Late paleozoic climate revealed by coral fossil patterns

Selecting the ideal sample and sampling path is the basic premise of coral research. The core drilled in this paper should be as close as possible to the direction of coral growth or at a small angle, so that the samples show clear bands of annual density. In this paper, two fast-growing samples with growth lines as wide as ~0.1 mm were selected. Every band on each specimen was presented in sequence from the left side of the coral fossil to the right side, with magnification under the PKU-SMZ1500 microscope. The number of ridges in each band was marked on the photographs and counted, and approximate maximum counts could be obtained. Two examples are shown in Figs 4 and 5. More measurement details are included in the “S1 File”. Results and discussion Bimodal phenomenon of the growth line width of the Late Carboniferous warm-water individual coral fossils The detailed statistical results on the width of the growth line are shown in Figs 6 and 7. Fig 7 reveals four different intervals after dividing the graph into strips because the width of the growth lines in fossil corals can indicate changes in day length or solar radiation. Except in equatorial regions, the different illumination time in most areas of the four seasons inevitably affects the accumulation of calcification, resulting in different growth line widths in the four seasons. Therefore, the four sections of coral growth line width are caused by the evident dif- ferences in the four seasons in Shiqiantan in the Late Carboniferous period. Fig 1. Basic structure of polyps and coral monomers [10].

https://doi.org/10.1371/journal.pone.0290127.g001 PLOS ONE Late paleozoic climate revealed PLOS ONE | https://doi.org/10.1371/journal.pone.0290127 August 15, 2023 3 / 13