Resumen de Arquitectura de las plataformas carbonatadas y litosomas de rudistas del Cretácico
Cretaceous carbonate platforms are typically made up of tabular cyclic beds. There is usually a gradation from low energy inner platform deposits - often with metre-scale peritidal cycles - to thicker outer platform cycles (generally < 1 Om), incorporating higher energy deposits. Low-angle slope deposits may follow distally though tectonic steepening sometimes occurred. Laterally extensive rudist lithosomes within outer platform cycles are tabular to lenticular and frequently overlain by bioclastic blankets. They did not form reefal rims - pace frequent misrepresentations in the literature - though some karstic rims have been recorded. Coral carpets developed downslope.
In the inner platform, thin pauci-, to monospecific rudist biostromes developed. Two historical contingencies of the Cretaceous are evident. First, predominant relative sea-level rise left little scope for antecedent karst topography (in contrast to the effect of Pleistocene glacioeustacy in modern reefs). Secondly, the typically small ('greenhouse'-style) increments of accommodation promoted rapid shoaling and lateral redistribution of bioclastic sediment. Consequently, platforms tended to a flat-topped profile, with broad outer zones across which bioclastic debris was swept both inward and outward. Rudists periodically formed vast 'meadows' of clustered shells both supported by, and contributing to, the ambient sediment. Platform development was episodically interrupted, with mass extinctions preferentially affecting outer platform taxa.
