Succession of Cambrian conodonts from South China

More than 4200 kg, the total weight, of 980 productive conodont samples mainly from four key sections in western Hunan and northwestern Hunan, South China have been processed. It is found that the paraconodonts occurring below Fengshanian (upper Upper Cambrian) may be used for stratigraphic subdivision and correlation. Accordingly, eight conodont zones ranging from upper Middle Cambrian to upper Upper Cambrian in South China are erected for the first time. The correlation between these zones and those of North China, North America and Iran is discussed. These eight zones are in ascending order as follows:Gapparodus bisulcatus-Westergaardodina brevidens zone, Shandongodus priscus-Hunano- gnathus tricuspidatus zone, Westergaardodina quadrata zone, Westergaardodina matsushitai-W. grandidens zone, Westergaardodina proligula zone, Westergaardodina cf. behrae-Prooneotodus rotundatus zone, Proconodontus zone, Cordylodus proavus zone.     

Two new species of Vestrogothia (Phosphatocopina, Crustacea) of Orsten-type preservation from the Upper Cambrian in western Hunan, South China

Although fossils of Orsten-type preservation represented by Skaracarida and Phosphatocopina were first reported from the Middle and Upper Cambrian in western Hunan, South China in 2005, diversified phosphatocopine species have never been appropriately described and elucidated in terms of their evolutionary relationships. Here, we described two new species of Phosphatocopina, Vestrogothia anterispinata sp. nov. and V. bispinata sp. nov. The evolutionary relationship among all the valid species of Phosphatoco...     

Cambrian integrative stratigraphy and timescale of China

The Cambrian Period is the first period of the Phanerozoic Eon and witnessed the explosive appearance of the metazoans, representing the beginning of the modern earth-life system characterized by animals in contrary to the Precambrian earth-life system dominated by microbial life. However, understanding Cambrian earth-life system evolution is hampered by regional and global stratigraphic correlations due to an incomplete chronostratigraphy and consequent absence of a highresolution timescale. Here we briefly review the historical narrative of the present international chronostratigraphic framework of the Cambrian System and summarize recent advances and problems of the undefined Cambrian stage GSSPs, in particular we challenge the global correlation of the GSSP for the Cambrian base, in addition to Cambrian chemostratigraphy and geochronology. Based on the recent advances of the international Cambrian chronostratigraphy, revisions to the Cambrian chronostratigraphy of China, which are largely based on the stratigraphic record of South China, are suggested, and the Xiaotanian Stage is newly proposed for the Cambrian Stage 2 of China. We further summarize the integrative stratigraphy of South China, North China and Tarim platforms respectively with an emphasis on the facies variations of the Precambrian-Cambrian boundary successions and problems for identification of the Cambrian base in the different facies and areas of China. Moreover, we discuss stratigraphic complications that are introduced by poorly fossiliferous dolomite successions in the upper Cambrian System which are widespread in South China, North China and Tarim platforms.     

Genesis and organic geochemical characteristics of the carbonaceous rock stratabound gold deposits, South China

The organic matter of three different chronological major carbonaceous rock gold-bearing formations of South China (Middle Proterozoic Shangqiaoshan group of northeastern Jiangxi, Lower Cambrian Shuikou group of northern Guangxi and Devonian Shetianqiao group of eastern Hunan) and related carbonaceous stratabound gold deposits such as Jinshan, Longshui and Shixia deposits, respectively, has been characterized by organic geochemical techniques. These organic geochemical results show that the average total organic carbon (TOC) content of the three chronological carbonaceous rock gold-bearing formations of South China ranges from 0.15% to 1.56%. The thermal maturity of the organic matter of host rocks in the three gold-bearing formations is high. The micro-component of the organic matter of the host rocks consists primarily of solid bitumen and graphite. The organic carbon and gold of the host rocks appear to syndepositin situ during the formation of the gold-bearing formations. The organic carbon played a certain role in controlling the geochemical environment of the gold-bearing formations. The metallogenetic mechanism of the carbonaceous rock stratabound gold deposits of South China is closely associated in genesis with the sedimentation, diagenesis and thermal evolution history of the organic matter of host rocks in the gold-bearing formations.     

