Deep ice drilling, bedrock coring and dust logging with the Rapid Access Ice Drill (RAID) at Minna Bluff, Antarctica

Rapid Access Ice Drill is a new drilling technology capable of quickly accessing the glacial bed of Antarctic ice sheets, retrieving ice core and rock core samples, and providing boreholes for downhole logging of physical properties. Scientific goals include searching for old ice near the glacial bed and sampling subglacial bedrock. During field trials near McMurdo Station on a piedmont glacier at Minna Bluff in the 2019–20 austral summer, we successfully completed a ‘top-to-bottom’ operational sequence in three boreholes by (1) augering through firn, (2) creating a borehole packer seal in non-porous ice, (3) establishing fluid circulation, (4) quickly drilling a borehole in ice at penetration rates up to 1.2 m min−1, (5) acquiring a short ice core at depth, (6) penetrating the glacial bed at a depth of ~677 m, (7) recovering a 3.2 m core of ice, basal till and subglacial bedrock, (8) optically logging the borehole on wireline, (9) testing hydrofracture potential by overpressuring the borehole fluid and (10) operating in an environmentally benign yet rapid field mode. Minna Bluff testing, therefore, demonstrates the effectiveness of this integrated system to drill rapidly through thick ice and penetrate across the glacial bed to take cores of bedrock.

3D Probabilistic Modelling and Uncertainty Analysis of Glacial and Post-Glacial Deposits of the City of Saguenay, Canada

Knowledge of the stratigraphic architecture and geotechnical properties of surficial soil sediments is essential for geotechnical risk assessment. In the Saguenay study area, the Quaternary deposits consist of a basal till layer and heterogeneous post-glacial deposits. Considering the stratigraphic setting and soil type heterogeneity, a multistep stochastic methodology is developed for 3D geological modelling and quantification of the associated uncertainties. This methodology is adopted for regional studies and involves geostatistical interpolation and simulation methods. Empirical Bayesian kriging (EBK) is applied to generate the bedrock topography map and determine the thickness of the till sediments and their uncertainties. The locally varying mean and variance of the EBK method enable accounting for data complexity and moderate nonstationarity. Sequential indicator simulation is then performed to determine the occurrence probability of the discontinuous post-glacial sediments (clay, sand and gravel) on top of the basal till layer. The individual thickness maps of the discontinuous soil layers and uncertainties are generated in a probabilistic manner. The proposed stochastic framework is suitable for heterogeneous soil deposits characterised with complex surface and subsurface datasets.

The Gröbminger Mitterberg (Austria): A time machine to the pre-LGM?

<p>The Last Glacial Maximum (LGM) is well understood in many parts of the European Alps, but open questions remain concerning glacial phases prior to the LGM as the record is fragmentary. The Gröbminger Mitterberg (GM), located among the Enns Valley in Styria (Austria) is one such location where pre-LGM glacial and paraglacial processes can be studied. The GM emerges roughly 200 m from the Enns Valley floor and is situated between unmetamorphosed Mesozoic carbonates in the north and crystalline basement units in the south. Strata occur below a cover of up to more than 10 m thick basal till attributed to the LGM. The sedimentary record rests on the phyllites and greenschists that crop out at the steep southern flank of the GM. The sediment consists of an assortment of pebble-sand deposits with individual sand lenses, sand bodies with climbing ripples and undulose bedding, and fine-sand/silt laminated strata. In grain-supported intervals, cracked pebbles occur, which are interpreted to record subglacial loading. Cross-bedding orientations, together with the limited amount of unmetamorphosed carbonate pebbles in the sequence, imply that sediment was sourced from the GM and deposited at its margins, rather than from surrounding mountains towards the centre of the Enns Valley. Three depositional regimes have been recognised: deltaic sediment (both distal sands with ripples and proximal, cross-bedded gravel), lake bottom sediment (laminated fine-sand and silt) and fluvial deposits (channels with basal lag deposits and local cross bedding). The delta facies testify to the presence of lacustrine conditions. By analogy to the Unterangerberg in the Inn Valley (Tyrol, Austria; Starnberger et al. 2013), the following sequence of events is proposed. Before the LGM, sediment derived from the wider catchment area accumulated in the Enns Valley in lakes and rivers. Aggradation within the whole Enns valley resulted in deposition on the present day GM. During the LGM, the large Enns Glacier eroded much of the sediment record, especially around the GM. Deposits on top of the GM were then concealed by > 10 m thick diamicts and thereby preserved. Future age dating of the sediments will provide a better-constrained chronology to the sequence of events proposed above.</p>

