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Minor Futures of St. Lucia Several details remain to be mentioned. The later lagoon deposits, which formed tile upper strata of the Preglacial lagoon floor around the greater part of the St. Lucia coast, must have encroached more and more upon the flanks of the subsiding island after whatever cliffs were cut around the shore in its youth were submerged; and such strata must therefore rest unconformably on the eroded volcanic slopes; but the deposits now accumulating on the submarine extension of the southwestern mud flows may lie on them conformably, just as those flows presumably lie conformably on the lagoon deposits previously accumulated there. Hence the ash beds and mud flows that were spread out around the island in the earlier stages of its history, as may be inferred from the numerous sections of their successive deposits now exposed in the headland cliffs, may also have extended smoothly off the shore of their time and may therefore bury conformably the earliest lagoon deposits; indeed, alternating volcanic and organic deposits may then have accumulated in the peripheral area to a considerable thickness, so long as intermittent outbursts were continued on the subsiding island. It was only after eruptions ceased and after the erupted lavas and agglomerates were eroded and in part submerged that the encroaching lagoon deposits could have overlapped their slopes in a markedly unconformable manner. This point will be adverted to in a later section when the tilted and degraded atoll of Antigua is discussed. The St. Lucia bank has already been described as extending seaward five miles on the north and two or three miles on the east of the island but to a less distance on the west. The present island is therefore probably somewhat eccentric with respect to the original island outline. If the original island had consisted of resistant rocks on the southwest and of weaker rocks on the northeast, it would be reasonable to suggest that the bank represents a lowland that was worn down on the weaker rocks and then submerged and somewhat aggraded; but there is not the slightest evidence that the island ever had such a dual structure, and it is therefore unreasonable to account for the bank in this way. Its foundation is much more probably of volcanic origin; and, while the oldest and weakest parts of the foundation may have been worn down to low relief before they were submerged and thus have provided a moderately uneven floor on which the bank strata were afterward deposited, this is only a less improbable supposition than the preceding one. A more probable supposition is that the northeastern part of the bank was built up on relatively smooth mud flows; but this also is without proof: the most probable supposition is that the bank foundation is a volcanic mass of earlier origin and therefore more completely submerged than the younger part of the total island. The effect of the southwestern mud flow in attaching several isolated mounts to the main body of the island has been briefly noted. A similar effect has been produced in the north by wave-built beaches broadened by progradation; the enclosed lagoons behind the beaches are now converted into low-lying alluvial flats. Thus a number of northern mounts of subdued form, thought to have formerly risen from the Preglacial reef-enclosed lagoon as satellite islets independent of the main island, are now tied to it. The physiographic configuration seen in St. Lucia has therefore been brought about by different processes in the north and south. The delta plains by which the potential area of the embayments is much reduced, as well as the beaches by which the northern mounts are attached to the main island, appear to be largely of Postglacial origin; for their Preglacial or Interglacial ancestors must have been drowned by subsidence or, if not, must have been largely worn away by low-level erosion in the Glacial epochs. It is interesting to note that the beaches, although swung in curves between mounts of volcanic rock, are composed almost wholly of calcareous sand, which must have been swept in from the offshore bank; some of the beaches have been thus prograded to a considerable width. If the offshore bank were planed down by low-level abrasion during the last Glacial epoch, the aggradation by which its present moderate depth of 30 or 40 fathoms was produced must have been about as great as the down-planing. The discontinuous bank reefs charted here and there around St. Lucia, doubtless were important agencies in supplying detritus for this aggradation as well as for beach building; but, as the reefs are frequently absent, many of the cliffs are still retreating under wave attack at present sea level. It may be suggested that, if the greater part of the headland cliffs had been cut at present sea level, the beaches ought to consist largely of volcanic sand and that, as they consist almost wholly of calcareous sand, the greater part of the cliff cutting must have been performed, as already inferred, while the ocean was lowered in the Glacial epochs; the beaches then formed are now submerged. But the above statement does not hold for the beach that lies for several miles along the cliffed shore of the southwestern mud flow; that beach includes a good share of volcanic detritus, part of which is contributed by outflowing streams, and part supplied from the cliff face. Home