Evolution of Quaternary Lithofacies, Ecology and Climate Environment

Due to the uplift of the crust at the end of Pliocene, the coastal area in southern Guangdong has been a weathering and denudation period since the early Pleistocene, which is called Weizhou weathering period. Late Early Pleistocene and Middle Pleistocene, Shikang weathering period and Haikou weathering period continued to appear. The successive appearance of weathering and denudation periods is not only restricted by regional crustal movement, but also mainly related to the sea level change affected by ice age. When the early Pleistocene in Shenzhen was equivalent to the Poyang Lake Ice Age, the sea level dropped, and it was generally rainy in the middle and low latitudes, with particularly strong erosion and accumulation, and the ground was leveled. During the Poyang Lake-Dagu Ice Age, the sea level rose, the flattening weakened, and the crustal movement rose, forming the thin lateritic weathering crust eluvial layer on the plateau (fourth-stage platform). Intermittent sea level fluctuation led to the formation of the weathering crust of the middle platform from the late Early Pleistocene to the Middle Pleistocene (Dagu Glacial Period and Dagu-Lushan Interglacial Period), and at the same time, some coastal and inland areas formed IV-level alluvial and diluvial terraces, and the middle Pleistocene alluvial and diluvial sediments found in Hong Kong were roughly formed during this period. From the late Late Pleistocene to the early Late Pleistocene (Lushan Glacial Period and Lushan-Dali Early Interglacial Period), the low sea level and crust continued to rise, and there was a convergence weathering period, forming a low platform (one or two platforms) weathering crust. The characteristics of weathered lithofacies forming the middle-low platform are the network residual of thick laterite weathering crust.

In the middle and early late Pleistocene (40,000 ~ 32,000 years ago), after the early interglacial period from Lushan to Dali, the sea level rose slightly, but it was still intermittent. At this time, lagoon facies deposits composed of sand, clay and peat began to appear in the coastal zone, and river alluvial facies composed of coarse sand, gravel and gravel developed well in the coastal zone, covering the underlying bedrock weathering crust with unconformity. The second-order terrace sedimentary facies with obvious binary structure in inland areas has also been formed. At this time, the dominant species of coastal hilly vegetation are conifers such as Castanopsis, Quercus, Pinus elliottii, Pinus thunbergii, Cycas, and Podocarpus in tropical and warm temperate zones, and the associated tropical plants are Palmae, Lauraceae, Elaeagnus and Moraceae. A small amount of mangrove pollen appeared, and a grass mangrove plant-halophyte grew around the swamp, indicating that it was influenced by seawater at that time and had the characteristics of river-sea interaction. The climate is hot and humid, and it is estimated that the annual average temperature is about 18 ~ 2 1℃. In the middle and late Late Pleistocene (32,000 ~ 22,000 years ago), transgression expanded and further evolved into marine-alluvial transition to coastal facies deposition, which was continuous with the underlying strata. Foraminifera containing marine micro-animals-Lepidoptera echinopods generally live in intertidal zones or estuaries and lagoons with water depths below 3.6m, and basically belong to estuaries and coastal species. At this time (about 30360a years ago), the south subtropical monsoon evergreen broad-leaved forest was dominated by evergreen oak, Castanopsis fargesii, Du Ying, Polypodiaceae and Cyatheaceae; Compared with the previous period, mangrove plants in coastal areas have increased, such as Kandelia candel, mangrove, Bruguiera gymnorrhiza and Paulownia. And a small number of sea mulberry and halophytes are high, reflecting the warm and humid coastal environment in the south subtropical zone, which may be the intertidal zone of mangrove. The late Late Pleistocene (22000 ~ 12000 a) ushered in the late Dali Glaciation, and the sea level began to decline again, and the river action was strengthened. The interbedding of coarse sand and silty clay at the bottom of the coast reflects the accumulation of fluvial facies and the continuous deposition with the underlying strata. At this time, with abundant rainfall and heavy rain in rainy season, the inland valley is easy to form II alluvial and diluvial terrace deposits. At this time, the climate basically changed from warm to cool. The uplift of the earth's crust led to the ritual and music weathering period at the end of the late Pleistocene, and the mottled variegated clay in this area represented the weathering product of low-sea red soil in the late Dali Glaciation.