Single zircon LA-ICPMS U-Pb dating of Weishan granite (Hunan, South China) and its petrogenetic significance

It is well-known that South China experienced suc- there are also the Indosinian granitoids in Jiangxi, cessively two important tectonic movements during Guangdong, Guangxi, Hainan and so on[4], most of Mesozoic time, i.e. Indosinian and Yanshanian move- them, in the mass, are fairly concentrated in Hunan ment[1], which yield widely-distributed granitoids and Province, in which the Indosinian granites outcrop abundant mineral resources[2]. Therefore, the geologic over an area of ca. 5000 k…     

Rhenium-osmium isotope constraints on the age and source of the platinum mineralization in the Lower Cambrian black rock series of Hunan-Guizhou provinces,China

The bottom of the Lower Cambrian series is an important bed typical of boundary event. The bed had been enriched with many useful elements such as Ni, Mo, Cu, Pb, Zn, Au, Ag, Ru, Rh, Pd, Os, Ir and Pt, many rare and dispersed elements such as Cd, Se, Tl, …     

Spatiotemporal variability of ocean chemistry in the early Cambrian,South China

Following the Ediacaran metazoan radiation, the “Cambrian Explosion” set up the major framework of todays’ animal phyla as well as modern marine ecosystem. Here, we present a preliminary investigation on the temporal and spatial (from shallow to deep waters) variations of the early Cambrian ocean chemistry in South China through analyzing a Fe-S-C systematic dataset integrated from literature. Our investigation indicates that the early Cambrian deep ocean in South China was still anoxic and Fe²⁺-enriched (i.e., ferruginous) although its surface was oxic, and in between a metastable euxinic (anoxic and sulfidic) water zone may have dynamically developed in anoxic shelf waters with an increasing weathering sulfate supply. Furthermore, accompanying marine transgression and regression cycles in the early Cambrian, such a “sandwich” structure in ocean redox chemistry demonstrates five evolutional stages, which can be well correlated to the spatiotemporal patterns of fossil records in South China. The good correlation between metazoan fossil occurrences and water chemistry in South China suggests that early animals possibly possessed ability to inhabit anoxic but generally not euxinic environments as free H₂S was fatal to most eukaryotes. This view can well explain why those small shell fauna and sponges disappeared from shelf to slope areas where sulfidic Ni-Mo-rich shales were widely deposited. Thus, we conclude that the spatiotemporal variations of ocean chemistry and its biological effects probably played a key role in the phased animal radiations and “extinctions” in the early Cambrian.     

Paleogeography of the North and South China blocks during the Cambrian

Paleomagnetic results demonstrate that during the Cambrian the South China block was close to the equator. We suggest that it was adjacent to North Australia. This reconstruction juxtaposes Cambrian marine basins in South China and Australia, explaining the affinity between Cambrian trilobites from the two areas, as well as the existence of phosphorite deposits in the Early and Middle Cambrian in Australia and in South China. The stratigraphic similarity between the late Precambrian Sinian System in South China and the Adelaide System in Australia, and the continuing fossil affinities from Cambrian through Ordovician of both areas suggest that the proposed geographic configuration lasted from the late Precambrian (800 Ma) to Early Ordovician (470 Ma). Paleomagnetic results from the Cambrian of North China indicate that it was in the southern hemisphere at that time. Based on the paleontological evidence, we suggest that the North China block was close to Tibet, Iran and northern India during the Paleozoic.     

Fossil nothofagaceous leaves from the Eocene of western Antarctica and their bearing on the origin, dispersal and systematics of Nothofagus

Fossil leaves resembling Nothofagaceae have been investigated from the Eocene of western Antarctica and a new form genus Nothofagofolia is proposed for these kinds of fossils. Some new specimens belonging to this form genus are described. They were collected from the Fossil Hill locality of Fildes Peninsula, King George Island, South Shetland Islands, western Antarctica. Two new species, two new combinations and an unnamed species are reported. A number of published Nothofagus leaf fossils from the same locality are discussed and revised. As a result of these studies of Nothofagus leaf morphology, we conclude that (1) Nothofagus probably originated in high latitudes of the Southern Hemisphere during the middle-late Late Cretaceous and diversified, dispersed gradually to the lower latitudes of the same hemisphere; (2) leaf morphological characters are significant for the systematics of the family Nothofagaceae, especially at the intrageneric level; and (3) extant species of Nothofagus known from southern temperate areas have more primitive leaf morphological characters and lower leaf ranks than those from tropical mountains as well as those of the Fagaceae and Betulaceae. Supported by the Foundation of State Key Laboratory of Palaeobiology & Stratigraphy, Nanjing Institute of Geology and Palaoentology, Chinese Academy of Sciences (Grant No. 013106), the National Natural Science Foundation of China (Grant No. 30670159) and the Fund of Innovation Program by Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences     

