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Tag Archives: stratigraphy
K-Pg Extinction Event: Boundary Characteristics
The end of the Cretaceous period and the start of the Paleogene period 65.5 million years ago is marked by a global extinction event at the K-Pg boundary. The Paleogene was previously part of the Tertiary before the term was … Continue reading
Horizontal Correlation
Why is it difficult to correlate time horizons over wide areas using lithostratigraphic units and how can fossils help resolve this problem? The best time-markers in stratigraphy are widespread, distinct, and geologically instantaneous. Rocks that form in moments, years, or … Continue reading
Stratigraphy as a Badly-Edited Tape
“The stratigraphic record is like a badly edited tape.” Discuss. The rock record is incomplete. Between limited exposure, erosion, and recycling, only patches are preserved, and deposits of the same age are no longer connected. Particular lithographies can be paired … Continue reading
Sequence Stratigraphy
Describe the sequences as described by Sloss (1963) and discuss the possible controls on their deposition. Sequence stratigraphy is a system of linking unconformity-bounded sediment packages to global events to temporally correlate sedimentary units across lithographic boundaries. This is important … Continue reading
Posted in Geoscience
Tagged sedimentation, Sedimentation Saturday, Sloss sequence, stratigraphy
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Golden Spike
In a stratigraphic context, what is a “golden spike?” Explain why the choice of the Ludlow Bone Bed in the Welsh Borderland was rejected as the Golden Spike for the Silurian / Devonian boundary. What alternate section was chosen and … Continue reading
Posted in Geoscience
Tagged Devonian, Golden Spike, Ludlow Bone Bed, sedimentation, Sedimentation Saturday, Silurian, stratigraphy, Welsh Borderland
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Modern vs. Ancient Marine Evaporite Environments
Compare and contrast modern and ancient marine evaporite environments. The mineral makeup of the earth has changed over time. Aside from mineral evolution, atmospheric and climate changes also impact what type of sediments are produced. In the era of a … Continue reading
Posted in Geoscience
Tagged ancient, evaporites, modern, sedimentation, Sedimentation Saturday, stratigraphy, submarine
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Mid-Ocean Ridge
Describe the sediments you would expect on the ocean floor near a mid ocean ridge, from the ridge crest to the deep ocean floor 4000m below sea level on either side of the ridge. How active divergent margins evolve determines … Continue reading
Posted in Geoscience
Tagged continental crust, deep ocean, mid-ocean ridge, oceanic crust, ooze, rifting, sedimentation, Sedimentation Saturday, stratigraphy, submarine
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Quartz Arenites
Detail the general characteristics of quartz arenites and describe an environment where you might expect them to be particularly common. Arenites contain less than 15% matrix (<15% material that is <30µm). Quartz arenite is a quartz sandstone (>95% quartz) held … Continue reading
Posted in Geoscience
Tagged quartz arenite, sedimentation, Sedimentation Saturday, stratigraphy
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Evaporites
If you evaporate a 1000m column of sea water only 1.5m of evaporites are produced. Given this, how would you account for the 2km thickness of Permian Zechstein deposits? In your answer make reference to the sequence of minerals you … Continue reading
Posted in Geoscience
Tagged evaporites, Permian, sedimentation, Sedimentation Saturday, stratigraphy, Zechstein
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