Walking around Phil Hardberger Park and the Geology Trail located within it, an interesting juxtaposition of geologic time can be noticed
The main bedrock in the area is limestone, specifically that of the Buda Limestone formation, dating back to the Cretaceous Period. On top of that limestone are more contemporary deposits. The borrow pit demonstrates this. What makes it all so interesting is the fact that these small clues give us an insight to the past, as well as an insight to the present.
Limestone deposits represent a time in the Earth’s history when massive outpourings of lava (such as the Deccan Traps in India and the Laramide Orogeny) created mountain-building events which helped form the Colorado Plateau and our modern Rocky Mountains. These events may have contributed a significant source of carbon dioxide to the atmosphere and caused a global rise of the sea. This transgression of the sea formed a massive interior seaway known as the Cretaceous interior seaway which extended from Hudson Bay, down through the Great Plains and the Rocky Mountains and across the whole of Texas. Deposits of this transgression, like the Buda Limestone found at Phil Hardberger Park, represent a vast global change and a time of great deposition of marine sediments.
Over time, these deposits have been re-deposited by larger, more kinetic and scouring floods and then cemented together by mud and fine particles when flooding is less severe. The overlook is a very good representation of this. On one side, the water is cutting deeper and deeper into the cliff face while on the other sediments are deposited mostly by slack water. The fluvial transition the park area has seen in the past few million years is evident even in the areas where there are only boulders. These limestone boulders are remainders of the bedrock after the wind and water eroded its surface.
The next time you walk on the Geology Trail in Hardberger Park, take notice of these clues left for us by nature. For it is by examining the past that we have a better view of our role in the grand scale of time.
Ethan Bucholz Wednesday, 16 January 2013