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Two episodes of meltwater influx from glacial Lake Agassiz into the Lake Michigan basin and their climatic contrasts

Geology

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Abstract

Two episodes of meltwater influx from glacial Lake Agassiz are recorded as prominent sedimentologic, isotopic, magnetic, and faunal signatures in southern Lake Michigan profundal sediments. As a tributary to the main path of eastward Lake Agassiz flow, southern Lake Michigan recorded only the largest, catastrophic discharges. The distinctive Wilmette Bed, a massive gray mud that interrrupts laminated red glaciolacustrine clays, marks the first episode, which occurred near the beginning of the Younger Dryas cooling events. The associated discharge may have played a role in the inception or severity of the Younger Dryas event. An oxygen isotope excursion in biogenic carbonate and changes in ostracode assemblages mark the second episode, which appears to have had at least two pulses, dated by accelerator mass spectrometer 14C ages on biogenic carbonate at about 8.9 and 8.6 ka. The second episode occurred during the early Holocene peak in global meltwater discharge and apparently had little widespread climatic or oceanographic effect. The contrast between the effects associated with these two episodes of meltwater discharge emphasizes the complexity of the ice sheet-ocean-climate system. -Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Two episodes of meltwater influx from glacial Lake Agassiz into the Lake Michigan basin and their climatic contrasts
Series title:
Geology
Volume
22
Issue:
6
Year Published:
1994
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
547
Last page:
550
Number of Pages:
4