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Abstract: Tamaki Estuary is an arm of the Hauraki Gulf situated on the eastern side of central Auckland. Over the last 100 years, Tamaki catchment has evolved from a nearly rural landscape to an urbanised and industrialised area. Pollen, 14C and glass shards analyses, were carried out on three cores collected along the estuary with the aim to reconstruct the estuary's history over the last ∼8000 years and trace natural and anthropogenic effects recorded in the sediments. Glass shard analysis was used to establish key tephra time markers such as the peralkaline eruption of Mayor Island, ∼6000 years BP. During the pre-Polynesian period (since at least 8000 years BP), regional vegetation was podocarp/hardwood forest dominated by Dacrydium cupressinun, Prumnopits taxifolia, and Metrosideros. Major Polynesian settler impact (commencing ∼700 yr BP) was associated with forest clearance as indicated by a sharp decline in forest pollen types. This coincided with an increase in bracken (Pteridium esculentum) spores and grass pollen. Continuing landscape disturbance during European settlement (commencing after 1840 AD) was accompanied by the distinctive appearance of exotic pollen taxa such as Pinus. [Copyright &y& Elsevier]

Abstract: Tamaki Estuary in northern New Zealand is a mixed-energy estuary that comprises three facies zones: (1) a wave- and tide-influenced inlet with sandspit; (2) a tide-dominated, funnel-shaped zone with wide intertidal flats and sandy tidal bars, and (3) a mixed fluvial influenced and tidal meandering upper zone. Each zone preserves a Holocene record of sedimentation that was reconstructed using six cores ranging between 3- and 6-m depth. Sample analyses included textural and mineralogical composition, organic and carbonate content, and radiocarbon dating of in situ shells. The Tamaki Estuary valley fill consists of transgressive marine sands and tidal bar sands in the lower estuary, mud and sand facies in the middle estuary, and mud and peat facies in the upper estuary. These facies were deposited in a marine–fluvial complex that included barriers, tidal flats and peat swamps. Based on radiocarbon dating, marine transgression in the Tamaki Estuary started at least 7500yr BP. Transgressive System Tract (TST) sediments were deposited on a pre-Early Holocene surface composed of massive compact grey plastic mud. Sediments of this initial transgressive stage consist of sandy muds with shell material in the lower estuary and mud to muddy sands with thin peat layers in the upper estuary. Deposition of Highstand System Tract (HST) sediments coincided with sea-level stabilisation at or near present day levels ca 6500yr BP and HST sedimentation continues to the present day. In addition to conventional lithostratigraphic characterization, the mineralogical composition of the sediments, in particular the proportion of quartz and feldspar (i.e. Q/F ratio), is proposed as a diagnostic tool for distinguishing depositional system tracts in siliciclastic sequences. [Copyright &y& Elsevier]