1. a large-scale depression in the Earth’s crust in which thick sequences of sedimentary and volcanic rocks accumulate over long periods of geological time
Usage: geology

Examples

• The Appalachian Mountains formed from sediments deposited in an ancient geosyncline.
• Geologists studied the rock layers that had accumulated in the geosyncline over millions of years.
• The theory of geosynclines helped explain how mountain ranges developed from sedimentary basins.
• Thick limestone deposits in the geosyncline indicated a long period of marine deposition.
• Modern plate tectonic theory has largely replaced the older geosyncline concept.
• The geosyncline gradually filled with sediments eroded from nearby landmasses.