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四川盆地聚居(ju)著(zhu)四川省(sheng)和(he)重慶市大部分人(ren)口、居(ju)民主要為(wei)漢族巴蜀民系。是中國和(he)世界(jie)上人(ren)口最多的區(qu)域之一。
中國著名(ming)紅層盆地，中國各大(da)盆地中形(xing)態最(zui)(zui)典(dian)型、緯度(du)最(zui)(zui)南、海拔最(zui)(zui)低的盆地。位于長江上游地區，海拔500米左右，長江把(ba)它和(he)東海一脈相連，它是中國最(zui)(zui)大(da)的外流盆地。
四川(chuan)(chuan)盆(pen)(pen)地(di)(di)(di)的(de)面積約26萬余平方(fang)千米（面積是(shi)(shi)居第五第六位的(de)兩湖(hu)盆(pen)(pen)地(di)(di)(di)和銀額盆(pen)(pen)地(di)(di)(di)的(de)兩倍(bei)），占四川(chuan)(chuan)省面積的(de)46%。四川(chuan)(chuan)盆(pen)(pen)地(di)(di)(di)西(xi)依青藏(zang)高原(yuan)和橫斷山(shan)(shan)脈，北近秦巴山(shan)(shan)脈，與漢中(zhong)盆(pen)(pen)地(di)(di)(di)相(xiang)望，東(dong)(dong)接湘鄂西(xi)山(shan)(shan)地(di)(di)(di)，南連云(yun)貴高原(yuan)，盆(pen)(pen)地(di)(di)(di)北緣(yuan)(yuan)(yuan)(yuan)米倉山(shan)(shan)，南緣(yuan)(yuan)(yuan)(yuan)大(da)婁山(shan)(shan)，東(dong)(dong)緣(yuan)(yuan)(yuan)(yuan)巫(wu)山(shan)(shan)，西(xi)緣(yuan)(yuan)(yuan)(yuan)邛崍山(shan)(shan)，西(xi)北邊(bian)緣(yuan)(yuan)(yuan)(yuan)龍門山(shan)(shan)，東(dong)(dong)北邊(bian)緣(yuan)(yuan)(yuan)(yuan)大(da)巴山(shan)(shan)，西(xi)南邊(bian)緣(yuan)(yuan)(yuan)(yuan)大(da)涼山(shan)(shan)，東(dong)(dong)南邊(bian)緣(yuan)(yuan)(yuan)(yuan)相(xiang)望于武陵山(shan)(shan)。這(zhe)里(li)的(de)巖(yan)石，主要由(you)紫(zi)(zi)紅(hong)色(se)砂巖(yan)和頁巖(yan)組成。這(zhe)兩種巖(yan)石極(ji)易風化發育成紫(zi)(zi)色(se)土。紫(zi)(zi)色(se)土含有豐富的(de)鈣、磷、鉀等營養元素，是(shi)(shi)南方(fang)最肥沃的(de)自(zi)然土壤(rang)。四川(chuan)(chuan)盆(pen)(pen)地(di)(di)(di)是(shi)(shi)全國(guo)紫(zi)(zi)色(se)土分布(bu)最集(ji)中(zhong)的(de)地(di)(di)(di)方(fang)，向有“紫(zi)(zi)色(se)盆(pen)(pen)地(di)(di)(di)”的(de)美稱。四川(chuan)(chuan)盆(pen)(pen)地(di)(di)(di)底部(bu)面積約16萬多平方(fang)千米，按其地(di)(di)(di)理差異，自(zi)西(xi)向東(dong)(dong)又(you)可分為成都平原(yuan)、川(chuan)(chuan)中(zhong)丘陵和川(chuan)(chuan)東(dong)(dong)平行嶺谷(gu)三部(bu)分。成都平原(yuan)西(xi)方(fang)是(shi)(shi)龍門山(shan)(shan)脈，東(dong)(dong)方(fang)是(shi)(shi)龍泉山(shan)(shan)脈。
四川盆地(di)可明(ming)顯分(fen)為邊緣(yuan)山(shan)地(di)和(he)盆地(di)底(di)部兩大部分(fen)，其面積分(fen)別約為10萬多和(he)16多萬平方公里。邊緣(yuan)山(shan)地(di)多中山(shan)和(he)低山(shan)。
景觀各(ge)要素(su)過(guo)渡性(xing)明(ming)顯，如動植物組成上(shang)分別滲透了華(hua)中(zhong)區、西南區、青藏(zang)高原區和華(hua)北區的(de)成分。邊(bian)(bian)(bian)緣(yuan)山地(di)區從下而上(shang)一(yi)般具(ju)有2～5個垂直自然分帶。邊(bian)(bian)(bian)緣(yuan)山地(di)是(shi)四川多種經濟(ji)林(lin)木(mu)和用材(cai)林(lin)基地(di)。農業上(shang)水土流失較為嚴(yan)重。盆地(di)底(di)部(bu)多丘陵、低(di)山和平原。地(di)表組成物質新而單一(yi)，多砂(sha)泥巖與(yu)第四紀沉積(ji)物。氣候上(shang)屬中(zhong)亞熱帶，熱量(liang)遠比邊(bian)(bian)(bian)緣(yuan)山地(di)為高，但降水量(liang)不及邊(bian)(bian)(bian)緣(yuan)山地(di)。植被為人(ren)工的(de)次生林(lin)木(mu)所代替，覆被率低(di)，耕(geng)地(di)連片，夏伏旱和洪澇是(shi)這(zhe)一(yi)地(di)區最大災害(hai)。
盆(pen)地(di)(di)(di)內部地(di)(di)(di)形地(di)(di)(di)貌(mao)顯(xian)示出明顯(xian)的三分(fen)特點，即(ji)盆(pen)西平原地(di)(di)(di)貌(mao)、盆(pen)中丘陵地(di)(di)(di)貌(mao)和(he)盆(pen)東山地(di)(di)(di)地(di)(di)(di)貌(mao)，三者(zhe)以龍泉山和(he)華鎣山為界。
