Chaohu Geology and Geomorphology Internship Report

Chapter 1 Introduction The tasks and results of the first section of the internship

First, the purpose and task of the internship

1. Internship purpose:

Through field internships, we will consolidate and enrich the Foundation of Resources and Environment, or General Geology, Structural Geology, Mineral Petrology, Paleontology, Measurement, Hydrogeology. The theoretical teaching content of basic geology, deepen the understanding of the relevant content of the course, learn the basic methods of observation, description and comprehensive analysis of typical geological phenomena; cultivate the basic skills of students to think independently, comprehensively analyze and solve problems, and unite Mutual help, hard work and hard work.

2. Internship tasks:

Through systematic observation of natural outcrops and artificially exposed geological points in the Fenghuangshan area of ​​Chaobei, systematically collect various surface geological information and other relevant materials, and study surface geological laws, including stratigraphic division and sequence, lithologic combination and lithofacies characteristics, geological structures. And structural changes, magma activities, and the occurrence of useful minerals.

Draw corresponding geological maps, such as integrated stratigraphic histograms, geological profiles, topographic geological maps, and structural outline maps.

Write a text report. A comprehensive analysis of the changes of the sedimentary environment of the stratigraphic sequence in the survey area, the evolution of paleontology, the combination of tectonic forms and the history of change.

Second, internship requirements

1. Master the stratigraphic sequence, lithologic facies, thickness, marking layer, contact relationship and geological body variation in the internship area, and the sedimentary environment changes, paleozoic evolution, tectonic form combination and change history of the stratigraphic sequence in the survey area. Comprehensive analysis and research.

2. Master the field observation, identification, description and naming methods of various types of rock and paleontological fossils in the internship area.

3. Master the methods of observation, description, recording and analysis of various geological phenomena in the field.

4. Master the steps, methods and requirements for measuring geological sections and field geological mapping.

5. Master the methods, formats and requirements for the preparation of topographic geological maps, geological profiles, and integrated stratigraphic maps.

6. Learn to conduct comprehensive analysis on the basis of geological observation and mapping, and master the requirements and methods for writing geological reports.

Third, the working method

Before each stage, classes are required to introduce the requirements and methods of this stage.

The first stage: the team led the team to conduct exploration, to the southeast of Qilin Mountain and the intersection of Qilin Mountain and Fenghuang Mountain, the 7410 Factory and the Ganlu Temple, Majiashan, Pingdingshan, Yaojiashan, and 177 Heights, for a total of 5 days. .

The second stage: grouping the measured formation profile for a total of 5 days.

The third stage: geological survey mapping, a total of 5 days.

Fourth, the results

1 regional geological survey report;

3 pieces of measured stratigraphic section;

1, 1:10000 topographic geological map;

, 1:10000 structure outline diagram 1;

1 1/2 thousand integrated strata histogram;

1, 1:10000 cut section view 2 sheets.

Section 2 Geography of the North Area

1, location

The internship area is located in the northern mountainous area of ​​Chaohu City in the central part of the province. It is surrounded by mountains and waters on three sides, Chaohu Lake, one of the five largest freshwater lakes in China, and the southern edge of Jianghuai Hilly Area in the north. It is about 65 kilometers away from Hefei City in the northwest and Wuhu City in the south. 80 kilometers east, about 120 kilometers east of Nanjing.

The lithology of the lower part of the group is characterized by gray-yellow medium-thick to thick argillaceous lithic quartz sandstone and silty mudstone with light gray thin-layer fine-grained quartz sandstone. The thick quartz strumite at the bottom is not integrated on the underlying strata.

fourth series

The Quaternary of this area is mostly developed on the south side. The mountainous areas generally develop slopes, which are composed of gravel, sand and clay, which can reach 3-4 meters thick. There are river and lake sediments near the lake. There are gravel and sub-clay, sub-sand soil, etc.; there are many caves in the carbonate rock area, and a large number of vertebrate fossils are collected; Chao County dog, Ningzhen bear, Kuanzhoukou rhinoceros, Bantang Li wild boar, Yang's bighorn deer Fossils such as goats, green sheep and bison.

Section 2 Geological Structure

I. Overview

The internship area is located in the northeastern margin of the stable Yangtze block in southern China. It was formed in the Paleoproterozoic and Paleoproterozoic metamorphic basal period, and entered the middle-late Late Paleo-Yu-Yi-Yi trough and the geotectonic evolution. The outward expansion and proliferation have basically created a stable and unified continental block, and then through the Sinian-Triassic marine sedimentary caprock development period, the surface geology in the present area has been affected by the eastern Pacific plate movement since the Late Triassic. Under the influence of the Western Tethys Sea Plate, strong tectonic, magmatic activities and mineralization occurred in the Indosinian, Yanshanian and Himalayan periods, and the characteristics of “floor activation” appeared.

