Next AQUA conference: “Quaternary in the City of Sails”, Auckland, NZ, 5-9 December 2016

The next AQUA biennial conference will be held in Auckland New Zealand, from the 5-9 December 2016!

Auckland

Topic sessions will be held on the 5-6 & 8-9 December, with calls for session themes and registration details to be sent out in February 2016.

At this stage, two mid-conference field trips will be held on the 7th December, with options to head to the buried OIS7 forest on the tidal flats and temperate rainforest walk or Rangitoto shield volcano excursion and Motutapu Island in the Hauraki Gulf.

A Conference dinner will be held on the 8th December (venue being discussed), with a Quiz nite and BBQ on the 9th December.

Two post conference field trip options (6 days each) are currently being planned, and will be run according to level of interest.

The post conference field trips would depart Auckland 10 December and end 15 December 2016.

Trip 1: The Quaternary of the winterless North (a loop around the sub-tropical Northland/Far North region starting and ending in Auckland; Three nights in Bay of Islands, two nights at Kai Iwi Lakes). The trip will focus on ancient kauri, changes in ecology as seen in pollen records over interglacial-glacial scales, and coastal barrier evolution from OIS5-present.

Trip 2: Quaternary volcanism and environmental change

(excursion south from Auckland through the Waikato, the central North Island and ending in Wellington; Three nights in Taupo, two nights in Palmerston North). There will be a focus on Quaternary volcanism, tectonism, sedimentation, and climate. Stops will include the Taupo and Rotorua volcanic centres, glaciation in the Tongariro National Park, Napier/Hawkes Bay and the Kapiti- Horowhenua / Wanganui Basin sequences.

A PDF flyer is available here to begin advertising within your organisations. More information will be published on the AQUA website and Facebook as it becomes available.

Travel grants available for Australian and New Zealand ECR Geoscientists

The Academy, together with the Australian Geoscience Council, has opened a call for applications for a travel grant scheme for Australian and New Zealand ECR Geoscientists. This is a new fund that offers annual grants of up to $5000 for career-enhancing travel, established with the proceeds of the 2012 Brisbane IGC.

For conditions and criteria head to the Australian Geoscience Council Website.

Applications close on 31 October 2015 for travel beginning in 2016.

The advent of the Anthropocene in Australasia

We’d love your opinion on this article!! Please head to https://www.surveymonkey.com/r/LTZ5HPP and choose your preferred definition of “The Anthropocene”.
If you choose the option of “other” then please email president@aqua.org.au with your other.Votes close at the end of September.
 
First published in Quaternary Australasia, July 2015. – PDF version
Helen C. Bostock1, David J. Lowe2, Richard Gillespie3, Rebecca Priestley4, Rewi M. Newnham5, Scott D. Mooney6
 

Introduction

As early as the late 19th Century, several scientists had suggested that humans were starting to influence the physical environment of planet Earth (e.g. Marsh, 1864; Stoppani, 1873; Arrhenius, 1896; Chamberlain, 1897). This idea was resurrected and expanded in 2000 by Paul Crutzen, a Nobel Prize-winning chemist, and the late Eugene Stoermer, a professor of biology specialising in diatoms, who suggested that we had left the Holocene and entered the “Anthropocene” (Crutzen and Stoermer, 2000). As summarised by Steffen et al. (2011) and Wolfe et al. (2013), these iconoclastic scientists were referring to the Anthropocene as the interval of demonstrable human alteration of global biogeochemical cycles, beginning subtly in the late 18th Century following James Watt’s invention of the coal-fired steam engine, and accelerating markedly in the mid-20th Century (termed “The Great Acceleration”). Thus Crutzen and Stoermer (2000) argued that the Anthropocene should be an epoch, and for a starting date at the beginning of the Industrial Revolution (Monastersky, 2015).

The term Anthropocene is now regularly used in the geological/environmental literature, appearing in nearly 200 peer-reviewed articles in 2012, and three new journals have been launched over the last few years specifically focussed on this topic, namely The Anthropocene Review, Anthropocene, and Elementa: Science of the Anthropocene. In 2014, the Geological Society, London, published A Stratigraphical Basis for the Anthropocene (Waters et al., 2014), a 321-page volume devoted to the subject. The problem is that the Anthropocene has not yet been formally defined and different disciplines (and even scientists within the same discipline) have different viewpoints as to when the Anthropocene began, if at all (Table 1). In addition, most perspectives on this issue are derived from the Northern Hemisphere, although Brown et al. (2013) and Ellis et al. (2013) and some others have taken a more global viewpoint. Continue reading

AQUA t-shirts for sale!

