Graptolite fauna indicates the beginning of the Kwangsian Orogeny

Science in China Press ^ | December 3, 2010 | Unknown

[decimon]

Our research at the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, has shown, based on a refined division and correlation of the graptolite-bearing strata in southern Jiangxi, China, that the Kwangsian Orogeny commenced in the early Katian Age of the Late Ordovician. Because of its significant research value, this study is published in Issue 11 of Science China Earth Sciences.

An angular unconformity separating the Lower-Middle Devonian and underlying strata is widespread in the Zhujiang region of South China, and occurs across most of Jiangxi, Hunan, Guangxi and Guangdong provinces. This angular unconformity indicates an orogeny in South China, named by V. K. Ting in 1929 as the Kwangsian Movement, and by T. K. Huang in 1945 as the Chinese 'Caledonian'. The precise age of the orogeny has until now not been well constrained. The present paper identifies the initiation age of the Kwangsian Orogeny, an important event in the geological evolution of South China.

In the Zhujiang region, strata of Cambrian to Silurian age are unconformably overlain by Lower-Middle Devonian rocks. Due to the Kwangsian Orogeny and subsequent tectonic events, the underlying Lower Paleozoic rocks were extensively but gently metamorphosed. Graptolites are the most important index fossils in these metamorphic rocks. Continuous Ordovician sections in Yongxin and Chongyi Counties, south Jiangxi, are widely regarded as type sections for the Zhujiang region. The Lower Ordovician (Tremadocian) to the lower part of the Upper Ordovician (Sandbian) is dominated by black shales (or slates) with a continuous graptolite sequence. In contrast the middle and upper parts of the Upper Ordovician (Katian), namely the Hanjiang, Shikou and Huamianlong Formations, are characterized by thick- to thin-bedded siltstone and sandstone several thousands of meters in total thickness, in which we recorded only rare graptolites with low diversity.

The Hanjiang Formation contains a Diplacanthograptus caudatus – D. spiniferus graptolite fauna zone of early Katian age. The Shikou and Huamianlong Formations, identified by previous research at separate localities, were in this study lithologically indistinct from the underlying Hanjiang Formation. Our re-analysis of graptolite specimens from the Shikou and Huamianlong Formations indicates these are of early Katian Age, and are not representative of the entire Katian as had been ascribed erroneously in previous research due to graptolite misidentifications. Thus, the Shikou and Huamianlong are virtually identical to the Hanjiang Formation, and we suggest their use be abandoned.

There is a sharp facies change from the deep-water black graptolitic shale of the Qixiling and Longxi Formations (Floian to Sandbian) to the thick, coarse, shallow-water near-shore clastics of the Hanjiang Formation (early Katian) which underlies unconformably the Devonian rocks. This facies change, occurring in the early Katian Age of late Ordovician as evidenced by graptolites, indicates the initiation of the Kwangsian Orogeny. Our palaeontological and biostratigraphic analysis has played a critical role in resolving the timing of this regional tectonic event, which has puzzled Chinese geologists for decades.

###

The authors are based at the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology. This laboratory conducts research primarily on five main topics: evolution of early life; palaeozoic biodiversity and environmental change; multidisciplinary stratigraphy and the geologic timescale; the origin and evolution of terrestrial ecosystem; and molecular palaeobiology.

This research was supported by funding from the Chinese Academy of Sciences (KZCX2-YW-122, 2008ZX05008-001-001), the Ministry of Science and Technology of China (2006CB806402), and the National Natural Science Foundation of China (40772002).

Reference:

Chen X, Zhang Y D, Fan J X, Cheng J F and Li Q J. Ordovician graptolite-bearing strata in southern Jiangxi with a special reference to the Kwangsian Orogeny. Sci China D. 2010, 53(11): 1602-1610. http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s11430-010-4117-6

[Bigh4u2]

Doh!

[Bigh4u2]

I knew that!

I was just kiddin’... hehe...

[ArrogantBustard]

Perhaps I’m just easily annoyed, this morning ...

For a Chinese scientific article (abstract, really) I’m actually quite impressed with the quality of the English translation. I’ve seen some real doozies over the years.

Then there’s the reaction of too many folks on this forum ... the article is of a technical nature, it uses words of more than one syllable ... and people react with derision and mockery, like a bunch of miseducated 10 year olds, to something that’s a challenge to their intellect. That’s just pathetic.

[Bernard Marx]

If this were in the US popular press, it would be all about how we feel solidarity with the poor, oppressed graptolites.

That's funny. I studied geology and understood the discussion, but you'll have to admit that geological jargon has become pretty convoluted and obscure.

That's sad because it's a barrier to communicating important principles of geology to a wider audience. If more people understood what's literally under their own feet maybe we could deal with many of our other problems more realistically.

[ArrogantBustard]

, but you'll have to admit that geological jargon has become pretty convoluted and obscure. That's true of almost any field. Listen to a bunch of French Chefs, or hotrodders, or overclockers, or musicians, or farmers, or ... talk about their activities. Same deal.

If more people understood what's literally under their own feet

For a supposedly technological culture, America is pretty bad about neglecting education in the sciences and engineering (with the exception of those who actually do science and engineering for a living). Knowing how to facebook, or having the latest iGadget in one's iLifestyle does not make one technologically aware.

[JimSEA]

In before the Himalayas! ;)

[JoeProBono]

[decimon]

...people react with derision and mockery, like a bunch of miseducated 10 year olds...

Gee, lighten up. I posted the article but didn't understand it and didn't expect most readers to understand it.

For who understands it - enjoy! For the rest of us there is some humor in such a mishmash of unfamiliar terms.

I'm annoyed by people who come in to a thread with no purpose but to disrupt. I don't see that in this thread.

[Bernard Marx]

That's true of almost any field.

Agreed. It's important to have precise, well understood technical language when communicating with peers. It's too bad we don't have more popularizers of geological concepts like John McPhee to make important concepts more understandable to laymen.

American "education" is a disaster. I'm amazed daily at the ignorance I encounter regarding fundamental concepts of geology, astronomy, biology etc. not to mention literature, history,language and so on. Every high school graduate should have some general understanding of these subjects even if they don't specialize in them.

[Louis Foxwell]

I have not been able to correlate this with Sarah's candidacy. A little help here.

[r9etb]

Graptolite fauna indicates the beginning of the Kwangsian Orogeny

Sounds like the plot line of one of Frank Herbert's post-Dune yawners.

[r9etb]

I have not been able to correlate this with Sarah's candidacy. A little help here.

Graptolite fauna are part of the RINO elite. Shun them.

[Louis Foxwell]

Yes. I see what you mean. They start as something small and benign. Then, suddenly, the mole hill has turned into a mountain.

[Tijeras_Slim]

Duplicate post. ;)

[decimon]

Duplicate post. ;)

I'm lucky they didn't pull the thread.

[SunkenCiv]

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