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1. Regional and Local Stratigraphic Markers in Three Hudson River Cores Taken Near Peekskill, New York: LWB4-3

   McCann, B. ; Abbott, D. H. ; Bostick, B. C. ; Diallo, M. B. ; Abdul, B. ; Adeghe, S. ( December 2018 , American Geophysical Union, Fall Meeting 2018, abstract #B53I-2172)

   We have been studying the stratigraphy of core LWB4-3 taken in 2001 in the Hudson River near Peekskill New York along the transit path of the Peekskill meteorite. We measured magnetic susceptibility at 1 cm intervals down to 108 cm and chemical composition at 1 cm intervals down to 192 cm. The highest magnetic susceptibility occurs at 18 cm depth. This inferred Peekskill meteorite layer with high magnetic susceptibility contains locally higher concentrations of Ni and higher Ni/Cr ratios. Our identification of the high susceptibility, high Ni layer as coming from the fall of the Peekskill meteorite in 1991 is consistent with a uniform sedimentation rate in the core and the occurrence of the base of modern Pb at > 192 cm depth (below the base of the core). From previous work on cores from Central Park Lake, the base of modern Pb represents the year 1880 A.D. We also found other prominent horizons whose ages fit a linear sedimentation rate model. We found a peak in As, whose inferred age matches 1988, the year when Pb and Cu arsenide were banned as pesticides. In addition, we found a modest susceptibility peak above the Peekskill layer whose inferred age matches that of the 1996 Hudson River flood. We found a second modest susceptibility peak below the Peekskill layer whose inferred age matches that of the "Great Catskill Toilet Flush Flood" in 1980. This layer also has local maxima in Pb, Cu and Ca. The Catskills contain Devonian limestone that might be the source of excess Ca. Copper Mine brook is located on the east bank of the Hudson north of Peekskill and is a potential source of Cu during floods. Our core exhibits a distinct increase in Ca content starting at 20 cm depth and increasing towards the top of the core. This prominent increase in Ca may represent 1991 A.D, the time of the invasion of the zebra mussel. We are testing this depth range for calcium carbonate to determine if the upward calcium increase could be from the invasion of the zebra mussel, increased soil erosion or anthropogenic pollution. We found a peak in Pb at 112 cm depth whose inferred age matches that of the cessation of incinerator burning in 1938. Cs-137 and Pb-210 ages are in progress and may be available by the time of the meeting. We also saw an unusual horizon at a depth of 118 cm with a high peak of Cr. This would be approximately the year 1936, which corresponds to a large flood in the Hudson. 

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2. Can We See Dust from the 1992 Fall of the Peekskill Meteorite in Hudson River Sediments and Can We Use It as a Stratigraphic Marker?(Regional and Local Stratigraphic Markers in Three Hudson River Cores Taken Near Peekskill, New York: LWB4-1)

   Diallo, M. B. ; McCann, B. ; Abdul, B. ; Adeghe, S. ; Abbott, D. H. ; Bostick, B. C. ; Chang, C. ; Block, K. A. ( December 2018 , American Geophysical Union, Fall Meeting 2018, abstract #B53I-2168)

   We have been studying the stratigraphy of core LWB4-1 taken in 2001 in the Hudson River about 100 meters north of the calculated transit path of the Peekskill meteorite in October 1992. We measured magnetic susceptibility at 1cm intervals from 0 -70 cm depth and found a layer with a magnetic susceptibility of 11 cgs units at 6 cm depth. This is the highest susceptibility in the top 40 cm of the core. Scanning X-Ray Fluorescence spectroscopy revealed the high susceptibility layer at 6 cm depth is part of a 3 cm interval with a high Ni/Cr ratio, but the depth of the peak in the Ni/Cr ratio is poorly resolved due to measurement error. We plan to dry and homogenize discreet samples for analysis on bench top XRF to reduce Ni and Cr error. Based on our identification of the base of modern Pb at 68 cm depth, the top 40 cm of the core covers the time interval from 2001 to 1930. From previous work on Central Park Lake, the base of modern Pb represents the year 1880 A.D. A uniform sedimentation rate model is supported a peak in Pb and As at 8 cm depth. The peak might represent the 1988 ban on the use of Pb arsenide and the start of use of DDT as a pesticide. We found a second peak in Pb at 37.5cm potentially from 1938, the date at which incineration was banned in New York City. We found a third peak in Pb at 50.5cm that might be from World War I around 1914. We found two deeper susceptibility peaks of 12 cgs at 43 cm and 8 cgs at 59 cm. These peaks could represent major Hudson River floods in 1927 and 1903. 137Cs and 210Pb 210 dating are in progress and will help us to determine if our age model is correct. Also, our core exhibits a distinct increase in Ca content starting at 18-25 cm depth and increasing towards the top of the core. This increase could be due to increased erosion, anthropogenic inputs or increased dissolution of CaCO3 rich rocks. We are measuring CaCO3 in the core to better determine the origin of this increase of Ca. 

