The Essex Naturalist 9
coarser loads and have higher peak discharges in spring, leading to braided rivers
and gravel accumulation. Further, the temperate fauna are rarely directly
associated with the gravels. They are either (a) usually derived if found in gravels
or (b) if found in warmer climate deposits they under- or overlie, or form discrete
beds within, the gravels. In fact lowering of sea level is unlikely to cause
downcutting, but merely lead to an extension of the rivers as the sea retreated and
the sea bed became exposed, as the gradient of the sea bed is comparable with that
of the lower reaches of rivers such as the Thames (Bridgland, 1988; Bridgland et
al., 1993) (see Fig. 7). Indeed, the terraces of the Thames can be traced as cold
climate gravel bodies across the southern part of the North Sea. Gibbard (1985,
1994, 1995) presents a chronology following this line of reasoning (Table 1).
Fig. 5. Model of terrace formation. (After Bridgland, 1995)