Paleomagnetism of the Lower Ordovician and Cambrian sedimentary rocks in the section of the Narva River right bank: For the construction of the Baltic Kinematic model in the Early Paleozoic

The paleomagnetic study of the Lower Ordovician and Cambrian sedimentary rocks exposed on the Narva River’s right bank revealed a multicomponent composition of natural remanent magnetization. Among four distinguished medium- and high-temperature magnetization components, the bipolar component, which carries the reversal test, is probably the primary component and reflects the geomagnetic field direction and variations during the Late Cambrian and Early Ordovician. The pole positions corresponding to this component have coordinates 22°N, 87°E (dp/dm = 5°/6°) for the Late Cambrian, and 18°N, 55°E (dp/dm = 5°/7°) for the Early Ordovician (Tremadocian and Arenigian). Together with the recently published paleomagnetic poles for the sections of the Early Ordovician in the Leningrad Region and the series of poles obtained when the Ordovician limestones were studied in Sweden, these poles form new key frameworks for the Upper Cambrian-Middle Ordovician segment of the apparent polar-wander path (APWP) for the Baltica. Based on these data, we propose a renewed version of the APWP segment: the model of the Baltica motion as its clockwise turn by 68° around the remote Euler pole. This motion around the great circle describes (with an error of A₉₅ = 10°) both variations in the Baltic position from 500 to 456 Ma ago in paleolatitude and its turn relative to paleomeridians. According to the monopolar components of natural remanent magnetization detected in the Narva rocks, the South Pole positions are 2°S, 351°E (dp/dm = 5°/9°), 39°S, 327°E, (dp/dm = 4°/7°), and 42°S and 311°E (dp/dm = 9°/13°). It is assumed that these components reflect regional remagnetization events in the Silurian, Late Permian, and Triassic.     

New observations on Vetulicola longbaoshanensis from the Lower Cambrian Guanshan Biota(Series 2, Stage 4), South China

Cambrian vetulicolians are enigmatic metazoans which play an important role in understanding the early animal evolution. Vetulicola longbaoshanensis Yang et al., 2010 is a unique species reported from the Guanshan Biota, Cambrian Series2, Stage 4 at eastern Yunnan, South China, which expands our understanding of vetulicolians. Here, new exceptionally preserved materials of V. longbaoshanensis from the Lower Cambrian Wulongqing Formation(which yields the so-called Guanshan Biota)in both Wuding and Kunming areas are described, in which the gill structures of V. longbaoshanensis are well preserved. The gill structures of our fossils are more complicated than those in the type species: the gill sac is gourd-shaped and can be divided into a smaller anterior part and a larger posterior part, prominent gill silt and dense gill filaments present in the joint of the two parts. Comparative analyses indicate that vetulicolians from the Guanshan Biota are similar to the Vetulicola rectangulata Luo et Hu, 1999 from the Chengjiang Biota in gross morphology. However, compared with the V. rectangulata, the Guanshan forms possess a larger body size, a higher length/height ratio of anterior body, and a higher ratio of gill sac width to anterior body height, probably typifying the derive characters anticipated of vetulicolians. These new materials, therefore, shed new light on our understanding of vetulicolians morphology and the early evolution of the gill structures.     