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3. Expedition 397 Preliminary Report: Iberian Margin Paleoclimate

   Hodell, D.A. ; Abrantes, F. ; Alvarez Zarikian, C.A. ( February 2023 , Preliminary report)

   During International Ocean Discovery Program Expedition 397, we recovered a total of 6176.7 m of core (104.2% recovery) at four sites (U1586, U1587, U1385, and U1588) from the Promontório dos Principes de Avis (PPA) (Figure F1), a plateau located on the Portuguese continental slope that is elevated above the Tagus Abyssal Plain and isolated from the influence of turbidites. The drill sites are arranged along a bathymetric transect (4691, 3479, 2590, and 1339 meters below sea level [mbsl], respectively) to intersect each of the major subsurface water masses of the eastern North Atlantic (Figures F2, F7). Multiple holes were drilled at each site to ensure complete spliced composite sections (Figure F3; Table T1), which will be further refined postcruise by a campaign of X-ray fluorescence core scanning. At Site U1586 (4691 mbsl), the deepest and farthest from shore, a 350 m sequence was recovered in four holes that extend as far back as the middle Miocene (14 Ma), which is nearly twice as old as initially predicted from seismic stratigraphy. Sedimentation rates are lower (averaging 5 cm/ky in the Quaternary) at Site U1586 than other Expedition 397 sites (Figure F4), and a few slumped intervals were encountered in the stratigraphic sequence. Despite these limitations, Site U1586 anchors the deep end-member of the bathymetric transect and provides an important reference section to study deepwater circulation, ventilation and carbon storage in the deep eastern North Atlantic. At Site U1587 (3479 mbsl), the second deepest site along the depth transect, we recovered a 567 m sequence of late Miocene to Holocene sediments that accumulated at rates between 6.5 and 11 cm/ky (Figure F4). The high sedimentation rates and long continuous record at this site will permit climate reconstruction at high temporal resolution (e.g., millennial) for the past 7.8 My. A complete Messinian Stage (7.246–5.333 Ma) was recovered, which provides a valuable opportunity to study the Messinian Salinity Crisis in an open marine setting adjacent to the Mediterranean. Site U1385 (Shackleton site) was a reoccupation of a position previously drilled during Integrated Ocean Drilling Program Expedition 339. Expedition 339 Site U1385 has yielded a remarkable record of millennial-scale climate change for the past 1.45 My (Marine Isotope Stage [MIS] 47) (Figure F6). During Expedition 397, we deepened the site from 156 to 400 meters below seafloor (mbsf), extending the basal age into the early Pliocene (4.5 Ma). Sedimentation rates remained high, averaging between 11 and 9 cm/ky throughout the sequence (Figure F4). The newly recovered cores at Expedition 397 Site U1385 will permit the study of millennial climate variability through the entire Quaternary and into the Pliocene, prior to the intensification of Northern Hemisphere glaciation. Site U1588 is the shallowest, closest to shore, and youngest site drilled during Expedition 397 and is also the one with the highest sedimentation rate (20 cm/ky). The base of the 412.5 m sequence is 2.2 Ma, providing an expanded Pleistocene sequence of sediment deposited under the influence of the lower core of the Mediterranean Outflow Water (MOW). Together with other Expedition 339 sites, Site U1588 will be important for determining how the depth and intensity of the MOW has varied on orbital and millennial timescales. In addition, it also provides a marine reference section for studying Quaternary climate variability at very high temporal resolution (millennial to submillennial). A highlight of the expedition is that sediment at all sites shows very strong cyclicity in bulk sediment properties (color, magnetic susceptibility, and natural gamma radiation). Particularly notable are the precession cycles of the Pliocene that can be correlated peak-for-peak among sites (Figure F10). These cyclic variations will be used to derive an orbitally tuned timescale for Expedition 397 sites and correlate them into classic Mediterranean cyclostratigraphy. The cores recovered during Expedition 397 will form the basis of collaborative postcruise research to produce benchmark paleoclimate records for the late Miocene through Quaternary using the widest range of proxy measurements. It will take many years to complete these analyses, but the records will lead to major advances in our understanding of millennial and orbital climate changes and their underlying causes and evolving contextuality. Outreach during Expedition 397 was highly productive, reaching a record number of students and the general public across the world through several diverse platforms, including live ship-to-shore events, webinars, social media, videos, radio pieces, blog posts, and in-person activities. 

