中国地质
中國地質
중국지질
Geology in China
2015年
5期
1188-1201
,共14页
卢海建%王二七%李仕虎%李海兵
盧海建%王二七%李仕虎%李海兵
로해건%왕이칠%리사호%리해병
磁性地层%旋转变形%新生代%盐源盆地%青藏高原东南缘
磁性地層%鏇轉變形%新生代%鹽源盆地%青藏高原東南緣
자성지층%선전변형%신생대%염원분지%청장고원동남연
magnetostratigraphy%rotational deformation%Cenozoic%Yanyuan basin%southeastern margin of the Tibet
探究青藏高原东南缘构造旋转变形有助于理解青藏高原内部物质向东南方向的挤出过程。目前，有关青藏高原东南缘的构造旋转研究主要针对于两套地层：侏罗系—始新统和中新统—第四系。对侏罗系—始新统研究表明了大范围的顺时针旋转变形的存在，而对中新统—第四系的研究则表明该区域可能同时存在逆时针旋转变形。然而，对这两种构造旋转变形的时间和幅度仍缺乏充分的制约。位于川滇地块的四川盐源盆地同时出露这两套地层。磁性地层研究表明，上新统—中更新统的时代为>3.6~0.6 Ma。磁偏角数据揭示上新统—中更新统经历了逆时针旋转变形(-14.4°±2.7°)，而古新统—始新统经历了明显的顺时针旋转(10°~21.5°)，两套地层间的旋转幅度高达36.6°。鉴于青藏高原东南缘发生大规模顺时针旋转变形的最年轻地层为始新统地层，因此顺时针旋转变形可能发生在始新世—中新世某个时间段。这个时间与红河—哀牢山走滑断裂带的活动时间基本一致，因此顺时针旋转变形可能与该大型断裂带的活动直接相关。盐源盆地记录到的逆时针旋转变形发生于至少3.6 Ma以来，平均旋转速率为4°/Ma。由于磁组构数据表明上新世—中更新世地层并未受到挤压变形作用，因此其逆时针旋转变形可能受周围走滑断裂带的控制。
探究青藏高原東南緣構造鏇轉變形有助于理解青藏高原內部物質嚮東南方嚮的擠齣過程。目前，有關青藏高原東南緣的構造鏇轉研究主要針對于兩套地層：侏囉繫—始新統和中新統—第四繫。對侏囉繫—始新統研究錶明瞭大範圍的順時針鏇轉變形的存在，而對中新統—第四繫的研究則錶明該區域可能同時存在逆時針鏇轉變形。然而，對這兩種構造鏇轉變形的時間和幅度仍缺乏充分的製約。位于川滇地塊的四川鹽源盆地同時齣露這兩套地層。磁性地層研究錶明，上新統—中更新統的時代為>3.6~0.6 Ma。磁偏角數據揭示上新統—中更新統經歷瞭逆時針鏇轉變形(-14.4°±2.7°)，而古新統—始新統經歷瞭明顯的順時針鏇轉(10°~21.5°)，兩套地層間的鏇轉幅度高達36.6°。鑒于青藏高原東南緣髮生大規模順時針鏇轉變形的最年輕地層為始新統地層，因此順時針鏇轉變形可能髮生在始新世—中新世某箇時間段。這箇時間與紅河—哀牢山走滑斷裂帶的活動時間基本一緻，因此順時針鏇轉變形可能與該大型斷裂帶的活動直接相關。鹽源盆地記錄到的逆時針鏇轉變形髮生于至少3.6 Ma以來，平均鏇轉速率為4°/Ma。由于磁組構數據錶明上新世—中更新世地層併未受到擠壓變形作用，因此其逆時針鏇轉變形可能受週圍走滑斷裂帶的控製。
탐구청장고원동남연구조선전변형유조우리해청장고원내부물질향동남방향적제출과정。목전，유관청장고원동남연적구조선전연구주요침대우량투지층：주라계—시신통화중신통—제사계。대주라계—시신통연구표명료대범위적순시침선전변형적존재，이대중신통—제사계적연구칙표명해구역가능동시존재역시침선전변형。연이，대저량충구조선전변형적시간화폭도잉결핍충분적제약。위우천전지괴적사천염원분지동시출로저량투지층。자성지층연구표명，상신통—중경신통적시대위>3.6~0.6 Ma。자편각수거게시상신통—중경신통경력료역시침선전변형(-14.4°±2.7°)，이고신통—시신통경력료명현적순시침선전(10°~21.5°)，량투지층간적선전폭도고체36.6°。감우청장고원동남연발생대규모순시침선전변형적최년경지층위시신통지층，인차순시침선전변형가능발생재시신세—중신세모개시간단。저개시간여홍하—애뢰산주활단렬대적활동시간기본일치，인차순시침선전변형가능여해대형단렬대적활동직접상관。염원분지기록도적역시침선전변형발생우지소3.6 Ma이래，평균선전속솔위4°/Ma。유우자조구수거표명상신세—중경신세지층병미수도제압변형작용，인차기역시침선전변형가능수주위주활단렬대적공제。
Investigating rotational deformation of the southeastern margin of the Tibet is the key to understanding how and why the Tibet material extruded to the southeast. Until now there are two sets of strata used to study the rotational deformation on the southeastern margin of the Tibet:the Jurassic-Eocene and the Miocene-Quaternary strata. Paleomagnetic studies of the Jurassic-Eocene strata indicate widespread clockwise rotational deformation, similar studies of the Miocene-Quaternary strata suggest multiple deformation patterns, including clockwise rotation, counter-clockwise rotation and also no rotation. However, it is still not well constrained as to the timing and degree of rotational deformation on the southeastern margin of Tibet. Two sets of strata (the Paleocene- Eocene and Pliocene- Quaternary sediments) are well exposed in the Yanyuan basin, Sichuan Province. Magnetostratigraphic studies indicate an age of>3.6-0.6 Ma for the Pliocene-Quaternary strata. Declination data suggest that the Pliocene-Quaternary sediments experienced counter-clockwise rotation (-14.4° ), and the Paleocene-Eocene deposits underwent notable clockwise rotation (10°-21.5° ). As the age of the youngest strata that experienced clockwise rotational deformation on the southeastern margin of Tibet is the Eocene, the clockwise rotational deformation likely occurred during a time interval between the Eocene and the Miocene. The counter-clockwise rotational deformation recorded in the Yanyuan basin happened before 3.6 Ma with an average rotational rate of 4°/Ma. Since anisotropy of magnetic susceptibility (AMS) data indicate that the Pliocene-Quaternary sediments underwent no compressional deformation at all, the counter-clockwise rotational deformation was initiated most likely by strike-slip faults around the Yanyuan basin.