Assembly and dispersal of supercontinents: The view from Avalon

Recent models for the post-750 Ma Rodinian supercontinent dispersal (e.g. Hoffman, 1991) envision that cratons margined by Grenvillian belts, were reorganized before ca 540 Ma to form the Gondwanan supercontinent. Laurentia and Baltica distanced themselves from Gondwana by moving out of the Rodinian cratonal cluster. West Gondwana, of which Avalon was a part during the late Proterozoic to Cambrian cratonal assembly, consisted mainly of Africa and South America.The main geological evidence is presented for: (1) a transition from continental platform conditions to those of a subduction-related volcanic arc regime in Late Proterozoic time during the dispersal of the Rodinian supercontinent, and the resulting assembly of the Gondwanan supercontinent; and (2) a second transition that marked a reversal from the volcanic arc regime to marine platformal environments by early Cambrian time.Evidence for progressive instability of the continental shelf margining the Rodinian supercontinent is contained in late Proterozoic olistostromes, mylonite zones, calc-alkaline magmatism, and arc-derived clastic rocks, some being glacigenic, during three phases of the Avalonian orogeny.By early Cambrian time the reversal from a tectonically unstable volcanic arc regime to more stable platformal conditions took place as Avalon, Armorica and related microcontinental blocks rifted from Gondwana. These Gondwanan fragments sequentially come into collision, first with each other and Baltica, and then with Laurentia in Mid to Late Paleozoic time as Pangaea was being assembled.     

South China Sea

The South China Sea is poorly understood in terms of its marine biota, ecology and the human impacts upon it. What is known is most often contained in reports and workshop and conference documents that are not available to the wider scientific community. The South China Sea has an area of some 3.3 million km² and depths range from the shallowest coastal fringe to 5377 m in the Manila Trench. It is also studded with numerous islets, atolls and reefs many of which are just awash at low tide. It is largely confined within the Tropic of Cancer and, therefore, experiences a monsoonal climate being influenced by the Southwest Monsoon in summer and the Northeast Monsoon in winter. The South China Sea is a marginal sea and, therefore, largely surrounded by land. Countries that have a major influence on and claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have some too. The coastal fringes of the South China Sea are home to about 270 million people that have had some of the fastest developing and most vibrant economies on the globe. Consequently, anthropogenic impacts, such as over-exploitation of resources and pollution, are anticipated to be huge although, in reality, relatively little is known about them. The Indo-West Pacific biogeographic province, at the centre of which the South China Sea lies, is probably the world's most diverse shallow-water marine area. Of three major nearshore habitat types, i.e., coral reefs, mangroves and seagrasses, 45 mangrove species out of a global total of 51, most of the currently recognised 70 coral genera and 20 of 50 known seagrass species have been recorded from the South China Sea. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Conflicts have in recent decades arisen over them because of perceived national rights. It is perhaps because of this that so little research has been undertaken on the South China Sea. What data are available, however, and if Hong Kong is used, as it is herein, as an indicator of what the perturbations of other regional cities upon the South China Sea are like, then it is impacted grossly and an ecological disaster has probably already, but unknowingly, happened.     

Negative carbon isotopic excursion on the Lower/Middle Cambrian boundary of Kaili Formation,Taijiang County,Guizhou Province,China: Implications for mass extinction and stratigraphic division and correlation

The stratigraphic division and correlation of the Lower/Middle Cambrian boundary is a global problem that has not yet been solved even up to now. That is because there existed two distinctly different biogeographic regions during the Early and Middle Cambrian[1]—— the Indian-Pacific biogeographic region and the Atlantic biogeographic region. In the Atlantic biogeographic region the traditional Lower/Middle Cambrian boundary was marked by the extinction of Olenellids trilobite and the in…     

New stylophorans (Echinodermata) from the upper Cambrian of Guangxi,South China

This paper describes for the first time the cornute stylophorans (Echinodermata) in China. The new material came from the Guole Formation of the Furongian (Late Cambrian) in the Guole area of Jingxi, Guangxi Province, South China. These new cornute specimens are preserved in situ and found along with well-preserved trilobites and brachiopods. One new species, Phyllocystis jingxiensis sp. nov., is proposed to accommodate these unusual materials. The new species is defined by the small, heart-shaped theca with the frame composed of ten narrow, smooth and thick marginal plates, three adoral plates and distinctive zygal and aulacophore. Both supracentrals and infracentrals are polygonal-outlined. The marginal plate M1' on the inferior face extends posteriorly to form zygal that possesses a broadened proximal end and the proximal portion joining with the conjunction between M4 and M5 on the inferior face. Aulacophore comprises ten segments at its proximal part and is conical at the middle part (named stylocone). Its distal portion is rather long and bears conspicuous ambulacrum grooves. Tectals are horizontally arranged on superior face and obliquely arranged on inferior face. Both cothurnopore and anal pyramid are vaguely seen on the right anterior corner and the extremity of theca's superior face.     