四(si)川盆地(di)其輪廓形(xing)態總體近似(si)長方形(xing)，形(xing)似(si)信封狀，右傾斜(xie)置(zhi)在(zai)亞(ya)洲大陸，因此被地(di)理學者稱之為信封盆地(di)。信封盆地(di)東部(bu)(bu)頂(ding)點(dian)(dian)(dian)云陽（靠近萬州），南(nan)(nan)部(bu)(bu)頂(ding)點(dian)(dian)(dian)敘永(靠近遵義)，西部(bu)(bu)頂(ding)點(dian)(dian)(dian)雅安，北部(bu)(bu)頂(ding)點(dian)(dian)(dian)廣元。信封盆地(di)幾何中(zhong)(zhong)心城市遂寧（幾何中(zhong)(zhong)心點(dian)(dian)(dian)大致在(zai)蓬(peng)溪南(nan)(nan)部(bu)(bu)地(di)區），中(zhong)(zhong)北部(bu)(bu)（內(nei)頂(ding)角）中(zhong)(zhong)心城市南(nan)(nan)充，中(zhong)(zhong)南(nan)(nan)部(bu)(bu)內(nei)頂(ding)角安岳。
四川盆地(di)西部的成(cheng)都和東南部的重(zhong)慶皆為國家中心城市。
四川盆地由盆周山(shan)地和盆地底部構成。
盆周東部(bu)(bu)為長(chang)江三峽(xia)，南部(bu)(bu)為云貴高原，西部(bu)(bu)為青(qing)藏高原，北部(bu)(bu)為大巴(ba)山。
盆(pen)地(di)底部主要分為川(chuan)東(dong)平(ping)行嶺(ling)(ling)谷(gu)、川(chuan)中(zhong)丘陵和川(chuan)西成都平(ping)原三部分。龍泉山(shan)(shan)是成都平(ping)原和川(chuan)中(zhong)丘陵的界山(shan)(shan)，華(hua)鎣(ying)山(shan)(shan)是川(chuan)中(zhong)丘陵和川(chuan)東(dong)平(ping)行嶺(ling)(ling)谷(gu)的界山(shan)(shan)。
（1）在龍泉山(shan)和龍門山(shan)、邛崍(lai)山(shan)之(zhi)間的盆(pen)西平(ping)原(yuan)，系(xi)(xi)斷(duan)裂下陷由(you)岷江(jiang)(jiang)水系(xi)(xi)的河流沖積(ji)而(er)成(cheng)(cheng)，面積(ji)約8000平(ping)方千米，為我國西南最大的平(ping)原(yuan)，因成(cheng)(cheng)都位于(yu)平(ping)原(yuan)之(zhi)中， 故稱成(cheng)(cheng)都平(ping)原(yuan)。成(cheng)(cheng)都平(ping)原(yuan)海拔460米～750米，地勢由(you)西北向(xiang)東(dong)南傾斜，地表平(ping)坦，相對高差一般(ban)不超過(guo)30米～50米，它由(you)岷江(jiang)(jiang)、沱(tuo)江(jiang)(jiang)、涪(fu)江(jiang)(jiang)、青衣江(jiang)(jiang)等八(ba)條河流沖積(ji)聯綴而(er)成(cheng)(cheng)，土壤肥沃，河渠稠密，有著名的都江(jiang)(jiang)堰自流灌溉，自古以來素有“天(tian)府(fu)”之(zhi)稱。
（2）在(zai)龍泉山和華(hua)鎣山之間的(de)盆中丘陵，地(di)(di)勢低矮，海拔大多(duo)在(zai)300米(mi)～500米(mi)之間，相(xiang)對高(gao)差50米(mi)～150米(mi)，地(di)(di)勢由北向南傾斜(xie)，巖層(ceng)近于水(shui)平(ping)，在(zai)流水(shui)的(de)長期侵蝕切割作用下，形成(cheng)臺階狀的(de)方山丘陵，南部(bu)多(duo)淺丘，北部(bu)多(duo)深丘。丘陵地(di)(di)表軟硬相(xiang)間的(de)紫紅(hong)色砂、頁(ye)巖極(ji)易風化為紫色土，富(fu)含磷鉀，自然肥力較高(gao)，宜種性廣，是四川(chuan)全省糧食(shi)、經濟作物主(zhu)產區。
（3）華(hua)鎣山(shan)以東(dong)為盆(pen)東(dong)平(ping)(ping)行嶺(ling)(ling)谷區，由(you)多條近東(dong)北西(xi)南走向的(de)(de)條狀背斜山(shan)地(di)與向斜寬谷組成，山(shan)地(di)陡而窄，高(gao)700米(mi)(mi)-1000米(mi)(mi)，其中，華(hua)鎣山(shan)高(gao)1705米(mi)(mi)，為盆(pen)地(di)底部(bu)最高(gao)峰。山(shan)地(di)頂部(bu)的(de)(de)石灰(hui)巖被雨(yu)水溶蝕后，常(chang)成凹槽，故山(shan)地(di)大多具(ju)有(you)“一(yi)山(shan)二嶺(ling)(ling)一(yi)槽”或“一(yi)山(shan)三嶺(ling)(ling)二槽”的(de)(de)特(te)色。山(shan)嶺(ling)(ling)間的(de)(de)谷地(di)寬而緩，海拔300米(mi)(mi)～500米(mi)(mi)，其間丘陵、平(ping)(ping)壩交錯分布，是平(ping)(ping)行嶺(ling)(ling)谷區工農業(ye)生產主要地(di)區。
四川盆地邊緣山地區屬強(qiang)烈上升的褶(zhe)皺(zhou)帶。
地貌(mao)顯著特征是，海拔(ba)較高(gao)(gao)(gao)，過渡性明顯，均為一系(xi)列中山(shan)(shan)和低山(shan)(shan)所圍(wei)繞。盆地北緣(yuan)米(mi)倉山(shan)(shan)、大巴山(shan)(shan)近東西走(zou)向，是秦(qin)巴山(shan)(shan)地南(nan)翼部分，海拔(ba)一般在1500米(mi)～2200米(mi)之間，山(shan)(shan)勢(shi)雄(xiong)偉，山(shan)(shan)坡(po)陡(dou)峭，溝谷深切，相對(dui)高(gao)(gao)(gao)差(cha)可達(da)500米(mi)～1000米(mi)；南(nan)緣(yuan)大婁山(shan)(shan)屬(shu)氣(qi)勢(shi)磅(bang)礴的(de)云貴高(gao)(gao)(gao)原(yuan)之一部分；西緣(yuan)有龍門山(shan)(shan)、邛崍(lai)山(shan)(shan)、峨眉山(shan)(shan)，山(shan)(shan)脊海拔(ba)都在1500米(mi)至～3000米(mi)以(yi)上，相對(dui)高(gao)(gao)(gao)差(cha)可達(da)1000米(mi)，屬(shu)中國地勢(shi)第一級階(jie)梯。峨眉山(shan)(shan)頂峰高(gao)(gao)(gao)3099米(mi)，與(yu)附近的(de)平原(yuan)相對(dui)高(gao)(gao)(gao)差(cha)達(da)2660米(mi)，山(shan)(shan)勢(shi)巍(wei)峨秀(xiu)麗，為中國四大佛教名(ming)山(shan)(shan)之一。
