title: Origin and occurrence of Antarctic lacustrine carbonates, with special reference to Lake Fryxell, Taylor Valley

authors: Lawrence, M. J.

abstract: Lake Fryxell is a permanently ice-covered 19 m deep lake located 15m  a.s.l. in the lower Taylor Valley, Antarctica (75° 35'S, 163° 35'E). The lake occupies the lowest part of the Fryxell drainage basin and is surrounded by glacial tills with associated lacustrine carbonate and algal material of about Ross Sea I age. Lake Fryxell is a mesotherrnal, stratified, amictic lake with a euphotic (aerobic) zone above 10 m depth and an anaerobic (anoxic) zone below. The lake waters were derived from glacial meltwater into which upward diffusion of salts deposited in the basin or remnant brines occurred creating a gradient in density, which results in a physically stable lake. The so formed diffusion cell gave an estimated age of about 1000 years. Analysis of both lake water and lake bottom sediment cores show precipitation of CaCO₃ to have occurred both in the past and the present. Current carbonate precipitation is a biologically induced process occurring in the euphotic zone lake waters. over deep waters, precipitated carbonates, in this case calcite, fall from suspension through the water column and form flakes on the lake bed. Where the lake bed is within the euphotic zone stromatolites occur. 
Dissolution processes predominate in Lake Fryxell bottom waters and account for the discontinuous carbonate record in the uppermost lithologic unit (unit E) of Lake Fryxell sediments. At the time of the Ross Sea I advance a calcareous mud (unit B) was deposited on top of fluvialglacial sediments. The mud, a mixed calcite-aragonite deposit of up to 20 wt% CaCO₃  is C ¹⁴ dated at about 20,000 yrs B.P., was deposited in a deep pro-glacial Lake Washburn. At this time the Ross Sea Ice occupied part of the Fryxell basin damming the lower Taylor Valley and supplying the lake with meltwater. In ~1is ancient lake precipitation occurred in a similar manner to present Lake Fryxell except that aragonite was precipitated. Post-depositional change in the form of the aragonite/calcite transformation caused the observed dual mineralogy. Retreat of the ice sheet caused the deposition of transitional unit C and an evaporite deposit (unit D). Unit D is a varve-like aragonite ~10,000 years old, deposited in a lake of much reduced volume. The iv ice retreat from the drainage basin meant that the lake had an increased ablation surface enabling evaporation to exceed lake inputs resulting in brine concentration and subsequent precipitation of aragonite. Comparison of the Lake Fryxell carbonates with those of the Marshall Valley indicates that the Lake Fryxell depositional model, particularly evaporitic unit D, can adequately explain other Dry Valley carbonate deposits.

text: Origin and occurrence of Antarctic lacustrine carbonates, with special reference to Lake Fryxell, Taylor Valley Lake Fryxell is a permanently ice-covered 19 m deep lake located 15m  a.s.l. in the lower Taylor Valley, Antarctica (75° 35'S, 163° 35'E). The lake occupies the lowest part of the Fryxell drainage basin and is surrounded by glacial tills with associated lacustrine carbonate and algal material of about Ross Sea I age. Lake Fryxell is a mesotherrnal, stratified, amictic lake with a euphotic (aerobic) zone above 10 m depth and an anaerobic (anoxic) zone below. The lake waters were derived from glacial meltwater into which upward diffusion of salts deposited in the basin or remnant brines occurred creating a gradient in density, which results in a physically stable lake. The so formed diffusion cell gave an estimated age of about 1000 years. Analysis of both lake water and lake bottom sediment cores show precipitation of CaCO₃ to have occurred both in the past and the present. Current carbonate precipitation is a biologically induced process occurring in the euphotic zone lake waters. over deep waters, precipitated carbonates, in this case calcite, fall from suspension through the water column and form flakes on the lake bed. Where the lake bed is within the euphotic zone stromatolites occur. 
Dissolution processes predominate in Lake Fryxell bottom waters and account for the discontinuous carbonate record in the uppermost lithologic unit (unit E) of Lake Fryxell sediments. At the time of the Ross Sea I advance a calcareous mud (unit B) was deposited on top of fluvialglacial sediments. The mud, a mixed calcite-aragonite deposit of up to 20 wt% CaCO₃  is C ¹⁴ dated at about 20,000 yrs B.P., was deposited in a deep pro-glacial Lake Washburn. At this time the Ross Sea Ice occupied part of the Fryxell basin damming the lower Taylor Valley and supplying the lake with meltwater. In ~1is ancient lake precipitation occurred in a similar manner to present Lake Fryxell except that aragonite was precipitated. Post-depositional change in the form of the aragonite/calcite transformation caused the observed dual mineralogy. Retreat of the ice sheet caused the deposition of transitional unit C and an evaporite deposit (unit D). Unit D is a varve-like aragonite ~10,000 years old, deposited in a lake of much reduced volume. The iv ice retreat from the drainage basin meant that the lake had an increased ablation surface enabling evaporation to exceed lake inputs resulting in brine concentration and subsequent precipitation of aragonite. Comparison of the Lake Fryxell carbonates with those of the Marshall Valley indicates that the Lake Fryxell depositional model, particularly evaporitic unit D, can adequately explain other Dry Valley carbonate deposits.