New fossil eccoptarthrids (Coleoptera: Curculionoidea) from the Yixian Formation of western Liaoning, China

One new genus and three new species of the weevil family Eccoptarthridae (Curculionoidea), Leptocar polychaetus gen. et sp. nov., Abrocar macilentus sp. nov., Cretonanophyes punctatus sp. nov., are described and illustrated. They pertain to the Upper Jurassic or Lower Cretaceous Yixian Formation of western Liaoning Province, China. The host plants to the living eccoptarthrids and the floras in Yixian Formation indicate that those archaic eccoptarthrids possibly lived on conifers with a phylogenetic closeness to Cupressaceae. Besides, the early diversification of eccoptarthrids is discussed: origi- nated in Central or East Asia in the Late Jurassic, spread into Western Europe and South America during the Early Cretaceous, underwent a dramatic decline after the Early Cretaceous which likely was caused by competitive pressure and the displacement of their host plants.     

Paleomagnetic study of Cambrian Potsdam Group sandstones,St. Lawrence Lowlands,Quebec

We report paleomagnetic results from oriented drill core samples collected at 10 sites (80 samples) from the Covey Hill and 19 sites (96 samples) from the overlying, fossiliferous Cha?teauguay Formations of the gently dipping Late Cambrian Potsdam Group sandstones exposed in the St. Lawrence Lowlands of Quebec. Stepwise thermal demagnetization analyses ave revealed the presence of two predominant groups of coherent magnetizations C-1 and C-2, after simple correction for bedding tilt. The C-1 group magnetization is a stable direction (D=332°, I=+18°) with unblocking temperatures (T_UB) between 550 and 650°C, present in the older Covey Hill Formation; this direction is probably a chemical remanence acquired during the Covey Hill diagenesis and carried predominantly by hematite. The C-2 group magnetization (D=322°, I=+9°) is present at 13 sites of the younger Cha?teauguay Formation; this is probably carried by magnetite and represents a penecontemporaneous, depositional DRM, characterized by T_UB spectra 400–550°C. We believe that C-2 is relatively younger than C-1 based on a combination of arguments such as the presence of opposite polarities, internal consistency, similarity and common occurrence of C-1 and C-2 respectively in the Covey Hill and Cha?teauguay members. The corresponding paleomagnetic poles C-1 (46°N, 149°E; dp, dm=3°, 5°) and C-2 (37°N, 156°E; dp, dm=2°, 5°) are not significantly different from most of the other Late Cambrian (Dresbachian-Franconian) poles derived from sediments exposed in the southern region (Texas) of the North American craton which are also believed to have been deposited during Croixian Sauk sea transgression similar to the Potsdam sandstones. Although adequate faunal control is lacking (in particular for the Covey Hill Formation), this comparison with the Cratonic poles suggests a Late Cambrian age to the Potsdam poles. The agreement between the results also gives the evidence for internal consistency of cratonic poles at least for Late Cambrian.The incoherent C-3 group remanence (D=250°, I=?15°) is commonly present at 7 sites in both the formations; this may not correspond to a reliable paleomagnetic signal. The other remanence C-4 (D=180°, I=+10°) is found only at 3 sites located in the uppermost stratigraphic levels of the Cha?teauguay Formation; the corresponding paleomagnetic pole (40°N, 107°E) does not differ significantly from the Ordovician and some Late Cambrian poles. The present data are insufficient to resolve a problem in apparent polar wander for Middle and Late Cambrian time posed by the existence of high-latitude poles for some strata of Middle Cambrian age and low-latitude poles for some strata of Late Cambrian age.     

