長江上游年產泥沙5.12×105t，經宜昌輸入中游，長江中游干流及各支流年產沙約0.80×108t, 這兩部分中約1.24×108t沉積于中游河湖中，4.68×108t經大通輸入下游，沉淤于河道及長江三角洲或入海。長江中游的泥沙，總體是淤大于沖，但是沖淤的地理分布、時間段分布和河床斷面分布不均衡。長江干流的宜昌-城陵磯段、九江-大通段沖大于淤或沖淤平衡，淤積主要發生在長江干流以武漢為中心的螺山-武漢-黃石段以及洞庭湖區和鄱陽湖區。即使在主要淤積江段，也有局部時段和江段以沖刷為主。主泓所在河槽以沖刷為主，而河道兩側或河道之間的洲灘，則以淤為主，形成高而平的漫灘，往往被人為改造成圩垸。荊江以北的江漢平原因有大堤從長江隔開，只有漢水少量泥沙供應，沖淤量很小，再加上構造沉降的累計效應，其地面高程絕大部分低于干流洲灘數米，螺山-武漢-黃石段的淤積導致該段及以上江段洪水位抬高。 干流斷面沖槽淤灘使長江中游河道的典型形態呈深河谷、高漫灘，靠干堤保護堤內平原。這種斷面在洪水時成為在同等水量下，水位不斷抬高的原因。高水位要高堤來防堵，這就增加了堤防壓力、水頭壓力，容易導致管涌、滲漏等險情。堤外灘及洪水位與構造沉降的堤內平原間的高差不斷增大，三峽工程建成后，水庫攔沙及中游河道沖深，可使同流量下水位大幅度降低，但城陵磯-武漢段沖刷量很小，不能解決該段及以下江段的泥沙淤積問題，因此江漢平原因相對于洪水位地勢過低而造成的洪澇災害及相關環境問題，仍將是中游長遠的重大隱患。

本文根據古地理、古生物地理、古地磙、地球化學及火山巖工作成果，提出鎮安-淅川地塊是早古生代自南秦嶺裂離而較早縫合于北秦嶺南的一小型地塊、早古生代秦嶺是個多島小洋盆，具有包括鎮淅地塊在內的五列島嶼。由于揚子、華北板塊及其間列島的同向不等速漂移，導致了縫合過程不同于經典的板塊碰撞，這是特提斯多島洋盆縫合的一大特點，以此解釋東秦嶺加里東期“碰撞而不造山”的問題。

The base of bed 27c in the Meishan section Changxing County, Zhejiang Province, China, is recommended as GSSP for the basal boundary of the Triassic System. The Meishan section is easily accessible, well exposed, and records continuous marine sedimentation from the Changxingian(latest Permian) into the Early Triassic. The global boundary stratotype point is placed at the first occurrence of the conodont species Hindeodus parvus in the evolutionary lineage latidentatus-parvus-turgida-isarcica, which is transitional between Hindeodus and Isarcicella. Integrated stratigraphic study of the Meishan section includes radiometric dating, and chemo, sequence, eco, and event-stratigraphy. The latter involves the records of possible impact events as well as volcanic, anoxic, and transgressive events. The latter three studies have identified events the appear to be recorded on a pan-Tethyan or even a global scale.

Biostratigraphic correlation of the ten most important Permian-Triassic boundary sections throughout Tethys enables establishment of four conodont and ammonoid subdivisions within a stratigraphic interval, one to a few metres thick, representing less than I Ma. In ascending order, they are conodonts(Clarkina chargxingensis-C. deflecta Zone; Hindeodus typicalis Interval; Isarcicella parva Zone and I. isarcica Zone) and ammonoids(Pseudotirolites-Pleuronodoceras Zone, lower Otoceras Zonel, upper Otoceras Zone and Ophiceras Zone). Most of them can be traced to Notrh America and the Arctic region. Carbon isotope investigations of 24 sections along Tethys and in Greenland and Spitzbergen confirm the consistency of 813 C negative excursions at the Permian-Triassic boundary, together with an ineonsistent Ir anomaly. Eight sections show that in most cases there is a succession of: Ir anomaly (denoting the end-Permian catastrophic envirorment); 813C excursion (biomass loss, extinction); P/T boundary (origination of newcomers; potentially capable of intercontinental correlation within that short time interval). There is an intercontinental sequence boundary at the top of the Permian, and a transgressive surface at the P/T boundary followed shortly by a maximum flooding surface. An intercontinental anoxia event accompanied the transgression. Three delineations of the mass extinction phases and three population explosions have been recognized and can be more or less correlated in South China and the Southern Alps. Radiometric dating of the volcanogenic boundary clays of Meishan, Shangsi and the main-stage Siberian Tunguss Traps give an almost identical age of 250 Ma, thus implying a synchronous interregional volcanic event. There are a few palaeomagnetic transforms within the PTB strata. Thus, multidisciplinary research of the P/T boundary strata allows subdivision of this short interval into more than ten intercontinentally correlatable pars. Each subdivision averages less than 100ka in duration. This may be the highest resolution obtained so far in pre-Cretaceous rocks. High-frequency. Milankovitch-type cyclic deposits within the P/T boundary beds enable correlation of even higher resolution in the Lower Yangtze area. This high resolution is made possible because the P/T transition is a time of saltation and catastrophy in geological history. Causality of the aggregation of events merits further investigation.