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Super stylish AQUA t-shirts are now available to purchase!

T-shirts are light blue and feature an AQUA logo on the front, and a quaternary-inspired design by Emily Field on the back.

T-shirts are only $39, including postage within Australia and New Zealand!

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Currently, we only have sizes L, XL, and 2XL available, however smaller sizes will be available to purchase soon.

 

If you would like to order a t-shirt, or would like to put in a request for a smaller size, please contact Scott Mooney (s.mooney@unsw.edu.au) to double check sizing availability. You will then be given AQUA’s bank details to pay via direct deposit.

Congratulations to Matt Ryan

PhD student Matt Ryan from Victoria University in Wellington, NZ was awarded a Student Poster award at the recent INQUA congress in Japan. With many hundreds of posters presented at the conference, this is an excellent achievement for Matt.

Congratulations!

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Blog 15: Two weeks in Patagonia – A fieldwork diary

By Ignacio Jara

26 January

It is somewhat symbolic that the initial stop of my field season in Chile is the very same place where, one year ago, Brent Alloway and I finished Victoria University, Wellington, School of Geography, Earth and Environmental Sciences first international field trip with a traditional Patagonian asado (spit barbeque)… but this summer the mission is different.

Last night Brent showed me satellite images depicting what looks like an unrecognized volcanic dome right next to Chaitén volcano. Based on the geochemical analysis of ash layers found in road cuts around Chaitén, Brent is convinced that this previously unrecognized dome has erupted at least once in the last millennium. The plan is try to get to the dome, have a look and take some rock samples to analyze and compare. Looking at the maps, we agreed that it will be a difficult objective since the area is covered by dense temperate rain-forest without any visible tracks. But we are optimistic.

27 January

For now, my field trip has been about planning and enjoying the hospitality of Brent which includes good food and of course the marvelous Chilean Carménère wines. However, tonight this enjoy-without-working scenario will change when we meet a fieldwork team from Universidad de Chile to embark on the Don Baldo ferry for an overnight trip that will take us down south to the Chaitén province, the northern gate of Patagonia.

Photo 1. “The arrival to Chaitén could not have been more beautiful”

Photo 1. “The arrival to Chaitén could not have been more beautiful”

28 January

Our arrival to Chaitén early this morning couldn’t have been more beautiful (photo 1). From the Ferry’s deck the greenness of the forest, the calm of the waters and the mountains on the background reminded me the Marlborough Sounds after crossing the Cook Strait. While the ferry slowly made its final way trough a narrow channel before arriving at the small landing platform, greeted by a couple of tourists waiting on the shore to take the same ferry back to mainland Chile. A calm tranquil morning in the small town of Chaitén.

29 January

With Brent and two other students we spent the whole day trekking up the Chaitén valley trying to reach the newly discovered lava dome. The devastation in Chaiten township and up the valley produced by the ashes and pyroclastic flow during the 2008 eruption is simply overwhelming. Tramping around burned trunks, strong smelling sulfide orange-coloured streams and being completely surrounded by tons of white ashes evokes a special feel of devastation and remind us that nature is both powerful and deadly (Photo 2).

At the end of the day we were unable to reach the dome. It was just too difficult to get to. We traversed the river valley as much as we could but we were impeded by a massive waterfall which prevented us from progressing further. Obviously we are bit disappointed and frustrated but trying to get around the waterfall through the impenetrable forest and vertical terrain would undoubtedly have been too risky.

Photo 2 “Tramping around tons of white ashes from the 2008 eruption evoked a special feel of devastation and remind us that nature is both powerful and deadly”. Prof. Brent Alloway, the steaming Volcán Chaitén and the devastated Chaitén valley with Volcán Corcovado on the background.

Photo 2 “Tramping around tons of white ashes from the 2008 eruption evoked a special feel of devastation and remind us that nature is both powerful and deadly”. Prof. Brent Alloway, the steaming Volcán Chaitén and the devastated Chaitén valley with Volcán Corcovado on the background.

31 January

Despite our failure in trying to reach the volcano, Brent still wants to have a closer look. He has contacted a local pilot to fly a small 1969 Piper Cherokee monoplane over the crater. A bit scary considering the size of the airplane was not bigger than Mini Cooper with wings (Photo 3)!

