Glacio-lacustrine sedimentation in newly discovered paleo-lakes, Westland, New Zealand

<p>The remnant effects of Quaternary glaciation dominate the geomorphology of South Westland, New Zealand. Well-constrained glaciogenic records for the Last Glacial Maximum (LGM) (~MIS 2) show ice to have extended significant distances across the Westland piedmont, becoming tidewater calving in places. Despite clear evidence for glacial advance, landscape response to glacial retreat remains relatively poorly understood, with few described sedimentary sequences clearly recording deglaciation processes. A 240-metre thick glacio-lacustrine sedimentary sequence intercepted by drilling in the Whataroa Valley (DFDP-2) provides the first compelling evidence of pro-glacial lake formation in response to glacial retreat in Westland. To understand the vertical facies succession observed in this sequence, two glacio-lacustrine facies schemes and depositional models were developed. To do this, previously unmapped glacio-lacustrine sedimentary sequences in the Westland region underwent detailed sedimentological analysis to identify key glacio-lacustrine facies. In the Waitangitaona and Arahura river valleys, the presence of glacio-lacustrine sequences is also used to mark paleo-lake formation in the respective catchments. Using the facies scheme and depositional models, together with 14C chronology and sedimentological analysis, a series of conclusions are developed from the DFDP-2 sequence: 1) Deposition occurred in an over-deepened glacial trough, with the sequence consisting of a basal diamictite, overlain by a ~ 140-metre interval of lacustrine siltstones and sandstones. 2) The lower ~ 180-metres of sediment accumulated in 659 ± 151 yrs between 16609 ± 151 and 15994 ± 94 cal. yr BP, as the depositional environment at the drill-site evolved from an ice contact to an ice distal lacustrine setting. 3) Extremely rapid sedimentation rates, as well as high lake levels allowed the preservation of glacially over-steepened bedrock slopes beneath the Whataroa Valley. The formation of a previously unknown, ~190 km2 pro-glacial lake on the Whataroa piedmont is inferred from the DFDP-2 sequence, with lake formation causing accelerated glacial retreat from the late LGM maxima. The presence of several catchments with comparable piedmont geometry suggests pro-glacial lake formation may have been a common response to glacial retreat in Westland. For a period, pro-glacial lakes may have been a significant transitory feature on the Westland landscape.</p>

Glacio-lacustrine sedimentation in newly discovered paleo-lakes, Westland, New Zealand

<p>The remnant effects of Quaternary glaciation dominate the geomorphology of South Westland, New Zealand. Well-constrained glaciogenic records for the Last Glacial Maximum (LGM) (~MIS 2) show ice to have extended significant distances across the Westland piedmont, becoming tidewater calving in places. Despite clear evidence for glacial advance, landscape response to glacial retreat remains relatively poorly understood, with few described sedimentary sequences clearly recording deglaciation processes. A 240-metre thick glacio-lacustrine sedimentary sequence intercepted by drilling in the Whataroa Valley (DFDP-2) provides the first compelling evidence of pro-glacial lake formation in response to glacial retreat in Westland. To understand the vertical facies succession observed in this sequence, two glacio-lacustrine facies schemes and depositional models were developed. To do this, previously unmapped glacio-lacustrine sedimentary sequences in the Westland region underwent detailed sedimentological analysis to identify key glacio-lacustrine facies. In the Waitangitaona and Arahura river valleys, the presence of glacio-lacustrine sequences is also used to mark paleo-lake formation in the respective catchments. Using the facies scheme and depositional models, together with 14C chronology and sedimentological analysis, a series of conclusions are developed from the DFDP-2 sequence: 1) Deposition occurred in an over-deepened glacial trough, with the sequence consisting of a basal diamictite, overlain by a ~ 140-metre interval of lacustrine siltstones and sandstones. 2) The lower ~ 180-metres of sediment accumulated in 659 ± 151 yrs between 16609 ± 151 and 15994 ± 94 cal. yr BP, as the depositional environment at the drill-site evolved from an ice contact to an ice distal lacustrine setting. 3) Extremely rapid sedimentation rates, as well as high lake levels allowed the preservation of glacially over-steepened bedrock slopes beneath the Whataroa Valley. The formation of a previously unknown, ~190 km2 pro-glacial lake on the Whataroa piedmont is inferred from the DFDP-2 sequence, with lake formation causing accelerated glacial retreat from the late LGM maxima. The presence of several catchments with comparable piedmont geometry suggests pro-glacial lake formation may have been a common response to glacial retreat in Westland. For a period, pro-glacial lakes may have been a significant transitory feature on the Westland landscape.</p>