year: 1982

title: Is there any Evidence for Regional Atmospheric 14C Offsets in the Southern Hemisphere?

authors: Hogg, Alan G.

abstract: Center for Accelerator Mass Spectrometry (CAMS) Tasmanian huon pine (Lagarostrobos franklinii) decadal measurements for the interval AD 745–855 suggest a mean interhemispheric radiocarbon offset (20 ± 5 yr), which is considerably lower than the previously reported mean interhemispheric offset for the last 2 millennia (44 ± 17 yr). However, comparable University of Waikato (Wk) New Zealand kauri (Agathis australis) measurements show significantly higher values (56 ± 6 yr), suggesting the possibility of a temporary geographic (intrahemispheric) offset between Tasmania, Australia, and Northland, New Zealand, during at least 1 common time interval. Here, we report 9 new Wk Tasmanian huon pine measurements from the decades showing the largest huon/kauri difference. We show statistically indistinguishable Wk huon and Wk kauri 14C ages, thus dispelling the suggestion of a 14C geographic offset between Tasmania and Northland.

text: Is there any Evidence for Regional Atmospheric 14C Offsets in the Southern Hemisphere? Center for Accelerator Mass Spectrometry (CAMS) Tasmanian huon pine (Lagarostrobos franklinii) decadal measurements for the interval AD 745–855 suggest a mean interhemispheric radiocarbon offset (20 ± 5 yr), which is considerably lower than the previously reported mean interhemispheric offset for the last 2 millennia (44 ± 17 yr). However, comparable University of Waikato (Wk) New Zealand kauri (Agathis australis) measurements show significantly higher values (56 ± 6 yr), suggesting the possibility of a temporary geographic (intrahemispheric) offset between Tasmania, Australia, and Northland, New Zealand, during at least 1 common time interval. Here, we report 9 new Wk Tasmanian huon pine measurements from the decades showing the largest huon/kauri difference. We show statistically indistinguishable Wk huon and Wk kauri 14C ages, thus dispelling the suggestion of a 14C geographic offset between Tasmania and Northland.

year: 2013

title: He whakanui i ēnei tau, e rima tekau o Te Whare Wānanga o Waikato

authors: Rewi, Poia

subjects: Tohu mātauranga

abstract: Aku tau ki Waikato: 1986-2003

A Block

Koia tērā, ko te Tari Māori (Māori Department), ko Timoti Kāretu te tumuaki, ko tōna kāhui kawe i ngā mahi ko te momo he wā tōna he pūkenga, he ahonuku, he ahorangi, he tākuta, he tohunga; he wā anō he pāpā, he whaea, he matua kēkē, he whaea kēkē; he wā anō he haututū, he hangarau, he whakatoi, he hoa tonu. Ko te tohu kē ia e whakaatuhia nei, ko te mātau o tēnei hanga ki te hāpai i te momo taera e hua ai te pai ki te ākonga, ki te mahi, ki te hapori.