Luckily, we enjoyed a stunning sunny day without any of those gusty winds that I usually experience in Wellington. Only one of those winds would have made the monoplane shake like a scared dog (Photo 3)!

Leaving all those concerns aside, the views were simply fantastic! The mountains, the endless coastline and the Chaitén volcano with all of its ash from the 2008 eruption mantling the surrounding area, created a wonderful visual experience. But more importantly, the views from the aircraft confirm that there is now a new satellite dome just a stone throw from Chaitén Volcano.

Photo 3 “We enjoyed a stunning sunny day flying the tiny 1969 Piper Cherokee monoplane, nothing compared with those gusty winds usually experienced in Wellington”. The Patagonian coastline, the Volcán Chaitén crater and the narrator posing with the 1969 Monoplane.

Photo 3 “We enjoyed a stunning sunny day flying the tiny 1969 Piper Cherokee monoplane, nothing compared with those gusty winds usually experienced in Wellington”. The Patagonian coastline, the Volcán Chaitén crater and the narrator posing with the 1969 Monoplane.

2 February

After our flying adventure we have now rejoined the group from Universidad de Chile in Futaleufú, a small town 80 kilometer inland from Chaitén. Over the next few days we will be on a raft coring two small lakes in the surroundings. Despite their small size, the access to the lakes is always a main issue and that wasn’t an exception during this fieldtrip. It turned out that one of the lakes was actually on the top of a small hill and there wasn’t any nearby road allowing for vehicles to get the coring platform to the lake edge. We therefore needed the assistance of a bow yoke with two old oxen to bring all our equipment up to a steep farm track. …..the Patagonian way (photo 4)!

Photo 4. “We needed the assistance of a bow yoke with two old oxen to bring all our equipment up to a steep farm track.  ...the Patagonian way”. The narrator in the middle of a coring day, the bow yoke with our field equipment and our second lake next to Futaleufú township.

Photo 4. “We needed the assistance of a bow yoke with two old oxen to bring all our equipment up to a steep farm track. …the Patagonian way”. The narrator in the middle of a coring day, the bow yoke with our field equipment and our second lake next to Futaleufú township.

5 February

After 3 days of pretty intense coring work are we now finished with our first lake and moving on to another lake, just on the outskirts of Futaleufú town (Photo 4). Very hot, dry, sunny days working on the raft and as a result I got a little sunburnt. I am tired and I miss all the comforts of the city, but I am also very excited with our progress as we retrieved a lot of core containing sediments that will be the final part of my PhD thesis. There is an impressive variety of layers preserved in the lake sediments, including countless volcanic ash layers (to keep Brent happy!), wood fragments, glacial silts and nasty black charcoal layers inter-fingered. So much work to do reconstruction the history of the lake!

8 February

Another three days working in our second lake and now we have even more sediment to analyse (I am not that sure how lucky I am now!) Our field trip is coming to an end. Tomorrow we will drive back to Chaitén and then board the overnight ferry that will take us back to mainland Chile. In Santiago, I will spend the next two months sampling and processing the sediment we got in the field.

For me this has been a great time to reconnect with the people I worked with during my Masters. Hard work? For sure. Rewarding? Absolutely! Now I must get to work in the lab – lots of samples to process, pollen to count and a PhD to finish!

Ignacio wants to thanks Dr. Patricio Moreno and all the members of Laboratorio de Palinologia Quaternaria at Universidad de Chile for all their support during the field and laboratory work described in the column above.   

Blog 14: The Blogger’s selection of 2014 Quaternary sciences publications

By Ignacio Jara

Saying goodbye to 2014 and welcoming in 2015 is a good time to reflect. Apart from being the hottest year ever recorded, 2014 has passed really fast; with so many good research articles!

Since good science always keeps my spirits high, I have decided to embark on the tricky task of recapping some of the 2014 papers I have found most interesting, innovative or insightful. And yes, let me clarify in advance that this is my “personal choice”, so I take full responsibility for the choices and I’m sure that others have their own selection.

First I have to mention that 2014 was a year with some great archaeological research. Aubert et al. (2014) published a remarkable dating analysis of small speleothems in association with rock art from Sulawesi, Indonesia (Image 1). This work pushes the dates of the aboriginal rock art tradition in Southeast Asia back as far as 40 kyr ago. Apart from positioning the Sulawesi rock painting among the oldest symbolic art in the world and providing the oldest evidence for humans on the island, their results suggest that rock painting was a cultural trait that accompanied the first human population that ventured beyond the African continent, thus challenging the long-standing notion that animal painting was a relatively late form of art originating in Europe.

