The terminal age for the Lower Wairarapa estuarine environment

Leach, Foss

doi:10.1080/03036758.1984.10418192

Cited by 4 publications

(9 citation statements)

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“…Considering chronological constraints, this timing roughly coincides with two major events ( Figure 3A). Sometime during 3.5-3.1 cal kyr BP, the Ruamahanga River diverted its course and began emptying into Lake Wairarapa, synchronous with the lake's isolation from marine influence (Leach & Anderson 1974;Leach 1984;Mitchell 1989;Wilson & Cochran 2008). The evidence for this shift from an estuarine to lacustrine environment is based on pits and cores taken from the Lower Wairarapa Valley.…”

Section: Paleoenvironmental Interpretationmentioning

confidence: 97%

“…Ruamahanga River mouth meandered northwest, discharging into the water body that eventually became Lake Wairarapa, a riverine-lacustrine complex completely separated from the sea (Leach & Anderson 1974;Leach 1984;Mitchell 1989;Wilson & Cochran 2008). Various explanations for the lake's formation have been postulated, including: sea-level fall, tectonic uplift or progradation associated with longshore drift that progressively narrowed the seaward end of the inlet (Leach & Anderson 1974;Leach 1984;Mitchell 1989).…”

Section: Study Areamentioning

confidence: 98%

“…Various explanations for the lake's formation have been postulated, including: sea-level fall, tectonic uplift or progradation associated with longshore drift that progressively narrowed the seaward end of the inlet (Leach & Anderson 1974;Leach 1984;Mitchell 1989).…”

Section: Study Areamentioning

confidence: 99%

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Late Holocene geomorphic history of Lake Wairarapa, North Island, New Zealand

Trodahl

Rees

Newnham

et al. 2016

New Zealand Journal of Geology and Geophysics

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The Wairarapa Valley possesses strong ecological, economic and cultural heritage in New Zealand; however, it has also been extensively modified by human land-use practices. Despite the value of the Wairarapa Valley's natural heritage, little has been done to quantify anthropogenic impacts. We integrate 'paleo' and modern analyses of sediment deposition and assess major changes in Lake Wairarapa's depositional environment. Accumulation rates and grain-size statistics indicate that a major natural disturbance occurred at 2.5 cal kyr BP, whereas charcoal counts register the regional impact of Polynesian forest clearing and GIS analysis quantifies the reduction of Lake Wairarapa's surface area following the Lower Wairarapa Valley Development Scheme. Critically, areas with historically slow accumulation rates are now depositional zones and areas with historically high accumulation rates are now losing sediment. This study illustrates how recent modifications to New Zealand lakes can be set in a long-term context, enabling direct comparisons between the impacts of human and natural processes. ARTICLE HISTORY

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Section: Paleoenvironmental Interpretationmentioning

confidence: 97%

Section: Study Areamentioning

confidence: 98%

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Late Holocene geomorphic history of Lake Wairarapa, North Island, New Zealand

Trodahl

Rees

Newnham

et al. 2016

New Zealand Journal of Geology and Geophysics

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“…Evidence suggests that Lake Wairarapa was once a shallow extension of Palliser Bay (Leach & Anderson 1974;Pickrell & Irwin 1978;Heath 1979;Leach 1984;Kamp 1992). It is thought that the lower valley was first flooded by the sea following the last glaciation and reached a maximum incursion around 6500 -6000 yr BP when sea-levels were at current levels or slightly higher (Leach & Anderson 1974;Heath 1979).…”

Section: Lake Wairarapamentioning

confidence: 99%

“…These dune sequences have been used in objectives 2 and 3 of this study (see Section 4) It appears the lower Wairarapa Valley remained a large estuary, with the Ruamahanga River prograding south along the eastern side of the valley until 3500-3100 yr BP. At this time it became a riverine-lacustrine complex and the Ruamahanga River outlet swung to the northwest to discharge into the newly formed Lake Waiararapa (Leach & Anderson 1974;Leach 1984;Mitchell 1989;Wilson 2008). Possible explanations for the complete separation of the estuary from the sea include a sea-level drop, tectonic uplift, or progradation associated with longshore drift (and possibly in conjunction with tectonic uplift) that progressively narrowed the seaward end of the inlet until it enclosed Lake Wairarapa (Leach & Anderson 1974;Leach 1984;Mitchell 1989).…”