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4. The chemical nature of the young 120-Myr-old nearby Pisces–Eridanus stellar stream flowing through the Galactic disc

   https://doi.org/10.1093/mnras/staa1673  

   Hawkins, Keith ; Lucey, Madeline ; Curtis, Jason ( August 2020 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Recently, a new cylindrical-shaped stream of stars up to 700 pc long was discovered hiding in the Galactic disc using kinematic data enabled by the Gaia mission. This stream of stars, dubbed Pisces–Eridanus (Psc–Eri), was initially thought to be as old as 1 Gyr, yet its stars shared a rotation period distribution consistent with a population that was 120 Myr old. Here, we explore the detailed chemical nature of this stellar stream. We carried out high-resolution spectroscopic follow-up of 42 Psc–Eri stars using McDonald Observatory and combined these data with information for 40 members observed with the low-resolution LAMOST spectroscopic survey. Together, these data enabled us to measure the abundance distribution of light/odd-Z (Li, Na, Al, Sc, V), α (Mg, Si, Ca, Ti), Fe-peak (Cr, Mn, Fe, Co, Ni, Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, Eu) elements along the Psc–Eri stream. We find that the stream is (1) near-solar metallicity with [Fe/H] = –0.03 dex and (2) has a metallicity spread of 0.07 dex (or 0.04 dex when outliers are excluded). We also find that (3) the abundance of Li indicates that Psc–Eri is ∼120 Myr old, consistent with its gyrochronology age. Additionally, Psc–Eri has (4) [X/Fe] abundance spreads that are just larger than the typical uncertainty in most elements, (5) it is a cylindrical-like system whose outer edges rotate about the centre, and (6) no significant abundance gradients along its major axis except a potentially weak gradient in [Si/Fe]. These results show that Psc–Eri is a uniquely close young chemically interesting laboratory for testing our understanding of star and planet formation. 

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5. The Paleogeography of Laurentia in Its Early Years: New Constraints From the Paleoproterozoic East‐Central Minnesota Batholith

   https://doi.org/10.1029/2021TC006751  

   Swanson‐Hysell, Nicholas L. ; Avery, Margaret S. ; Zhang, Yiming ; Hodgin, Eben B. ; Sherwood, Robert J. ; Apen, Francisco E. ; Boerboom, Terrence J. ; Keller, C. Brenhin ; Cottle, John M. ( May 2021 , Tectonics)

   Theca. 1.83 Ga Trans‐Hudson orogeny resulted from collision of an upper plate consisting of the Hearne, Rae, and Slave provinces with a lower plate consisting of the Superior province. While the geologic record ofca. 1.83 Ga peak metamorphism within the orogen suggests that these provinces were a single amalgamated craton from this time onward, a lack of paleomagnetic poles from the Superior province following Trans‐Hudson orogenesis has made this coherency difficult to test. We develop a high‐quality paleomagnetic pole for northeast‐trending diabase dikes of the post‐Penokean orogen East‐Central Minnesota Batholith (pole longitude: 265.8°; pole latitude: 20.4°; A₉₅: 4.5°; K: 45.6 N: 23) whose age we constrain to be 1,779.1 ± 2.3 Ma (95% CI) with new U‐Pb dates. Demagnetization and low‐temperature magnetometry experiments establish dike remanence be held by low‐Ti titanomagnetite. Thermochronology data constrain the intrusions to have cooled below magnetite blocking temperatures upon initial emplacement with a mild subsequent thermal history within the stable craton. The similarity of this new Superior province pole with poles from the Slave and Rae provinces establishes the coherency of Laurentia following Trans‐Hudson orogenesis. This consistency supports interpretations that older discrepant 2.22–1.87 Ga pole positions between the provinces are the result of differential motion through mobile‐lid plate tectonics. The new pole supports the northern Europe and North America connection between the Laurentia and Fennoscandia cratons. The pole can be used to jointly reconstruct these cratonsca. 1,780 Ma strengthening the paleogeographic position of these major constituents of the hypothesized late Paleoproterozoic supercontinent Nuna.

    

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