So the oceans were higher thousands of years ago. You mean global warming in pre-historic days?
In the Western portion of Dallas County TX, there are earthen mounds near the shore of a man-made lake. I was a Boy Scout in the early ‘50s and we would hike about 5-6 miles from the camp to those mounds that were named “Sharks Tooth”. We always came away with teeth that we dug up.
This location is currently about 300 miles North of the nearest shoreline of the Gulf of Mexico. There was a period when the Dallas and Fort Worth area was covered by a portion of what today is the Gulf.