In the early Holocene (12000 ~ 7500a), the sea level rose, and lenticular beach facies deposits such as argillaceous sand, gravel sand and round gravel appeared on the west coast, which were unconformity covered on the underlying late Pleistocene sediments. The vegetation in coastal mountainous areas is dominated by Castanopsis kawakamii, Quercus acutissima and Pinus koraiensis, and mixed with mushrooms, Hamamelidaceae, Euphorbiaceae, Rutaceae, Araliaceae, Alpinia, Ranunculaceae and so on. In addition, there are a small number of deciduous birch, alder and hornbeam. Beach plants such as mangroves and pitcher plants have appeared on the seashore. These vegetation plants are quite close to modern species, indicating that they have entered the Holocene. At this time, the river alluvial sediments in the coastal valley area contain freshwater species and brackish water species algae, which also shows the strengthening of river action and reflects that the sea level has begun to rise. At this time, the rainfall is still abundant, and the secondary alluvial-diluvial terrace deposits in inland valleys are still very developed. The climate is warm, hot and humid. It is estimated that the annual average temperature is about 19 ~ 22℃.

In the early Middle Holocene (7500 ~ 5000 years ago), the sea level continued to rise, and estuarine and coastal facies deposits containing shellfish rotten wood silt and silty silt were formed in the western coastal areas. Foraminifera are Bi Ke rotifers, rotifers, bread fish and five-flowered worms, which are continuously deposited with the underlying strata. In the lower reaches of rivers in coastal areas, alluvial deposits of silty fine sand and rotten wood silty fine sand were formed, which contained brackish water species and brackish water species algae, reflecting the environment strongly influenced by seawater at that time. Due to the influence of rainy season in inland areas, I-level alluvial-diluvial terrace facies deposits are often formed near river valleys. About 7080 years ago, evergreen oak, Castanopsis carlesii, mangrove, spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny spiny fern were the main beaches in the western coastal mountain plain. There are abundant mangrove plants on the seashore, such as paulownia, Kandelia candel, Bruguiera gymnorrhiza, mangrove, red olive, sea lily, sea lacquer, etc., and a small amount of sea mulberry, which reflects the hot and humid climate, but the temperature in the later period is lower than that in the previous period. About 6000a years ago was the peak period of transgression in this period, and the coastal sediments may reach the maximum range. At that time, wide beach sandbars were deposited in some bays in the eastern part of Shenzhen, which shaped the gravel coast of Dapeng Bay and Daya Bay. Freshwater streams often flow into the sea by the bay, and the more suitable climate environment provides a favorable place for the earliest human activities in this area. From the fact that only simple building foundations, scattered column holes, braised mounds and ash pits were found in the site of Xiantouling, it can be seen that the life style of ancestors basically belonged to primitive, scattered, seasonal mobile coastal settlements that lived by fishing and hunting. Judging from the cultural characteristics divided into one phase at this time, it is only found in painted pottery unearthed during the construction period. The painted patterns are different from Yangshao culture in the Central Plains and Fujian and Taiwan cultures. The most unearthed pottery with sand is characterized by uneven thickness, coarse sand, thick pottery, low temperature, fragility and common interlayer phenomenon. The decorative patterns are mainly string patterns and grate patterns, especially the shoulders of cans and pots are double-line arc grate patterns; There are few unearthed stone tools, such as scrapers and waist-shaped net pendants made of river pebbles, which all show some primitiveness and belong to the middle Neolithic age. In the late Middle Holocene (5,000-2,500 years ago), fine sand, silty sand and riparian deposits containing sandy silty sand with shells were continuously deposited in coastal areas, including Bi Ke rotifers, mesophilic rotifers, pentaphyllum hemiphyllum and other microorganisms. In the first stage (about 5,000 years ago), evergreen oak, Castanopsis fargesii, mangrove, pine, Polypodiaceae and Pteris. Compared with the early Middle Holocene, the number of coastal mangroves decreased slightly, while the number of conifers-pines increased, which also indicated that the temperature was low, the humidity was low, and the climate was cool and dry. In the second stage, evergreen oak, Castanopsis kawakamii, Du Ying, Gramineae, Cyperaceae, Polypodiaceae, Alsophila spinulosa, etc. Mainly growing in coastal mountainous areas, mangrove plants in coastal areas have increased compared with the first stage, including paulownia, red olive, Bruguiera gymnorrhiza, Kandelia candel, sea lily, sea paint and so on. And the climate is hot and humid. It can be seen that there are two stages: cooler, slightly dry, not too hot mangroves, wet and more mangroves. Corresponding to the climate environment in the first stage of this period, alluvial-diluvial facies (river terrace I) with gravel mixed with sand was formed in the coastal valley, which contained brackish water species and freshwater algae, and the function of seawater was weakened, which was also the reason for the decrease of coastal mangroves. About 5000 years ago, human activities in this area have been one step closer, which is temporarily called the second stage culture. From the eastern coast as the activity center, the first phase of culture gradually developed to the western coast (even now Neilingding Island), and the settlement sites gradually developed from coastal sand dunes to deep mountains, so primitive agriculture came into being. Pottery production in this period has adopted slow wheel processing, with regular shape and firing temperature above 800℃. The proportion of pottery with sand unearthed from Shaqiu site is relatively large, while that unearthed from Qiuqiu site is relatively small, which may be related to the serious rain erosion and the difficulty of sand inclusion preservation at that time. Most of the pottery with sand is cookware, utensils rack and stove. The color of pottery is mainly black, and the decorative pattern of grey sand pottery is mostly rope pattern, followed by basket pattern, sawtooth pattern, Yin Bei pattern and a small amount of Yun Leiwen and woven pattern. Shoulder stone tools are more common, grinding stone tools account for the absolute majority, and there are fewer tools for making natural stone materials. Most stone tools are well-made and have sharp blades. In addition, there are arrows and decorations that are difficult to make, such as rings and earrings. The second period of culture, from the appearance of geometric printed pottery to the more popular stage, lasted for a long time, inheriting the first period of culture, followed by the Bronze Age, which generally lasted until the Shang and Zhou Dynasties in the Central Plains. From the second-stage culture to the so-called third-stage culture, according to the analysis of the discovered sites, in addition to the original coastal settlements of ancestors, there are also valley plains or hilly areas in the western region, such as the middle and upper reaches of Xixiang River, the west side of Dasha River, the east of Guanlan River, Fenghuang Cave, Sungang Mountain and Gaotongling Mountain, which may be related to the expansion of agricultural activities at that time or the needs of war. The biggest feature of the third period culture is that the pottery-making technology has been greatly improved, and the fast wheel processing has been adopted, so that the quality of pottery is high and the firing temperature can reach1200℃; More than two patterns of Kuiwen-themed pottery patterns are widespread; The decorative patterns of pottery are similar to those of Shang and Zhou bronzes in the Central Plains. The printed geometric patterns are clear and tidy; It's a big shape. Glass-shaped yellow-green glaze appears on pots, beans and other utensils, which can be called Guangdong primitive porcelain. During this period, Kuiwen's pottery types were often accompanied by unearthed bronzes. Has entered the bronze age, which should be in the Spring and Autumn Period.

