Limestone cliff morphology on Curaçao (Netherlands Antilles), with special attention to the origin of notches and vermetid/coralline algal surf benches ("cornices", "trottoirs")
The coasts of Curacao as well as the other leeward islands of the Netherlands Antilles, consists predominately of limestone cliffs, cut into Pleistocene reef rocks. Several erosional cliff types are distinguised as examples from a continuous range of variations, depending largely upon the degree of exposure (water turbulence). The most sheltered end member of this range shows only marine undercutting of the cliff, basically representing the difference between marine and terrestial erosion rates. The most exposed end member is characterized by a zone fo karren, a well developed surf platform, and a subtitdal notch. Intermediate cliffs show combinations of notches and benches. One of the intermediate profiles consists of a surf bench and two separate notches, both of which are contemporaneous. The surf benches result from the protective effect of organic accretions, build predominately by vermetid gastropods and coralline algae, are are shown to be genetically similar to world=wide features described as platforms, cornices, trottoirs,e tc. The term notch is redefined as an indention in a cliff, genertically related to sea level. Notches occur below and above, rather than within tidal intervals, and condequently the term tidal nip is not maintained. Eroison fo the cliffs results primarily from biodegradation of limestone, and the morphological units of the prifles correspond to the zonate occurance of those orgnaizms which are crucial in eroding the cliff, or reversely, protectin gthe cliff anaginst erosion with accretions..
The coast of Curacao as well as the other leeward islands of the Netherlands Antilles consist predominantly of cliffs cut into Pleistocene limestone. Several erosional cliff types are distinguished as a function of the degree of exposure to wind and surf. The most sheltered cliff type shows only marine undercutting, basically representing the difference between marine (relatively fast) and non-marine (relatively slow in this dry climate) erosion rates. The most exposed cliff type is characterized by a zone of karren, a well-developed surf platform, and a subtidal notch. Intermediate cliff types can be found everywhere. One type consists of a surf bench and two notches, above and below the bench. The benches result from the protective effect of vermetid/coralline algal accretions, with fabrics similar to those of boiler reefs in Bermuda, including internal sediment and marine cements (aragonite and magnesian calcite). The entire cliff profile is erosional, the accretions only delay erosion. Ultimately the bench collapsed when the notch below it reaches a certain depth. All erosion is caused by marine organisms, there is no sign of mechanical erosion. The morphological components of the cliff profile correspond to the zonate occurrence of boring and accretionary organisms.