Glacial Geology of the Burroughs Glacier Area, Southeastern Alaska

On Cover: "RF 2809"Burroughs Glacier is a sprawling, stagnating remnant of a much larger Neoglacial ice mass in Glacier Bay National Monument. In 1892, when the earliest photographs were taken of it, an ice plateau 10 km by 25 km was present. Since that time the ice surface has downwasted as much as 750 m and its calving margin has retreated 27 km. The ice mass separated into the Burroughs Glacier with its margin on land and Plateau Glacier with its terminus at sea level. Between 1960 and 1970 ice surface lowering averaged 9.5 m/yr at 205 m elevation (in 1960) to 4.6 m/yr at 440 m elevation (in 1960). Retreat of the land-based ice front was up to 140 m/yr and of the calving ice margin up to 350 m/yr during this time. During deglaciation, the ice-flow direction changed because of the emergence of hills. Vertical sections of till show changes in lithology and fabric direction with depth. Because the rate of change of ice-flow direction is known the rate of till deposition has been calculated. Rates at seven localities on stoss and lee sides of nunataks range from 0.4 cm/yr to 2.8 cm/yr. Most till deposition took place after 1890 except on the stoss side of nunataks where thick till has been deposited. Hilltop striations were cut until just before the hills emerged. Moraine ridges up to 2 m high have been squeezed into crevasses from below near the calving Plateau Glacier margin. Within the ridges, till fabric diagrams have modes with azimuths that are not necessarily perpendicular to the ridges but are parallel to the horizontal component of the last ice-flow direction. With the emergence of nunataks near the southeastern Burroughs terminus, small, stagnant bodies of ice were left in the lee of nunataks. Here sand and gravel eskers up to 100 m long and 4 m high and with sharp crests head at the break in slope between the valley wall and valley bottom. In one case they were deposited between 1959 and 1960 by streams flowing at the base of the ice in the same direction as the ice surface gradient. Another esker, composed of laminated silt and sand at its downstream end, was deposited between 1965 and 1967 in a closed tube under hydrostatic pressure. In some cases water flowing around nunataks did not flow under the ice but flowed along the ice margin depositing kame terraces, or into the ice leaving a hummocky blanket of sand and gravel on the till. Three ice-dammed lakes were present at the southeast terminus of Burroughs Glacier at times between 1941 and 1960. Sand and silt up to 2 m thick remain, but distinct shorelines were not formed. Meltwater flowing directly from the glacier has deposited outwash both on and off ice. The major stream began depositing outwash between 1941 and 1948. By 1970 outwash at the 1948 margin position had been incised about 23 m. During this interval the ice withdrew about 1300 m up the valley. Outwash deposited on ice between about 1956 and 1964 had collapsed by 1970. Water flowing from the ice has cut marginal channels in till to depths of 20 m. Sets of three and four large channels were occupied 10 to 15 years. Smaller marginal channels, 1-2 m deep, were cut along the stoss sides of several hills. At least 8 successively lower channels up to 100 m in length were formed in one year. The gradients of these channels reflect the ice margin gradient.National Science Foundation Grant GA-12300U.S. National Park Service (for logistical support

Runaway evaporation for optically dressed atoms

Forced evaporative cooling in a far-off-resonance optical dipole trap is proved to be an efficient method to produce fermionic- or bosonic-degenerated gases. However in most of the experiences, the reduction of the potential height occurs with a diminution of the collision elastic rate. Taking advantage of a long-living excited state, like in two-electron atoms, I propose a new scheme, based on an optical knife, where the forced evaporation can be driven independently of the trap confinement. In this context, the runaway regime might be achieved leading to a substantial improvement of the cooling efficiency. The comparison with the different methods for forced evaporation is discussed in the presence or not of three-body recombination losses

Correlation of glacial deposits of the huron, lake Michigan and green bay lobes in Michigan and Wisconsin

