Paleogeographic regionalization of Triassic seas based on conodontophorids

Geographic differentiation of conodontophorids between northern and southern latitudes commenced in the Triassic since the early Induan. Cosmopolitan long-lived genera of predominantly smooth morphotypes without sculpturing were characteristic of high-latitude basins of the Panboreal Superrealm. Since the early Olenekian until the Carnian inclusive, this superrealm consisted of the Siberian Realm that extended over Northeast Asia and the Canada-Svalbard Realm that included the Svalbard Archipelago and northern regions of Canada. Throughout the Triassic period, conodontophorids characteristic of the Tethys-Panthalassa Superrealm spanning the Tethys and low-latitude zones of the Pacific were highly endemic, very diverse in taxonomic aspect, having well-developed sculpturing and tempos of morphological transformations. Distinctions between the Early-Middle Triassic conodontophorids from northern and southern zones were not as great as afterward, and their impoverished assemblages from southern Tethyan basins were close in some respects to the Boreal ones. Their habitat basins of that time can be grouped into the Mediterranean-Pacific and India-Pakistan realms. Hence, the extent of geographic differentiation of conodontophorids was not constant and gradually grew, as their taxonomic diversity was reducing in northern basins but relatively increasing in southern ones. The Panboreal e Tethys-Panthalassa superrealms of conodontophorids, which are most clearly recognizable, are close to first-rank paleobiochores (superrealms) established earlier for ammonoids and bivalve mollusks. Main factor that controlled geographic differentiation of Triassic conodontophorids was climatic zoning. Initially lower diversity of southern Tethyan assemblages points probably to relatively cooler water regime in the peri-Gondwanan part of the Tethys. The established patterns in geographic distribution of conodontophorids characterize most likely the real trend of their differentiation and evolution, i.e., the distribution area contraction prior to complete extinction at the end of the Triassic     

Triassic ammonoids of Northeast Asia: Diversity and evolutionary stages

The history of Triassic ammonoids in the Siberian Province of the Boreal Paleobiogeographic Realm is recorded in detail in sections of Northeast Asia. In this region there are known at present 123 Triassic ammonoid genera of 41 family and 3 orders. Six stages and 14 substages are defined based on main levels of taxonomic restructuring of Triassic ammonoids, changes in their genera and families diversity, and changes in percentage of endemic and cosmopolitan taxa in assemblages. Each stage and substage is characterized by individual taxonomic composition of ammonoids, dominant groups, trends of changes in taxonomic diversity, and percentages of endemic and cosmopolitan taxa. Boundaries of ammonoid evolution stages coincide as a rule with boundaries of series and stages, whereas boundaries of evolutionary substages match those of substages. In the history of Triassic ammonoids of Northeast Asia, the periods of a rather monotonous fauna represented mainly by cosmopolitan or panboreal taxa (early Induan, early Olenekian, early Anisian, late Anisian, early Carnian, early and middle Norian) alternated with periods, typical of which were higher rates of taxa origination and endemism of ammonoids (late Induan, late Olenekian, middle Anisian, Ladinian, late Carnian). Changing degree of cosmopolitism and endemism of Triassic ammonoid faunas from Northeast Asia is shown to be connected with global eustatic sea-level fluctuations and climatic changes.     

中国及邻区石炭纪构造古地理及生物古地理

本文包括3部分:（1）扼要回顾了中国及邻区晚海西阶段的地质构造背景和构造古地理特征。根据全球构造活动论和地壳发展阶段论的观点,把中国及邻区晚海西阶段的大地构造单元分为4个构造域,10个亚构造域。（2）论述中国和世界石炭纪生物古地理分区。根据四射珊瑚和腕足动物群分析,把全球早石炭世生物古地理区系分为两个生物大区、6个生物区和8个生物亚区。在中国境内对生物亚区内部生物地方中心的分异作了进一步划分。（3）简述中国石炭纪古地理和某些有关的沉积矿产。中国石炭系矿产除了重要的煤以外,还有石膏矿、铝土矿和不同类型的铁矿。这些沉积矿产的分布主要受到古气候、古地理和构造条件的控制。     