Differentiation of subglacial conditions on soft and hard bed settings and implications for ice sheet dynamics: a case study from north-central Poland

We reconstruct patterns of subglacial processes on a hard bedrock and a soft bed under the southern sector of Scandinavian Ice Sheet (SIS) occurring in the basal till of the Late Saalian Glaciation at the Wapienno, Barcin and Młodocin sites (north-central Poland). Based on detailed sedimentological studies, two phases of SIS transgression were recognised. In the initial phase of the transgression, the SIS advanced onto a frozen substrate (continuous permafrost). The low permeability of the substratum led to a high subglacial water pressure (SWP) and increased basal sliding. The local increase of SWP led to the development of different types of structures and sediments. On a hard bedrock, with low SWP, abrasion predominated and linear structures were developing, while in the case of high SWP, the ice was decoupled from the hard substrate, pressurised liquefied sediment flowed, and structures of the p-form and s-form type developed. On a soft bed, the ice-bed contact was of a mosaic type and the ice movement had an ice-stream character. The ice-stream developed towards the east in the marginal zone of the SIS and used a W-E oriented valley filled by the Wapienno Formation fluvial complex. During a later phase, the ice movement was slower and did not have a stream character. Its direction changed to SE. The deposition of the main part of the diamicton occurred mainly as a result of the lodgement process.

Catchment-scale groundwater age stratification reveals groundwater recharge and discharge processes

<p>The distribution of groundwater ages with depth provides information about subsurface structures and flow dynamics. Upslope measured groundwater age stratifications are commonly used to estimate groundwater recharge rates, whereas downslope measured age stratifications are influenced by recharge conditions, the aquifer structure and interactions between groundwater and surface water. In our study we address the question whether downslope measured groundwater ages from different locations can provide spatial and temporal information about catchment-scale groundwater dynamics and the relationship between groundwater recharge and discharge.<br>We derived an overall groundwater age stratification, representative for the Svartberget subcatchment (0.47 km<sup>2</sup>) located within the Krycklan study site, by measuring CFCs from 9 different sampling locations with depths of 2 m to 18 m. All sampling locations were downslope and located in basal till which is overlain by ablation till. <br>The CFC-based groundwater age stratification reveals an unexpected pattern, with groundwater ages of already 30 years immediately below the water table. Groundwater ages increase then with depth. We could reproduce the observed groundwater age stratification by using a groundwater flow model and show that the lag of rejuvenation, noticeable in groundwater ages of 30 years at the water table, derives from return flow of groundwater at a subsurface discharge zone that evolves at the interface between the two soil types (basal and ablation till). Furthermore, we demonstrate by varying the infiltration rate how the extent of the discharge zone and the partitioning of the infiltration amount to the two layers change, i.e. young runoff in the upper layer (ablation till) and old groundwater circulation through the deeper layer (basal till).<br>By providing a simple analytical approximations of the observed groundwater age stratification, we show that the extent of the subsurface discharge zone is a powerful indicator of the relation between the recharge and discharge zone, while the vertical gradient of the age-depth relationship provides information about the overall aquifer recharge.</p>

Effect of peripartum nutritional supplementation on postpartum fertility and blood biochemical and steroid hormone profile in crossbred cows

