当前位置: X-MOL 学术J. South Am. Earth Sci. › 论文详情
Structural characteristics of the “Puquios chaos” and its relationship with the Andean middle Cretaceous extensional tectonics at 27°S, northern Chile
Journal of South American Earth Sciences ( IF 1.704 ) Pub Date : 2019-12-06 , DOI: 10.1016/j.jsames.2019.102454
Felipe Reinoso; Juan Díaz-Alvarado; Carlos Fernández

In the Precordillera of the Atacama region (~27°S), the Puquios chaos corresponds to a singular tectonic unit traditionally ascribed to a mid-Cretaceous extensional stage affecting the Mesozoic formations that were deposited between the arc and the backarc settings of the Andean margin. The mélange-like unit consists of blocks of limestones in a mainly volcanic matrix that includes andesitic lavas, volcanic breccias and red vulcarenites of Upper Jurassic to Lower Cretaceous age. These rocks constitute a conformable succession of andesites, limestones and vulcarenites (from the base to the top) in the Cerro Águila strata, observed to the south of the study area.

The Puquios chaos is characterized by often isolated, tight to isoclinal folds and a set of low- and high-angle normal faults that were responsible for the block-in-matrix mesoscopic structure of the tectonic unit. These structures are easily observable in the calcareous rocks as the volcanic matrix shows a tectonically brecciated texture. The detailed structural study presented in this work allows us to propose the deformational mechanisms that finally constituted the apparently chaotic unit, including the restoration of the structures related to late contractive stages. Thus, we suggest that the singularity of the Puquios chaos is associated with a local, wide, extensional shear zone linked to a regional detachment surface. The intimate relation between recumbent folds and low- and high-angle normal faults, besides the similar orientation of fold hinges and fault planes, point to the actuation of a brittle-ductile shear zone where the calcareous competent layers gave rise to decametric-scale folds as the volcanic matrix responded to strain by brecciation. Stretching calculations carried out in a domino fault system yielded horizontal extension of around 30% for the high-angle faults.

We obtained a relative age of the Puquios chaos formation according to the field relations and the structural determinations. A NE-directed intense extensional stage promoted a significant crustal thinning that exhumed but not affected the late Paleozoic basement. The Puquios structures and the related regional detachments affected the pre-Barremian arc and back-arc formations and were unconformably covered by the latest Cretaceous and Paleocene thick volcanic and volcanosedimentary deposits.

更新日期:2020-01-04

 

全部期刊列表>>
施普林格自然
最近合集,配们化学
欢迎访问IOP中国网站
GIANT
自然职场线上招聘会
ACS ES&T Engineering
ACS ES&T Water
屿渡论文,编辑服务
何川
苏昭铭
陈刚
姜涛
李闯创
复旦大学
刘立明
隐藏1h前已浏览文章
课题组网站
新版X-MOL期刊搜索和高级搜索功能介绍
ACS材料视界
天合科研
x-mol收录
上海纽约大学
曾林
天津大学
何振宇
史大永
吉林大学
卓春祥
张昊
刘冬生
试剂库存
down
wechat
bug