Evidence for Holocene ice sheet history from geomorphology, cosmogenic isotopes, and bird vomit, East Antarctica.

<p>The post-LGM thinning history of the East Antarctic Ice Sheet is not yet well constrained. Here we report some integrated observations and analyses that constrain the ice sheet thinning history in Western Dronning Maud Land and Coats Land, adjacent to the easternmost Weddell Sea, which is a key area of uncertainty in ice sheet reconstructions. Geomorphological observations show a distinct series of weathering zones with fresh erratics only found in a relatively narrow zone above the present ice sheet margin. We report cosmogenic surface exposure dates of erratics in the different weathering zones, using <sup>10</sup>Be and in situ <sup>14</sup>C. We further report a large number of radiocarbon ages on sub-fossil bird vomit (regurgitated proventricular stomach oil, sometimes termed ‘mumiyo’) from nesting snow petrels (Pagodroma nivea) which record periods of ice sheet absence. Together these analyses allow us to determine a more tightly constrained thinning history of the ice sheet in this sector. We discuss the implications of this thinning history for geologically-based ice sheet reconstructions and for ice sheet models.</p>

Laser to fight fire?

Wildfires spread as long as burnable organic matters fuel them, such as grasses and trees. When there is nothing more to burn, fires will put out naturally. Here, I would propose to fight “fire by fire” or by Laser using specific Laser devices to immediately and punctually carbonize a narrow zone in front of crawling wildfires to create a protective area that will stop fires from further propagation when the fire reaches the Laser-carbonized zone. Empirical studies will be required to determine the best conditions of Laser intensity, wavelength, and period of Laser irradiation that would be required to only carbonize organic matters in narrow targeted zone without spreading fire further.

Genetic interpretation of CSD for olivine through the dunite section of the Dovyren layered intrusion: linking with geochemistry and probable dynamics of the cumulate mush.

<p>The Yoko-Dovyren ultramafic-mafic intrusion (the northern Baikal region, Russia) has excellent outcropping as well as layering falls vertically. It`s age is 728 Ma. Length of the main body is 26 km. The modal layering of its central part (~3 km thick) includes a basal reversal (from chilled rocks to plagiolherzolites) followed with Pl-bearing to adcumulate dunite, troctolite and gabbroic sequence.</p><p>Over the past 20 years, several sections of the massif have been studied in detail. (Ariskin et al 2018) have determined two major types of parental magmas recorded in the FeO vs MgO trends for the Ol cumulates through the first 500 m of the cross-section. These two geochemically similar magmas are consistent with equilibrium olivine Fo88 and Fo86 in the range of temperatures from 1290°C to ~1200°C.</p><p>We present the results of quantification of CSD of olivine from the dunite succession, which argue for two types of olivine grain populations differing for the more primitive and relatively evolved magma.</p><p>The slope of the log-linear CSD function in the lower-temperature magmas has a less steep as compared to the higher temperature ones.  Both populations can be considered to represent intratelluric olivine crystallized at a pre-emplacement stage. At a stratigraphic level of 200 m from the lower contact, in some of the samples we observed changes in the CSD patterns, which evidence a coarsening of the populations within the Dovyren chamber. Starting from 350-400 m coarsening is noticeable everywhere, so that the CSD cease to be log-linear. In addition, in a narrow zone of 500-550 m dunite are found to display a pronounced bimodal (kinked) distribution of olivine. In a larger population, olivine has highest aspect ratio (up to 3-3.5) compared to other dunite samples. The origin of such dunite can be explained by the intrusion of hot portions of magma into the colder cumulus. In this case such elongated crystals may be due to the increased growth rate of the original olivine grains. The smaller population may be due to a new nucleation event after emplacement. CSD in cumulates above the «kinked dunites» demonstrate coarsening of olivine, with the most coarse-grained populations typical of highly contaminated dunite.</p><p>Thus, a rather narrow zone is distinguished in dunite, where we can observe primary intratelluric CSD, which is not substantially altered nither by peritectic reactions in the loose cumulus of the reversal sequence, where the temperature drops rapidly, nor by coarsening during long history of temperature oscillations close to the primary magmas condition above this zone.</p><p>This work support from the Russian Science Foundation (RSF, grant No. 16-17-10129)</p><p>Ariskin Alexey, Danyushevsky Leonid, Nikolaev Georgy, Kislov Evgeny, Fiorentini Marco, McNeill Andrew, Kostitsyn Yuri, Goemann Karsten, Feig Sandrin, and Malyshev Alexey. The dovyren intrusive complex (southern siberia, russia): Insights into dynamics of an open magma chamber with implications for parental magma origin, composition, and cu-ni-pge fertility. Lithos, 302:242–262, 2018.</p>