In the late Holocene (before the lower limit of 2500a), the western coast included a vast area where the lower reaches of rivers flowed into the sea, and a small amount of shell fragments, carbonaceous argillaceous materials or muddy gravel were formed in the lower part; The upper part is mainly sandy clay or mixed with argillaceous sand, which is a sea-river interaction deposit and covered by pseudo-conformity on the underlying sedimentary layer. Today, the area from Shajing in the northwest coast to Nantou was about 2500 ~ 1500 years ago, which was equivalent to the Jin Dynasty, and gradually silted up from the sea to the land. Vegetation growth and climate environment have changed many times. In the first stage (before 2500a), the evergreen broad-leaved forest-grassland vegetation is flourishing, the coastal mangrove plants are less than in the previous stage, and the effect of seawater is weakened. The increase of pine trees and Pteris Pteris reflects the warm and dry climate. In the second stage, mangroves grew along the coast, but due to the rapid withdrawal of seawater, the fern and herb communities growing in the plain area flourished and the climate was warm and dry. In the third stage, evergreen broad-leaved forest-grassland is mainly composed of evergreen oak, deciduous oak, mangrove, Gramineae, Cyperaceae, Polypodiaceae and Alsophila. Compared with the previous stage, mangrove plants have decreased, reflecting the warm, hot and humid climate. In the fourth stage (957 100) a, the composition of evergreen broad-leaved forest is reduced, human activities are gradually strengthened, farmland reclamation and grassland area are expanded, so that vegetation gradually changes to evergreen broad-leaved forest-grassland vegetation and evergreen broad-leaved coniferous mixed forest-secondary grassland vegetation, the number and area of coastal mangroves are further reduced, and the climate is warm and dry. Since 2250a, it has gradually entered the so-called IV culture, which is mainly characterized by the emergence of new types of utensils, such as urns, reeds, boxes, cups, conical pot-shaped ding and so on. In terms of ornamentation, in addition to the popular rice grain, the shoulder of the vessel is marked with double-line chords, and there are double-line continuous water ripples in the middle. The greatest feature of this period is the existence of bronzes and ironware, Kuiwen pottery and herringbone pottery. Some scholars believe that it may represent the end of the Bronze Age and the beginning of the Iron Age, and the relative age should be in the Warring States Period.