Orbital Insolation Variations, Intrinsic Climate Variability, and Quaternary Glaciations

The relative role of external forcing and of intrinsic variability is a key question of climate variability in general and of our planet’s paleoclimatic past in particular. Over the last 100 years since Milankovitch’s contributions, the role of orbital forcing has been well established for the last 2.6 Myr and their Quaternary glaciation cycles. A convincing case has also been made for the role of several internal mechanisms that are active on time scales both shorter and longer than the orbital ones. Such mechanisms clearly have a causal role in Dansgaard-Oeschger and Heinrich events, as well as in the mid-Pleistocene transition. We introduce herein a unified framework for the understanding of the interplay between internal mechanisms and orbital forcing on time scales from thousands to millions of years. This framework relies on the fairly recent theory of nonautonomous and random dynamical systems and it has been successfully applied so far in the climate sciences for problems like the El Niño-Southern Oscillation, the oceans’ wind-driven circulation, and other problems on interannual to interdecadal time scales. Finally, we provide further examples of climate applications and present preliminary results of interest for the Quaternary glaciation cycles in general and the mid-Pleistocene transition in particular.

Deglaciation and neotectonics in South East Raasay, Scottish Inner Hebrides

Changes in the physical landscape of SE Raasay at the end of the last Quaternary glaciation are examined. The area is marked by a major fault system defining the Beinn na Leac Fault Block, and field survey shows this to comprise a rollover anticline in the SW, with extensional movement towards the NE along an oblique transfer fault, the Main Beinn na Leac Fault. The fault system was reactivated after the Last Glacial Maximum (the LGM). Survey of a distinctive ridge of detached scree along the Main Beinn na Leac fault shows it to have involved a single movement of at least 7.12m vertical displacement, arguably the greatest fault movement since before the Younger Dryas in Scotland. The present work confirms that the scree became detached during the Younger Dryas, but finds that it overlies a lacustrine deposit of at least 5.6m of laminated sediments from a lake which had begun to accumulate earlier. Radiocarbon dating of peat overlying the lake sediments gave 10,176 – 10,315 cal. BP, but morphological and stratigraphical evidence indicates that drainage of the lake occurred earlier and only shortly before movement of the scree. Possible causes of displacement at the fault system are briefly discussed.

Timing and Extent of Late Quaternary Glaciation in the Ahuriri River Valley, Southern Alps, New Zealand

&lt;p&gt;Some valleys in South Island, New Zealand already have a number of well-dated glacier records. However, understanding of the precise timing of old glacial events in many valleys still remains poor. For this purpose, the cosmogenic &lt;sup&gt;10&lt;/sup&gt;Be surface exposure dating technique was used to constrain the timing and extent of late Quaternary glaciation in the Ahuriri River valley, Southern Alps, New Zealand. The 33 &lt;sup&gt;10&lt;/sup&gt;Be surface-exposure ages from two different moraine complexes range from 16.6&amp;#177;0.4 ka to 19.7&amp;#177;0.5 ka suggesting rapid glacier recession (~17 km) during the last deglaciation.&lt;/p&gt;&lt;p&gt;Field observation and geomorphological mapping were also used to investigate the extent and drivers of glaciation in this valley. For the final step, we created detail and comprehensive map of the glacial geomorphology in an area covered by palaeo Ahuriri Glacier, in the central Southern Alps. Geomorphological mapping from high-resolution aerial imagery, large scale topographical maps, average resolution DEM, and several field investigations allowed us to produce the 1:38,000 scale map for the entire study site covering an area of about 532 km&lt;sup&gt;2&lt;/sup&gt;.&lt;/p&gt;&lt;p&gt;This newly created map along with the new &lt;sup&gt;10&lt;/sup&gt;Be surface exposure dataset will help us in better understanding of past glacier-climate interactions in the Southern Alps and in the Southern Hemisphere in general.&lt;/p&gt;

