Geology for ELR HDY is based on British Geological Survey (BGS) low-resolution data sampled at 100 metre intervals along the ELR. The geology presented should not be treated as accurate or complete. Data marked with Ⓤ is classed as undifferentiated by the BGS.
| Mileage | Material | Deposit | Bedrock |
|---|---|---|---|
| 0M -004y to 0M 0275y | Clay, Silt and Sand | Alluvium | South Wales Upper Coal Measures Formation - Mudstone, Siltstone, Sandstone, Coal, Ironstone and Ferricrete |
| 0M 0275y to 0M 0495y | Sand and Gravel | Glacial Sand and Gravel | South Wales Upper Coal Measures Formation - Mudstone, Siltstone, Sandstone, Coal, Ironstone and Ferricrete |
| 0M 0495y to 0M 0935y | Clay, Silt and Sand | Alluvium | South Wales Upper Coal Measures Formation - Mudstone, Siltstone, Sandstone, Coal, Ironstone and Ferricrete |
| 0M 0935y to 0M 1172y | South Wales Upper Coal Measures Formation - Mudstone, Siltstone, Sandstone, Coal, Ironstone and Ferricrete |