THE BATTLE AT GETTYSBURG: COMPETITION BETWEEN UTILIZATION AND REMEDIATION FOR A LIMITED GROUNDWATER RESOURCE

Svitana, D. D., and Krissek, Lawrence, 2005, The Battle at Gettysburg: competition between utilization and remediation for a limited groundwater resource [poster]: Geological Society of America Annual Meeting, 2005, Session 68, Paper 68-4. Abstract published: Geological Society of America, Abstracts with Programs, Vol. 37, No. 7, p. 169; http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_92376.ht

A Sedimentological Record of Early Miocene Ice Advance and Retreat, AND-2A drill hole, McMurdo Sound, Antarctica

The lowest 501 m (∼1139–638 m) of the AND-2A core from southern McMurdo Sound is the most detailed and complete record of early Miocene sediments in Antarctica and indicates substantial variability in Antarctic ice sheet activity during early Miocene time. There are two main pulses of diamictite accumulation recorded in the core, and three significant intervals with almost no coarse clasts. Each diamictite package comprises several sequences consistent with ice advance-retreat episodes. The oldest phase of diamictite deposition, Composite Sequence 1 (CS1), has evidence for grounded ice at the drill site and has been dated around 20.2–20.1 Ma. It likely coincides with cooling associated with isotope event Mi1aa. This is overlain by a diamictite-free, sandstone-dominated interval, CS2 that includes three coarsening-upward deltaic cycles, is inferred to mark substantial warming, and has an inferred age range between 20.1 and 20.05 Ma. Above this is an interval with variable amounts of diamictite (CS3), with indicators of ice grounding, that is inferred to record ice advance relative to CS2, and is overlain by an ∼100-m-thick mud-rich interval (CS4) with no sedimentological evidence for direct glacial influence at the drill site (ca. 19.4–18.7 Ma). A third overlying diamictite-rich interval (CS5) overlies an unconformity spanning 18.7–17.8 Ma (coinciding with isotope event Mi1b), and records a return to more ice-influenced conditions at the drill site in late early Miocene time. The overall picture for the early Miocene (spanning the period 20.2–17.35 Ma) is one of ice advance alternating with periods of ice retreat and hence significant global climate fluctuations after the permanent establishment of the Antarctic ice sheet at the Eocene/Oligocene boundary, and preceding the relative warmth of the middle Miocene climatic optimum (ca. 17.5–14.5 Ma). Sedimentary cyclicity in CS1 and CS2 is consistent with ∼21 k.y. precession but in CS3 the frequency is closer to 100 k.y. (consistent with eccentricity), with a possible change to 20 k.y. precession in CS4. CS5 cyclicity is consistent with obliquity forcing. Provenance data are consistent with local Transantarctic Mountains glacial activity under precessional control in CS1 and more southerly ice-cap build up under 100 k.y. eccentricity and obliquity control during CS3 and CS5, respectively

Onset of Mediterranean outflow into the North Atlantic

Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics

A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin

We produced a composite depth scale and chronology for Site U1385 on the SW Iberian Margin. Using log(Ca/Ti) measured by core scanning XRF at 1-cm resolution in all holes, a composite section was constructed to 166.5 meters composite depth (mcd) that corrects for stretching and squeezing in each core. Oxygen isotopes of benthic foraminifera were correlated to a stacked δ^18O reference signal (LR04) to produce an oxygen isotope stratigraphy and age model. Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulation of these cycles provides a powerful tool for developing an orbitally-tuned age model. We tuned the U1385 record by correlating peaks in L* to the local summer insolation maxima at 37^oN. The benthic δ^18O record of Site U1385, when placed on the tuned age model, generally agrees with other time scales within their respective chronologic uncertainties. The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflect relative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacial and interstadial climate states and decreases during glacial and stadial periods. Much of the variance in the log(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereas the residual signal reflects suborbital climate variability. The strong correlation between suborbital log(Ca/Ti) variability and Greenland temperature over the last glacial cycle at Site U1385 suggests that this signal can be used as a proxy for millennial-scale climate variability over the past 1.5 Ma. Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5 Ma, including glacial periods of the early Pleistocene (‘41-kyr world’) when boundary conditions differed significantly from those of the late Pleistocene (‘100-kyr world’). Suborbital variability was suppressed during interglacial stages and enhanced during glacial periods, especially when benthic δ^18O surpassed ~ 3.3-3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation was preceded by a terminal stadial event. Suborbital variability may be a symptomatic feature of glacial climate or, alternatively, may play a more active role in the inception and/or termination of glacial cycles.This research was supported by the Natural Environmental Research Council Grant NE/K005804/1 to DH and LS and NE/J017922/1 to DH.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.gloplacha.2015.07.00

A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin

Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulation of these cycles provides a powerful tool for developing an orbitally-tuned age model. We tuned the U1385 record by correlating peaks in L* to the local summer insolation maxima at 37°N. The benthic δ18O record of Site U1385, when placed on the tuned age model, generally agrees with other time scales within their respective chronologic uncertainties. The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflect relative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacial and interstadial climate states and decreases during glacial and stadial periods. Much of the variance in the log(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereas the residual signal reflects suborbital climate variability. The strong correlation between suborbital log(Ca/Ti) variability and Greenland temperature over the last glacial cycle at Site U1385 suggests that this signal can be used as a proxy for millennial-scale climate variability over the past 1.5 Ma. Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5 Ma, including glacial periods of the early Pleistocene (‘41-kyr world’) when boundary conditions differed significantly from those of the late Pleistocene (‘100-kyr world’). Suborbital variability was suppressed during interglacial stages and enhanced during glacial periods, especially when benthic δ18O surpassed ~ 3.3–3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation was preceded by a terminal stadial event. Suborbital variability may be a symptomatic feature of glacial climate or, alternatively, may play a more active role in the inception and/or termination of glacial cycles