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Department of Earth Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA
From Aptian to Maastrichtian times, the development of broad tracts of anomalously shallow ocean floor in the Pacific, studded with reef-rimmed seamounts and islands, allowed some Caribbean benthos to spread westwards by larval drift between staging posts in Tethyan/Atlantic waters debouching between the Americas. There is as yet no compelling evidence that the Pacific was completely traversed in this manner during the first and major phase of intra-plate volcanothermal activity in the Aptian-Albian: evidently there still existed a sufficiently wide region of Pacific abyss to the west to serve as a barrier to larval dispersal. However, clear evidence for the ‘landfall’ of Caribbean-derived species on eastern Tethyan shores in Campanian to Maastrichtian times is provided by several examples of disjunct endemics from the two regions. Such taxa include rudist bivalves, gastropods, larger foraminifera, and calcareous algae. This episode coincides with a second, smaller phase of mid-plate volcanothermal activity in the Pacific, which, in conjunction with the relict topography from the earlier phase, evidently furnished a temporarily continuous chain of staging posts for the trans-Pacific spread of the shallow-marine benthos.
