地質(zhì)學(xué)

地質(zhì)學(xué)

封面介紹：受早二疊世岡瓦納冰川作用及岡瓦納北緣裂解的影響，拉薩地塊晚古生代構(gòu)造演化環(huán)境演化及生物演變一直是學(xué)術(shù)界討論的熱點(diǎn)問(wèn)題。拉薩地塊下二疊統(tǒng)拉嘎組是一套與岡瓦納地區(qū)晚古生代大規(guī)模冰川作用有直接聯(lián)系的沉積地層，具有近岸冰海環(huán)境的特點(diǎn)，是對(duì)應(yīng)岡瓦納大陸北緣晚古生代裂解過(guò)程的沉積響應(yīng)，其中所產(chǎn)早二疊世孢粉化石與早二疊世大規(guī)模冰川消退期事件有著密切的聯(lián)系。該套孢粉組合中除Parasaccites obscurus，P. cf. radiplicatus，Plicatipollenites indicus等岡瓦納型分子，其余皆為亞安加拉區(qū)常見(jiàn)的雙囊具肋花粉Striatoabieites，Hamiapollenites和單氣囊花粉Cordaitina等分子。初步研究表明，在早二疊世岡瓦納北緣和亞安加拉區(qū)共有某些植物類群的可能性是極大的，甚至拉薩、南羌塘等地塊由岡瓦納北緣向華夏區(qū)轉(zhuǎn)換的過(guò)程中微植群中發(fā)生的混生可能比古動(dòng)物群響應(yīng)的更早，至少在早二疊世的冰期末或冰期結(jié)束后就已經(jīng)發(fā)生了。封面顯示了西藏申扎地區(qū)早二疊世地層剖面，近景為拉嘎組冰海雜礫巖，其中產(chǎn)出早二疊世孢子與花粉化石，遠(yuǎn)景為早二疊世石灰?guī)r。詳見(jiàn)張予杰等人文（p2227）。

西藏申扎地區(qū)早二疊世冰海相地層中孢粉化石的發(fā)現(xiàn)

張予杰，安顯銀，張以春，等

拉薩地塊下二疊統(tǒng)拉嘎組是一套與岡瓦納地區(qū)晚古生代大規(guī)模冰川作用有直接聯(lián)系的沉積地層，作者在西藏申扎地區(qū)的拉嘎組中分析出孢粉化石，說(shuō)明早二疊世蕨類植物孢子和裸子植物花粉的出現(xiàn)與岡瓦納大陸冰川消退事件有密切聯(lián)系。該套孢粉組合中蕨類植物孢子含量遠(yuǎn)低于裸子植物花粉含量，雙囊具肋花粉和單囊花粉含量最高，Hamiapollenites與Striatoabieites兩屬地位尤為突出；組合中蕨類植物孢子含量雖低但分異度較高，單氣囊花粉Cordaitina所占比例較大，雙囊具肋花粉Hamiapollenites，Striatoabieites，Protohaploxypinus的種數(shù)很多，可建立Hamiapollenites-Striatoabieites組合。值得注意的是，除了少數(shù)“岡瓦納型”分子Parasaccites obscurus，P. cf. radiplicatus，Plicatipollenites indicus的存在外，其余含量極高的分子則可與新疆北部早二疊世孢粉組合相對(duì)比，說(shuō)明早二疊世岡瓦納和亞安加拉共有某些植物類群的可能性是極大的。這類孢粉組合在早二疊世冰海相沉積物中的出現(xiàn)表明，拉薩、南羌塘等地塊由岡瓦納北緣向華夏區(qū)轉(zhuǎn)換的過(guò)程中，微植群發(fā)生的混生可能比古動(dòng)物群響應(yīng)的更早，至少在早二疊世的冰期末或冰期結(jié)束后就已經(jīng)發(fā)生了。

西藏；申扎；早二疊世；冰海相地層；孢粉化石

來(lái)源出版物：科學(xué)通報(bào)，2015，60（23）： 2227-2235聯(lián)系郵箱：張予杰，zebiac@163.com

來(lái)源出版物：SCIENCE CHINA Earth Sciences，2015，58（8）： 1305-1319聯(lián)系郵箱：WANG Li-ning； wanglining@petrochina.com.cn

封面介紹：The extreme modern elevation of the Tianshan Mountains reflects the Cenozoic deformation. However，uncertainties remain over timing constraints on its thermal history since the Cenozoic. Modern river sands are ideal samples to explore the thermal history in a large scale by detrital Apatite Fission Track（AFT）study with statistical features. For more details see the research paper by WANG Li-ning et al. on pages 1305-1319.

Chronological constraints on multi-staged rapid cooling of the Tianshan Mountains inferred from apatite fission track analysis of modern river sands

WANG Li-ning； JI Jian-qing； SUN Dong-xia； et al.

The extreme modern elevation of the Tianshan Mountains reflects the Cenozoic deformation. Apatite Fission Track（AFT）chronometry is widely used to study the latest cooling stages caused by tectonic process or by exhumation in the uppermost crust. However，uncertainties remain over timing constraints on thermal history of the Tianshan Mountains since the Cenozoic though a great mount of dating work had been done in this area. To address this issue，modern river sands from the drainage basin on the piedmont of the Tianshan Mountains were sampled to integrate regional information. Single grains were dated with the AFT method，and then different grain-age components were identified to provide thermochronological constraints of their sources. Combined with discussion of previous dataset，our results show the multi-staged rapid cooling cluster at 46-32，25-24，19-13，8-6，and ～3 Ma，respectively. We interpreted these cooling events as a result of interplays between the Cenozoic tectonic uplift of the mountains and regional climate change.

Tianshan Mountains； detrital apatite fission track； cooling stages； exhumation； thermal history