Time Resolution of the Phanerozoic Rock Records: Challenges of High-Resolution Palaeobiological and Geochemical Proxy-Based Interpretations

The understanding of the Earth’s processes in the geologic past has advanced due to the ability to resolve geologic time in the rock records at progressively higher levels of time resolution. The rock records are now being probed to decipher short-term processes of palaeobiological and palaeoclimatic interests operating at a few tens of kyr to centennial and decadal scales. How good are the stratigraphic records to answer such questions? The fragmentary nature of the stratigraphic records is well recognized, and it is best summed up by the catchphrase “more gaps than record” or “a set of frozen accidents” of some leading stratigraphers. Quantitative analysis of sedimentary records in the 1980s and taphonomic studies supported by radiometric dating of shells in 1990s gave insight into an estimation of temporal resolutions of rock records. Two distinct types of resolutions are recognized, stratigraphic resolution (among strata) and palaeontological resolution (within stratum). The stratigraphic resolutions in 10 6 -years scale can be achieved by biostratigraphy alone in the Cenozoic, and it can be raised to 10 5 to 10 4 -years scale when integrated with as many means as magnetostratigraphy, radiometric dating, and cyclostratigraphy. Taphonomic processes deteriorate the palaeontological resolutions, and it is of major concern in bridging the gap between 10 4 -years scale resolutions in the geological records and the human-life observations. The palaeobiological and palaeoclimatic processes at this scale may require exceptional records and rigorous approach to demonstrate that the requisite time-resolution is achievable in the investigated rock record.