One of the earliest examples of rock art in the world: a Babirusa (deer-pig) pig and a hand stencil from Sulawesi Island, Indonesia. Modified from: Aubert et al., 2014. Pleistocene cave art from Sulawesi, Indonesia. Nature 514, 223-227.

Image 1: One of the earliest examples of rock art in the world: a Babirusa (deer-pig) pig and a hand stencil from Sulawesi Island, Indonesia. Modified from: Aubert et al., 2014. Pleistocene cave art from Sulawesi, Indonesia. Nature 514, 223-227.

Following in the archaeological line, I do not want to miss the opportunity to mention the large amounts of archaeological research coming from China. Here, the research focus has been on studying past human-climate interactions by linking archaeological evidence with the growing number of well-dated high-resolution climate proxy data available from this region. Wang et al. (2014) produced a compilation of thousands of radiocarbon dates from multiple archaeological sites scattered all over China. This article provides a detailed human population reconstruction that covers the last 50 kyr, but also shows interesting correlations with long-term changes in monsoonal activity and high-latitude temperature . The evidence suggests that periods of warm/moist conditions are associated with peaks in Chinese population; whereas the cold/dry conditions experienced during the Heinrich events and the Younger Dryas seem to match declines in human population. Moreover, the past demographic changes revealed by their reconstruction show that the greatest population expansion in China’s prehistory took place at about 9 kyr ago, coeval with the onset of agricultural practices. Although still preliminary, the finding of a succession of shorter-term warm/cold phases observed during the middle and late Holocene suggests fascinating links with the complex cultural evolution observed between the Yellow and the Yangtze Rivers, the formative area of the classic Chinese civilisation.

Volcanic eruptions are well known to produce changes in climate conditions at annual or even decadal scales. However, a paper published late last year –back in 2013, but it is a pretty nice article- turns this notion on its head and provides convincing evidence of orbitally-forced variability in Quaternary volcanism (Kutterolf et al., 2013). The study performed a statistical analysis on a time series of volcanic eruptions obtained from tephra layers deposited in marine sediment cores around the Pacific “Ring of Fire”. The results of this analysis show a statistically robust frequency peak in global volcanism at 41 kyr, the Milankovitch obliquity frequency. The authors use the benthic foraminifera oxygen isotope stack as a proxy for changes in global ice volume to link orbitally-induced variations in ice-sheet extent to volcanic activity. Peaks in volcanic activity lag the deglaciation by about 4 kyr. Volcanic eruptions are more frequent when the ice-sheets retreat, when there is a reduction in the continental surface pressure. Several millennia of sustained deglaciation seem to be the precondition to not only decrease pressure over continental areas, but also to increase loading on the ocean the result of higher sea level resulting from the melting of ice sheets. According to the authors, this mass reorganization might be associated with the migrations of magma material from the oceanic plates towards the continents, which might ultimately result in a rise in onshore volcanic activity.

Continuing with the theme of ice-melting and ocean loading, a new detailed record of Antarctic ice discharge and modelling study provide interesting clues about the interactions between Antarctic ice sheet and ocean temperatures during the last deglaciation (Weber et al., 2014; Golledge et al. 2014). The first of these publications presents a highly-resolved reconstruction based on the accumulation of iceberg-rafted debris in two ocean records located to the northwest of the Antarctic Peninsula, a region known as the “Iceberg Alley” since it is the area through which icebergs from all parts of Antarctica abandon the continent and enter into the Southern Ocean. The record exhibits a series of well-defined centennial-scale peaks in iceberg debris between 20 and 9 kyr ago, suggesting the existences of several rapid pulses of ice loss during the Last Termination. The record also reveals that these episodes of enhanced iceberg movement started abruptly, quickly releasing fresh water into the Southern Ocean and contributing to global sea level rises. The melt water pulses cooled down the surface of the Southern Ocean, and ice-ocean modelling analysis shows that this same pulses might have produced more ice melting, as the release of melt water was also associated with an increase in the transport of warm deep waters from the Atlantic Ocean, which caused the intermediate and deep waters of the ocean to warm, which upwell around Antarctica and further accelerate the thinning of ice masses by basal melting. Interestingly, very similar results are obtained from the ice sheet, sea level and ocean temperatures modelling work presented in the second of these publications.

