Abundant Cretaceous carbonate lithoclasts have been found in modern volcanic beach and river sands between Tecolutla and Punta Delgada, Veracruz, Mexico.

The major rivers (Rio Nautla and Rio Misantla) drain a volcanic terrane which also has outcrops of Lower Cretaceous cherty micrite (Tamaulipas Formation). The stream sediments are composed primarily of volcanic rock fragments and quartz except just downstream from the carbonate outcrop where lithoclasts may make up 50% of the stream sediment. The lithoclast content then drops to 10% at the river mouth.

Micritic lithoclasts make up 35-60% of the beach sands, the rest being volcanic rock fragments and quartz. The lithoclast content increases irregularly from south to north, but drops to 20% or less at the river mouths. Volcanic rock fragment trends are opposite. Wind concentrates the lithoclasts in dunes and the upper beach backslope. The lithoclast percentage is directly proportional to grain size.

The lithoclasts probably were delivered to the coast at a time when the gradient was steeper and/or the climate drier. They are presently being mixed with volcanic debris brought in by the river system and a northward-flowing longshore current.

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