Abstract:
The submergent Kerguelen Plateau (KP), a large igneous province (LIP) in the Southern Indian Ocean, was initiated after rifting of India from Antarctica. Its construction, fed by the long-lived Kerguelen hot spot, has taken place in three main phases over the past approximately 110 m.y. Preliminary shipboard paleontologic and paleomagnetic dates from Ocean Drilling Program Leg 183 (Dec.-Feb., 1999; Sites 1136-1140), in conjunction with those obtained from previous drill and dredge samples (some dated radiometricly), constrain the growth history of the plateau, which can be subdivided into four domains (Southern, Central, and Northern KP plus Elan Bank) and dated as follows: 1. Southern KP, the oldest domain: subaerial plateau basalts ( approximately 110 Ma) are overlain successively by non-marine (lower Albian at ODP Site 750) and marine (middle Albian at Site 1136) sediments (the latter = approximately 105-107 Ma based on the absence of the calcareous nannofossils Sollasites falklandensis and Eiffellithus turriseiffelii across the Axopodorhabdus dietzmannii-albianus evolutionary transition). 2. Central KP, intermediate in age: approximately 95 Ma based on the successive first evolutionary occurrences at Site 1138 of the calcareous nannofossils Eprolithus octopetalus and E. eptapetalus near the base of the pelagic marine sequence and just above a m-thick black shale that apparently represents the Cenomanian/Turonian Oceanic Anoxic Event (OAE2). 3. Elan Bank: >75 Ma, a minimal date based on upper Campanian sediments at Site 1137 that thicken appreciably off site; subjacent basement basalts and tuffs are interbedded with a fluvial conglomerate with rare clasts of garnet-biotite gneiss, an indication that Elan Bank may secrete continental fragments of much older crustal age. 4. Northern KP (plus the currently active Kerguelen Archipelago), the youngest domain: > approximately 38 Ma; volcanism began when the hot spot was recaptured by the Antarctic plate, as confirmed by basal sediment age dates of 34 Ma above subaerial volcanics at Site 1139 on the outlying Skiff Bank and above pillow basalts at Site 1140 on the northern nose of the plateau.