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= Manlius Formation =

The Manlius Formation (also referred to as the Manlius Limestone) is a unit of marine sedimentary rock found in eastern North America, and is primarily composed of blue limestone in thin, three-inch beds, interbedded with very thin films of shale. Named for an exposure at Manlius, NY, near Syracuse, NY, it underlies the Coeymans Formation (Lower Devonian) and extends as far west as Onondaga County, NY. The Manlius is part of the Helderberg Escarpment, a prominent topographic feature of eastern and central New York. The Helderberg Escarpment was formed because the limestone of the Manlius and Coeymans Formations (part of the Helderberg Group) is more resistant to erosion than underlying Ordivician and Silurian units. Stratigraphically, the Manlius is the lowest unit of the Lower Devonian Helderberg Group, and is underlain by the Ordivician sandstone to the east and Silurian units to the west, and is overlain by the Lower Devonian Coeymans Formation.

Depositional Setting
410 million years ago, much of what now is New York State was flooded by marine waters of the Appalachian Basin. The Helderberg Group of rocks was deposited in this shallow sea. More specifically, the Manlius Formation was deposited in an intertidal zone resulting in thin, three inch beds of limestone interbedded with very thin films of shale. Mud cracks and ripple marks further indicate tidal flat and lagoon environments. The surrounding topography was likely a low, flat landscape, as high topography tends to erode quickly and bring in large amounts of mud, sand, and gravel, which are not present in the Manlius.

Tectonics/Regional Setting
During the Devonian, Laurentia (what is now North America) collided into what is now Europe, forming Euramerica between 408-387 million years ago. This collision resulted in the formation of new mountains in what is now Greenland and Scandinavia. Following the deposition of the Manlius Formation, in the Middle Devonian, the Acadian Orogeny occurred in what is now the eastern United States, forming the Appalachian Mountains.

Fossils
At several levels of the Manlius Formation there are very thin, wavy beds characteristic of deposition of carbonate mud trapped by algal or bacterial mats in an intertidal environment. The Manlius also contains beds with shelly fossils such as brachiopods, ostracods, and tentaculitids. Only a few species are found and these often occur in great abundance, indicating ecologically stressful conditions such as high salinity (the few species that can tolerate these conditions are not kept in check by competition or predation). At the top of the Manlius beds there is an interval containing abundant stromatoporoids – a mound-like calcified sponge that formed low reefs in the Devonian. These fossils indicate deepening sea level (shallow subtidal) and the transition to the Coeymans Limestone, which is a highly fossiliferous skeletal limestone containing abundant and diverse brachiopods, corals, and crinoids.