Saturday, October 10, 2015

Turbidity Currents, Turbidites and You

Turbidites are gravity flow formations often generated by earthquakes. [1]  The 1929 Grand Banks earthquake (off Newfoundland, M=7.2) and turbidity current caused telegraph cables to break and thus record its speed.  The current deposited at least 175 km3 of sediment and formed a bed more than 1 m thick (gravel to coarse silt).  A significant portion of the rock record is made up of turbidites.  If much of the Geologic Column was formed rapidly, then maybe this is a young planet after all.  Young Earth Science?  YES you can!
The Cambrian Burgess Shale is a significant challenge to evolution.  Multiple phyla are found in the earliest rocks and no transitional forms are found in Pre-Cambrian layers.  This conundrum, known as the Cambrian Explosion, is delineated in my book. [2]  The Burgess Shale is considered to be a turbidite!  So we find more evidence that the rock record was formed quickly.  So the next time you bring up the Cambrian Explosion in a conversation, be sure to point out that it favors Young Earth Science (YES).


A classic turbidite follows the pattern of the Bouma sequence.  Turbidites are very common.  As St├ęphanie Girardclos et al point out in Marine Geology, “Gravity flow deposits, and particularly turbidite deposits, are ubiquitous in the sedimentary and rock record, and are economically important as potential hydrocarbon reservoirs.” [3]  GerardMiddleton (Geology Dept., McMaster Univ., Canada) concurs:  “Beds deposited from turbidity currents (called turbidites) are one of the commonest types of sedimentary rocks … the majority of sandstones in the geologic record were deposited either from rivers or from turbidity currents …” [4]

Even some gypsum beds, often thought to be the result of a long process of evaporation, have been interpreted as turbidites. [5]  Actually, gypsum may form directly as a precipitate from hot volcanic springs. [6]  So the next time you look at your wall (gypsum board), know that it supports Young Earth Science (YES).

Notes:
1) YES – Young Earth Science by Jay Hall (IDEAS, Big Spring, TX, 2014), p. 130.
2) Hall, pp. 84, 85, 116.
3) “The 1996 AD delta collapse and large turbidite in Lake Brienz” by St├ęphanie Girardclos et al, Marine Geology 241 (2007) 137–154, p. 138, emphasis added.
4) “Sediment Deposition from Turbidity Currents” by Gerard Middleton, Annual Review Of Earth And Planetary Sciences, Volume 21, pp. 89-114, p. 90, emphasis added.
5) Evaporites: Sediments, Resources and Hydrocarbons by John Warren (Springer, 2006), p. 350.
6) Simon & Schuster’s Guide to Rocks and Minerals by Annibale Mottana et al (Simon & Schuster, NYC, 1978), entry 122 (gypsum).