. Pitty Structure and Relief 1985 Page 28 "An overstep is a geological term describing the deposition of a stratum across inclined, progressively older rocks, as seen on both flanks of the Market Weighton axis (figure 9). In South East England, the Lower Greensand is another very ..."
2. Indira Gandhi National Open University (School of Sciences), (Undated). BGYCT-131 - Physical And Structural Geology, Block 3 - Structural Geology, Unit 12 - Joints And Unconformities. egyankosh.ac.in. Archived.