SYNRIFT STRATIGRAPHY OF THE LAURENTIAN RIFTED MARGIN
An along-strike cross-sectional representation of synrift and rift-to-drift stratigraphy from the Pennsylvania embayment (southernmost Pennsylvania) through the St. Lawrence promontory (western Newfoundland) displays sedimentary accumulations with a range of thicknesses and facies. The synrift sedimentary units overlie Grenville basement rocks. Deposition during Iapetan rifting produced a synrift stratigraphy that may be correlated along the entire Laurentian margin. Significant lithologic variations in synrift stratigraphy along the northeastern part of the Laurentian margin include a range of rock types, for example, variegated mudstones, thick-bedded quartzose sandstone turbidites, and quartz-rich feldspathic sandstones with local to dominant shales. Sedimentary rocks are interstratified with volcanic rocks in some locations. Substantial variations in thicknesses of synrift successions are distributed along the rifted margin. A laterally continuous Early Cambrian quartzose sandstone of varying thickness represents the transition from rift-stage deposition to a passive-margin environment. Lateral variations in facies and thicknesses of the synrift stratigraphy are related to the promontories and embayments of the Laurentian margin.