冶力关旅游区地质构造

冶力关旅游区是享誉全国的国家级地质公园,地处秦（岭）-祁（连山）-昆（仑山）造山系结合部的西秦岭褶皱带。特殊的地质发展史造就了旅游区特有的丹霞地貌、岩溶地貌、滑坡堰塞湖、地质遗迹剖面、峡谷地貌、流水地貌以及古生物化石等地质遗迹资源。其中，赤壁幽谷片区发育的丹霞地貌为高寒区湿润型丹霞，是我国西北地区发育的典型的具有南方丹霞特征的丹霞地貌，全国唯一；天池冶海为大型高山滑坡堰塞湖，国内稀有；森林、水体景观丰富，在西部地区独具魅力；地质遗迹类型丰富、特征典型，具有极高的美学欣赏价值和历史文化价值。

冶力关旅游区地层隶属于东昆仑—中秦岭地层分区，地层出露以上古生界为主，缺失中生界，新生界发育。其中上古生界以海相沉积为主，新生界为陆相沉积。石炭系、二叠系、新近系地层剖面清晰，作为旅游区内主要地质遗迹的成景地层，其本身也是一种重要的地质遗迹资源。

冶力关旅游区的地层形成的地质时代分别有泥盆纪、石炭纪、二叠纪、古近纪和第四纪。旅游区内分布的最老地层为最南部一套被地质学界称之为“大草滩群”的灰绿色厚层状长石石英砂岩。该套地层的形成时代为距今约3.5亿年左右的晚泥盆世。其次是分布在“天池冶海”片区内的距今约3.2亿年前的石炭纪碳酸盐岩地层，该套地层被地质学家称为“巴都组”“下加岭组”和“上加岭组”。由于该套地层以在湿润环境下较易溶解的“碳酸盐岩”或“石灰岩”地层为主，所以其稳定性较差，较易形成喀斯特地貌或者崩塌地貌。“天池冶海”的形成即与该种岩性地层的广泛分布有密切关系。另外还有一套石灰岩地层同样分布在“天池冶海”片区内，该套地层以含大量的“䗴”化石为特征，是形成于距今约2.77亿年左右的早二叠世。这套地层被地质学家们称之为“大关山群”“杨家河组”和“崖下组”。

旅游区内比较年轻的一套地层即为分布在“赤壁幽谷”片区内的丹霞地貌的成景地层。该套地层大约形成于距今约5000万年以来的古近纪。由于该套地层颜色赤红、分布稳定、色泽鲜艳、形态奇异，是“赤壁幽谷”片区内的主要旅游吸引物。

Yeliguan Tourist Area is a national geological park with a good reputation in China, which is located in the western Qinling fold belt at the junction of Qin (Ling)-Qi (Lianshan)-Kun (Lunshan) orogenic system. The special geological development history has created the unique geological relic resources such as Danxia landform, karst landform, landslide dammed lake, geological relic profile, canyon landform, flowing water landform and paleontological fossils in the tourist area. Among them, the Danxia landform developed in Chibi Yougu area is humid Danxia in alpine region, which is a typical Danxia landform developed in northwest China with the characteristics of southern Danxia and the only one in China; Tianchi Yehai is a large-scale mountain landslide dammed lake, which is rare in China; Rich in forest and water landscape, it has unique charm in the western region; Geological relics are rich in types and typical in characteristics, and have high aesthetic appreciation value and historical and cultural value.

The strata of Yeliguan Tourist Area belong to the East Kunlun-Middle Qinling stratigraphic subdivision, and the strata are mainly exposed in Pegazoic, but lack of Mesozoic and Cenozoic development. Among them, the Upper Paleozoic is dominated by marine sediments, while the Cenozoic is continental sediments. Carboniferous, Permian and Neogene strata have clear profiles. As the main geological relics in the tourist area, the landscape-forming strata are also important geological relics resources.

The geological ages of strata formation in Yeliguan tourist area are Devonian, Carboniferous, Permian, Paleogene and Quaternary. The oldest stratum distributed in the tourist area is a set of gray-green thick layered feldspar Shi Ying sandstone in the southernmost part, which is called "Dacaotan Group" by geologists. This set of strata was formed in the Late Devonian about 350 million years ago. Secondly, Carboniferous carbonate strata distributed in "Tianchi Yehai" area about 320 million years ago, which are called "Badu Formation", "Xiajialing Formation" and "Shangjialing Formation" by geologists. Because this set of strata is mainly "carbonate rock" or "limestone" which is easy to dissolve in humid environment, its stability is poor, and it is easy to form karst landform or collapse landform. The formation of "Tianchi Yehai" is closely related to the wide distribution of this lithologic stratum. In addition, there is a set of limestone strata also distributed in the "Tianchi Yehai" area, which is characterized by containing a large number of fossils and formed in the Early Permian about 277 million years ago. This set of strata is called "Daguanshan Group", "Yangjiahe Formation" and "Yaxia Formation" by geologists.

A relatively young set of strata in the tourist area is the landscape-forming strata of Danxia landform distributed in the "Chibi Valley" area. This set of strata was formed in Paleogene about 50 million years ago. Because this set of strata is crimson in color, stable in distribution, bright in color and strange in shape, it is the main tourist attraction in the "Red Cliff Valley" area.