Research on climate change based on carbonate porosity analysis in Jinping, China

climate change curve. When using polarized images of carbonate rocks for climate research, linking the results of the image analysis to the time axis is a difficult problem. If the time axis is not convincing, the climate change curve obtained will not be easy to believe or useful to the engineers. Since each rock sample is collected from a certain formation, the time axis of the cli- mate change curve can be determined based on the formation age. Such a time axis is easy to understand and is readily accepted by engineers. Since the porosity of the carbonate rocks is related to the karst development rate, and the karst development rate is related to climate change, the porosity value of the carbonate rocks can be used to reflect the climate change. In this study, the carbonate porosity and pore size obtained from the image analysis were used as the climate change indicators. As is shown in Fig 7, when the porosity and pore size of the car- bonate rocks were relatively large, as the climate was assumed to have been warm and humid. When the porosity and pore size of the carbonate rock were relatively small, as the climate was assumed to have been dry and cold. Fig 7a shows the climate change (porosity change) curve obtained using the gray values in Table 2 (Column D). Fig 7c shows the climate change (porosity change) curve obtained using R values in Table 2 (Column F). Fig 7e shows the climate change (porosity change) curve obtained using G values in Table 2 (Column H). Fig 7g shows the climate change (porosity

change) curve obtained using B values in Table 2 (Column J). Fig 7b shows the climate change (porosity change) curve obtained using saddle line 1 in Table 1 (Column D). Fig 7d shows the Fig 7. Climate change curves obtained using porosity changes. https://doi.org/10.1371/journal.pone.0281630.g007 PLOS ONE Research on climate change based on carbonate porosity analysis in Jinping PLOS ONE | https://doi.org/10.1371/journal.pone.0281630 March 30, 2023 13 / 21