REFINED SOUTH CHINA EARLY CAMBRIAN SMALL SHELLY FOSSIL FIRST APPEARANCES BASED ON DYNAMIC TIME WARPING OF δ13CCARB SEQUENCES

The Cambrian “explosion” of animal life describes an ~30 million year interval in which animal life increased in both disparity and diversity at an extraordinary rate. Evidence of this event can be found in the fossil records of strata from around the world, though few of those locations have precise ages given a lack of material within them that can be radiometrically dated. One solution to finding the missing age information for skeletal fossil appearances may be found through a technique called dynamic time warping. Dynamic time warping involves the use of a computer algorithm to produce optimized alignments of two time-dependent data series (in this case chemostratigraphic stable carbon isotope data, or δ¹³C_carb) by warping the time axis of one to align to the other.

Here we apply dynamic time warping to combine data from eight early Cambrian (Terreneuvian Series, ~539-521 Ma) stratigraphic sections in South China to create three possible regional δ¹³C_carb composites based on lithostratigraphy (formation boundaries), biostratigraphy (fossil first appearances), and the correlation coefficients (r) of the alignments. These composites explore differing relative age chronologies for skeletal fossil appearances in South China. The regional composites were then compared to the high resolution δ¹³C_carb–U/Pb age model from the Anti-Atlas region of Morocco (Maloof et al., 2010) whose four volcanic ash layers have been radiometrically dated to establish an absolute chronology. These comparisons allow the extrapolation of the Moroccan absolute age chronologies to refine the ages of the Precambrian-Cambrian boundary and various fossil first appearances in South China.