Introduction to Sequence Stratigraphy

SEQUENCE BOUNDARY TYPES Type 1 sequence boundary (SB 1): for shelf-­‐slope seZng where sea level drops below the shelf-­slope break or for a ramp causes fluvial incision of a significant por]on of the ramp surface • Composed of lowstand, transgressive, and highstand systems tracts bounded beneath by type-­‐1 unconformi,es and their correla,ve conformi,es. Type 2 sequence boundary (SB 2): for ramp margins without significant break in slope and where sea level does not drop below the shelf-­‐slope break for shelf systems. • A more subtle shib in facies basinward above what would be considered a highstand systems tract. • Also results in unconformi,es with less amounts of erosion and less basinward shib in facies (i.e., can’t shove everything off the shelf). • Composed of shelf-­‐margin, transgressive, and highstand systems tracts bounded beneath by type-­‐2 unconformi,es and their correla,ve conformi,es. Can see these at the outcrop scale -­‐ but best seen in seismic sec,on or when you have enough data to construct a detailed regional cross-­‐sec,on. SEQ-­‐26