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Konfirst, Matthew Alan; Scherer, Reed P; Hillenbrand, Claus-Dieter; Kuhn, Gerhard (2012): (Figure 2) Diatom relative abundance of sediment core PS58/254-1. PANGAEA,, Supplement to: Konfirst, MA et al. (2012): A marine diatom record from the Amundsen Sea – Insights into oceanographic and climatic response to the Mid-Pleistocene Transition in the West Antarctic sector of the Southern Ocean. Marine Micropaleontology, 92-93, 40-51,

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The goal of this study is to assess the changes that have occurred during the Mid-Pleistocene Transition, an important transitional period in cryosphere evolution, by examining the siliceous microfossil record of sediments collected proximal to a major ice drainage outlet for the West Antarctic Ice Sheet. Core PS58/254 was collected from a sediment drift on the upper continental rise in the Amundsen Sea, directly offshore from Pine Island Bay, one of the three main discharge areas for the West Antarctic Ice Sheet (WAIS). Published data on physical properties, geochemical composition, grain size and clay mineral assemblages are complemented here by a high-resolution record (sample spacing 10 cm) of the siliceous microfossil assemblages (diatoms and silicoflagellates). Between 1200 ka and 621 ka, the assemblage is relatively diverse, with Actinocyclus ingens, Thalassiothrix antarctica and Fragilariopsis kerguelensis dominating the assemblages, but diatom abundance is variable from low to barren. Additionally, the occurrence of A. ingens, Thalassiosira elliptipora and Thalassiosira fasciculata is used to confirm and further refine the existing age model and extend it back to 1200 ka. Species composition during the last ca. 621 ka is dominated by F. kerguelensis, which consistently comprises 80-90% of the assemblage. A clear relationship between diatom abundance and glacial/interglacial variability is apparent after 621 ka, which resembles the glacial-interglacial variability previously observed in other proxy data.
A significant change in both sediment composition and diatom assemblages is observed at 621 ka. This change concurs with the last abundant occurrence of A. ingens and the end of the Mid-Pleistocene Transition (MPT, i.e. the onset of modern eccentricity/precession-paced glacial cycles around 650 ka). We suggest that during interglacial periods after 621 ka the Amundsen Sea Low pressure system shifted seasonally southwestwards towards the shelf and thereby increased the advection of relatively warm Circumpolar Deep Water (CDW) onto the Amundsen Sea shelf, which is a major factor for present ice-sheet melting in this part of West Antarctica.
Latitude: -69.313000 * Longitude: -108.453000
Date/Time Start: 2001-03-09T23:34:00 * Date/Time End: 2001-03-10T00:46:00
Minimum DEPTH, sediment/rock: 0.22 m * Maximum DEPTH, sediment/rock: 18.42 m
PS58/254-1 * Latitude: -69.313000 * Longitude: -108.453000 * Date/Time Start: 2001-03-09T23:34:00 * Date/Time End: 2001-03-10T00:46:00 * Elevation: -4014.0 m * Recovery: 18.31 m * Location: Southeast Pacific * Campaign: ANT-XVIII/5a (PS58) * Basis: Polarstern * Method/Device: Piston corer (BGR type) (KL) * Comment: 19 core sections: 0-0.32, 0.32-1.31, 1.31-2.31, 2.31-3.31, 3.31-4.31, 4.31-5.31, 5.31-6.31, 6.31-7.31, 7.31-8.31, 8.31-9.31, 9.31-10.31, 10.31-11.31, 11.31-12.31, 12.31-13.31, 13.31-14.31, 14.31-15.31, 15.31-16.31, 16.31-17.31, 17.31-18.31 m
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1DEPTH, sediment/rockDepthmGeocode
2AGEAgeka BPGeocode
3Actinocyclus actinochilusA. actinochilus%Konfirst, Matthew AlanCounting, diatoms
4Actinocyclus ingensA. ingens%Konfirst, Matthew AlanCounting, diatoms
5Azpeitia tabularisA. tabularis%Konfirst, Matthew AlanCounting, diatoms
6Chaetoceros spp.Chaetoceros spp.%Konfirst, Matthew AlanCounting, diatomsof non-Chaetoceros diatoms
7Eucampia antarcticaE. antarctica%Konfirst, Matthew AlanCounting, diatoms
8Fragilariopsis curtaF. curta%Konfirst, Matthew AlanCounting, diatoms
9Fragilariopsis kerguelensisF. kerguelensis%Konfirst, Matthew AlanCounting, diatoms
10Fragilariopsis separandaF. separanda%Konfirst, Matthew AlanCounting, diatoms
11Hemidiscus karsteniiH. karstenii%Konfirst, Matthew AlanCounting, diatoms
12Rhizosolenia spp.Rhizosolenia spp.%Konfirst, Matthew AlanCounting, diatoms
13Rouxia antarcticaR. antarctica%Konfirst, Matthew AlanCounting, diatoms
14Rouxia constrictaR. constricta%Konfirst, Matthew AlanCounting, diatoms
15Thalassionema spp.Thalassionema spp.%Konfirst, Matthew AlanCounting, diatoms
16Thalassiosira elliptiporaT. elliptipora%Konfirst, Matthew AlanCounting, diatoms
17Thalassiosira fasciculataT. fasciculata%Konfirst, Matthew AlanCounting, diatoms
18Thalassiosira gracilisT. gracilis%Konfirst, Matthew AlanCounting, diatoms
19Thalassiosira lentiginosaT. lentiginosa%Konfirst, Matthew AlanCounting, diatoms
20Thalassiosira oestrupiiT. oestrupii%Konfirst, Matthew AlanCounting, diatoms
21Thalassiosira oliveranaT. oliverana%Konfirst, Matthew AlanCounting, diatoms
22Thalassiosira tetraoestrupiiT. tetraoestrupii%Konfirst, Matthew AlanCounting, diatoms
23Thalassiosira tetraoestrupii var. reimeriT. tetraoestrupii var. reimeri%Konfirst, Matthew AlanCounting, diatoms
24Thalassiothrix antarcticaT. antarctica%Konfirst, Matthew AlanCounting, diatoms
25Distephanus speculumD. speculum%Konfirst, Matthew AlanCounting, diatomsof non-Chaetoceros diatoms
26Diatoms, reworkedDiatom rew%Konfirst, Matthew AlanCounting, diatomsreworked or unidentifiable diatom frustules
27Diatoms, total abundance per unit sediment massTDA/sed106 #/gKonfirst, Matthew AlanCounting, diatoms
28Diatoms, sea-iceDiatom sea-ice%Konfirst, Matthew AlanCounting, diatoms
29Diatoms, marineDiatom mar%Konfirst, Matthew AlanCounting, diatoms
30Diatoms tropical/subtropicalDiatom trop/subtrop%Konfirst, Matthew AlanCounting, diatoms
31Accumulation rate, sediment, meanMARg/cm2/kaKonfirst, Matthew AlanCalculated
5307 data points

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