Holocene and late Last Glaciation pollen record from drillholes at Miramar and Lambton Harbour, Wellington, New Zealand

Abstract

Pollen and spores obtained from condensed late Last Glaciation sequences of carbonaceous silts, with occasional gravel and peat horizons, from drillholes at Miramar and Lambton Harbour, Wellington, indicate a bleak, windswept, grassland/shrubland environment dominated by Poaceae. The dominant tree pollen type is Phyllocladus, probably P. alpinus. The 50.7 m thick Miramar sequence contains the Kawakawa Tephra at 24.5 m below ground level; this tephra was also identified in the field 16–17 m below ground level in two of the Lambton Harbour drillholes, the deepest of which went to 40 m. A disconformity exists between the late Last Glaciation sediments deposited immediately after deposition of the Kawakawa Tephra and the onset of Holocene sedimentation. This disconformity occurs in most sequences of this age in the Wellington area and is caused by unstable climatic and depositional conditions at the time. Recycling of spores, pollen, and dinoflagellates from Late Cretaceous and Cenozoic sediments occurs at both localities. It is inferred that sediments of this age were being locally eroded during the deposition of both Last Glaciation and Holocene sediments. No sediments of corresponding age range crop out close to Wellington today. Holocene spores and pollen at Miramar indicate warm, moist, frost‐free conditions during which time podocarp forest dominated by Podocarpus, Prumnopitys, and Dacrydium cupressinum existed. The spores Bryosporis problematicus (Couper) and B. anisopolaris Mildenhall & Bussell occur at Miramar in the Holocene and are now regarded as fossil representatives of two modern species of an unidentified bryophyte.