内蒙占珠斯楞海尔罕地区中、晚泥盆世地层及四射珊瑚群的古地理意义

前人(张研等,1983)曾将珠斯愣海尔罕地区的泥岔系分为4个组:珠斯楞组、依克乌苏组、卧驼山组和西屏山组,分别属于埃姆斯期、艾菲尔期、吉维特期和弗拉斯期。本文描述了该区中、上泥盆统4个剖面,将其划分为4个沉积旋网,每个旋回构成一组,自下而上依次为依克乌苏组、卧驼山组、下西屏山组和上西屏山组。根据四射珊瑚组合和其它共生化石,把依克乌苏组上部到下西屏山组下部归入吉维持期,下西屏山组上部相上西屏山组的时代为弗拉斯期,木区缺乏法门期的沉积。 关于珠斯楞海尔罕地区所在的北方槽区泥盆纪的生物地理区系特征尚无统一认识。作者根据四射珊瑚动物群的地方性分子含量,Otsuka相似性系数和构造古地理,将中同泥岔纪的珊瑚分为3个大区:北方大区、北特提斯大区和南特提斯大区。这种划分方案也非常适用于吉维特期和弗拉斯期。 吉维持期到弗拉斯期,巴丹吉林区和扬子区珊瑚群的关系最为密切,与北天山——准噶尔区和内蒙古——兴安区共同的属很少。因此,广大的北方槽区属于两个不同的生物大区,北方大区和北特提斯大区,二者的界线是居延海——林西地壳对接带。这种认识与王鸿祯(1981)所划分的中国大地构造单元一致。     

Jurassic ammonite faunas from Nepal and their bearing on the palaeobiogeography of the Himalayan belt

From the Upper Bathonian up to the Tithonian–Berriasian, six main faunas and twelve basic faunal assemblages within them are distinguished in Nepal. The successive faunas show (1) low taxonomic diversity and (2) the dominance of a small number of genera and the subordinate place of the associated taxa.The assemblages include: (1) strictly Tethyan (e.g., Mediterranean or European Tethyan) species and/or genera, very few in number and occurring as isolated individuals or discontinuous faunal horizons; (2) Indo-Malagasian components, some scattered, others with a wide occurrence in the SW Pacific, some as far as Antarctica and/or Patagonia; (3) indigenous genera endemic for the Himalayas and the SW Pacific region. Faunas of the same age for the Sula Islands, Papua-New Guinea, Australia, New Zealand, Antarctica and South America are also considered.In spite of common components, the Himalayan faunas contrast with the relatively higher diversity of the Indo-Malagasian faunas. Low diversity and dominance of indigenous genera mean that the faunas extending from the Himalayas to Antarctica and Patagonia represent an actual biogeographical unit, the Indo Pacific (faunas and) Realm.Indo Pacific and Tethyan faunas show a less marked contrast than the Tethyan and Boreal. Transitional or mixed faunas of subaustral type developed in the Indo-Malagasian and Andean regions. This is explained by the absence of a geographical trap comparable to the land-locked palaeogeography of the Arctic Basin. The palaeogeography of the Arctic amplified the role of the other environmental factors. Among these the high latitude seasonal effects are likely to have resulted in environmental instability, controlling trophic resources and therefore the structure of the ecosystems, for instance low diversity and high density of the high latitude ammonite faunas.     

Tectonic and Hydrocarbon Accumulation Elements Characteristics of the Tethyan Realm in South China

Abstract: The evolution of the global Tethys Sea can be classified into three stages, Proto-Tethys, Paleo-Tethys and Neo-Tethys. The Tethyan realm has distinctive features of zonations and segmentations along north-south and east-west, respectively, and has variable richness in oil and gas. The petroleum geological conditions of Tethys are complicated, partly represented by multi-layer of source and seal rocks, and reservoirs. The hydrocarbon accumulation elements and periods of the Tethyan realm show gradually younger from west to east and north to south. South China is located in the north belt and Yangtze segment of the Tethyan realm, and its polycyclic tectonic movements were governed by the Tethyan and Pacific realms. The blocks in South China rotated clockwise and counter-clockwise during their drift northward from Gondwana. The belts and segmentations of Tethys in South China are also clear, with six tectonic belts including: Chuxiong-Sichuan; middle Guizhou-Hunan-Hubei; lower Yangtze; Xuefeng-Jiangnan; Guangxi-Hunan-Jiangxi; and Cathaysia. Numerous faults, including compressional, compressional-shear, extensional, extensional-shear and shear are well developed in South China. The fault strikes are mainly NE, NW and NS, in which the NE is the dominant direction. Lower, middle and upper hydrocarbon assemblages, respectively corresponding to Proto-, Paleo- and Neo-Tethys, formed in the Tethyan realm of South China with the lower and middle having excellent hydrocarbon accumulation conditions. An integrated analysis of tectonic evolution, superimposed deformation and later hydrocarbon preservation shows that during the Neo-Tethyan stage in South China, continental sediments were deposited and experienced intense tectonic deformation, which had resulted in different hydrocarbon pool-forming features from those of the Neo-Tethyan realm.     

