The Chic-Choc Mountains are the last southern refuge for Arctic lichens in eastern North America

2016 ◽  
Vol 2 (4) ◽  
pp. 183-193 ◽  
Author(s):  
Richard Troy McMullin ◽  
Briann C. Dorin
Keyword(s):  
North American ◽  
Vascular Plants ◽  
Lichen Species ◽  
Eastern North America ◽  
Last Glacial Period ◽  
The North ◽  
Additional Layer ◽  
Alpine Species ◽  
Disjunct Populations ◽  
The Last Glacial

Endemic and disjunct populations of vascular plants and cryptogams occurring in the Chic-Choc Mountains on the Gaspé Peninsula in eastern Québec, Canada, have been attracting botanists for over a century. Although controversial, these ancient mountains have been hypothesized to have been nunataks during the Wisconsin glaciation in part because they contain vascular plants that are not known to colonize nearby mountains with similar environments that were not thought to be nunataks. To determine whether there are lichen species that have the same pattern as the vascular plants, we examined the North American distribution of all the approximately 600 lichens known from the Chic-Chocs. Fifteen Arctic-alpine species were found to reach the edge of their southeastern North American range in the Chic-Chocs. Six of these species are not known to occur again for over 1000 km to the north. These results provide an additional layer of biogeographic knowledge about the unusual flora of the Chic-Chocs and lend some support to the hypothesis that the Chic-Chocs might have been nunataks during the last glacial period. Any Arctic-alpine species occurring in the Chic-Chocs are good candidates for monitoring the effects of climate change, but the 15 lichen species that reach their southeastern limit in this range might be the most vulnerable.

Cymbopleura laszlorum spec. nov. (Cymbellaceae, Bacillariophyceae), a glacial relic from a calcium-rich floodplain fen in southwestern Montana, USA

Phytotaxa ◽  
2018 ◽  
Vol 349 (1) ◽  
pp. 47 ◽  
Author(s):  
LOREN BAHLS ◽  
TARA LUNA
Keyword(s):  
New Species ◽  
Rare Species ◽  
Vascular Plants ◽  
Vascular Plant ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Southwestern Montana ◽  
Alpine Species ◽  
Wetland Habitats ◽  
The Last Glacial

Cymbopleura laszlorum is described using LM and SEM microscopy from a recently rehabilitated floodplain fen in southwestern Montana, USA. The new species is most similar to C. mongolica and C. stauroneiformis and shares features with several other northern/alpine species. Cymbopleura laszlorum lives in cold, calcareous, spring-fed pools where it is associated with Mastogloia lacustris, Cymbopleura florentina and Epithemia argus. The fen also supports three rare vascular plants that have northern/alpine affinities. These diatom and vascular plant associates and the close morphological resemblance of C. laszlorum to C. mongolica and C. stauroneiformis suggest that the new species is a glacial relic and survives at the type locality because it has retained the muskeg-like conditions that were more widespread during the last glacial period. Wetland habitats that support rare species of vascular plants are also likely to support new and rare species of diatoms.

New multituberculate mammal from the Early Cretaceous of eastern North America

2013 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Richard L. Cifelli ◽  
Cynthia L. Gordon ◽  
Thomas R. Lipka
Keyword(s):  
North America ◽  
Iberian Peninsula ◽  
Early Cretaceous ◽  
North American ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Relative Length ◽  
Central Position ◽  
Eastern North America ◽  
The North

Multituberculates, though among the most commonly encountered mammalian fossils of the Mesozoic, are poorly known from the North American Early Cretaceous, with only one taxon named to date. Herein we describe Argillomys marylandensis, gen. et sp. nov., from the Early Cretaceous of Maryland, based on an isolated M2. Argillomys represents the second mammal known from the Arundel Clay facies of the Patuxent Formation (Lower Cretaceous: Aptian). Though distinctive in its combination of characters (e.g., enamel ornamentation consisting of ribs and grooves only, cusp formula 2:4, presence of distinct cusp on anterobuccal ridge, enlargement of second cusp on buccal row, central position of ultimate cusp in lingual row, great relative length), the broader affinities of Argillomys cannot be established because of non-representation of the antemolar dentition. Based on lack of apomorphies commonly seen among Cimolodonta (e.g., three or more cusps present in buccal row, fusion of cusps in lingual row, cusps strongly pyramidal and separated by narrow grooves), we provisionally regard Argillomys as a multituberculate of “plagiaulacidan” grade. Intriguingly, it is comparable in certain respects to some unnamed Paulchoffatiidae, a family otherwise known from the Late Jurassic – Early Cretaceous of the Iberian Peninsula.

scholarly journals Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

2016 ◽  
Vol 4 (4) ◽  
pp. 831-869 ◽  
Author(s):  
Andrew D. Wickert
Keyword(s):  
North American ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Drainage Basins ◽  
Last Glacial ◽  
Isostatic Adjustment ◽  
The North ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins – the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.