There is growing interest amongst paleoclimate researcher to reconstruct the past history of climate modes. Two new high-resolution reconstructions of the Southern Annular Mode (SAM) have been developed. Firstly, a composite SAM reconstruction based on proxies from mainland Antarctica, Antarctic Peninsula and South America was published early this year by Abram et al. (2014), which sets the recent trend in theSAM variation within the context of the last millennium. This paper also looks at the interaction of the SAM with climate variations in the tropical latitudes (see blog #9 for more details). Then more recently, a SAM reconstruction based on changes in vegetation and fire history from Patagonia (Moreno et al., 2014). In this article the present-day strong relationship between the Patagonian climate and the SAM is used to infer centennial-scale positive/negative phases of this climate mode over the last 3,000 years. Notably, positive SAM phases detected in this reconstruction broadly match the timing of the Industrial revolution, the Medieval Climate Anomaly, the Roman and the Bronze Age warm periods; while the negative SAM matches the Little Ice Age, the Dark Ages and the Iron Age Cold Period. Since all of these “climate ages” have been originally described in the Northern Hemisphere, their results point out to a continuous and rapid inter-hemispheric link at timescales of centuries.

The transition between forest and grassland in Patagonia is controlled by changes in precipitation which are in turn correlated with present-day modes of climate variation such as the Southern Annular model. Photo from Northern Patagonia.

The transition between forest and grassland in Patagonia is controlled by changes in precipitation which are in turn correlated with present-day modes of climate variation such as the Southern Annular model. Photo from Northern Patagonia.

Overall 2014 has been a great year for Quaternary Sciences. A broad range of good Quaternary science has been published. I hope you have enjoyed this compilation. What is coming up in 2015? Well, I am surely not a seer, but I hope to discuss some of the new research in more depth in the AQUA blogs and, hopefully, there will be some unexpected new discoveries that will get us out of our Quaternary comfort zone. Have a great new year!

 

References

Abram, N.J., Mulvaney, R., Vimeux, F., Phipps, S.J., Turner, J., England, M.H., 2014. Evolution of the Southern Annular Mode during the past millennium. Nature Clim. Change 4, 564-569.

Aubert, M., Brumm, A., Ramli, M., Sutikna, T., Saptomo, E.W., Hakim, B., Morwood, M.J., van den Bergh, G.D., Kinsley, L., Dosseto, A., 2014. Pleistocene cave art from Sulawesi, Indonesia. Nature 514, 223-227.

Golledge, N.R., Menviel, L., Carter, L., Fogwill, C.J., England, M.H., Cortese, G., Levy, R.H., 2014. Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning. Nat Commun 5.

Kutterolf, S., Jegen, M., Mitrovica, J.X., Kwasnitschka, T., Freundt, A., Huybers, P.J., 2012. A detection of Milankovitch frequencies in global volcanic activity. Geology.

Moreno, P.I., Vilanova, I., Villa-Martínez, R., Garreaud, R.D., Rojas, M., De Pol-Holz, R., 2014. Southern Annular Mode-like changes in southwestern Patagonia at centennial timescales over the last three millennia. Nat Commun 5.

Wang, C., Lu, H., Zhang, J., Gu, Z., He, K., 2014. Prehistoric demographic fluctuations in China inferred from radiocarbon data and their linkage with climate change over the past 50,000 years. Quaternary Science Reviews 98, 45-59.

Weber, M.E., Clark, P.U., Kuhn, G., Timmermann, A., Sprenk, D., Gladstone, R., Zhang, X., Lohmann, G., Menviel, L., Chikamoto, M.O., Friedrich, T., Ohlwein, C., 2014. Millennial-scale variability in Antarctic ice-sheet discharge during the last deglaciation. Nature 510, 134-138.

Blog 13: LGM in NZ through the lens of cosmogenic studies

By Ignacio Jara

The issue of whether the last glacial-interglacial transition was synchronous between the Northern Hemisphere (NH) and Southern Hemisphere (NH) has been an ongoing and often controversial debate amongst Quaternarists. There is now considerable amounts of proxy data for the Last Glacial Maximum (LGM; 22-19 ka) and the Last Glacial Termination (19-11 ka) and yet there are still conflicting opinions about the phase -or anti-phase- of warming and cooling events between the hemispheres. The dominant view for many years was that the orbital-driven variations of the NH summer insolation were the main factor behind the waxing and waning of the continental ice sheets at global scales. However, conspicuous climate oscillations at timescales shorter than the orbital cycles have widely been recognized in Antarctica, Greenland and marine records from different latitudes, suggesting that a more complex –and fascinating- dynamic has been driving the climate. Despite all these new findings, the paradigm has remained more or less the same, i.e. that the SH glaciers have been ultimately responding to a NH signal. However, new evidence might suggest that the LGM in the SH may have occurred several thousand years earlier than the NH.

