I haven't seen enough evidence myself to be an old-earth creationist, but I remember reading many years ago a scientific article that sought to find evidence and effects of a global flood on the perceived age of things via different dating methods. In the study, the researchers had sampled air from deep in a pocket of the ocean (and possibly frozen in ice? I can't recall). The study found that the air was evidence for a young earth. I wish I could provide a link to the study. It was interesting, but very technical and mostly over my head. It has stuck with me that such a global flood that is often ignored in the scientific dating of things and throws throws them into question since the possibility and effects of such a flood aren't considered.
https://biologos.org/resources?query=flood&hierarchicalMenu[topics.lvl0]=Bible > The Flood&page=1