四周為海拔2000～3000米(mi)的山脈和高原所(suo)環繞(rao)，北(bei)面(mian)(mian)是大巴山、米(mi)倉山、龍門山，西面(mian)(mian)是青藏高原邊緣的邛崍山、大涼山，南面(mian)(mian)是大婁(lou)山，東面(mian)(mian)是巫山。
無論從(cong)構造還是(shi)人地(di)(di)貌上看(kan)，四(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)都是(shi)一(yi)個典(dian)型的(de)(de)(de)(de)(de)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)。它從(cong)震旦紀以來就是(shi)地(di)(di)殼比較穩定(ding)的(de)(de)(de)(de)(de)大型拗陷(xian)(xian)區(qu)(qu)。晚(wan)三(san)迭紀的(de)(de)(de)(de)(de)印支運動中(zhong)成為(wei)(wei)(wei)一(yi)個內(nei)陸湖(hu)盆(pen)(pen)(pen)(pen)(pen)(pen)，但范圍要比今日的(de)(de)(de)(de)(de)四(si)川(chuan)(chuan)大得多，中(zhong)生(sheng)(sheng)(sheng)代(dai)(dai)堆積(ji)了厚達3000～4000米(mi)的(de)(de)(de)(de)(de)紫紅色的(de)(de)(de)(de)(de)砂巖(yan)和(he)頁(ye)巖(yan)，因此(ci)人們又稱它為(wei)(wei)(wei)“紅色盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)”或(huo)“紫色盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)”。中(zhong)生(sheng)(sheng)(sheng)代(dai)(dai)末(mo)期的(de)(de)(de)(de)(de)四(si)川(chuan)(chuan)運動使(shi)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)周圍褶皺成山(shan)，中(zhong)間相對下(xia)(xia)陷(xian)(xian)，輪廓基本形(xing)成，盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)內(nei)部(bu)地(di)(di)層也(ye)發生(sheng)(sheng)(sheng)大規模的(de)(de)(de)(de)(de)變(bian)形(xing)。東部(bu)出現一(yi)組北(bei)東向的(de)(de)(de)(de)(de)褶皺，稱盆(pen)(pen)(pen)(pen)(pen)(pen)東褶皺帶；中(zhong)部(bu)形(xing)成穹(qiong)窿構造，稱盆(pen)(pen)(pen)(pen)(pen)(pen)中(zhong)穹(qiong)窿帶；西部(bu)表現成為(wei)(wei)(wei)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)沉陷(xian)(xian)帶，為(wei)(wei)(wei)今天盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)的(de)(de)(de)(de)(de)三(san)個地(di)(di)貌區(qu)(qu)奠(dian)定(ding)了基礎。新生(sheng)(sheng)(sheng)代(dai)(dai)的(de)(de)(de)(de)(de)喜馬拉雅(ya)運動使(shi)周圍山(shan)地(di)(di)再次上升，盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)再次相對下(xia)(xia)陷(xian)(xian)， 成都一(yi)帶下(xia)(xia)陷(xian)(xian)更深。同(tong)時，長江(jiang)切穿巫山(shan)，滾滾東流(liu)，完成了統一(yi)的(de)(de)(de)(de)(de)長江(jiang)水系，使(shi)內(nei)流(liu)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)轉變(bian)為(wei)(wei)(wei)外(wai)流(liu)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)。四(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)可明(ming)顯(xian)分為(wei)(wei)(wei)邊緣山(shan)地(di)(di)和(he)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)底部(bu)兩大部(bu)分，其面積(ji)分別約為(wei)(wei)(wei)10萬(wan)多和(he)16萬(wan)多平方千米(mi)。 四(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)是(shi)我國最大的(de)(de)(de)(de)(de)外(wai)流(liu)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)，面積(ji)26萬(wan)多平方千米(mi)。四(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)內(nei)部(bu)丘(qiu)陵(ling)、平原交錯，地(di)(di)勢北(bei)高南低。由于地(di)(di)表形(xing)態的(de)(de)(de)(de)(de)不同(tong)，以華鎣山(shan)、龍泉山(shan)為(wei)(wei)(wei)界。
盆底可分為三部分：
