Untangling the Quaternary Period—A Legacy of Stephen C. Porter

Stephen C. Porter was an international leader in Quaternary science for several decades, having worked on most of the world’s continents and having led international organizations and a prominent interdisciplinary journal. His work influenced many individuals, and he played an essential role in linking Chinese Quaternary science with the broader international scientific community. This volume brings together nineteen papers of interdisciplinary Quaternary science honoring Porter. Special Paper 548 features papers from six continents, on wide-ranging topics including glaciation, paleoecology, landscape evolution, megafloods, and loess. The topical and geographical range of the papers, as well as their interdisciplinary nature, honor Porter’s distinct approach to Quaternary science and leadership that influences the field to this day.
Late Pleistocene glaciers and climate in the High Atlas, North Africa
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Published:April 07, 2021
ABSTRACT
Extensive glaciers covered the High Atlas mountains in Morocco during the late Pleistocene. On the northern escarpments of the Marrakech High Atlas, a series of cirques perched at ~3000–3500 m above sea level (asl) fed their valley glaciers that, in some cases, extended to as low as 2000 m asl. Cosmogenic exposure dating with 10Be and 36Cl has shown that at least three phases of glaciation are preserved in glacial deposits over the last glacial cycle at 50, 22, and 12 ka, which appear to correlate with marine isotope stage (MIS) 3, the global Last Glacial Maximum (LGM), and the Younger Dryas chronozone. This geochronological framework is sufficiently robust to allow for time-constrained glacier-climate reconstructions. The glaciers associated with these three phases of advance had equilibrium line altitudes (ELAs) of 2761 m asl (ca. 50 ka), 2919 m asl (ca. 22 ka), and 3213 m asl (ca. 12 ka). Glacier-climate modeling suggests that all of these phases were driven by both colder temperatures and wetter conditions than today. The dominant moisture supply to these glaciers in all phases would have been sourced from Atlantic depressions. The influence of an extended and enhanced West African monsoon on glacier development during African Humid Periods is unlikely to have been a significant influence on glacier dynamics. The climate conditions associated with the three glacier phases indicate sustained moisture supply to the highest mountain areas when records from other areas, such as the Middle Atlas lakes and marine sediment cores offshore, indicate marked aridity.
- Africa
- alkaline earth metals
- Atlas Mountains
- Be-10
- beryllium
- Cenozoic
- cirques
- climate-induced circulation
- equilibrium line altitude
- exposure age
- glacial environment
- glacial features
- glaciers
- High Atlas
- isotopes
- last glacial maximum
- metals
- MIS 3
- moraines
- Moroccan Atlas Mountains
- Morocco
- North Africa
- North Atlantic Oscillation
- paleoatmosphere
- paleoclimatology
- paleorelief
- paleotemperature
- Pleistocene
- Quaternary
- radioactive isotopes
- upper Pleistocene
- upper Weichselian
- Weichselian
- Younger Dryas
- Toubkal Massif
- Adrar el Hajj Morocco
- Bou Iguenouane Morocco
- Aksoual Mountain