The internship scope is located in the Fenghuang Mountain area in the north of Chaohu City, Anhui Province. The exposed strata are the Paleozoic and Mesozoic, and the eastern, southern and western sides are covered by the Quaternary, and the north is stopped at the Xiaoluo fault. Its tectonic form is two oblique and one anticline. From east to west, it is Yufu Dacun syncline, Fenghuangshan anticline, Pingdingshan syncline, and fault development.

Second, the description of the fold

The development of fold structure is the basic structural feature of the practice area. The internship area is a part of the west wing of the Bantang compound anticline in the region. It consists of Yufu Dacun Xiangling, Fenghuangshan anticline and Pingdingshan syncline from east to west. The exposed strata are Silurian, Devonian and Carboniferous. Department, Permian, Triassic. The three folds of the continuous foldback are basically normal, with many skews, partial reversal, and the folds are arranged parallel to each other, and the plane has an "m"-shaped low mountainous terrain. The direction of the track is 20o-30ooo, the pivot of the hub is ssw, and the angle of inclination is 15o-26o. Affected by multi-stage tectonic action, the axial plane is inclined and curved; the secondary small folds are quite developed in the inclined part of the chute groove; the folds are mostly broken by the parallel axial plane and the transverse plane fracture.

Phoenix Mountain Anticline

Located in the middle of the district, it is distributed in the area of ​​Fenghuang Mountain - Qilin Mountain - Changyao Mountain - Mianpan Mountain. Large scale, the direction of the overall construction line nee-sww. The Phoenix Mountain anticline hub undulates, roughly sloping in the sw direction, and the axial plane tends to nw and has a twisting phenomenon. According to the Ricard fold classification, it can be named as a sloping fold.

The core is composed of Silurian strata, and the two wings are in turn Devonian, Carboniferous, and Permian. The east wing stratum has a large dip angle and is partially inverted. The west wing stratum is relatively slow, and the dip angle is generally about 30 。. Because the Silurian strata in the nucleus are mostly mudstone and siltstone, the corrosion resistance is poor. The two-story Devonian Wutong Formation is mostly quartz sandstone, which has strong corrosion resistance and often forms a special landform of the anticline valley, while the two wings are composed of The Devonian Wutong Formation quartz sandstone forms a monoclinic mountain, such as Qilin Mountain, Dajian Mountain, and Chaoyang Mountain.

The anticline turns out of the formation and the formation is obvious. Radial small faults and joints are particularly developed, forming a fan-shaped fault combination that spreads toward the sloping end.

The Phoenix Mountain back slope is about 7 kilometers long and about 4 kilometers wide. In the western part of Dajianshan at the northern end, the turning part of the nuclear stratum is visible. Most of the anticline nucleus is composed of Silurian shale, which is strongly denuded, forming a small inter-mountain basin and covered by Quaternary loose sediments.

2. Pingdingshan syncline

Located in the western part of the district, it is distributed in Majiashan-Pingdingshan-to-Nucleon Mountain. The scale of exposure is second only to Yufu Dacun, and the overall tectonic line is nee-sww. The syncline nucleus is the middle stratum of the Triassic Dongmaanshan Formation and the Nanlinghu Formation; the two wings are the strata of the lower part of the Nanlinghu Formation, the Yinkeng Formation, the Longshan Formation and the Permian Dalong Formation, and the two-wing formations: the southern slope of Pingdingshan At the foot of the mountain, the east wing is 277 ゚∠52 ゚, the west wing is 132 ゚∠83 ゚; the top east wing is 261 ゚∠51 ゚, and the west wing is 150 ゚∠44 ゚.

The upward tilting end is clear, the west wing rock layer is upright, and the partial slope is turned. The turning edge of the north slope of the mountain top is clear, and the tumor-like limestone is crushed and broken, but no displacement occurs. The north slope turning end occurs: 235 ゚∠ 46 东 in the east wing and 146 ゚∠ 44 西 in the west wing.

The factors affecting the development of the Pingdingshan syncline are:

1 The rise of the rock in the core is very steep, and the weathering and erosion are mainly carried out along the joint surface of the rock.

2 The Triassic Yinkeng Formation has soft rock formations, poor corrosion resistance, and easy weathering, which is caused by lithological differences.

Similarly, due to the influence of multi-phase tectonic movement, its syncline shape is complex and variable, and is destroyed by many faults. In the turning point to the nuclear hill, it is affected by a right-shifting normal fault, and the Carboniferous strata are falling down, and the terrain is reversed to the east.

