Abstract
The distribution of trace-making organisms in coastal settings is largely controlled by changes in physicochemical parameters, which in turn are a response to different climatic and oceanographic conditions. The trace fossil Macaronichnus and its modern producers are typical of high-energy, siliciclastic foreshore sands in intermediate- to high-latitude settings characterized by cold-water conditions. However, it has been found in Miocene Caribbean deposits of Venezuela, prompting the hypothesis that upwelling of cold, nutrient-rich waters rather than latitude was the main control of its distribution. To test this hypothesis that was solely based on the fossil record, several trenches and sediment peels were made in two high-energy sand beaches having different oceanographic conditions along the Pacific and Caribbean coasts of the Central American Isthmus. As predicted, the burrows were found only in the highly productive waters of the Pacific coast of Costa Rica in connection with upwelling, while they were absent from the warm, oligotrophic waters of the Caribbean coast of Panama. This finding demonstrates that sometimes the past may be a key to the present, providing one of the few documented examples of reverse uniformitarianism.
Highlights
The distribution of trace-making organisms in coastal settings is largely controlled by changes in physicochemical parameters, which in turn are a response to different climatic and oceanographic conditions
Trace fossils in coastal environments are highly indicative of ecology and environment, shallow-marine bioturbation structures have not been adequately evaluated as paleoclimatic indicators
The opposite situation, using the fossil record to state a prediction for modern environments, is rare[16], and here we present such a case
Summary
The distribution of trace-making organisms in coastal settings is largely controlled by changes in physicochemical parameters, which in turn are a response to different climatic and oceanographic conditions. The trace fossil Macaronichnus and its modern producers are typical of high-energy, siliciclastic foreshore sands in intermediate- to high-latitude settings characterized by cold-water conditions It has been found in Miocene Caribbean deposits of Venezuela, prompting the hypothesis that upwelling of cold, nutrient-rich waters rather than latitude was the main control of its distribution. Quiroz et al.[12] recorded an unusual occurrence of this ichnogenus in Miocene tropical deposits of Venezuela, representing a departure from the currently accepted model These authors linked this occurrence to upwelling of cold, nutrient-rich waters and the high primary productivity of the Caribbean Sea before the final uplift of the Panama Isthmus. Increase in nutrients and high planktonic productivity favors the growth of seaweeds and plankton-feeding organisms over coral reefs and seagrasses[17]
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