马达加斯加, 留尼汪,坦桑尼亚, 毛里求斯和塞舌尔旅游新闻

马达加斯加,留尼汪, 坦桑尼亚, 毛里求斯和塞舌尔最新消息

塞舌尔可能是地球古代大陆”毛利提亚Mauritia”的一部分

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Map of Rodinia

据”自然-地球科学”杂志刊登的一项研究报告显示, 塞舌尔可能是地球古代大陆”毛利提亚Mauritia”的一部分.
这项研究由挪威奥斯陆大学的研究人员主持. 奥斯陆大学教授特龙-托尔斯维克说,研究人员分析毛里求斯海滩沙砾,从中提取出的锆石年代可追溯至6亿年前,可能是沉没的古代大陆毛利提亚”遗骸”.
托尔斯维克说,这些锆石可能是火山喷发时被冲上海洋表面.
英国广播公司(BBC)网站25日报道,依据研究人员理论,在大约7.5亿年之前,地球上的陆地是连在一起的,形成一块被称为”罗迪尼亚(Rodinia)”的巨大陆地.
尽管印度和马达加斯加被数千公里的海洋隔开,但两者一度是相连的.
现在,研究人员相信他们发现的证据表明:一块被称为微大陆的长条状大陆曾经夹在印度和马达加斯加岛之间.经过研究毛里求斯沙滩上的沙粒,研究小组得出了上述结论.
这些沙粒可以追溯到发生于大约900万年前的一次火山爆发,尽管如此,沙粒中所包含的矿物在时间上要久远得多.特龙-托尔斯维克说:”我们从沙滩沙粒提取物中发现了锆石,而锆石通常是存在于大陆地壳中的矿物,这是一种很古老的矿物.”锆石可以追溯到19.7亿年至6亿年前,因此研究小组得出结论:锆石是古代陆地的遗留物,在火山爆发期间被喷发到岛屿的表面.
托斯维克教授称:他认为”毛里提亚”可能存在于毛里求斯之下大约10公里处以及印度洋的一片水域之下.从土地荒芜,没有生命的前寒武纪时代到恐龙漫步于地球的时代,那块陆地经历了数百万年的历史.
然而,大约在8500万年之前,随着印度从马达加斯加岛开始漂移到其目前的位置,那块微大陆也开始分崩离析,最终消失在海洋的波涛之下.可是,其中的一小部分可能保存了下来.
“目前,塞舌尔群岛是一块花岗岩质地的大陆地壳,几乎坐落在印度洋的中心区,”托斯维克教授解释说,”但是,从前塞舌尔群岛位于马达加斯加岛的北部.我们想说的是,那块微大陆的分布范围也许要大得多,可能有许多这样的古大陆地块散布于印度洋之下.”
要想对这一失踪地区的遗留之物进行全面的调查,仍需要进一步研究
托尔斯维克说:”我们需要反映该地区地质结构的地震资料,这将是我们的根本证据.或者也可以往深处钻探,但那样做将会付出极高的成本.”

原文:

Fragments of ancient continent buried under Indian Ocean

By Rebecca Morelle

Land on Earth was once gathered together in a supercontinent known as Rodinia, shown here as it was during its break-up 750 million years ago. Now scientists believe they have found a fragment of it buried under the Indian Ocean.

Fragments of an ancient continent are buried beneath the floor of the Indian Ocean, a study suggests.

Researchers have found evidence for a landmass that would have existed between 2,000 and 85 million years ago.

The strip of land, which scientists have called Mauritia, eventually fragmented and vanished beneath the waves as the modern world started to take shape.

The study is published in the journal Nature Geoscience.

Supercontinent

Until about 750 million years ago, the Earth’s landmass was gathered into a vast single continent called Rodinia.

And although they are now separated by thousands of kilometres of ocean, India was once located next to Madagascar.

Now researchers believe they have found evidence of a sliver of continent – known as a microcontinent – that was once tucked between the two.

The team came to this conclusion after studying grains of sand from the beaches of Mauritius.

While the grains dated back to a volcanic eruption that happened about nine million years ago, they contained minerals that were much older.

Professor Trond Torsvik, from the University of Oslo, Norway, said: “We found zircons that we extracted from the beach sands, and these are something you typically find in a continental crust. They are very old in age.”

The zircon dated to between 1,970 and 600 million years ago, and the team concluded that they were remnants of ancient land that had been dragged up to the surface of the island during a volcanic eruption.

Prof Torsvik said that he believed pieces of Mauritia could be found about 10km down beneath Mauritius and under a swathe of the Indian Ocean.

It would have spanned millions years of history, from the Precambrian Era when land was barren and devoid of life to the age when dinosaurs roamed the Earth.

But about 85m years ago, as India started to drift away from Madagascar towards its current location, the microcontinent would have broken up, eventually disappearing beneath the waves.

However, a small part could have survived.

“At the moment the Seychelles is a piece of granite, or continental crust, which is sitting practically in the middle of the Indian Ocean,” explained Prof Torsvik.

“But once upon a time, it was sitting north of Madagascar. And what we are saying is that maybe this was much bigger, and there are many of these continental fragments that are spread around in the ocean.”

Further research is needed to fully investigate what remains of this lost region.

Prof Torsvik explained: “We need seismic data which can image the structure… this would be the ultimate proof. Or you can drill deep, but that would cost a lot of money.”

Written by antananarivo

二月 26th, 2013 at 12:10 下午