Advanced pregnant healthy HF crossbred cows (n=20) of 2-4 parity were equally divided in to control (routine farm feeding-RFF) and treatment/nutrients supplementation (RFF + bypass fat @ 100-200 g/h/d and ASMM @ 50 g/h/d) groups and were studied from 2 wks prepartum to 8 wks postpartum for plasma profile of steroid hormones and metabolites on days -14, -3, 0, +3, +14, +28 and +42 as well as for puerperal events and postpartum fertility. The mean plasma progesterone values were maximum (>6 ng/ml) on day 14 prepartum, which declined significantly (p>0.01) on day 3 prepartum reached to the basal levels (>1 ng/ml) on the day of calving, remained basal till day 14, and thereafter showed a rising trend on days 28 and 42 postpartum. The oestradiol-17b values were at its peak on the day of calving (p>0.01), showed a rapid fall by day 3 postpartum and remained low till recrudesce of follicular activity around day 35 postpartum. However, there were no statistical differences between the two groups in either of the hormones, except on day 42 postpartum. The levels of cortisol and PGF2 a Metabolites (PGFM) were 3-8 times higher on the day of parturition as compared to values at day 14 pre- and postpartum, and declined further till day 42 postpartum reaching to prepartum levels. The plasma cholesterol gradually decreased as parturition approached and increased in postpartum days to reach the highest value (p>0.01) at day 42. The nutrients supplemented cows had significantly (p>0.01) higher plasma cortisol, PGFM and cholesterol values than the control cows around parturition. However, no such variation was noted in plasma protein profile. The period of uterine involution in control and supplemented groups was identical (31.97±1.82 and 30.27±1.41 days), yet the cows in treatment group resumed estrous cycle earlier (38.00±1.95 vs 42.32±4.14 days, p>0.05) and had shorter service period (85.22±7.17 vs 100.67±5.60 days) with improved pregnancy rate (80 vs 60 %) as compared to those in control group. Thus, the peripartum nutrient supplementation in crossbred cows was beneficial and had positive effect on the postpartum fertility and plasma cortisol, PGFM and cholesterol profile.

Subaqueous conglomerates above pre-LGM basal till: Another element of the ‘classic’ interglacial mountain-flank succession (Hötting Breccia Auct.) north of Innsbruck, Austria

Die „Höttinger Brekzie“ bei Innsbruck – eine klassische interglaziale Sedimentabfolge entlang einer Bergflanke – besteht vorwiegend aus verfestigten subaerischen Schuttfächern und Haldenhängen. Am NW-Rand Innsbrucks lagert eine bis >20 m dicke prä-LGM Grundmoräne (Riss?) auf einer Schlifffläche auf Fels, die ostgerichtete Eisbewegung anzeigt. Die Grundmoräne ist von Karbonatgesteinen der Nördlichen Kalkalpen dominiert; Leitgeschiebe des LGM-Eisstroms fehlen. Die Grundmoräne wird von einem Konglomerat überlagert, dessen Schichtung 20–30° Süd fällt und dessen Klastenbestand dem des liegenden Tills entspricht. Das Konglomerat – bisher als Teil der Höttinger Brekzie geführt – wurde von einem Fächerdelta oder einem Haldenhang in einen See geschüttet; es wird von unverfestigten Sedimenten des LGM bis Holozän überlagert. Folgendes Szenario wird vorgeschlagen: Während oder nach Zerfall des Eisstroms, der die Grundmoräne gebildet hatte, wurde durch Umlagerung des Tills in einen (Eisrand?-) See die Konglomerat-Abfolge geschüttet. Die subaerischen Schuttfächer der Höttinger Brekzie bauten sich unabhängig vom Konglomerat von einem eigenständigen Schuttfächer-System auf. Die Altersbeziehung zwischen dem Hauptteil der Höttinger Brekzie und der Grundmoräne/Konglomerat-Abfolge ist unklar. Diese Arbeit zeigt erneut, dass die Abfolge, die bisher kollektiv als Höttinger Brekzie zusammengefasst wurde, aus Sedimentkörpern verschiedener Bildung und Alter besteht.