①華鎣山以東(dong)(dong)為大(da)致平行的川東(dong)(dong)嶺谷(gu)，由東(dong)(dong)北(bei)—西南走向的許多條狀山體組(zu)成，海拔(ba)一般在(zai)700～800米(mi)，谷(gu)地(di)中(zhong)多低丘與平壩，海拔(ba)200～500米(mi)，是川東(dong)(dong)農業和(he)人口集中(zhong)的地(di)方。
②華鎣(ying)山(shan)(shan)和龍泉山(shan)(shan)之(zhi)間為方(fang)(fang)山(shan)(shan)丘(qiu)陵，即(ji)川中丘(qiu)陵。區(qu)內由于紫(zi)紅色砂頁巖傾(qing)角平緩(huan)，受切割后形成(cheng)大片方(fang)(fang)山(shan)(shan)式(shi)丘(qiu)陵。海拔350～450米，相(xiang)對(dui)高(gao)度幾十(shi)米。當地(di)勞(lao)動人民利用(yong)方(fang)(fang)山(shan)(shan)山(shan)(shan)丘(qiu)土層深厚的特點，把梯田一(yi)直修到山(shan)(shan)頂。
③龍(long)泉山以西(xi)(xi)為平(ping)(ping)原(yuan)(yuan)。稱為川(chuan)西(xi)(xi)平(ping)(ping)原(yuan)(yuan)或成都平(ping)(ping)原(yuan)(yuan)，面積6000多平(ping)(ping)方千米，是(shi)四川(chuan)盆地(di)最(zui)大(da)的平(ping)(ping)原(yuan)(yuan)，也是(shi)西(xi)(xi)南(nan)地(di)區最(zui)大(da)的平(ping)(ping)原(yuan)(yuan)，海拔約600米。
四(si)(si)(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)屬揚子準地(di)(di)(di)(di)(di)(di)(di)(di)(di)臺(tai)四(si)(si)(si)川(chuan)(chuan)臺(tai)坳。古生(sheng)(sheng)代(dai)(dai)(dai)時(shi)相(xiang)對隆起，缺乏泥盆(pen)(pen)(pen)(pen)系和石(shi)(shi)(shi)炭(tan)系。印支運(yun)(yun)動轉(zhuan)換(huan)為(wei)大型拗陷，晚燕山(shan)(shan)(shan)運(yun)(yun)動，特別是(shi)喜(xi)馬拉(la)雅運(yun)(yun)動后發生(sheng)(sheng)褶皺(zhou)隆起。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)的格局主(zhu)要受北(bei)(bei)東—南(nan)(nan)西(xi)(xi)向及(ji)北(bei)(bei)西(xi)(xi)向兩條構(gou)造線(xian)(xian)(xian)控(kong)制，構(gou)成了(le)(le)典型的菱(ling)形(xing)(xing)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)，四(si)(si)(si)川(chuan)(chuan)廣元、四(si)(si)(si)川(chuan)(chuan)雅安、四(si)(si)(si)川(chuan)(chuan)敘(xu)永(yong)為(wei)菱(ling)形(xing)(xing)的四(si)(si)(si)頂點，東西(xi)(xi)兩邊稍長(chang)，為(wei)380～430公里(li)，南(nan)(nan)北(bei)(bei)兩邊略短(duan)，為(wei)310～330公里(li)。以(yi)(yi)上(shang)(shang)菱(ling)形(xing)(xing)四(si)(si)(si)頂點的連線(xian)(xian)(xian)與(yu)(yu)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)內(nei)650～750米(mi)(mi)(mi)的等(deng)(deng)(deng)高(gao)線(xian)(xian)(xian)大體相(xiang)當，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)底部(bu)與(yu)(yu)邊緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)(di)(di)(di)(di)也以(yi)(yi)此(ci)為(wei)分(fen)(fen)界。四(si)(si)(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)在(zai)距今1.4億(yi)年以(yi)(yi)前(qian)，還是(shi)內(nei)陸湖(hu)盆(pen)(pen)(pen)(pen)。至距今6.6千萬年時(shi)，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)邊緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)(di)(di)(di)(di)迅速(su)隆升，長(chang)江中上(shang)(shang)游水(shui)系開始溝通。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)內(nei)湖(hu)水(shui)東瀉奠定了(le)(le)現今之(zhi)地(di)(di)(di)(di)(di)(di)(di)(di)(di)貌形(xing)(xing)態(tai)。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)邊緣(yuan)多(duo)低山(shan)(shan)(shan)和中山(shan)(shan)(shan)，山(shan)(shan)(shan)勢(shi)陡峻，發源盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)邊緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)(di)(di)(di)(di)的河流大多(duo)為(wei)“V”型谷，嶺谷高(gao)差都逾(yu)500～1 000米(mi)(mi)(mi)， 地(di)(di)(di)(di)(di)(di)(di)(di)(di)表崎嶇，故歷(li)史上(shang)(shang)就(jiu)有“蜀道(dao)難(nan)(nan)，難(nan)(nan)于上(shang)(shang)青(qing)天(tian)”之(zhi)說(shuo)。