札格羅斯盆地洛雷斯坦弧凸之構造演化

Structural Evolution of Lorestan Salient in Zagros Basin

彭俊維(Jun-Wei Pang)

指導教授 ： 胡植慶

國立臺灣大學/理學院/地質科學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003036

摘要

札格羅斯山脈是世界上最年輕的造山帶之一，由阿拉伯板塊與歐亞大陸板塊碰撞所形成，其前陸盆地至今已發現至少60個油氣田，是富含油氣資源之區域，透過研究區域在構造上的演化，亦是石油探勘重要的前置工作。本研究區域洛雷斯坦位於札格羅斯盆地，整體構造呈西北-東南向，範圍沿構造走向長375公里，寬200公里，擁有許多排列緊密之褶皺。本研究首先透過平衡剖面法，將前人發表之剖面進行回復，亦即將受擠壓以及斷層作用而變形的地層回復到原始沉積水平形貌，在過程中探討其構造演化的先後順序。結果顯示斷層在時序上的演化依序為卡比爾庫斷層、馬勒庫斷層、希洛什斷層、蘇丹斷層和庫特貝斷層，在發育方式上兼具順時序與逆時序發育，順時序之發育主要集中於沉積層，而逆時序之斷層發育則普遍與基盤有關。回復後得到地殼30.81公里的縮短量，按照札格羅斯盆地早中新世開始發生地殼縮短來算，洛雷斯坦區域平均縮短速度為1.33 mm/yr至1.92 mm/yr，又根據現今GPS速度場解算出洛雷斯坦位於簡單褶皺帶兩側的速度差異為3.31 mm/yr，從長期的平均速率與短期速率來看，洛雷斯坦區域的縮短速度在近期有明顯增加的趨勢。在斷層活動性上，洛雷斯坦區域的斷層分佈密度高但破裂多數未出露於地表，大多屬於盲斷層系統，因此本研究藉由地震觀察來解讀區域主要活動構造，地震的分佈主要集中於山前斷層處，簡單褶皺帶內的地震相對稀少，推測是因為應力沿著深處滑脫面由東北往西南方向傳遞，但在山前斷層底部因遇斷層轉折處而受阻擋，造成此構造地震發生率遠高於洛雷斯坦其他區域，表示應力正在累積，深部基盤的滑脫構造持續發育當中。

關鍵字

平衡剖面 ； 札格羅斯盆地 ； 洛雷斯坦弧凸 ； 構造演化 ； 剖面回復 ； 構造縮短量

並列摘要

The Zagros Mountain Belt is one of the youngest orogenic belts in the world, formed by the collision of the Arabian Plate and the Eurasian Plate, at least 60 oil and gas fields have been discovered in foreland basin. Therefore, the research of the structural evolution of these areas is an important preparatory work for petroleum exploration. The research area Lorestan is located in the southwestern part of the Zagros Basin, overall structure is northwest-southeast trending, with a length of 375 kilometers and a width of 200 kilometers along the structural trending. In this study, we first used Move 2017 to restored the previously published balanced cross section across Lorestan Salient. Namely, restored the stratum deformed by compression and faulting to the original sedimentary horizontal morphology, and discuss its tectonic evolution in the process. The results show that evolution of the faults in the sequence is Kabir Kuh fault, Maleh Kuh fault, Halush fault, Sultan fault and Qutbeh Fault, respectively. The faults evolution are both in-sequence and out-of-sequence, in-sequence development is mainly concentrated in sedimentary layers, while the out-of-sequence faults are generally related to the basement structure. The average shortening rate across Lorestan is 1.33 mm/yr to 1.9 mm/yr according to the shortening of the crust from the Early Miocene of Zagros orogeny. The difference in GPS velocity between the two sides of Lorestan Simple Folded Belt is 3.31 mm/yr calculated by present GPS velocity field, and the shortening rate of Lorestan simple folded belt has a significant tendency to increase.In terms of fault activity, because most of faults in Simple Folded Belt are blind fault systems and most fractures are not exposed to the surface. Therefore, this study interprets the main active structures through seismic analysis. The distribution of earthquakes is mainly concentrated along the Mountain Front fault, and the earthquakes within Simple Folded Belt are relatively rare. It is speculated that the stress is transmitted from northeast to southwest along the deep tectonic, and accumulate at the bottom of Mountain Front fault, so the occurrence rate of earthquakes in this structure is much higher than that in other areas of Lorestan salient, indicating that the stress is accumulating and the detachment structure in the basement is developing continuously.

並列關鍵字

Balanced cross-section ； Zagros basin ； Lorestan Salient ； Structural evolution ； Restoration ； Shortening

參考文獻

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英文文献：