ABSTRACT Sedimentary records were analyzed from three lakes in the Ruby Mountains and East Humboldt Range of northeastern Nevada. Lakes are rare in the arid Great Basin, and these represent the highest-elevation lacustrine records from this region. The three cores cover overlapping time intervals: One, from a lake located just beyond a moraine, is interpreted to represent the Last Glacial Maximum, extending back to 26 cal ka; another extends to deglaciation ca. 14 cal ka; and the third extends to deposition of the Mazama ash, ca. 7.7 cal ka. Multiproxy analysis focused on measurements of bulk density, organic matter content, C:N ratio, biogenic silica abundance, and grain-size distribution. Depth-age models were developed using optically stimulated luminescence (OSL) dating, along with accelerator mass spectrometry (AMS) 14 C dating of terrestrial macrofossils (wood and conifer needles), charcoal, and pollen concentrates (for deep sediment in one lake). Collectively, the three lakes record a series of discrete intervals spanning an unusually long stretch of time. These include the local Last Glacial Maximum (26.0–18.5 cal ka), local deglaciation (18.5–13.8 cal ka), the onset of biologic productivity (13.8–11.3 cal ka), early Holocene aridity (11.3–7.8 cal ka), deposition and reworking of the Mazama ash (7.8–5.5 cal ka), a neopluvial interval (5.5–3.8 cal ka), a variable late Holocene climate (3.8–0.25 cal ka), and a latest Holocene productivity spike (250 yr B.P. to the present) that may be anthropogenic. Data from all three lakes are presented, and the collective record of climate and environmental change for the Ruby Mountains and East Humboldt Range is compared with other paleorecords from the Great Basin.

ABSTRACT The Searles Lake Formation in Searles Valley, southeastern California, represents deposition of the paleo–Owens River into a Pleistocene and Holocene pluvial terminal lake. A prior 32–10 ka estimated age for the upper part of the Searles Lake Formation relied on uncalibrated, conventional radiocarbon dates. We present accelerator mass spectrometer radiocarbon dates that indicate the base of the Searles Lake Formation at the Poison Canyon type section is 46 ka. That age is consistent with paleomagnetic data at Poison Canyon and the Tire Farm locality, which record high-latitude Southern Hemisphere virtual geomagnetic poles that we assign to the 41 ka Laschamp excursion. The presence of Searles Lake at 46–43 ka also is consistent with a Pacific storm track that extended south of 37.5°N at that time. At the head of Salt Wells Valley–Poison Canyon, sediments that we interpret as a Searles Lake highstand were radiocarbon dated at 14.1 ka.

Abstract: Fjord valleys are carved during glaciation and then form local sediment sinks, which fill during retreat of the ice. Thus fjord valleys appear analogous to lower-latitude incised valleys, but they are remarkably different because fjords experience isostatic rebound during deglaciation, causing relative sea level to fall during infill. This paper explores stratigraphic architecture of fjord valley fills based on Late Quaternary deposition in Clyde Inlet, Baffin Island, Arctic Canada, as constrained by 11 cosmogenic dates and 9 accelerator mass spectrometry (AMS) 14 C datings. A major ice stream of the Laurentide Ice Sheet occupied Clyde Inlet at last glacial maximum and bulldozered through a U-shaped valley forming a lower sequence boundary. During the Early Holocene the system entered a deglacial stage; tidewater glaciers retreated rapidly (>100 km in 1000 yrs) through the fjord from 10.4 ka onward. Grounded ice lobes started retreating from the Clyde fjordhead by 9.4 ka. Then ice-contact fans (ICF) were deposited consisting of flat-topped fan deltas, covered with channels and boulder-strewn bars. Elevations of the surfaces vary between 62 and 77 m above sea level, which marks the relative sea level at the time of deposition and is considered to be the marine flooding surface. Marine muds have been draped directly onto the ICF complexes. Subsequently, coarse-grained glaciofluvial valley trains (GFVTs) prograde downstream caused by rapid base-level fall, despite possibly high sediment supply (i.e., forced regression). During the Late Holocene (3.5 ka) the last remaining lobes of the Laurentide Ice Sheet retreated from the middle parts of Clyde River basin to form the present Barnes Ice Cap. At this phase, the rate of base-level fall has decreased (~1.6 m/ka over the last 3.5 ka), still the river incises significantly, marking a reduced sediment supply. Narrow coarse sandy fluvial terraces were being deposited at the lowest level of the incised river valley. Clyde fjordhead may not have entered a postglacial stage by definition, nevertheless a strongly reduced sediment flux is apparent. Numerous upland lakes likely play a role in trapping sediment in the hinterland. In addition, we speculate that the glacial regime of the Barnes Ice Cap switched from a sediment producing regime to a nonerosive cold-based regime. In conclusion, stratigraphic patterns of valley fills in high-latitude areas display an evident signature of isostatic rebound and a strongly varying sediment supply. Rapid uplift causes ice proximal units to occur high in the infill and reverses classic fining upward valley fill sedimentary trends. The exact interplay of local sea-level change and sediment supply dictates the complexity of the valley fill, but coarsening upward trends with younger sandy fluvial deposits incising into the fill deposits ultimately have important implications for the interpretation of similar deglacial valley fill settings.