山(shan)(shan)(shan)脊海(hai)拔大多(duo)在(zai)2000～3000米(mi)(mi)(mi)，西(xi)(xi)北(bei)(bei)部(bu)與(yu)(yu)西(xi)(xi)部(bu)可(ke)超過3000～4000米(mi)(mi)(mi)，如龍門山(shan)(shan)(shan)4984米(mi)(mi)(mi)，峨(e)(e)眉(mei)山(shan)(shan)(shan)3099米(mi)(mi)(mi)，小(xiao)相(xiang)嶺4 791米(mi)(mi)(mi)。地(di)(di)(di)(di)(di)(di)(di)(di)(di)表廣泛出露古生(sheng)(sheng)代(dai)(dai)(dai)及(ji)其以(yi)(yi)前(qian)的石(shi)(shi)(shi)灰(hui)巖(yan)(yan)，其次為(wei)板巖(yan)(yan)、片(pian)巖(yan)(yan)、結晶灰(hui)巖(yan)(yan)、石(shi)(shi)(shi)英巖(yan)(yan)、砂(sha)泥巖(yan)(yan)和礫巖(yan)(yan)，局部(bu)有花(hua)崗(gang)巖(yan)(yan)和玄(xuan)武(wu)巖(yan)(yan)。石(shi)(shi)(shi)灰(hui)巖(yan)(yan)分(fen)(fen)布(bu)區可(ke)見石(shi)(shi)(shi)林(lin)(lin)、溶洞、暗河、槽谷等(deng)(deng)(deng)喀斯特地(di)(di)(di)(di)(di)(di)(di)(di)(di)貌，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)南(nan)(nan)緣(yuan)興文縣(xian)素有“石(shi)(shi)(shi)林(lin)(lin)洞鄉(xiang)”之(zhi)稱（見興文石(shi)(shi)(shi)林(lin)(lin)）。巫山(shan)(shan)(shan)十二峰和金佛(fo)山(shan)(shan)(shan)等(deng)(deng)(deng)名山(shan)(shan)(shan)主(zhu)要也由(you)(you)石(shi)(shi)(shi)灰(hui)巖(yan)(yan)發育(yu)而(er)成。由(you)(you)石(shi)(shi)(shi)灰(hui)巖(yan)(yan)、玄(xuan)武(wu)巖(yan)(yan)、花(hua)崗(gang)巖(yan)(yan)等(deng)(deng)(deng)組成的峨(e)(e)眉(mei)山(shan)(shan)(shan)及(ji)由(you)(you)砂(sha)泥巖(yan)(yan)、礫巖(yan)(yan)組成的青(qing)城山(shan)(shan)(shan)，素有“峨(e)(e)眉(mei)天(tian)下秀(xiu)”、“青(qing)城天(tian)下幽”之(zhi)稱，為(wei)中國著名游覽(lan)勝地(di)(di)(di)(di)(di)(di)(di)(di)(di)。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)底部(bu)海(hai)拔多(duo)數在(zai)250～700米(mi)(mi)(mi)，地(di)(di)(di)(di)(di)(di)(di)(di)(di)勢(shi)東南(nan)(nan)傾，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)內(nei)各河流均由(you)(you)邊緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)(di)(di)(di)(di)匯聚盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)底部(bu)的長(chang)江干流，形(xing)(xing)成向心狀水(shui)系。地(di)(di)(di)(di)(di)(di)(di)(di)(di)表為(wei)大面積的中生(sheng)(sheng)代(dai)(dai)(dai)紫紅(hong)色砂(sha)巖(yan)(yan)與(yu)(yu)泥巖(yan)(yan)所覆蓋，故稱為(wei)“紅(hong)層(ceng)(ceng)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)”，是(shi)中國中生(sheng)(sheng)代(dai)(dai)(dai)陸相(xiang)紅(hong)層(ceng)(ceng)分(fen)(fen)布(bu)最(zui)集中地(di)(di)(di)(di)(di)(di)(di)(di)(di)區。四(si)(si)(si)川(chuan)(chuan)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)為(wei)丘陵性盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)(di)(di)(di)，底部(bu)以(yi)(yi)丘陵為(wei)主(zhu)，次為(wei)低山(shan)(shan)(shan)和平原(yuan)。
四川盆(pen)(pen)地(di)屬揚(yang)子陸臺(tai)(tai)一(yi)部(bu)分(fen)，稱(cheng)為(wei)四川陸臺(tai)(tai)，屬較穩定的(de)地(di)區，但仍經過兩次(ci)大規模的(de)海(hai)(hai)浸。第一(yi)次(ci)從5億(yi)(yi)多年前的(de)寒武(wu)紀(ji)(ji)開始，延續到(dao)3.7億(yi)(yi)多年的(de)志(zhi)留紀(ji)(ji)，不斷下陷成了海(hai)(hai)洋盆(pen)(pen)地(di)，志(zhi)留紀(ji)(ji)時(shi)發(fa)生加里(li)東(dong)運動，除了西(xi)部(bu)的(de)龍門山地(di)槽繼續下陷外，其余地(di)區上升為(wei)陸。2.7億(yi)(yi)年前的(de)石炭(tan)紀(ji)(ji)末，發(fa)生范圍(wei)更大的(de)第二(er)次(ci)海(hai)(hai)浸，盆(pen)(pen)地(di)再次(ci)為(wei)海(hai)(hai)洋占據(ju)。二(er)疊紀(ji)(ji)時(shi)海(hai)(hai)陸交替，形成重慶附(fu)近的(de)南酮、松藻、天府等煤礦。二(er)疊紀(ji)(ji)末，盆(pen)(pen)地(di)西(xi)部(bu)巖漿噴出，峨(e)眉山小金頂及清音閣一(yi)帶的(de)玄武(wu)巖就(jiu)在這時(shi)生成。
