Crundwell, M.P. 2014 Pliocene to Late Eocene foraminiferal and bolboformid biostratigraphy of IODP Hole 317-U1352C, Canterbury Basin, New Zealand. Lower Hutt, N.Z.: GNS Science. GNS Science report 2014/15 49 p.
Abstract: This report describes the foraminiferal and bolboformid biostratigraphy of the fully cored Pliocene (Waipipian) to Late Eocene (Runangan) sedimentary succession at Integrated Ocean Drilling Programme (IODP) Hole 317-U1352C – the deepest of four holes drilled at this site on the upper continental slope, 87 km southeast of Timaru, New Zealand. The cored bathyal succession at Hole U1352C is subdivided on the basis of foraminifera and bolboformids into four biostratigraphic units, each reflecting different faunal facies and styles of sedimentary architecture: The upper part of the succession between sequence boundaries U12 and U6-1 (U1352C-2R-CC and 90R-CC; 576.47-1394.62 m) penetrates a progradational sequence of sedimentary packages with sigmoidal reflection geometries and rounded paleo shelf-slope edges. Dated Pliocene to latest Miocene (Waipipian to upper Kapitean, 3.2-5.6 Ma), this sequence was deposited at a rapid rate (0.33 m/ky) with no biostratigraphically-resolved hiatuses, except at the base. Transported shelfal species of benthic foraminifera are relatively common in the upper part of the sequence, deposited in upper bathyal water depths, and they are less common in the lower part of the sequence, deposited in lower bathyal water depths (1000-1500 m). The paleontological and seismic data associated with this succession are consistent with a decrease in downslope sediment transport as the sedimentary prism of the continental margin prograded out into the basin. The succession between sequence boundaries U6-1 and U2 (U1352C-91R-1W-15/17 and 107R-5W-64/67; 1399.95-1551.57 m) penetrates a series of sediment drifts with subtle seismic geometries. The drift succession is dated Late to Middle Miocene (upper Tongaporutuan to middle Clifdenian, 8.19-15.7 Ma) and it is biostratigraphically subdivided into five unconformity bound sedimentary packages. As a whole the sedimentary drift succession is estimated to represent ~25% of Late to Middle Miocene time, and sedimentation rates during periods of net accumulation are estimated to be relatively slow (0.03-0.09 m/ky). Reworked foraminifera and bolboformids from older Miocene sediments are common, especially in the Late Miocene, and shelfal species of benthic foraminifera that have been transported downslope are relatively rare, except for isolated specimens in the early Late Miocene. Calibrated benthic foraminiferal depth indicators that are presumed to be in situ, suggest deposition was in lower bathyal (1000-1500 m) water depths throughout the Miocene. These paleontological and seismic data support current (contourite) reworking of sediment parallel to the continental slope during successive episodes of sediment drift development and erosion. The succession between sequence boundary U2 and the Marshall Paraconformity (U1352C-107R-5W-115/118 and 140R-2W-32/34; 1552.05-1852.50 m) penetrates an Early Miocene (upper to lower Altonian, possibly uppermost Otaian, 15.97-18.31 Ma) sequence of sedi ments with poorly defined seismic reflectors. There are no biostratigraphically-resolved hiatuses, except at the base of the succession, and deposition is estimated to have been moderately rapid rate (0.13 m/ky). Unequivocal evidence of microfossil reworking from Miocene sediments is confined to the uppermost part of the sequence, and downslope reworking is extremely rare. These paleontological and seismic data suggest the sedimentary succession constitutes part of a sediment drift or an aggradational fan, deposited at the base of the continental slope. (auth)