Tag Archives: ancient environments

Walking to Great Barrier Island

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A short hike to the beach 20,000 years ago

The Last Glaciation began about 110,000 years ago with massive expansion of ice-sheets in northern Europe, north Asia, North America and Antarctica.  The source of water for the ice-sheets was the oceans.  Based on geological mapping, dating of glacial deposits, and other physical evidence for ice movement it has been determined that the maximum extent of glacial ice from a global perspective occurred about 20000 years ago; this is referred to as the Late Glacial Maximum or (LGM).  Mapping also indicates that global sea-level was on average about 100m -120m below present sea-level. Continue reading

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How do we know which way is up? #1. Getting started

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How Geologists Interpret Ancient Environments. 1 Getting started

You are confronted with rock formations that might look something like this…

Folded sandstone exposed on a ridge - great place to examine the rocks

The local geologist tells you that the rocks you see here originally were deposited as sands and muds in shallow seas, where beaches and broad coastal tidal flats passed seawards to deeper waters, and landwards to marshes and scrubby coastal plains across which rivers and streams coursed. How did our geologist figure this out? What is it that geologists see in the rocks that help them paint this picture of an idyllic world that existed so many millions of years ago – a world beyond memory, where, in a different eon, a summer cottage would have been rather nice. Continue reading

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