Jurassic radiolarians and age of cherty rocks in the Povorotnyi Cape,the Taigonos Peninsula (northeast Russia)

Radiolaria-based dating of chert intercalations in basaltic sequences of ophiolitic associations, which are widespread in the west of circum-Pacific foldbelt being barren of macrofossils, is an important source of information about tectonic events and factors responsible for opening and destruction of basins floored by oceanic crust and for emplacement of relevant tectonic sheets into accretionary prisms and orogenic structures. Described in the work are the Middle (Bajocian-Callovian), Middle-Late (Callovian-Oxfordian) and Late Jurassic (Kimmeridgian-Tithonian) radiolarian assemblages. According to taxonomic composition and morphology of radiolarian tests, the first assemblage is of the North Tethyan type, while the other two are of the Boreal affinity.     

The problems of radiolarian-based dating of Jurassic-Cretaceous siliceous rocks from accretionary complexes,the Russian East

Radiolarians, which represent the most widespread fossil faunal group in jaspers and cherts, are the best tool for determining the geological age of Jurassic-Cretaceous volcanogenic-siliceous sequences in the Pacific margin of Russia, because they meet all the conditions required for orthostratigraphic groups, i.e., demonstrate rapid evolutionary changes of their assemblages, completeness of their record through the geological section, and a wide lateral distribution. The selection of biostratigraphic scales for determining the age of radiolarian assemblages is of principal significance. The significant difficulty in correlating Tethyan and Pacific assemblages is similar to that appearing in the case of the correlation between the Tethyan and Boreal ammonite standards. The existing discrepancies are explained by the different life spans of some guide species that determine the stratigraphic range of particular zones in their geographic type areas and may be different in other paleobiogeographic regions and provinces. The program of scientific studies should include the search for and thorough analysis of Jurassic-Cretaceous sections in Russia that contain simultaneously radiolarians, buchians, and ammonites. Such sections might provide the possibility for developing a single scale for the transitional sections and outlining ways for correlating the Tethyan and Pacific assemblages.     

The Roadian Stage of the Permian and problems of its global correlation

Ammonoids, conodonts, and fusulinids from the type sections of the Roadian and contiguous stages in western Texas and adjacent areas are analyzed and partially revised. Four successive Roadian ammonoid assemblages are distinguished and correlated with conodont zones; data on their distribution are presented. Based on the results obtained, the Roadian Stage is identified in the Boreal and Tethyan regions. Boundaries of the Roadian Stage defined accurately in the type sections of Texas are hardly recognizable elsewhere. Recognition of the upper boundary is especially difficult. Occurrence of Roadian fossils means that deposits of this age are present in a sequence, but they cannot be differentiated from underlying and overlying beds. Like in the type area, the stage lower boundary based on conodonts is above the level of significant changes in marine biota within the Boreal and Tethyan realms as well. The upper boundary is not marked by noticeable biotic events either. Correlation of the Roadian deposits is imprecise because their boundaries are formally established using distribution of relatively rare conodonts.     

Stratigraphic framework and calcareous nannofossil productivity of the Essaouira-Agadir Basin (Morocco) during the Aptian–Early Albian: Comparison with the north-Tethyan margin

