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L67 Unconformity - a Landscape Unconformity. Nottinghamshire, UK
Position:
N53° 30'
W001° 30' approx.
Elevation:
250' / 75m approx.
Image format:
35mm
UNCORNFORMITY - A LANDSCAPE UNCORNFORMITY. NOTTINGHAMSHIRE, UK
UNCONFORMITIES are common but interesting geological features
that represent breaks in what is called the 'GEOLOGICAL SUCCESSION'.
Imagine a large lake. Over time, SEDIMENTS brought in by rivers
would accumulate on the lake bottom. In the future it would be
possible to trace the geological succession from the oldest sediments
at the bottom of the pile to the youngest at the top.
If, however, the lake had dried up and a river had eroded the
topmost sedimentary deposits before the lake flooded again, there
would be a break in the succession (quite a common occurrence
in arid regions). These breaks are called UNCONFORMITIES.
In this quarry in England, there are two geological successions.
Numerous thin beds of red rock lie in a dish-shaped depression.
The depression is an ancient river channel (perhaps a hundred
million years old or more). The thin beds have filled the valley
, which had been eroded in 350 million year old LIMESTONES.
Where ancient landform feature is buried under and preserved by
younger rock, the feature is called a LANDSCAPE UNCONFORMITY.
Less detail
Image Trail:
L30 Debris flow. Henry Mountains. Utah, USA - this image shows a
modern unconformity in the making |
