Zuñi sequence

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The Zuñi sequence was a cratonic sequence that began in the latest Jurassic, peaked in the late Cretaceous, and ended by the start of the following Paleocene.^[1] Though it was not the final major transgression, it was the last complete sequence to cover the North American craton; the following Tejas sequence was much less extensive.

Contents 1 Cause and Progression 2 See also 3 Footnotes: 4 References:

[edit] Cause and Progression

Like other sequences, the the Zuñi was probably caused by a mantle plume - more specifically, the Mid-Cretaceous Superplume event. A mass of unusually hot rock rose from the lower mantle to the base of the lithosphere, fueling a dramatic increase seafloor spreading rates; this caused the hotter mid-ocean ridges to increase in volume, thus displacing the oceans onto the continents.^[2]

Sea level rose in earnest beginning in the early Cretaceous, until by Cenomanian time it was roughly 250 meters (800+ feet) higher than today.^[3] This was the time of the great Western Interior Seaway, and the widespread continental deposition of carbonates and shale elsewhere.^[4],^[5] There were also intervals where black shale accumulated in abundance on the continents, indicative of a stagnant water column; apparently water in the polar oceans was too warm to sink and oxygenate the deep-sea, as it does today.^[6] Many of these black shales are now rich petroleum sources.^[7]

The waters of the Zuñi sequence began to subside late in the Cretaceous period, and by early in the Cenozoic a new craton-wide unconformity in North America indicates a complete regression before the Tejas sequence of the late Paleogene.^[8]

[edit] See also

• Otong-Java Plateau
• Sequence stratigraphy

[edit] Footnotes:

1. ^ Stanley, Steven M. Earth System History. p. 175
2. ^ Larson, Roger L. "The Mid-Cretaceous Superplume Episode". Scientific American Special: Our Ever Changing Earth. p. 26
3. ^ Larson, pp. 25-6
4. ^ Larson, pp. 25-6
5. ^ Stanley, pp. 479-80
6. ^ Stanley, p. 480
7. ^ Stanley, p. 480
8. ^ Stanley, p. 175

[edit] References:

• Larson, Roger L. "The Mid-Cretaceous Superplume Episode". Scientific American Special: Our Ever Changing Earth. Vol. 15, No. 2, 2005. pp. 22-7.

• Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999. ISBN 0716728826