Section: Lake Wairarapamentioning

confidence: 99%

Late Holocene Sediment Deposition in Lake Wairarapa

Trodahl¹

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<p>Lake Wairarapa is a highly modified lacustrine system at the southern end of the North Island, New Zealand. Not only is it situated in a region that is affected by catchment altering natural phenomena such as earthquakes, storms and fire, but both the catchment and hydrology of the lake have also been significantly altered by humans. Polynesian settlers arrived in the area approximately 700BP and proceeded to deforest the lowlands. European settlers began arriving from 1844AD onwards, completing deforestation of the lowlands and Eastern Uplands. In 1964 the Lower Wairarapa Valley Development Scheme was commissioned in an effort to alleviate flooding. This scheme significantly altered the hydrological regime of the lake. Interest in the condition of the lake and associated wetlands, and the realization that it has important recreational, cultural and ecological value, began to develop in the 1990's. This has led to a desire to see the lake restored to a more natural condition while still maintaining its flood protection capabilities. However, the lake has only been monitored over the last several decades. Any evidence of the lakes condition prior to this time is anecdotal and little is known of its natural tendencies and functions. This research has investigated and quantified morphological changes to Lake Wairarapa at the decadal and millenial scale using a combination of aerial photograph analysis, bathymetric survey comparison and lakebed core analysis. Study at these diverse scales has allowed the observed changes to be related to human environmental modification, while also being juxtaposed against natural trajectories of change. It is hoped that this can inform lake management and restoration efforts and provide a benchmark for measuring future changes to the lake, while also addressing wider issues concerning natural versus anthropogenic landscape change at the local and regional scale. The results of this project suggest that the lake has been steadily infilling over the last 6000BP – particularly along the eastern shore. For the two decades after significant hydrological changes to the lake associated with the Lower Wairarapa Valley Development Scheme, the rate of infilling on the eastern shore increased more than tenfold. However, this was accompanied by deepening in other parts of the lake. Today infilling along the eastern shore appears to have returned to natural rates and overall the lake in 2010 is only slightly smaller in volume than in 1975. Longer term anthropogenic influence on the lake and catchment was also evident. In particular Polynesian settlement and subsequent deforestation by fire was apparent in the lakebed cores. This result not only addresses the immediate issue of anthropogenic influence on this particular lacustrine system, but also informs the debate surrounding the dating of Polynesian arrival in New Zealand.</p>

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A database of biological and geomorphological sea-level markers from the Last Glacial Maximum to present

et al. 2018

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The last deglacial was an interval of rapid climate and sea-level change, including the collapse of large continental ice sheets. This database collates carefully assessed sea-level data from peer-reviewed sources for the interval 0 to 25 thousand years ago (ka), from the Last Glacial Maximum to the present interglacial. In addition to facilitating site-specific reconstructions of past sea levels, the database provides a suite of data beyond the range of modern/instrumental variability that may help hone future sea-level projections. The database is global in scope, internally consistent, and contains U-series and radiocarbon dated indicators from both biological and geomorpohological archives. We focus on far-field data (i.e., away from the sites of the former continental ice sheets), but some key intermediate (i.e., from the Caribbean) data are also included. All primary fields (i.e., sample location, elevation, age and context) possess quantified uncertainties, which—in conjunction with available metadata—allows the reconstructed sea levels to be interpreted within both their uncertainties and geological context.

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The terminal age for the Lower Wairarapa estuarine environment

Cited by 4 publications

References 1 publication

Late Holocene geomorphic history of Lake Wairarapa, North Island, New Zealand

Late Holocene geomorphic history of Lake Wairarapa, North Island, New Zealand

Late Holocene Sediment Deposition in Lake Wairarapa

A database of biological and geomorphological sea-level markers from the Last Glacial Maximum to present

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