Structure
The full extent of the Sudbury Basin is 62 km (39 mi) long, 30 km (19 mi) wide and 15 km (9.3 mi) deep, although the modern ground surface is much shallower.
The main units characterizing the Sudbury Structure can be subdivided into three groups: the Sudbury Igneous Complex (SIC), the Whitewater Group, and footwall brecciated country rocks that include offset dikes and the Sublayer. The SIC is believed to be a stratified impact melt sheet composed from the base up of sublayer norite, mafic norite, felsic norite, quartz gabbro, and granophyre.
The Whitewater Group consists of a suevite and sedimentary package composed of the Onaping (fallback breccias), Onwatin, and Chelmsford Formations in stratigraphic succession. Footwall rocks, associated with the impact event, consist of Sudbury Breccia (pseudotachylite), footwall breccia, radial and concentric quartz dioritic breccia dikes (polymict impact melt breccias), and the discontinuous sublayer.
Because considerable erosion has occurred since the Sudbury event, an estimated 6 km (3.7 mi) in the North Range, it is difficult to directly constrain the actual size of the Sudbury crater, whether it being the diameter of the original transient cavity, or the final rim diameter.
The deformation of the Sudbury structure occurred in five main deformation events (by age):
- formation of the Sudbury Igneous Complex (1849 Ma)
- the Penokean orogeny (1890-1830 Ma)
- the Mazatzal orogeny (1700-1600 Ma)
- the Grenville orogeny (1400 - 1000 Ma)
- the Lake Wanapitei impact (37 Ma)
Read more about this topic: Sudbury Basin
Famous quotes containing the word structure:
“A special feature of the structure of our book is the monstrous but perfectly organic part that eavesdropping plays in it.”
—Vladimir Nabokov (1899–1977)
“A committee is organic rather than mechanical in its nature: it is not a structure but a plant. It takes root and grows, it flowers, wilts, and dies, scattering the seed from which other committees will bloom in their turn.”
—C. Northcote Parkinson (1909–1993)
“I’m a Sunday School teacher, and I’ve always known that the structure of law is founded on the Christian ethic that you shall love the Lord your God and your neighbor as yourself—a very high and perfect standard. We all know the fallibility of man, and the contentions in society, as described by Reinhold Niebuhr and many others, don’t permit us to achieve perfection.”
—Jimmy Carter (James Earl Carter, Jr.)