Figure F18. Quantitative comparison of clay mineral assemblages from DSDP Leg 90 Site 594 (water depth = 1204 m; northwest flank of Bounty Trough) and ODP Site 1123 (water depth = 3290; North Chatham Drift) (after Dersch and Stein, 1991; Winkler and Dullo, this volume). A compositional shift toward chlorite + illite-rich and smectite-poor clay assemblages starts under the DWBC at ~21 Ma (early Miocene) at Site 1123. Clover-leaf asterisks identify culminations in chlorite content that occur at ~18, 8.5, 5.3, and 1.2 Ma and are inferred to represent irregular pulses of uplift along the South Island alpine chain.

Figure F18. Quantitative comparison of clay mineral assemblages from DSDP Leg 90 Site 594 (water depth = 1204 m; northwest flank of Bounty Trough) and ODP Site 1123 (water depth = 3290; North Chatham Drift) (after Dersch and Stein, 1991; Winkler and Dullo, this volume). A compositional shift toward chlorite + illite-rich and smectite-poor clay assemblages starts under the DWBC at ~21 Ma (early Miocene) at Site 1123. Clover-leaf asterisks identify culminations in chlorite content that occur at ~18, 8.5, 5.3, and 1.2 Ma and are inferred to represent irregular pulses of uplift along the South Island alpine chain.