华南地区岩石圈电性特征及其地球动力学意义

岩石圈-软流圈界面（The Lithosphere-Asthenosphere Boundary,LAB）是地球内部主要界面之一.大地电磁测深（Magnetotelluric,MT）是研究地球壳幔电性结构最有效的方法,利用长周期大地电磁测深数据可以较好地探测LAB.在SinoProbe-01-03课题的资助下,首次获得了华南地区4°×4°网度的高质量大地电磁测深数据.利用一维奥卡姆（Occam）算法反演了MT阻抗的反对角线元素所计算出的平均视电阻率.根据一维地电结构可以将华南地区岩石圈划分为五种类型：以湖南邵阳和贵州施秉为代表的克拉通型,以四川达州和彭州及湖北荆门为代表的构造边界型,以浙江湖州和广东云浮为代表的岩石圈中等改造型,以江西赣州、广东揭阳及福建霞浦为代表的岩石圈强烈改造型,以湖北英山为代表的造山带型.除湖南邵阳、贵州施秉及广东揭阳外,华南地区岩石圈厚度为60~145 km.本文研究表明华南地区岩石圈显示出南北两侧上抬、中部下凹、东部受不均匀改造的趋势,这一结果与之前发表的文献所揭示的华南地区岩石圈东薄西厚的典型特征是不同的.研究结果反映华南地区岩石圈稳定性较好,晚中生代以来的构造伸展作用对岩石圈的改造程度有限,可能主要以不同形式的软流圈底辟为主.     

Paleomagnetic constraints on the tectonic history of the major blocks of China duing the Phanerozoic

Paleomagnetic study of China and its constraints on Asia tectonics has been a hot spot. Some new paleomagnetic data from three major blocks of China. North China Block (NCB), Yangtze Block (YZB) and Tarim Block (TRM) are first reported, and then available published Phanerozoic paleomagnetic poles from these blocks with the goal of placing constraints on the drift history and paleocontinental reconstruction are critically reviewed. It was found that all three major blocks were located at the mid-low latitude in the Southern Hemisphere during the Early Paleozoic. The NCB was probably independent in terms of dynamics. its drift history was dominant by latitudinal placement accompanying rotation in the Early Paleozoic. The YZB was close to Gondwanaland in Cambrian, and separated from Gondwanaland during the Late-Middle Ordovician. The TRM was part of Gondwanaland, and might be close to the YZB and Australia in the Early Paleozoic. Paleomagnetic data show that the TRM was separated from Gondwanaland during the Late-Middle Ordovician, and then drifted northward. The TRM was sutured to Siberia and Kazakstan blocks during the Permian, however, the composite Mongolia-NCB block did not collide with Siberia till Late Jurassic. During Late Permian to Late Triassic, the NCB and YZB were characterized by northern latitudinal placement and rotation on the pivot in the Dabie area. The NCB and YZB collided first in the eastern part where they were located at northern latitude of about 6°—8°, and a triangular oceanic basin remained in the Late Permian. The suturing zone was located at northern latitude of 25° where the two blocks collided at the western part in the Late Triassic. The collision between the two blocks propagated westward after the YZB rotated about 70° relative to the NCB during the Late Permian to Middle Jurassic. Then two blocks were northward drifting (about 5°) together with relative rotating and crust shortening. It was such scissors-like collision procedure that produced intensive compression in the eastern part of suturing zone between the NCB and YZB, in which continental crust subducted into the upper mantle in the Late Permian, and then the ultrahigh-pressure rocks extruded in the Late Triassic. Paleomagnetic data also indicate that three major blocks have been together clockwise rotating about 20° relative to present-day rotation axis since the Late Jurassic. It was proposed that Lahsa Block and India subcontinent successively northward subducted and collided with Eurasia or collision between Pacific/Philippines plates and Eurasia might be responsible for this clockwise rotating of Chinese continent.     

南海北部潮汕坳陷上白垩统盆地原型及其大地构造背景分析

潮汕坳陷MZ-1井揭示的中生界为深入分析南海北部晚中生代的构造演化提供了关键性的资料.基于MZ-1井的标定,开展了系统的地震剖面构造-地层解释,在中生代地层内识别出Tm30区域性不整合面,同位素定年确定该界面发育于早白垩世末至晚白垩世初,落实了潮汕坳陷上白垩统的分布.此外,在研究区西南部识别出大型的兴宁—东沙逆冲推覆带,主要由多条NW—SE向延伸、西倾的叠瓦状逆冲断层及其伴生的不对称褶皱组成,其明显控制了上白垩统厚度分布.由此可见,上白垩统构造层不具有张裂盆地的典型特征,因此南海北部主动陆缘向被动陆缘的转换不会早于晚白垩世末.研究认为,在南海地区特提斯残留洋盆关闭的总背景下,在约80 Ma时期,南海地块与华南陆块强烈碰撞挤压,在靠近碰撞带处的礼乐滩、潮汕坳陷西南部形成褶皱冲断构造体系,进而控制了潮汕坳陷晚白垩世周缘前陆盆地的发育.