Postglacial dispersal of freshwater fishes into Ontario

1992 ◽  
Vol 70 (11) ◽  
pp. 2247-2259 ◽  
Author(s):  
Nicholas E. Mandrak ◽  
E. J. Crossman
Keyword(s):  
North America ◽  
Freshwater Fishes ◽  
Eastern North America ◽  
Glacial Period ◽  
Before Present ◽  
Last Glacial Period ◽  
Historical Processes ◽  
Dispersal Routes ◽  
Atlantic Coastal ◽  
The Last Glacial

The present-day distributions of 117 native freshwater fishes in Ontario have been shaped by processes active following the Wisconsinan glacial period, 80 000–10 000 years before present. During this glacial period, these species survived in unglaciated réfugia. To understand the processes that resulted in the recolonization of Ontario by fishes following the last glacial period, the refugial areas occupied by each species were determined using a refugial index, and glacial water bodies used as dispersal routes were identified. The refugial origins of the Ontario populations of 91 species were resolved. Seventy-two species resided in the Mississippian refugium, 13 species in the Atlantic Coastal refugium, 4 species in dual Atlantic Coastal – Mississippian refugia, 1 species in a Missourian refugium, and 1 species in Atlantic Coastal, Mississippian, and Missourian refugia. These conclusions differed significantly from those of other studies. Five general patterns were identified from the distributions of 104 species. In addition, there are 13 species that do not fit any of the general patterns. Most species with similar distributions in Ontario shared the same refugia and dispersal routes in eastern North America, therefore it is hypothesized that historical processes were important in shaping the present-day distributions of Ontario freshwater fishes.

scholarly journals The origin of till sequences by subglacial sediment deformation beneath mid-latitude ice sheets

1996 ◽  
Vol 22 ◽  
pp. 75-84 ◽  
Author(s):  
G. S. Boulton
Keyword(s):  
North American ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Erosion And Deposition ◽  
The North ◽  
Sediment Deformation ◽  
Source Materials ◽  
The Last Glacial

A theory of erosion and deposition as a consequence of subglacial sediment deformation over beds of unlithified sediment is reviewed and applied to large-scale till sequences formed on the southern flanks of the North American and British and European ice sheets during the last glacial cycle. The distribution of till thickness, till lithology in relation to source materials and intra-till erosion surfaces along a flowline in the Michigan lobe of the North American ice sheet are shown to be compatible with the deformational theory but not with other modes of till genesis. It is then demonstrated, in the case of the British ice sheet, how the assumption of a deformational origin for tills can be used to infer time-dependent patterns of ice-sheet dynamic behaviour. By reference to an example from the Netherlands, it is argued that many till sequences interpreted as melt-out tills are more likely to have formed by subglacial sediment deformation.

Link between the North and South Atlantic during the Heinrich events of the last glacial period

1999 ◽  
Vol 15 (12) ◽  
pp. 909-919 ◽  
Author(s):  
L. Vidal ◽  
R.R. Schneider ◽  
O. Marchal ◽  
T. Bickert ◽  
T.F. Stocker ◽  
...  
Keyword(s):  
South Atlantic ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Heinrich Events ◽  
The North ◽  
North And South ◽  
The Last Glacial

Key Role of the North Pacific Oscillation–West Pacific Pattern in Generating the Extreme 2013/14 North American Winter

2015 ◽  
Vol 28 (20) ◽  
pp. 8109-8117 ◽  
Author(s):  
Stephen Baxter ◽  
Sumant Nigam
Keyword(s):  
North America ◽  
North American ◽  
North Pacific ◽  
Eastern North America ◽  
North Pacific Oscillation ◽  
Winter Climate ◽  
West Pacific ◽  
The North ◽  
The Tropics ◽  
The North Pacific

Abstract The 2013/14 boreal winter (December 2013–February 2014) brought extended periods of anomalously cold weather to central and eastern North America. The authors show that a leading pattern of extratropical variability, whose sea level pressure footprint is the North Pacific Oscillation (NPO) and circulation footprint the West Pacific (WP) teleconnection—together, the NPO–WP—exhibited extreme and persistent amplitude in this winter. Reconstruction of the 850-hPa temperature, 200-hPa geopotential height, and precipitation reveals that the NPO–WP was the leading contributor to the winter climate anomaly over large swaths of North America. This analysis, furthermore, indicates that NPO–WP variability explains the most variance of monthly winter temperature over central-eastern North America since, at least, 1979. Analysis of the NPO–WP related thermal advection provides physical insight on the generation of the cold temperature anomalies over North America. Although NPO–WP’s origin and development remain to be elucidated, its concurrent links to tropical SSTs are tenuous. These findings suggest that notable winter climate anomalies in the Pacific–North American sector need not originate, directly, from the tropics. More broadly, the attribution of the severe 2013/14 winter to the flexing of an extratropical variability pattern is cautionary given the propensity to implicate the tropics, following several decades of focus on El Niño–Southern Oscillation and its regional and far-field impacts.

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