Dh. Rousell et Dgf. Long, ARE OUTLIERS OF THE HURONIAN SUPERGROUP PRESERVED IN STRUCTURES ASSOCIATED WITH THE COLLAPSE OF THE SUDBURY IMPACT CRATER, The Journal of geology, 106(4), 1998, pp. 407-419
Several outliers of the Paleoproterozoic Huronian Supergroup are prese
rved in a 20 km wide arcuate belt northwest of the Sudbury Igneous Com
plex. Forty years ago it was suggested that these outliers represented
the remnants of a discontinuous rim syncline developed around a domal
structure. Thirteen years later it was proposed that they were preser
ved in grabens formed as a result of collapse of the central uplift of
a multi-ring impact crater and the simultaneous emplacement of the Su
dbury Igneous Complex. This interpretation has been accepted by most i
nvestigators without question, to the extent that the position of the
outliers has been used to estimate the size of the supposed crater. Ou
r observations indicate that Huronian strata in the outliers were depo
sited in a series of paleo-valleys on a terrane with considerable topo
graphic relief. The asymmetric nature of the fill in some of the outli
ers suggests deposition may have taken place in half-grabens. The outl
iers are preserved in synclines developed by orogenic activity prior t
o the 1850 Ma impact event. They are cut by later transverse and longi
tudinal faults. The geometry of the outliers, combined with the charac
ter and directional attributes of the sedimentary fill, indicates that
the outliers are not related to the Sudbury Event.