距今(jin)1.9億(yi)年(nian)的(de)三疊(die)紀，“印(yin)支運動”使盆地(di)邊(bian)緣逐漸隆起成山，被(bei)海水(shui)淹沒的(de)地(di)區逐漸上升(sheng)成陸，由(you)海盆轉(zhuan)為(wei)湖盆。當時湖水(shui)幾乎(hu)占據現今(jin)四(si)川(chuan)盆地(di)的(de)全(quan)境，稱為(wei)“蜀湖”，從(cong)此結束了海浸的(de)歷(li)史。在中生代漫長的(de)1億(yi)多(duo)年(nian)里，盆地(di)氣(qi)(qi)候溫暖濕潤，到(dao)處生長蕨類、蘇鐵和裸子植(zhi)物，是(shi)又一個成煤期，永榮煤礦即(ji)在三疊(die)紀和侏羅紀時形成。東起長壽(shou)、墊江，西到(dao)江油(you)、邛崍，北抵大(da)巴(ba)山麓，南(nan)到(dao)貴州赤水(shui)，還是(shi)天(tian)然氣(qi)(qi)富集(ji)區。這一時期爬行動物恐龍稱霸一時。1957年(nian)在合州發現的(de)“合州馬門溪龍”身(shen)長22米，高3.5米，是(shi)中國亞洲(zhou)最(zui)大(da)和最(zui)完整的(de)恐龍化石。
7000萬年前的(de)(de)(de)(de)(de)白(bai)堊紀(ji)末期，發(fa)生(sheng)又一次強烈的(de)(de)(de)(de)(de)地(di)(di)(di)(di)(di)殼運(yun)動(dong)“燕(yan)山(shan)(shan)(shan)(shan)運(yun)動(dong)”。盆(pen)(pen)地(di)(di)(di)(di)(di)四(si)周山(shan)(shan)(shan)(shan)地(di)(di)(di)(di)(di)繼續隆起(qi)，同(tong)時產(chan)生(sheng)不(bu)少大(da)(da)(da)斷層(ceng)(ceng)，如(ru)西部(bu)的(de)(de)(de)(de)(de)龍門山(shan)(shan)(shan)(shan)大(da)(da)(da)斷層(ceng)(ceng)和東部(bu)的(de)(de)(de)(de)(de)華瑩(ying)山(shan)(shan)(shan)(shan)大(da)(da)(da)斷層(ceng)(ceng)，把盆(pen)(pen)地(di)(di)(di)(di)(di)分(fen)為(wei)(wei)三部(bu)分(fen)。蜀湖(hu)縮小為(wei)(wei)僅有2萬平(ping)方公里的(de)(de)(de)(de)(de)蜀湖(hu)。封閉的(de)(de)(de)(de)(de)盆(pen)(pen)地(di)(di)(di)(di)(di)地(di)(di)(di)(di)(di)形(xing)及(ji)急(ji)劇縮小的(de)(de)(de)(de)(de)水面，使氣(qi)候逐漸變(bian)得干(gan)熱，沉積物由(you)海相、海陸(lu)交替相變(bian)為(wei)(wei)陸(lu)相，大(da)(da)(da)量風化、侵(qin)蝕、剝蝕的(de)(de)(de)(de)(de)物質(zhi)在盆(pen)(pen)地(di)(di)(di)(di)(di)堆積了(le)數(shu)千米厚，形(xing)成紅色和紫紅色的(de)(de)(de)(de)(de)砂、泥(ni)、頁(ye)巖(yan)。裸子植物不(bu)斷衰退，恐龍滅絕了(le)。內陸(lu)湖(hu)泊在干(gan)燥條件下，經強烈蒸發(fa)，濃(nong)度(du)增(zeng)大(da)(da)(da)，鹽(yan)分(fen)不(bu)斷積累，形(xing)成鹽(yan)湖(hu)，后來(lai)泥(ni)沙掩埋而(er)保存于地(di)(di)(di)(di)(di)層(ceng)(ceng)之中，經過(guo)漫長(chang)的(de)(de)(de)(de)(de)地(di)(di)(di)(di)(di)質(zhi)作用形(xing)成巖(yan)層(ceng)(ceng)，自貢一帶是(shi)著名的(de)(de)(de)(de)(de)井鹽(yan)產(chan)地(di)(di)(di)(di)(di)。 2000多萬年前的(de)(de)(de)(de)(de)新第(di)(di)三紀(ji)，受喜馬拉雅(ya)造山(shan)(shan)(shan)(shan)運(yun)動(dong)的(de)(de)(de)(de)(de)影響。距今二、三百萬年的(de)(de)(de)(de)(de)第(di)(di)四(si)紀(ji)，地(di)(di)(di)(di)(di)殼再(zai)次發(fa)生(sheng)構造運(yun)動(dong)。從(cong)而(er)，四(si)川盆(pen)(pen)地(di)(di)(di)(di)(di)由(you)內流(liu)(liu)盆(pen)(pen)地(di)(di)(di)(di)(di)變(bian)為(wei)(wei)外(wai)(wai)流(liu)(liu)陸(lu)盆(pen)(pen)，由(you)封閉的(de)(de)(de)(de)(de)內流(liu)(liu)區(qu)變(bian)為(wei)(wei)外(wai)(wai)流(liu)(liu)區(qu)，由(you)以(yi)堆積為(wei)(wei)主變(bian)為(wei)(wei)侵(qin)蝕為(wei)(wei)主，經歷(li)了(le)海盆(pen)(pen)——湖(hu)盆(pen)(pen)——陸(lu)盆(pen)(pen)的(de)(de)(de)(de)(de)滄桑之變(bian)。 第(di)(di)四(si)紀(ji)是(shi)冰(bing)川廣(guang)布(bu)的(de)(de)(de)(de)(de)時代，盆(pen)(pen)地(di)(di)(di)(di)(di)西北山(shan)(shan)(shan)(shan)地(di)(di)(di)(di)(di)發(fa)育(yu)大(da)(da)(da)量冰(bing)川。冰(bing)川消(xiao)融(rong)后，大(da)(da)(da)量沉積物由(you)岷江(jiang)、沱江(jiang)等(deng)攜帶，堆積在西部(bu)的(de)(de)(de)(de)(de)凹陷區(qu)，即以(yi)前的(de)(de)(de)(de)(de)蜀湖(hu)之中，最(zui)終形(xing)成了(le)成都平(ping)原。 四(si)川盆(pen)(pen)地(di)(di)(di)(di)(di)地(di)(di)(di)(di)(di)貌(mao)豐富，平(ping)原7%，丘陵52%，低山(shan)(shan)(shan)(shan)41%。