In the southern Tethyan margin, the Essaouira-Agadir Basin (EAB), south of Morocco, exhibits well-exposed and fossiliferous sections of Aptian–Albian age. Biostratigraphy by ammonoids and sedimentological analysis have been realized for five sections located along an E-W transect in the EAB. The studied successions were dated from the latest Early Aptian to the Early Albian and are characterized by five major sedimentary discontinuities defining at least four main sedimentary sequences. The Late Aptian–Early Albian succession can be considered a gently westward-dipping ramp, marked by a deepening upward evolution. A quantitative study of calcareous nannofossils and calcium carbonate content has been performed on three of these sections. At this time, the EAB was located in the tropical-equatorial hot arid belt. The decrease in both calcium carbonate content and Nannoconus abundances at the Aptian–Albian transition could be the result of cooler climatic conditions recognized in the EAB, and/or of the associated increasing terrigenous input and nutrients, which hindered carbonate production. In the EAB, the nannofossil productivity is higher below the deposition of dark levels, which are coeval with the Niveau Paquier, recognized as the expression in southern France of the OAE 1b (Early Albian). During the Early Albian, the EAB was characterized by nannofossil fluxes two times lower than the upwelling-influenced Mazagan Plateau (southern Tethyan margin) and eight times lower than the Vocontian Basin (northern Tethyan margin). These results show that, with respect to the northern Tethyan margin, trophic conditions in sea surface waters of the pelagic realm of the southern Tethyan margin were lower. Comparable results obtained by Heldt et al. in the neritic realm of the southern Tethyan margin have been ascribed to more arid climatic conditions.     

Stratigraphy of the Bathonian-Callovian boundary deposits in the Prosek section (Middle Volga Region). Article 1. Ammonites and infrazonal biostratigraphy

In European Russia, the most complete succession of Boreal sediments of the terminal Bathonian and lower Callovian is exposed near the Prosek Settlement. After its revision, the infrazonal division of the upper Bathonian and lower Callovian and position of the Bathonian-Callovian boundary are difined more carefully. The Calyx Zone and bodylevskyi Biohorizon are established in the upper Bathonian. The base of the lower Callovian is defined at the first occurrence level of Macrocephalites jacquoti. Based on four successive ammonite assemblages occurring in lower part of the Elatmae Zone, the breve, frearsi, quenstedti, and elatmae biohorizons are identified. The joint occurrence of Boreal, Subboreal, and Tethyan ammonites in the section facilitate its correlation with the other sections of the Panboreal paleobiogeographic superrealm.     

Upper Triassic stratigraphy and paleobiogeography of Kotel’nyi Island (New Siberian Islands)

The thorough study of the Upper Triassic reference section located at the Tikhaya River in the central part of Kotel??nyi Island and characterized by uniform clayey lithology and containing diverse cephalopod, molluscan, and radiolarian assemblages made it possible to specify its structure and paleontological characteristic and establish for the first time the upper Anisian Sirenites yakutensis Zone. It is shown that different Late Triassic faunal groups are represented by mixed dominant Boreal and subordinate Tethyan elements. Such proportions are observable through the entire section beginning from the lower Carnian to upper Norian layers. The peculiar taxonomic composition of Late Triassic radiolarian and cephalopod assemblages provides grounds for attributing the region to an autonomous paleobiochore (New Siberian subprovince). The occurrence of both Siberian and Canadian elements in the Late Triassic faunas emphasizes the specific position of this paleobiochore determined by wide connections between basins at that time.     

The Early Jurassic to Aalenian paleobiogeography of the Arctic realm: Implication of microbenthos (Foraminifers and Ostracodes)

Stages in evolution of the Early Jurassic to Aalenian foraminifers and ostracodes are established based on the analyzed diversity dynamics of respective microfauna associations. Evolution of foraminifers is divided in two, the Hettangian-initial early Toarcian and the late early Toarcian-Aalenian stages, while the identical first stage in evolution of ostracodes has been followed by the late early Toarcian-Callovian stage. During the Jurassic, periodic migrations of foraminiferal and ostracod genera and species, which were interrelated with large transgressions and climatic changes, took place in the initial late and mid-late Pliensbachian, initial early Toarcian, and the late Toarcian-early Aalenian. Being isolated to the maximum extent in the second half of the late Aalenian, the Arctic basin lost connections with seas of northwestern Europe. The Early Jurassic to Aalenian biogeography of the Arctic basin is established based on the results of cluster analysis (group average link method, Jaccard coefficient, presence or absence of foraminifers and ostracodes genera) with due account for preceding and subsequent formation history of microbenthos structure in biochores. The distinguished biochores are ranked as realms and provinces of foraminifers and ostracodes. As is established, contours of the realms and provinces populated by different groups of microbenthos did not coincide and changed with time. Ecotones between the realms (e.g., the North Sea province) changed their localitization to be a part of the Arctic or Boreal Atlantic realms in different epochs. The Early-Middle Jurassic sedimentary successions of the Arctic basins reveal several levels of sharp taxonomic changes in composition of microbenthos under influence of the first-order abiotic factors.     