2019 Mw5.8 Silivri Earthquake Reveals the Complexity of the Main Marmara Shear Zone

<p>The North Anatolian Fault (NAF) is a 1600 km dextral transform fault accommodating the motion between Anatolia and Eurasia Plates. The segments beneath the Marmara Sea, are the only part of the NAF that did not break since the 20<sup>th</sup>century. Recent studies show that this 150 km seismic gap is characterized by heterogeneous interseismic behavior and significantly high background seismicity with respect to the other parts of the NAF.</p><p>On September 24 2019, an activity started north of the Main Marmara Fault (MMF) including a M<sub>w</sub>4.7 earthquake, which led to the Mw5.8 mainshock several days later. The 2019 M<sub>w</sub>5.8 Silivri earthquake is the largest since 1963 M<sub>w</sub>6.3 Cinarcik earthquake in the Marmara Sea. This sequence occurred at a location that is immediate north west of the Central Basin; between a zone that is possibly partially creeping (Central Basin) to the west and a possibly locked segment to the east (Kumburgaz Basin).</p><p> </p><p> In this study we used template search for detection of earthquakes, relocated the earthquakes, obtained focal mechanism solutions of earthquakes that are M>4 and obtained a finite-fault slip model of the M<sub>w</sub>5.8 mainshock. Using template cross-correlation, a total of 400 earthquakes were detected in this sequence. The activity started in a relatively narrow zone and spread to larger distances following the M<sub>w</sub>4.7 mainshock. The depth distribution shows that the earthquakes are confined to a narrow zone between the depths of 9-13 km. The focal mechanisms show that there are two clusters; the cluster to the northwest show a ~70°north dipping fault with rake angles about ~160°, while the activity toward east converges to the Main Marmara Fault and dip angle is close to ~70°with rake angles of ~140°. The finite-fault model shows a bilateral rupture that propagated down-dip from the hypocenter.</p><p>We conclude that the seismic activity occurred on a fault that is within the Main Marmara Shear Zone beneath the sedimentary basin. This secondary fault possibly connects to the Main Marmara Fault to the east. There is no evidence that the causative fault continues up-dip into the basin.  Another characteristic of this sequence is that all of the focal mechanisms show significant thrust component in addition to the expected right-lateral motion. The January 2020 M<sub>w</sub>4.7 earthquake that occurred in the same zone  between the two clusters have predominantly thrust mechanism, confirming that this zone is under local compression. The observed thrust component is possibly related to change of the width of the shear zone with narrowing from Central Basin to the west to Central High to the east and/or the change of the interseismic behavior of the fault from partially creeping Central Basin and locked Kumburgaz Basin segments.</p>

Origin, Organization, Dynamics, and Function of Actin and Actomyosin Networks at the T Cell Immunological Synapse

The engagement of a T cell with an antigen-presenting cell (APC) or activating surface results in the formation within the T cell of several distinct actin and actomyosin networks. These networks reside largely within a narrow zone immediately under the T cell's plasma membrane at its site of contact with the APC or activating surface, i.e., at the immunological synapse. Here we review the origin, organization, dynamics, and function of these synapse-associated actin and actomyosin networks. Importantly, recent insights into the nature of these actin-based cytoskeletal structures were made possible in several cases by advances in light microscopy.

Identification of early biomarkers in proteomic profiles of the phaeophyte Saccharina japonica proximal to and beneath the front of bryozoan colonies

The sessile bryozoanMembranipora membranaceafrequently colonizes the phaeophyteSaccharina japonica.Identifying early colonization markers using proteomics could assist in the early detection of epiphytic contamination. Different sections of thallus tissue proximal to the bryozoan (i.e. the 1-cm zone beyond the boundary of the colony) and tissue from the colony-front (i.e. the narrow zone under the newly formed front of the colony after removing the bryozoans) were separated. From the proteomic profiles ofS. japonica, we detected 151 protein spots (99 up-, 50 down-, and 2 similarly regulated) from proximal tissues and 151 spots (69 up-, 75 down-, and 7 same-regulated) from colony-front tissues. Hundred and ten spots were detected from distal healthy thallus tissue, used as a control. The protein SSP15 was specifically up-regulated in the proximal tissues by ca. 1395-fold, while it exhibited little expression at the colony-front and in distal healthy tissues. ATPases were markedly up-regulated in both the proximal and colony-front tissues by 3198- and 2475-fold, respectively. Rpl1P and SRSF proteins were specifically up-regulated only in colony-front tissues by 5724- and 273-fold, respectively. Therefore, these proteins may be used as specific biomarkers for the early detection of bryozoan colonization on each tissue type of the seaweed.

Evaluation of Interpretive Media Use and Effectiveness at a Nature Center

This exploratory study is a contribution to the body of research on exhibit evaluation. It applied the concept of zones of tolerance to assess the effectiveness of interpretive themes in two exhibits at Dillon Nature Center in Kansas. It also assessed the use of QR codes installed along the Woodard Interpretive Trail, and analyzed visitors’ attitudes toward this technology. Major findings indicate visitor thoughts were within the narrow zone of tolerance for one of the exhibits and outside of that zone of tolerance for the other. QR codes are not widely accepted yet at the center, but visitors’ attitudes towards the technology show potential for future use. Last, it is essential for the nature center to research their visitors’ profile to facilitate better interpretive encounters with their audience. These results, although limited in scope, provide insights to managers and interpreters involved in evaluating the meaning-making process and considering the use of interpretive technologies in their sites.