New Zealand is one of the few landmasses in the SH mid-latitudes that experienced extensive glacier advances during the last ice age, and therefore it is arguably a key region to test some of these ideas. Not surprisingly, this region has not been absent of the debate about the timing and structure of the New Zealand LGM and the Termination, with different –and sometimes opposite- interpretations being common.

Figure 1. Lake Tekapo with the Southern Alps in the background in central South Island, New Zealand. Cosmogenic chronologies from moraines around glacial lakes like this are giving valuable information about the glacial activity during the transition out of the last Ice Age.

Figure 1. Lake Tekapo with the Southern Alps in the background in central South Island, New Zealand. Cosmogenic chronologies from moraines around glacial lakes like this are giving valuable information about the glacial activity during the transition out of the last Ice Age.

Trends in New Zealand cosmogenic studies

Glacial reconstructions based on cosmogenic chronologies in New Zealand are a good example of this debate. Numerous well-preserved glacial landforms on both sides of the Southern Alps have provided a great opportunity to develop detailed cosmogenic glacial chronologies. Nevertheless, the relative novelty of this method, the lack of compelling datasets and the documenting of new cosmogenic production rates have all contributed to a wide range of different interpretation and hypotheses.

The first attempt to date New Zealand glacial landforms using cosmogenic dating was in 1999 (Ivy-Ochs et al., 1999). In 2006 a set of cosmogenic dates (n=7) from the Lake Pukaki area (44°S) showed that the timing for the final LGM ice retreat in New Zealand was centred at 18 ka (Schaefer et al., 2006), coincident with the onset of other glacial retreat in mid-latitude regions from both the NH and the SH. Based on similar results, but with a much more extensive cosmogenic dataset (n=39) from the Rakaia valley (43°S), Putnam et al., (2013) also proposed 18 ka as the onset of widespread glacial retreat in the Southern Alps. Additionally they showed that the rate of glacial retreat was very fast, with almost half of the total LGM ice lost in less than 2000 years.

An alternative view to this “fast and furious” ice retreatment was presented by Schulmeister et al (2010) and supported by a new article published this year (Rother et al., 2014). In this recent publication, Rother et al. (2014) presents a new set of cosmogenic ages (n=48) also from the Rakaia valley and suggests a series of glacial advances and retreatments from 28 to 16 ka, comprising the whole LGM interval. Based on their chronology the authors divide the New Zealand LGM into four main stages, with two periods of sustained ice retreat between 28-25 ka and 25-19 ka punctuated by two shorter phases of ice re-advance or more stable ice positions. While these results support a date of 18-19 ka for final LGM ice retreat, the authors also argue for a longer and more gradual glacial recession that lasted until 16 ka. According to Rother et al., (2014) the critical factor that could have misleadingly led previous cosmogenic researchers to argue for a “fast and furious” ice withdrawal is the formation of large glacial lakes at their base. Glacial lakes are a common feature in glacial valleys on the eastern side of the Southern Alps, and in that type of lacustrine environment, ice melting at the lake base is enhanced by water heat advection and not necessary by a regional climate (temperature) signal.

Rother et al., (2014) also suggest that the largest glacial extent was between 28-25 ka, several thousand years earlier than any other glacial reconstruction, and earlier than the LGM maximum extension in the NH. This time frame is more or less contemporaneous with an interval of cold conditions from the recently published NZ climate stratigraphy (NZCS; Barrell et al., 2013), however, it does not match the coldest interval proposed by the NZCS (occurring between 22-18 ka). Interestingly, the authors overcome this disparity by suggesting that their reported period of maximum ice extension did not occur during the coldest interval of the last glacial termination, but instead as a result of the combination of “not-the coldest-but-still-cold” conditions combined with higher than normal precipitation.

