Tag Archives: sedimentation

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

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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

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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

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Sandstone Diagenesis

During diagenesis a sandstone may undergo compaction, cementation and dissolution. Detail these processes and explain why they are important factors that must be considered by petroleum geologists. Diagenesis is the lithification of loose sediment into solid rock through compaction, cementation, … Continue reading

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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

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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

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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

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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

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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

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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

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