Koia hoki te momo e whakamātauhia ana e te ao Pākehā; te mōhio kē, te tirohanga kē, te pōhēhē, te ture, te kawa me ngā tini aha kē. Koia tonu te momo e whakamātauhia ana e te ao Māori; ōna manako, ōna wawata, ōna taumahatanga, ōna piki, ōna heke. Ko te wā hui ki ngā kaimahi i Te Tari Māori he whakamoemoe i ngā utanga a te whare wānanga me ā te iwi kia whakapōtaehia he ākonga, me te mea, kia puta tonu hei tamāhine, hei tāhae, hei irāmutu, hei mokopuna e “toa ai rātou hei iti kotahi harakoa mō te iwi”. Kātahi nā te whiu ko tēnā, he taumahatanga kāore e pērā rawa te wahatanga e ngā kaimahi Pākehā i roto i ngā kura wānanga pēnei. Heoi anō, ko ia tērā ngā wheako o te wā, ahakoa nō nākua rawa nei i mārama ai taua here ki aua kaimahi, ka mahara iho au ki taua wā, ka mīharo tonu i te kaha o ērā pūkenga2 ki te whakatutuki i te wāhi ki a rātou. I tēnei punua hokinga mahara, ka aro ki ēnei mātua marau e rua, arā, ko te kawea o ngā mahi e taea ai e te Māori, ākonga mai, pūkenga mai, kaupapa mai, i te ao whare wānanga Pākehā, ka tahi; ka rua, ka aro ki ētahi o ngā āhuatanga e honohono ana ki te iwi.

text: He whakanui i ēnei tau, e rima tekau o Te Whare Wānanga o Waikato Aku tau ki Waikato: 1986-2003

A Block

Koia tērā, ko te Tari Māori (Māori Department), ko Timoti Kāretu te tumuaki, ko tōna kāhui kawe i ngā mahi ko te momo he wā tōna he pūkenga, he ahonuku, he ahorangi, he tākuta, he tohunga; he wā anō he pāpā, he whaea, he matua kēkē, he whaea kēkē; he wā anō he haututū, he hangarau, he whakatoi, he hoa tonu. Ko te tohu kē ia e whakaatuhia nei, ko te mātau o tēnei hanga ki te hāpai i te momo taera e hua ai te pai ki te ākonga, ki te mahi, ki te hapori.

Koia hoki te momo e whakamātauhia ana e te ao Pākehā; te mōhio kē, te tirohanga kē, te pōhēhē, te ture, te kawa me ngā tini aha kē. Koia tonu te momo e whakamātauhia ana e te ao Māori; ōna manako, ōna wawata, ōna taumahatanga, ōna piki, ōna heke. Ko te wā hui ki ngā kaimahi i Te Tari Māori he whakamoemoe i ngā utanga a te whare wānanga me ā te iwi kia whakapōtaehia he ākonga, me te mea, kia puta tonu hei tamāhine, hei tāhae, hei irāmutu, hei mokopuna e “toa ai rātou hei iti kotahi harakoa mō te iwi”. Kātahi nā te whiu ko tēnā, he taumahatanga kāore e pērā rawa te wahatanga e ngā kaimahi Pākehā i roto i ngā kura wānanga pēnei. Heoi anō, ko ia tērā ngā wheako o te wā, ahakoa nō nākua rawa nei i mārama ai taua here ki aua kaimahi, ka mahara iho au ki taua wā, ka mīharo tonu i te kaha o ērā pūkenga2 ki te whakatutuki i te wāhi ki a rātou. I tēnei punua hokinga mahara, ka aro ki ēnei mātua marau e rua, arā, ko te kawea o ngā mahi e taea ai e te Māori, ākonga mai, pūkenga mai, kaupapa mai, i te ao whare wānanga Pākehā, ka tahi; ka rua, ka aro ki ētahi o ngā āhuatanga e honohono ana ki te iwi.

year: 2016