Odonata Timetree; Exponentially Increased Base Substitution Rate Toward The Recent and Within the Carboniferous

Using BEAST v1.X, we constructed a credible timetree of 115 specimens of Odonata and five species of Ephemeroptera (Paleoptera; Pterygota) and two species of Archaeognatha and three species of Zygentoma (Apterygota). 88 specimens we ourselves analyzed were collected from the Ryukyu islands, Taiwan, Japan, and China, and the resting sequence data were mostly from whole mitochondrial data found in GenBank / DDJB. The combined gene (not concatenated gene) analysis of the mitochondrial COI (795 bp), COII (548 bp), and 16S rRNA (517 bp), and the nuclear 28S rRNA (825 bp) were performed. Using the calibration function of BEAST v1.X, the timetree was constructed by applying a 1.55 Ma geological event (isolation of the Ryukyu islands from China), in addition to chronologically robust fossil dates ranging from 400 Ma for Archaeognatha, 300 Ma for Ephemeroptera, and 200 Ma for Odonata and to 1.76 Ma for Calopterygidae, for a total of 13 calibration points (event: 6, fossil: 12; Quaternary 7, pre Quaternary 11). The resultant timetree showed that molecular clock was not uniformly progressed, and the base substitution rate has exponentially increased from ca. 20 Ma to the Recent by over an order of magnitude. Our new and attractive finding indicates that the Quaternary severe climatic change including a start of glacial and interglacial cycle might have resulted in the extensive radiation and speciation of Odonata, and consequently increased the biodiversity. C4 pores generated in the Miocene effectively decreased atmospheric CO2, and triggered the Quaternary glaciation. Another peak of base substitution rate was found in the Carboniferous time around 320 Ma, and this may be analogous to the late Paleozoic icehouse. This glaciation has been triggered by the development of terrestrial plants to form thick coal layers, because this process also reduced the atmospheric CO2.

Hepatica transsilvanica Fuss (Ranunculaceae) is an Allotetraploid Relict of the Tertiary Flora in Europe – Molecular Phylogenetic Evidence

The <em>Hepatica </em>section <em>Angulosa </em>consists of mainly tetraploid (2<em>n </em>= 28) species that are distributed disjunctly throughout Eurasia. Karyological evidence proves the hybrid origin of the polyploid species of this section. <em>Hepatica transsilvanica </em>is a member of this species group with a conspicuous distribution restricted to the Eastern Carpathians. Based on genome size and cytotypes, the paternal parent of <em>H. transsilvanica </em>is described to be the only diploid species in section <em>Angulosa</em>, <em>H. falconeri</em>. The maternal species is hypothesized to be <em>H. nobilis</em>, a European species with entirely lobed leaves and a wider distribution area. Although the hybrid origin of <em>H. transsilvanica </em>is well documented by karyological evidence, the time of hybridization has never been studied. By using sequences of both the nuclear and plastid genome, we reconstructed the phylogenetic relationships and divergence times of <em>H. transsilvanica </em>and its parental species. The identity of the parental species is corroborated by discordant gene tree topologies of the nrITS and plastid sequences. Moreover, both gene copies of the parental species could be identified with the low-copy nuclear gene, <em>MLH1</em>. Divergence dating analysis using Bayesian phylogenetic methods strongly supported the long-term survival of <em>H. transsilvanica </em>in the Southeastern Carpathians, as the most recent common ancestor of the hybrid and parent species existed not later than the beginning of the Pleistocene, ca. 3 million years ago. These results not only highlight the biogeographic importance of the Southeastern Carpathians in the Quaternary glaciation periods, but also emphasize that Tertiary lineages could have survived in a Central European cryptic refugium.