Fluid inclusions in sedimentary and diagenetic systems

Some of the major problems in sedimentary geology can be solved by using fluid inclusions in sedimentary and diagenetic minerals. Important fluids in the sedimentary realm include atmospheric gases, fresh water of meteoric origin, lake water, seawater, mixed water, evaporated water, formation waters deep in basins, oil, and natural gas. Preserving a record of the distribution and composition of these fluids from the past should contribute significantly to studies of paleoclimate and global-change research, is essential for improving understanding of diagenetic systems, and provides useful information in petroleum geology. Applications of fluid inclusions to sedimentary systems are not without their complexities. Some fluid inclusions exposed to natural conditions of increasing temperature may be altered by thermal reequilibration, which results in stretching, or leakage and refilling, of some fluid inclusions. Similarly, overheating in the laboratory can also cause reequilibration of fluid inclusions, so fluid inclusions from the sedimentary realm must be handled carefully and protected from overheating. Natural overheating of fluid inclusions must be evaluated through analysis of the most finely discriminated events of fluid inclusion entrapment, fluid inclusion assemblages (FIA). Consistency in homogenization temperatures within a fluid inclusion assemblage, consisting of variably sized and shaped inclusions, is the hallmark of a data set that has not been altered through thermal reequilibration. In contrast, fluid inclusion assemblages yielding variable data may have been altered through thermal reequilibration. If a fluid inclusion assemblage has not been altered by thermal reequilibration, its fluid inclusions may be useful as geothermometers for low- and high-temperature systems, or useful as geobarometers applicable throughout the sedimentary realm. If a fluid inclusion assemblage has been altered partially by thermal reequilibration, techniques for distinguishing between altered and unaltered fluid inclusions may be applied.

In studies of global change, fluid inclusions can be used as sensitive indicators of paleotemperature of surface environments. Fluid inclusions also preserve microsamples of ancient seawater and atmosphere, the analysis of which could figure prominently into discussions of past changes in chemistry of the atmosphere and oceans. In petroleum geology, fluid inclusions have proven to be useful indicators of migration pathways of hydrocarbons; they can delineate the evolution of the chemistry of hydrocarbons; and they remain important in understanding the thermal history of basins and relating fluid migration events to evolution of reservoir systems. In studies of diagenesis, fluid inclusions can be the most definitive record. Most diagenetic systems are closely linked to temperature and salinity of the fluid. Thus, fluid inclusions are sensitive indicators of diagenetic environments.     

MULTIPLE ISLAND ARC-BASIN SYSTEM AND ITS EVOLUTION IN GANGDISE TECTONIC BELT,TIBET

MULTIPLE ISLAND ARC-BASIN SYSTEM AND ITS EVOLUTION IN GANGDISE TECTONIC BELT,TIBET     

滇中地区上侏罗统叶肢介化石及其地层学意义

在回顾似东方叶肢介科(新科)Eosestlherlopseidae Niu(fam．nov．)内各属的特征、产出层位和分布的基础上，探讨了该科与真叶肢介科的亲缘关系，该科的起源，地层间的沉积间断和该科的迁移，以及Chuanjieestheria(gen．nov．)，Eosestheriopsis，Yunnanograpta(gen．nov．)等属在滇中上侏罗统中的层位演化关系，首次提出麻地山组至安宁组和蛇店组至妥甸组的时代可能为晚侏罗世早期的意见．大体可与中国北方土城子组对比。Eosestheriopsis群和Pseudograpta群分别为中国南方特提斯区和北方太平洋区2个不同生物地理区的产物。这些成果对中国陆相侏罗纪地层划分与对比、生物地理区及其变迁、古构造研究等，都具有理论意义和实际价值。文中还描述了叶肢介的一些新属种。     

Stratigraphy of the Lower Cretaceous Sediments from the Carpathian Bend Area, Romania