四(si)川盆(pen)地(di)(di)(di)中植(zhi)(zhi)物近(jin)萬(wan)種，古(gu)老而特(te)有(you)(you)種之多為中國其他地(di)(di)(di)區(qu)所不(bu)及。在(zai)盆(pen)地(di)(di)(di)邊緣(yuan)山(shan)地(di)(di)(di)及盆(pen)東(dong)平行(xing)嶺(ling)谷(gu)尚可見(jian)水杉(shan)、銀(yin)杉(shan)、鵝掌楸(qiu)、檫木(mu)(mu)、三尖(jian)杉(shan)、珙桐、水青(qing)(qing)樹(shu)、連香樹(shu)、領(ling)春(chun)木(mu)(mu)、金錢槭、蠟梅、杜(du)仲、紅(hong)(hong)豆杉(shan)、鐘萼木(mu)(mu)、福建柏、穗花杉(shan)、崖柏、木(mu)(mu)瓜紅(hong)(hong)等珍稀(xi)孑(jie)遺植(zhi)(zhi)物與(yu)特(te)有(you)(you)種。在(zai)濕熱(re)(re)河谷(gu)可見(jian)桫欏(luo)、小羽桫欏(luo)、烏毛蕨、華南紫萁、里白等古(gu)熱(re)(re)帶(dai)(dai)孑(jie)遺植(zhi)(zhi)物。 四(si)川盆(pen)地(di)(di)(di)的地(di)(di)(di)帶(dai)(dai)性(xing)植(zhi)(zhi)被(bei)是(shi)亞(ya)(ya)熱(re)(re)帶(dai)(dai)常(chang)綠(lv)(lv)闊(kuo)(kuo)葉(xie)(xie)林(lin)(lin)(lin)，其代表樹(shu)種有(you)(you)栲(kao)樹(shu)、峨眉栲(kao)、刺果米櫧、青(qing)(qing)岡(gang)、曼青(qing)(qing)岡(gang)、包石櫟、華木(mu)(mu)荷(he)、大包木(mu)(mu)荷(he)、四(si)川大頭茶、楨楠、潤楠等，海拔一(yi)般(ban)情況下(xia)在(zai)1600～1 800米以下(xia)。其次有(you)(you)馬尾松、杉(shan)木(mu)(mu)、柏木(mu)(mu)組成 的亞(ya)(ya)熱(re)(re)帶(dai)(dai)針葉(xie)(xie)林(lin)(lin)(lin)及竹林(lin)(lin)(lin)。 邊緣(yuan)山(shan)地(di)(di)(di)從下(xia)而上是(shi)常(chang)綠(lv)(lv)闊(kuo)(kuo)葉(xie)(xie)林(lin)(lin)(lin)、常(chang)綠(lv)(lv)闊(kuo)(kuo)葉(xie)(xie)與(yu)落葉(xie)(xie)闊(kuo)(kuo)葉(xie)(xie)混交林(lin)(lin)(lin)，寒溫帶(dai)(dai)山(shan)地(di)(di)(di)針葉(xie)(xie)林(lin)(lin)(lin)，局部有(you)(you)亞(ya)(ya)高山(shan)灌叢草(cao)甸。
四川盆(pen)地(di)(di)是中(zhong)(zhong)國(guo)(guo)(guo)動(dong)物(wu)種(zhong)(zhong)類(lei)(lei)最多(duo)、最齊全(quan)的(de)(de)(de)地(di)(di)區(qu)(qu)之一(yi)(yi)。據統計，除魚類(lei)(lei)外(wai)，盆(pen)地(di)(di)底部共有動(dong)物(wu)417種(zhong)(zhong)，盆(pen)地(di)(di)西(xi)緣(yuan)(yuan)(yuan)、北(bei)緣(yuan)(yuan)(yuan)和南(nan)緣(yuan)(yuan)(yuan)山地(di)(di)分別(bie)為487種(zhong)(zhong)、317種(zhong)(zhong)與288種(zhong)(zhong)，其中(zhong)(zhong)經濟動(dong)物(wu)均(jun)占一(yi)(yi)半以(yi)上。盆(pen)地(di)(di)西(xi)緣(yuan)(yuan)(yuan)山地(di)(di)是中(zhong)(zhong)國(guo)(guo)(guo)特(te)有而(er)古老動(dong)物(wu)保(bao)(bao)存最好、最集中(zhong)(zhong)的(de)(de)(de)地(di)(di)區(qu)(qu)，屬于一(yi)(yi)類(lei)(lei)保(bao)(bao)護動(dong)物(wu)的(de)(de)(de)有大熊(xiong)(xiong)貓、金(jin)絲(si)猴、扭(niu)角羚、灰金(jin)絲(si)猴、白(bai)唇鹿等(deng)。還(huan)有珍貴特(te)有動(dong)物(wu)小熊(xiong)(xiong)貓、雪豹、鬣羚、短尾猴、獼猴、毛冠鹿、水獺及鴛鴦、血雉(zhi)(zhi)、紅腹(fu)角雉(zhi)(zhi)、綠尾虹雉(zhi)(zhi)、白(bai)腹(fu)錦雞(ji)、紅腹(fu)錦雞(ji)等(deng)。 盆(pen)地(di)(di)西(xi)緣(yuan)(yuan)(yuan)的(de)(de)(de)平武、青川、北(bei)川、寶興、天全(quan)、洪雅、馬(ma)邊等(deng)地(di)(di)，均(jun)為中(zhong)(zhong)國(guo)(guo)(guo)大熊(xiong)(xiong)貓的(de)(de)(de)主要分布區(qu)(qu)。已(yi)設(she)立(li)唐家(jia)河(he)、王朗、臥龍（見臥龍自然(ran)保(bao)(bao)護區(qu)(qu)）、蜂桶寨、喇叭河(he)等(deng)7處大熊(xiong)(xiong)貓、金(jin)絲(si)猴等(deng)自然(ran)保(bao)(bao)護區(qu)(qu)。 酉(you)陽、馬(ma)邊、平武等(deng)盆(pen)地(di)(di)邊緣(yuan)(yuan)(yuan)山地(di)(di)溪溝中(zhong)(zhong)的(de)(de)(de)大鯢及長江(jiang)、金(jin)沙江(jiang)中(zhong)(zhong)的(de)(de)(de)中(zhong)(zhong)華鱘、白(bai)鱘也為四川所特(te)有，均(jun)屬國(guo)(guo)(guo)家(jia)保(bao)(bao)護動(dong)物(wu)。
