The Thames is the largest drainage basin in Britain. For convenience it is subdivided into three regions. The Upper Thames occurs upstream of Reading where it crosses gently dipping Jurassic rocks. Its upper catchment includes the Cotswold Hills and south English Midlands. The Middle and Lower Thames occupy the London Basin, where the Thames is a broadly west to east aligned stream along the axis of the basin, with tributaries from the north and south, before it the North Sea through the Thames Estuary.
Deposits of the Thames and its tributaries occur from the tops of the highest hills on the basin margin (c.180 m O.D.) to below sea level in the Thames Estuary. The earliest Thames deposits, the Pebble Gravel Formation consists of fragmentary gravels composed predominantly of local materials, particularly flint.
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A revised correlation of Quaternary deposits in the British Isles
Realization that continental records of Quaternary rocks were more complex that hitherto believed came with the re-interpretation of oxygen isotope stratigraphy in the late 1960s and early 1970s. This necessitated a comprehensive re-evaluation that has been assisted by the emergence of new geochronological methods for terrestrial as well as land-sea correlations. The current state of such correlations is presented in this revised set of proposals for correlations in England, Ireland, Scotland and Wales, which also includes the Quaternary geology of the continental shelf. Correlation with the global standard of oxygen isotope stratigraphy enables the significance of British lithostratigraphical units to be appreciated in a wider context that includes the evolution of the climate system on the margin of the northeast Atlantic Ocean. It thus provides timely British data for the international palaeoceanographical and palaeoclimatological community and the correlations proposed are primarily on Milankovitch timescales. But their appearance coincides with the early stages of a paradigm shift to the search for both terrestrial and land-sea correlation on millennial timescales and then on centennial and decadal ones. This is the first of many similar terrestrial and land-sea correlations.