Regional climate drivers

The date of 18 ka for the beginning of the LGM termination in the Southern Alps (Schaefer et al., 2006) was in good agreement with other reported ages for glacial terminations in both hemisphere mid-latitudes. Based on this inter-hemispheric consistency the authors postulated that NH summer temperatures were the main driver for the global glacial recessions at the end of the LGM. By comparing their cosmogenic ages with other glacial chronologies and marine proxies from the SH, Putnam et al (2013) argued for a southward displacement of the Southern Westerly Winds (SWW) and their associated ocean fronts as the direct driver responsible for the final LGM termination in New Zealand.

This interpretation fits with the “bipolar seesaw” hypothesis. While the LGM glacial recession in the SH mid-latitudes showed a coherent timing that matches a gradual increase in Antarctic temperatures and rise in CO2, the NH showed a much more complex picture with the final LGM warming also triggering a massive discharge of icebergs into the North Atlantic Ocean during the so-called Heinrich Event 1, reducing the Atlantic meridional overturning circulation, and finally pushing the NH into a new cooling period for the next couple of thousand years. Moreover, it seems clear now that this bipolar seesaw switches between a “south-warm” and a “north-warm” phase several times over the last 60 ka. A new cosmogenic dataset (n=44) from Lake Pukaki supports this anti-phase relationship by dating an extensive Southern Alps glacial advance to 42 ka, a time coeval not only with a prominent cold episode in Antarctica and the Southwest Pacific, but also a warm interval in the NH (Kelley et al., 2014).

But which hemisphere started the last termination, driving the seesaw and opposite response in its counterpart?

The fact that the NH did not experience any long-lasting or prominent warming trend until 15 ka and that the SH experienced a much more coordinated warming response starting at least 3000 years before might be interpreted as evidence towards the SH as the “leading end” of the seesaw. However, a more detailed observation of the Greenland temperature record reveals that the initial warming in the NH occurred around 24 ka, at the same time that summer insolation in this hemisphere started to increased. Denton et al., (2010) suggest that the main condition for triggering the last glacial Termination was the orbitally-driven widespread collapse of Laurentide ice sheet after it reached an LGM maximum. Paradoxically, this collapse may have triggered a succession of large-scale changes that ultimately led to intense cooling in the NH, while in the SH these changes may have been associated with a more gradual warming via the southward shift of the SWW and the Subtropical front.

It is clear that the discussion about the timing and structure of the LGM and the Termination in New Zealand is still ongoing more than 15 years after the pioneering cosmogenic work. Although in some respects the publications over the last few years look more controversial than ever before, there seems to be a general consensus on at least two things: (1) a widespread ice retreat in the Southern Alps started about 18 ka, and (2) there was a close link between the glacial activity, temperature changes and the SWW during the Termination. Future cosmogenic studies from this part of the globe should test whether the retreat was “fast and furious” despite the relatively gradual changes in Antarctica temperatures, as well as other relevant topics such as the potential links between ice dynamics and atmospheric CO2 (something that is undoubtedly relevant to future climate change scenarios). Get out your rock hammers Quaternarist!

References

Barrell, D. J. A., Almond, P. C., Vandergoes, M. J., Lowe, D. J., and Newnham, R. M., 2013, A composite pollen-based stratotype for inter-regional evaluation of climatic events in New Zealand over the past 30,000 years (NZ-INTIMATE project): Quaternary Science Reviews, v. 74, no. 0, p. 4-20.

Denton, G. H., Anderson, R. F., Toggweiler, J. R., Edwards, R. L., Schaefer, J. M., and Putnam, A. E., 2010, The Last Glacial Termination: Science, v. 328, no. 5986, p. 1652-1656.

Ivy-Ochs, S., Schlüchter, C., Kubik, P. W., and Denton, G. H., 1999, Moraine Exposure Dates Imply Synchronous Younger Dryas Glacier Advances in the European Alps and in the Southern Alps of New Zealand: Geografiska Annaler: Series A, Physical Geography, v. 81, no. 2, p. 313-323.

Kelley, S. E., Kaplan, M. R., Schaefer, J. M., Andersen, B. G., Barrell, D. J. A., Putnam, A. E., Denton, G. H., Schwartz, R., Finkel, R. C., and Doughty, A. M., 2014, High-precision 10Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago: Earth and Planetary Science Letters, v. 405, no. 0, p. 194-206.

