کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8907935 | 1635332 | 2018 | 16 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Beach ridge sets reflect the late Holocene evolution of the St Lucia estuarine lake system, South Africa
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
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چکیده انگلیسی
Sets of sandy beach ridges and intervening swales define shoreline sections of the shallow St Lucia wetland system within the iSimangaliso Wetland Park, World Heritage Site in northern KwaZulu-Natal province, South Africa. The sets comprise 3-10 beach ridges, the most prominent being 80-150â¯m wide and rising 0.5-2â¯m above the adjacent swales. The highest beach ridge crests elevated 3.2-4.6â¯m above mean sea level are furthest from the present shoreline and the lowest ridges, rising about 0.5â¯m above the swales, occur closest to the present mean lake level shoreline. This investigation assesses the genesis of the sandy beach ridges on five strand plain remnants within the estuarine lake. The ridges were topographically surveyed and their ages estimated using optically stimulated luminescence (OSL) dating. OSL dating reveals that the oldest beach ridge formed around 6240â¯years ago, with a sequence of beach ridges having accumulated during the period ~4000 to 1500â¯years ago reflecting coeval accretion around the lake. The present mean lake level shoreline was only reached within the past ~600â¯years. Sedimentation changed from marine-dominated to lacustrine deposition in the estuary during the period of beach ridge accretion. The dated beach ridges, supported by new radiocarbon dates of fixed biological indicators from Holocene intertidal zone settings on the coast, are used with published sea-level curves to set the context of periodic beach ridge accretion in the marine-linked estuarine lake. The dated ridges suggest that episodic regression of the estuarine lake shoreline occurred after a mid-Holocene sea-level highstand. The record of sea-level change is also reflected by the long-term natural shrinking and shallowing of the proto-St Lucia lagoon/estuarine lake in the context of reduced marine influences due to closure of former marine channels by progressive barrier dune accretion. The sequence of coeval beach ridges reflects a pulsed lowering of relative sea-level in the shallowing estuarine lake. Height differences between the coeval ridges at sites around the lake reflect local environmental controls including the range of wind fetch distances across shallow lake compartments, wave height and wind-induced seiche effects.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geomorphology - Volume 318, 1 October 2018, Pages 112-127
Journal: Geomorphology - Volume 318, 1 October 2018, Pages 112-127
نویسندگان
Greg A. Botha, Naomi Porat, Sylvi Haldorsen, Geoff A.T. Duller, Ricky Taylor, Helen M. Roberts,