Abstract:

The submerged Pleistocene beach conglomerate is an underwater shelly and cobble-rich formation that has been found only on the southern flanks of the English Channel. It resulted from the cementation of beach deposits that were overlain by loessic silts at a time of lower sea level. Study of the fauna within this conglomerate allows the separation of three shelly belts located between −24 and −54 m around the Channel Islands of the Normano-Breton Gulf, −40 and −65 m off Tregor, and −52 and −80 m off Leon. These belts are correlated with three regressive Pleistocene episodes. A comparison with one of Shackleton's published sea-level curves has produced age estimates that date the three beach deposits at around 105–110, 73–80 and 30–57 ka, respectively. These beaches were sealed by three phases of loess deposition around 103, 67 and 18 ka. We assume that there are at least three different Pleistocene beach conglomerates in the English Channel. Some of them show differences in their fossil fauna that could be partly a factor of contemporaneous water temperature. A fourth beach conglomerate without fossil fauna may exist at −93 m.

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