Geologic Evolution of Eastern North America Maps after slide two by Ronald Blakey, Northern Arizona University and downloaded from http://cpgeosystems.com/globaltext2.html PowerPoint by Martin Schmidt Slide 21 edited from Blakey slide 22.
Rodinia - about 1 billion years ago. Baltimore Gneiss forms in Grenville Mountains, later exposed by erosion & then subsides at the continent edge as rifting occurs. Rodinia supercontinent- about 1 billion years ago. Source: hhmi BioInteractive EarthViewer
Early Cambrian 540 mya (550-530) Part of South America moving away
Late Cambrian 500 mya (505-495) created by subduction zone Volcanic islands 30o S
Early Ordovician 485 mya (488-480) Iapetus Ocean Islands move closer to North America Iapetus Ocean
Taconic Mtns formed late Ordovician Late Silurian 420 mya (425-418) Collison of island arc creates mountains Sediments deposited in varying shallow seas here will make the rocks we find in western MD today. Continued motion toward North America Taconic Mtns formed late Ordovician
Acadian Mtns formed in Devonian Late Devonian 375 mya (380-370) Africa (part of Gondwana) relativemotion Further collisions create new mountains. 30o S Acadian Mtns formed in Devonian
Early Mississippian 345 mya (350-345) Africa (part of Gondwana) relativemotion
Pangaea Middle Pennsylvanian 308 mya (311-307) Alleghanian Mtns formed about 310 mya
Pangaea Early Permian 280 mya (282-275) Collision continuing over a long time creates high mountains.
rifting Early Triassic 245 mya (247-245) Rifting and sediments here will later become the Frederick Valley.
Middle Jurassic 170 mya (175-169) Africa relativemotion 30o N
Early Cretaceous 130 mya (130-135) Atlantic Ocean 30o Africa relativemotion 30o Atlantic Ocean
Early (“Mid”) Cretaceous 105 mya (110-100) Start of a long period of shoreline location movements - deposition of sediments in shallow water creates the Coastal Plain
Late Cretaceous (Santonian) 85 mya (87-83)
Paleogene (Paleocene) 60 mya (62-58) 30o N
Paleogene (Eocene) 50 mya (52-48)
Paleogene (Eocene-Oligocene) 35 mya (36-33) Meteorite impact occurs in what will be SE Virginia.
Neogene (Early Miocene) 20 mya (22-19)
Neogene (Pliocene) 5 mya (6-4)
20,000 ya Glaciers Shorelines move out as ocean water becomes locked up in glacier ice on land. During low sea levels in ice ages, Susquehanna and other rivers cut deep channels, draining toward old impact depression.
Present Chesapeake Bay forms as rising sea levels flood the river valleys.