Figure 1. The lower diagram is the raw number (column C, Table 1) of species on both sides of the boundary within 2 degrees longitude and latitude. The upper diagram is the percentage (column E, Table 1) of species below the boundary that straddle the boundary. Key: On the x-axis, 1 through 5 are the lithostratigraphic erathem boundaries of the Archean, 5 through 14 are the lithostratigraphic system boundaries of the Proterozoic, and 15 through 114 are the biostratigraphic stage boundaries of the Phanerozoic—all numbered as per column A of Table 1; C/O is the Cambrian/Ordovician boundary; H/A is the Hadean/Archean boundary; K/T is the Cretaceous/Tertiary (and Mesozoic/ Cenozoic) boundary; M/P is the mid-Carboniferous Mississippian/Pennsylvanian boundary; P/C is the Precambrian/Cambrian boundary; P/T is the Permian/Triassic (and Paleozoic/Mesozoic) boundary; and T/Q is the Tertiary/Quaternary boundary. icity. DISCUSSION A. The Precambrian-Cambrian zone (boundaries 1-25) 1. Precambrian fossilization potential Two observations in the Precambrian data might lead to the impression that fossils are absent from Precambrian sediments. First, although the global stratigraphic units utilized by the PBDB are bio-stratigraphic units from the Ediacaran up, the sub-Ediacaran units are not. This might suggest that fossils are unavailable to define Precambrian stratigraphic units. Second, the zeros in column B of Table 1 might suggest that no fossils at all are found in five of the 14 globally defined stratigraphic units of the Precambrian. Concerning non-fossil definitions of Precambrian stratigraphic units, few sub-Ediacaran fossils show specificity to particular stratigraphic levels. In fact, the PBDB reports fossils in every globally-defined stratigraphic unit of the Precambrian-Cambrian zone. It is just that few of them have a narrow enough stratigraphic range to be useful for biostratigraphy. Concerning the zeros in column B of Table 1, many of the fossil taxa in the Precambrian-Cambrian zone are simply not reported at the species level. So again, all the globally defined Precambrian stratigraphic units contain fossils. It is just that few of those fossils are identified at the species level. So, unlike Hunter (2000a, 2000b) claims, not only are Precambrian sediments quite capable of preserving fossils, they, in fact, do contain fossils. 2. Biostratigraphic pulses in the Precambrian-Cambrian zone There is too little data in the Precambrian-Cambrian zone to place statistical confidence on quantitative tests of periodicity. Qualitatively, however, there seems to be no evidence of periodicity in the radiometric ages of stage boundaries or their logarithms (in case there is exponential change in decay rates during the deposition of these stratigraphic units). However, there may be regularity in the NLSSS zeros and highs. A rough test of periodicity for every 2nd boundary was performed by (1) summing the %NLSSS values (column F, Table 1) for every 2nd boundary starting at boundary 1 (2s 1), then summing the %NLSSS values for every 2nd boundary starting at boundary 2 (2s2), (2) calculating the percentage that each of these sums are of the sum of all %NLSSS values (2p1 and 2p2), and (3) comparing these percentages with what would be expected if there was no 2nd boundary periodicity (1/2 = 50%). The same test was performed for periodicity for every 3rd boundary (by summing %NLSSS values for every 3rd boundary to get 3s 1, 3s2, and 3s3, then comparing calculated WISE and RICHARDSON Biostratigraphic continuity and earth history 2023 ICC 616
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