The Lower Cretaceous sediments of the Ceahl?u Nappe (from the bend region of the Romanian Carpathians) were investigated from lithological and micropaleontological (calcareous nannoplankton) points of view. Our investigations revealed that the studied deposits were sedimented within the latest Tithonian-Albian interval. The calcareous nannofossil assemblages of the turbidite calcareous successions (the Sinaia Formation) were assigned to the NJK-?NC5 calcareous nannofossil zones, which cover the Late Tithonian-Early Barremian interval. The sandy-shaly turbidites, which followed the calcareous turbidites of the Sinaia Formation, are Early Barremian-Early Albian in age (interval covered by the ?NC5-NC8 calcareous nannofossil zones). Because the studied deposited are mainly turbidites, many reworked nannofossils from older deposits are present in the calcareous nannofloras. Thus, some biozones (i.e., NC5), defined based on the last occurrences of nannofossils, could not be identified. The calcareous nannofossil assemblages are composed of Tethyan taxa (which dominate the nannofloras) and cosmopolitan taxa. During two intervals (the Late Valanginian and across the Barremian/Aptian boundary), Tethyan and cosmopolitan nannofossils, together with Boreal ones, were observed. This type of mixed calcareous nannoplankton assemblage is indicative for sea-level high-stand, which allows the nannofloral exchange between the Tethyan and Boreal realms, within the two-above mentioned intervals.     

黄土高原晚更新世的植被与气候环境

在被认为孢粉贫乏的黄土中分析出了大量孢粉,首次作出了黄土地层的孢粉浓度图式。根据10余个剖面上孢粉组合的变化,阐明了晚更新世的植被与气候在时间上演变与空间上分布的规律,证明了各地植被在时间上的演变韵律十分相似,说明它们同受全球气候变化的控制,但在同一时期各地植被不尽相同,此乃局部自然环境差异所致。根据植被变化重建了古气温曲线。      

Radiolarians from Upper Jurassic (Middle Oxfordian and Upper Kimmeridgian) deposits of Yaroslavl oblast

The middle Oxfordian and late Kimmeridgian radiolarian assemblages from Upper Jurassic deposits of Yaroslavl oblast are studied for the first time. The middle Oxfordian assemblage is dominated by stauraxonic morphotypes of genera Paronaella and Pseudocrucella occurring in association with discoid forms. Nassellarian radiolarians are very rare in this assemblage of extremely low taxonomic diversity, which is lacking spheroidal morphotypes. The late Kimmeridgian assemblage is more diverse in morphological and taxonomic aspects. It includes spheroidal forms, those of the family Pantanelliidae Pessagno inclusive, and more frequent nassellarian species, but stauraxonic radiolarians are less abundant in its composition. This assemblage is comparable to a considerable extent with the Kimmeridgian radiolarians from Moscow oblast, being of the South Boreal type according to its composition.     

Diversity of recent planktonic foraminifera in the southern Indian Ocean and Late Pleistocene paleotemperatures

Planktonic foraminiferal assemblages have been examined in 25 trigger core top samples and 51 piston core top samples collected between latitudes 28° S and 55° S and longitudes 79° E and 120° E from the southern Indian Ocean during cruises of the U.S.N.S. Eltanin. Samples taken from water depths exceeding 4000 m and/or showing evidence of calcium carbonate dissolution were eliminated from further analysis. The final piston core data set consists of 34 samples; the trigger core data set containing 21 samples. A close relationship exists between changes in the planktonic foraminiferal assemblages in the surface sediments and surface water temperatures. Species diversity values were computed for each of the core top assemblages using the Shannon-Wiener Index and the Brillouin Index, each of which takes into consideration the number of species and the proportionment of individuals among the species. The Shannon and Brillouin diversity values for all samples are positively correlated (correlation coefficient (r) = +.999). Regression analysis of latitude versus Shannon diversity values in the trigger core samples clearly shows a decrease in diversity with increasing latitude (r = ?.979). Furthermore, a strong correlation (r = +.977) exists between decreasing species diversity (Shannon) and decreasing average summer-winter temperature of the overlying surface waters. A paleotemperature equation derived from the relationship of diversity in trigger core samples and surface water temperature was used to generate paleotemperature curves for five trigger cores and a 6 m piston core of Late Pleistocene age, located beneath the present position of the Subtropical Convergence. A 7–8° C temperature range is suggested between the interglacial and glacial episodes in this Late Pleistocene sequence, and probably reflects latitudinal shifts of the Subtropical Convergence and Australasian Front during the Late Pleistocene.