Luminescence chronology and climatic implication of the late quaternary glaciation in the Nubra valley, Karakoram Himalaya, India

SynopsisThe Upper Palaeozoic bedrock, which is of sedimentary and volcanic origin, is briefly described. The origin of the Forth as a series of depressions in the bedrock surface probably owes much to erosion of a pre-existing Tertiary landscape during phases of Quaternary glaciation. The late Quaternary history of the area is described, relating the distribution of the sediments deposited in the Forth to climatic events and changes in relative sea-level. Since the acme of the last main glaciation about 20,000 years ago, late Devensian marine and estuarine sediments have been deposited on the underlying glacial till sheet at altitudes ranging from more than 120 m below O.D. to at least 46 m above O.D. Similarly, raised and buried beaches and their deposits occur at altitudes from 40 m above O.D. down to around 10 m below O.D. in the estuary. During the Flandrian, sea-level has fluctuated, reaching its maximum (about 11 to 15 m above O.D.) about 6500 years ago. The typical deposit of this period is the carse clay which forms a series of extensive, fertile raised mudflats around the estuary. The calcareous marine faunas of the carse clay and older deposits are outlined.

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Past and future sky-island dynamics of tropical mountains: A model for two Geotrupes (Coleoptera: Geotrupidae) species in Oaxaca, Mexico

The Holocene ◽

10.1177/0959683620932977 ◽

2020 ◽

Vol 30 (10) ◽

pp. 1462-1470 ◽

Cited By ~ 1

Author(s):

Alfonsina Arriaga-Jiménez ◽

Bert Kohlmann ◽

Lorenzo Vázquez-Selem ◽

Yhenner Umaña ◽

Matthias Rös

Keyword(s):

Dynamic Process ◽

Late Quaternary ◽

Continuous Distribution ◽

Ice Age ◽

Mountain Range ◽

Tropical Mountains ◽

Quaternary Glaciation ◽

Mountain System ◽

Genetic Differentiation Of Populations ◽

Sky Island

Recent collecting and taxonomic studies of dung beetles of the genus Geotrupes Latreille (Coleoptera: Geotrupidae) in the mountains of Oaxaca have evidenced the existence of a vicariant speciation pattern, where one species occupies the northern mountain system and the other one the southern mountain range. A study of this possible vicariant speciation mechanism is presented using a paleobiogeographic mapping analysis of both Geotrupes species distribution during Late Quaternary glaciation events. Based on these paleomaps a possible speciation mechanism (vicariant speciation) is suggested, in which one common ancestor (mother species) lived at the bottom of the Valle de Oaxaca (Oaxaca Valley) during the last local glacial maximum (LLGM, 21-17.5 kyr) and whose possible continuous distribution was broken into two (or more) separated areas on mountaintops as the climate became warmer toward the present. We propose that the fragmentation and isolation of habitats may have promoted genetic differentiation of populations resulting in vicariant speciation, as suggested by a sky-island dynamic process. The example of a possible effect of the Little Ice Age in the mountains of Oaxaca is also discussed. Finally, a projection is made into the XXII century, based on climatic modeling predictions. These last results suggest the possible disappearance of the sky-island dynamic process through the accelerated speed of climatic change.

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