Slumps, debris flows and sandy deep-water channel systems: implications for the application of sequence stratigraphy to deep water clastic sediments

The Hecho Gorup is a classic sedimentary system from which turbidite classifications have been defined. This study of mudstone-rich intervals from this group suggests that published models in which Type 2 or 3 systems develop in response to changes in relative sea level or tectonic activity need to be reassessed. Intervals developed between channel/lobe sandstones comprise mud-matrix supported conglomeratic debris flows and/or slump deposits which blanket the underlying sand-rich channel-fills. They record periods of major disturbance and re-organization of the sedimentary regime. The sandstone bodies are not strongly incised and have high aspect ratios. Previous interpretations of these intervening muddy intervals as overbank wedge/levee deposits, developed during a relative rise in sea level (Type 3) are considered inappropriate for the sections studied.