四川盆地(di)有煤、鐵(tie)、天(tian)(tian)然(ran)氣(qi)、石油、鹽(yan)、芒硝、石膏(gao)、磷、硫、鋁、金、銅、錳、石墨、汞等礦產資源，其中天(tian)(tian)然(ran)氣(qi)、芒硝為全中國之冠，并有中國重(zhong)要的(de)鍶礦。川東北是世界最大的(de)天(tian)(tian)然(ran)氣(qi)富集區之一，川中和(he)南(nan)充等地(di)鹽(yan)巖礦儲量很大。
四川盆地地形閉塞，由于(yu)北部秦嶺阻擋冷(leng)空氣，冬季氣溫(wen)高于(yu)同緯(wei)(wei)度其他(ta)地區。最冷(leng)月(yue)北部均(jun)溫(wen)3～5℃，南部5~8℃，較同緯(wei)(wei)度的(de)(de)上(shang)海、湖北、安徽及(ji)緯(wei)(wei)度偏南的(de)(de)貴(gui)州高1～4℃。盆地北部極(ji)端最低(di)溫(wen)-8～-5℃，南部-5℃~-2℃。霜(shuang)雪少見，年無(wu)霜(shuang)期長(chang)280～350天(tian)，同緯(wei)(wei)度上(shang)的(de)(de)武(wu)漢冬天(tian)卻霜(shuang)雪不斷，盆地位于(yu)長(chang)江河谷(gu)中的(de)(de)長(chang)寧全(quan)年無(wu)霜(shuang)。 盆地各地夏季始于(yu)5月(yue)底，終于(yu)9月(yue)中旬，夏長(chang)4個月(yue)，溫(wen)度上(shang)東高西低(di)。盆地西部夏天(tian)平均(jun)氣溫(wen)約25℃，較同緯(wei)(wei)度的(de)(de)上(shang)海、武(wu)漢等城市偏低(di)3-4度，但濕(shi)度較大，所以悶熱難忍。
東(dong)(dong)部最(zui)熱月氣(qi)溫(wen)(wen)高(gao)(gao)達26～29℃，長(chang)江河谷(gu)(gu)局地(di)(di)達到30℃。盛夏連晴高(gao)(gao)溫(wen)(wen)天氣(qi)又造成盆(pen)(pen)地(di)(di)東(dong)(dong)南(nan)部嚴重的夏伏旱。盆(pen)(pen)地(di)(di)氣(qi)溫(wen)(wen)東(dong)(dong)南(nan)高(gao)(gao)西北低，盆(pen)(pen)底高(gao)(gao)邊緣低； 各(ge)地(di)(di)年(nian)(nian)均溫(wen)(wen)16～18℃。10℃以上活動積溫(wen)(wen)4500～6000℃，持續期8～9個月，屬中亞(ya)熱帶(dai)。東(dong)(dong)南(nan)部的長(chang)江河谷(gu)(gu)積溫(wen)(wen)超過6000℃，相(xiang)當(dang)于中國南(nan)嶺(ling)以南(nan)的南(nan)亞(ya)熱帶(dai)氣(qi)候(hou)。盆(pen)(pen)地(di)(di)氣(qi)溫(wen)(wen)東(dong)(dong)高(gao)(gao)西低，南(nan)高(gao)(gao)北低，盆(pen)(pen)底高(gao)(gao)而邊緣低，等溫(wen)(wen)線分(fen)布(bu)呈現同(tong)心圓狀。盆(pen)(pen)地(di)(di)邊緣山地(di)(di)氣(qi)溫(wen)(wen)具有垂(chui)直分(fen)布(bu)特點，如峨(e)眉(mei)山、金佛山海拔升高(gao)(gao)百米，氣(qi)溫(wen)(wen)遞減(jian)0.55℃和0.61℃。峨(e)眉(mei)山頂年(nian)(nian)均溫(wen)(wen)僅3℃，10℃以上活動積溫(wen)(wen)586℃，氣(qi)候(hou)上相(xiang)當(dang)于寒溫(wen)(wen)帶(dai)和亞(ya)寒帶(dai)。
四川盆(pen)地(di)年(nian)(nian)降(jiang)水(shui)量(liang)1000～1300毫(hao)米(mi)(mi)，盆(pen)地(di)邊(bian)緣山(shan)地(di)降(jiang)水(shui)十分充(chong)沛，如樂(le)山(shan)和雅安間的西(xi)緣山(shan)地(di)年(nian)(nian)降(jiang)水(shui)量(liang)為1 500～1800毫(hao)米(mi)(mi)，為中(zhong)國(guo)突出(chu)的多(duo)雨(yu)(yu)區(qu)，有(you)“華西(xi)雨(yu)(yu)屏”之(zhi)(zhi)稱(cheng)。但冬干、春旱、夏澇、秋綿雨(yu)(yu)，年(nian)(nian)內分配不均，70～75%的雨(yu)(yu)量(liang)集中(zhong)于6～10月。最大(da)日(ri)(ri)降(jiang)水(shui)量(liang)可(ke)達300～500毫(hao)米(mi)(mi)。“巴山(shan)夜雨(yu)(yu)”自古聞名，夜雨(yu)(yu)占總(zong)雨(yu)(yu)量(liang)的60～70%以上。盆(pen)地(di)區(qu)霧大(da)濕重，云低陰(yin)天(tian)多(duo)。峨眉山(shan)、金佛山(shan)是中(zhong)國(guo)霧日(ri)(ri)最多(duo)地(di)區(qu)之(zhi)(zhi)一，年(nian)(nian)相對濕度之(zhi)(zhi)高也為中(zhong)國(guo)之(zhi)(zhi)冠(guan)。盆(pen)地(di)年(nian)(nian)日(ri)(ri)照僅900～1300小(xiao)時，年(nian)(nian)太陽輻(fu)射量(liang)為370～420千焦(jiao)耳(er)/平方厘米(mi)(mi)，均為中(zhong)國(guo)最低值，故有(you)“蜀犬吠日(ri)(ri)”之(zhi)(zhi)說(shuo)。
