31 Quaternary Geology of the Great Central Valley of California: What Have We Learned in the Past 60 Years?

Friday, 4 April 2025
8:00 AM - 12:00 PM
El Dorado

DISTINGUISHING GLACIAL DIAMICTONS AND LANDFORMS USING TILL MACROFABRIC AND GRAIN SIZE ANALYSIS: SERRA DA ESTRELA MOUNTAINS, CENTRAL PORTUGAL

Paper number: 31-6
Program: Theme Sessions
Time: 9:25 AM – 9:45 AM

Authors

  • Joao Santos Presenting Author
    San Jose State University, San Jose, CA

Abstract

Till macrofabric and grain-size analysis of glacial diamictons and landforms present in several valleys of the Serra da Estrela Mountains in central Portugal were used to interpret till types and to reconstruct the glacial paleoprocess history of this mountainous region. Supraglacial melt-out and flow tills are dominant in this range. Supraglacial melt-out tills, representative of periods of glacial stability and stagnation followed by recession, present weaker fabric data and coarser, poorly sorted sediments. Flow tills, mainly representative of glacial stability followed by recession, present crude layering, and soft-sediment deformation structures with moderate fabric data and coarser to fine, poorly sorted sediments. Glacial diamictons affected by postglacial paraglacial activity in the form of debris flows were also observed in three valleys. These present weaker to moderate fabric data and coarser, poorly sorted sediments. These glacial diamictons and landforms are of particular importance in the reconstruction of the glacial dynamics and history of the Serra da Estrela Mountains because these mountains represent the southernmost Atlantic range in Europe where significant glaciation took place, which makes it an interesting area to investigate mountain glacial dynamics in low elevation humid Atlantic coastal ranges and compare it with other Atlantic ranges.

Geological Society of America Abstracts with Programs. Vol. 57, No. 4

doi: 10.1130/abs/2025CD-409460

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