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26331/1/0000418.pd

Selective G-Quadruplex DNA Recognition by a New Class of Designed Cyanines

A variety of cyanines provide versatile and sensitive agents acting as DNA stains and sensors and have been structurally modified to bind in the DNA minor groove in a sequence dependent manner. Similarly, we are developing a new set of cyanines that have been designed to achieve highly selective binding to DNA G-quadruplexes with much weaker binding to DNA duplexes. A systematic set of structurally analogous trimethine cyanines has been synthesized and evaluated for quadruplex targeting. The results reveal that elevated quadruplex binding and specificity are highly sensitive to the polymethine chain length, heterocyclic structure and intrinsic charge of the compound. Biophysical experiments show that the compounds display significant selectivity for quadruplex binding with a higher preference for parallel stranded quadruplexes, such as cMYC. NMR studies revealed the primary binding through an end-stacking mode and SPR studies showed the strongest compounds have primary KD values below 100 nM that are nearly 100-fold weaker for duplexes. The high selectivity of these newly designed trimethine cyanines for quadruplexes as well as their ability to discriminate between different quadruplexes are extremely promising features to develop them as novel probes for targeting quadruplexes in vivo

Greatlakean Substage: A replacement for Valderan Substage in the Lake Michigan basin

New evidence from recent field and seismic investigations in the Lake Michigan basin and in the type areas of the Valders, Two Creeks and Two Rivers deposits necessitates revision of late-glacial ice-front positions, rock- and time-stratigraphic nomenclature and climatic interpretations and deglaciation patterns for the period ca. 14,000-7,000 radiocarbon years B.P. The previously reported and long accepted pattern of deglaciation for the Lake Michigan basin started with a regular retreat from the Lake Border Morainic System, with a minor oscillation marked by the Port Huron moraine(s) and then an extensive Twocreekan deglaciation followed by a major (320 km) post-Twocreekan advance (Valders). However, we now record a major retreat between the times of the Lake Border and Port Huron moraines, followed by a gradual retreat from the Port Huron limit and interrupted by a minor standstill (deposition of Manitowoc Till), a retreat (Twocreekan) and a readvance (Two Rivers Till). No Woodfordian or younger readvance was as extensive as had been the preceding one. This sequence argues for a normal, climatically controlled, progressive deglaciation rather than one interrupted by a major post-Twocreekan (formerly Valderan) surge. This revision appears finally to harmonize the geologic evidence and the palynological record for the Great Lakes region. Our investigations show that Valders Till from which the Valderan Substage was named is late-Woodfordian in age. We propose the term "Greatlakean" as a replacement for the now misleading time-stratigraphic term "Valderan". The type section and the definition of the upper and lower boundaries of the Greatlakean Substage remain the same as those originally proposed for the Valderan Substage but the name is changed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21685/1/0000075.pd

Reply to comments by P. F. Karrow and R. F. Black

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22713/1/0000268.pd

A major grain protein content locus on barley (Hordeum vulgare L.) chromosome 6 influences flowering time and sequential leaf senescence

Timing of various developmental stages including anthesis and whole-plant (‘monocarpic’) senescence influences yield and quality of annual crops. While a correlation between flowering/seed filling and whole-plant senescence has been observed in many annuals, it is unclear how the gene networks controlling these processes interact. Using near-isogenic germplasm, it has previously been demonstrated that a grain protein content (GPC) locus on barley chromosome 6 strongly influences the timing of post-anthesis flag leaf senescence, with high-GPC germplasm senescing early. Here, it is shown that the presence of high-GPC allele(s) at this locus also accelerates pre-anthesis plant development. While floral transition at the shoot apical meristem (SAM; determined by the presence of double ridges) occurred simultaneously, subsequent development was faster in the high- than in the low-GPC line, and anthesis occurred on average 5 d earlier. Similarly, sequential (pre-anthesis) leaf senescence was slightly accelerated, but only after differences in SAM development became visible. Leaf expression levels of four candidate genes (from a list of genes differentially regulated in post-anthesis flag leaves) were much higher in the high-GPC line even before faster development of the SAM became visible. One of these genes may be a functional homologue of Arabidopsis glycine-rich RNA-binding protein 7, which has previously been implicated in the promotion of flowering. Together, the data establish that the GPC locus influences pre- and post-anthesis barley development and senescence, and set the stage for a more detailed analysis of the interactions between the molecular networks controlling these important life history traits