In particular, the secondary folds of the Pingdingshan syncline are extremely developed, mainly distributed in the area of ​​the Zizishan-Majiashan-Chaohu Cement Plant. The typical secondary folds are mainly the following three:

Cement plant fan anticline

It is located in the northwest direction of Chaohu Cement Plant and in the circular pit near the tilting end of Pingdingshan. The surrounding rock layers of the circular mining pit are all Triassic Nanlinghu Formation strata, and they are all inclined to the center of the pit. The core of the fan-shaped anticline is the lower strata of the Triassic Nanling Lake Formation. The two wings are the central and upper strata of the Nanling Lake Formation and the East Maanshan Formation. Its appearance is 280 ゚∠ 54 东 east, 135 ゚∠ 78 西 in the west wing, and 196 ゚∠ 41 转 in the turning end. On the east and west sides of the fan-shaped anticline, two small syncies with the Triassic Dongmaanshan Formation as the core are present and inverted. The Pingdingshan syncline hub has undulations from north to south, and the fan-shaped anticline appears. The hub is undulating and rolling.

According to the regional stress analysis, the formation of the fan-shaped anticline is caused by the Indosinian-Yanshan period, first north-south direction, and then east-west direction extrusion and transformation. The east and west sides of the fan-shaped anticline, especially the west side extrusion The characteristics are very obvious, the squeezing zone rock layer is intensified, the squeezing is elongated, and the sharp-edged pleats are extremely developed.

Located in the southwest corner of the Zizi Mountain. Its core is mainly composed of the East Ma'anshan Formation. The two wings are composed of the Longshan Formation. The transition from the east wing to the west wing is 254 ゚∠ 45 ゚, 200 ゚∠ 59 ゚, 146 ゚∠ 86 ゚. . At its turning end, since the pivot angle of the pivot is larger than the slope angle, the turning end of the small skew gives the illusion of the anticline.

Majiashan - Yanzishan inverted anticline

Located between Majiashan and Zizishan. The turning end of the secondary inverted fold is seen about 150 meters southeast of the Xiaozishan small syncline. It consists of the Triassic and Longshan limestones with a shape of 236 ゚∠48 ゚. The anticline has two wings: 209 ゚∠85 东 in the east wing and 254 ゚∠45 西 in the west wing.

According to the regional stress analysis, the formation of the fan-shaped anticline is caused by the Indosinian-Yanshan period, first north-south direction, and then east-west direction extrusion and transformation. The east and west sides of the fan-shaped anticline, especially the west side extrusion The characteristics are very obvious, the squeezing zone rock layer is intensified, the squeezing is elongated, and the sharp-edged pleats are extremely developed.

Located in the southwest corner of the Zizi Mountain. Its core is mainly composed of the East Ma'anshan Formation. The two wings are composed of the Longshan Formation. The transition from the east wing to the west wing is 254 ゚∠ 45 ゚, 200 ゚∠ 59 ゚, 146 ゚∠ 86 ゚. . At its turning end, since the pivot angle of the pivot is larger than the slope angle, the turning end of the small skew gives the illusion of the anticline.

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Majiashan - Yanzishan inverted anticline

Located between Majiashan and Zizishan. The turning end of the secondary inverted fold is seen about 150 meters southeast of the Xiaozishan small syncline. It consists of the Triassic and Longshan limestones with a shape of 236 ゚∠48 ゚. The anticline has two wings: 209 ゚∠85 东 in the east wing and 254 ゚∠45 西 in the west wing.

3. Yufu Da Cun syncline

Located in the eastern part of the area, it is distributed along the north-north-east direction in the area of ​​Mao Erdong-Dali Temple-Chongjing Village-Yufu Dacun. The scale is relatively large, and the overall tectonic line direction is nne-ssw. The slanting nucleus consists of the Permian Dalong Formation, Longtan Formation, Gufeng Formation and Qixia Formation. The two wings are respectively composed of the Carboniferous Chuanshan Formation, Huanglong Formation, Hezhou Formation, Gaochunshan Formation, Jinling Formation and Devonian Wutong Formation. And the Silurian system. The slant is affected by multi-phase tectonic activities. The slanting wing is nearly erect, partially inverted, and even distorted. Especially in its core, the Dalong Formation, Longtan Formation, Gufeng Formation and Qixia Formation are strongly wrinkled, and the hub ssw, The undulations, the axial surface nw-nww are inclined, and the inclination angle changes greatly. The slanting nne end is turned up in the north of the test knives. The ssw end is cut by the ew to the bridgehead set - the East Gate fracture and the dumping is terminated. According to the morphological characteristics of the different parts of the Yufu Dacun, it shows a sloping-deep-sloping sloping, upright asymmetrical sloping fold, the east wing is slow, the west wing is steep, and the whole is axial curved, the undulating slant of the hub The sloping secondary complex is skewed.

The observation point is the orphan core group, and the two-wing formation is from the Qixia Formation to the Wutong Formation from the new to the old, and the northwest wing formation is 152o.