Posted on June 17, 2022June 17, 2022 by L. L. CoblePhoto of the Day If you’re looking for evidence of Jurassic dinosaurs in the Lower Susquehanna valley, well, you’re out of luck. If you want to understand why, just visit Dinosaur Rock on Pennsylvania State Game Lands #145 along Colebrook/Mount Wilson Road northwest of its Pennsylvania Turnpike overpass in Lebanon County. Dinosaur Rock is the unique remnant of a subterranean Early Jurassic diabase intrusion, a sill, around which softer Triassic Hammer Creek sediments (sandstone and conglomerate) have eroded away. Spheroidal weathering has left the exposed diabase boulders with rounded edges. In the lower Susquehanna region, igneous diabase is the only remaining rock from the Jurassic Period. Any sediments that may have contained dinosaur fossils have been eroded away during the millions of years since. Be certain to click on the “Geology, Fossils, and More” tab at the top of this page to check out Jurassic Diabase and the earlier dinosaurs of the region, those of the Triassic Period.