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Blog 12 – A journey through Australian prehistory

By Ignacio Jara

After the 2014 AQUA and biennial conference at Mildura, a group of attendees had the chance to travel north to visit the Mungo National Park in the Willandra Lakes region, New South Wales. This area features a series of dry lake basins bordered by old sand dunes. From the road the region looked quite flat and deserted to eyes accustomed to lush, green, New Zealand scenery. But soon the flatness of the desert was replaced by an overwhelming feeling of significance. This region has an outstanding Quaternary history to tell based on 40 years of research.

The Willandra Lakes system can be understood as “stairway” of dry lake basins linked by one river system, the Willandra Creek. Although at present the river is not more than a narrow meandering dip in the ground, during the recent past it was way more active, filling and empting the lake basins many times during the Quaternary period. This wetting and drying activity was associated with the build-up of extensive shoreline rings or “barrier beaches” that captured and preserved a wide range of different sediments including sands, gravel, plant and animal remains. Over time, these fossil-rich shorelines were buried and sealed by clays derived from the dry basins floor, building up bordering dunes systems or “lunettes” on the eastern edges of the Willandra lake basins.

Lake Mungo is one of these lake basins in the southern part of the Willandra system. Archaeological findings suggested that during wet phases the lake shore sustained continuous human population that exploited the lake’s aquatic resources (figure 1). The last evidence of a water-filled lake occurs around 15,000 years ago and since then the continuous erosion of the lunettes has revealed a great number of old animal and human remains from those early times, becoming an outstanding region for archaeological research in Australia. Early investigations of the lakes history were focused on its complex Quaternary sedimentary sequence, however the archaeological significance of this region was greatly enhanced by a series of exceptional archaeological findings during the lake 1960’s and 1980s, including the discovery one of the world’s oldest cremated remains named “Mungo Girl”, followed by the discovery of a near-complete red ochre-covered skeleton called “Mungo Man. These two human remains represent one of the oldest evidence of modern Homo sapiens outside of Africa and their dating (from OSL) is now accepted to be~40,000 years old.

Our group had the privilege to visit the Lake Mungo area in the company of some of the leading scientists who discovered the bodies and have been working here for many years. The aim or the field trip was to review the geological and archaeological investigations at Willandra, as well as see some of the new ongoing scientific research at the park.

On our arrival at the Mungo Visitor centre, the group was welcomed by some elders from the traditional tribal groups of the Willandra area. After sharing a welcome morning tea that warmed our bodies on the cold dessert morning, we visited the southern edge of Lago Mungo where the first human remains were found in 1969 (Figure 2). The colourful moon-like background of the eroding dunes was undoubtedly beautiful, and we had the privilege to listen not only to Prof. Jim Bowler talk about the scientific implications of some his archaeological findings, but also to the aboriginal elders comments on the significance of Mungo for their ancestral culture and heritage.

In the afternoon the group visited an ongoing archaeological dig on the Lake Mungo Lunette. Since 2007 a multidisciplinary research group have been working here with the purpose of gathering new information about the extensive human occupation record of this area and to improve the understanding of the past environmental evolution of the lake. Walking through the colourful landscape of the lunette at dusk with the vastness of the desert as a background, watching the archaeological excavation, and listening to the archaeologists describe some of the findings, was undoubtedly an inspiring experience that made us – mostly geologist, biologist and climate scientist- appreciate the overall relevance of archaeological investigation. Bearing in mind the significance of the Willandra Lakes as an area of world heritage did nothing but boost this “sacred” feeling of visiting this venerated site.

During the second day we had the chance to spot a great number of wild kangaroos and emus. The final stop for the field trip occurred in the afternoon of the second day, when the group visited the eastern border of Lake Mungo. A series of ancient footprints were discovered here in 2003. Detailed studies of the foot tracks have revealed intimate insights into the transportation of the family groups that inhabited Lake Mungo 20,000 years ago, including children’s escapades and even evidence of a one-legged individual. However, the paradox here is that erosion is working against the archaeologists, slowly erasing the ancient steps of ancestral Australians and hence this priceless cultural heritage.

Overall this field trip presented a unique opportunity to visit an important region for Australian science and history. The presence of some of the scientists who have discovered and studied this area made the trip even more informative and special. Covering more than 40 years of outstanding research in two days was a major challenge and of course many pieces and details of this history were left for another occasion. However, if you want read more details about this exciting field trip experience, an extended version of this article will be published in the upcoming Quaternary Australasian newsletter.

 

PhotosPhotos from the field trip (Ignacio Jara)