A 230 ka record of glacial and interglacial events from Aurora Cave, Fiordland, New Zealand

Abstract

Caves overrun by glaciers are known to accumulate dateable evidence of past glacial and interglacial events. Results are reported from an investigation of Aurora Cave on the slopes above Lake Te Anau in Fiordland. The cave commenced to form before c. 230 ka B.P. Sequences of glacifluvial sediments interbedded with speleothems are evidence of the number and timing of glacial advances and the status of intervals between them. Twenty-six uranium series dates on speleothems underpin a chronology of seven glacial advances in the last 230 ka, with the peak of the late Otira glaciation, Aurora 3 advance, at c. 19 ka B.P. With five advances in the Otiran, the last glaciation is more complex than previously recognised. Comparison of the record with that recorded offshore from DSDP Site 594 reveals little matching, but the correspondence of the Aurora sequence with that interpreted from other onshore deposits is more convincing. Glacial deposits on slopes above the cave for a further 660 m may be evidence of the "missing" glacial events of the mid-early Pleistocene.

The timing and cause of glacial advances in the southern mid-latitudes during the last glacial cycle based on a synthesis of exposure ages from Patagonia and New Zealand

“…48 ka (Williams, 1996). However, the Aurora Cave speleothem indicates continuous growth between 55.3 ka and 42.8 ka, implying local icefree conditions at this time (Williams, 1996;Williams et al, 2015). The implication is that while millennial-scale events may have caused some glacial activity that is not well recorded in our compilation (e.g.…”

“…In New Zealand, speleothem records suggest a cooler period at 51-45 ka (Williams et al, 2015), and the Te Anau cave stratigraphy suggests a glacial advance at ca. 48 ka (Williams, 1996). However, the Aurora Cave speleothem indicates continuous growth between 55.3 ka and 42.8 ka, implying local icefree conditions at this time (Williams, 1996;Williams et al, 2015).…”

Sedimentological investigation of late glacial (Otiran) exposures along the southern margins of Lake Wanaka, South Island, New Zealand

“…If the gravels are immediately deposited before the delta, they may coincide with the onset of an interstadial, recorded in Aurora cave (Williams, 1996) where a set of flowstone radiogenic dates bracket ages between circa 66.0 ± 2 -61.4 ± 2.7 ka (intervening incision and glaciofluvial deposition), and 58.7 ± 3.2 ka. This unit is interpreted as a braided river gravel, deposited within the outwash head associated with a nonglacial period.…”

“…Te Anau in the Fiordland (Williams, 1996) has recorded seven glacial advances within the last 230 ka, associating speleothem accretion with glacial advance. If the gravels are immediately deposited before the delta, they may coincide with the onset of an interstadial, recorded in Aurora cave (Williams, 1996) where a set of flowstone radiogenic dates bracket ages between circa 66.0 ± 2 -61.4 ± 2.7 ka (intervening incision and glaciofluvial deposition), and 58.7 ± 3.2 ka.…”

“…The chronology of these deposits is further solidified with speleothem deposits in the Aurora cave. Williams (1996) …”