摘要：地球表層的土壤沉積物記錄了第四紀以來與氣候、環(huán)境、人類等有關(guān)的地球演化信息, 是重要的研究過去歷史的載體.成土體系中土壤的諸多特性都與成土期的氣候環(huán)境信息息息相關(guān), 通過地質(zhì)學研究方法可以提取某些特性并作為反演風化強度以及古氣候的風化指標, 即古氣候替代指標.重點討論了成土體系中新生的礦物學風化指標——粘土礦物與鐵礦物的表征意義、研究方法與實例分析, 并評述了其在反演氣候方面的優(yōu)勢與局限性.成土作用中新生的粘土礦物直接受成土期盛行的環(huán)境與氣候條件的影響, 所以其組成、粒度、含量、結(jié)晶度等礦物學特征充分記錄了成土期的氣候與環(huán)境信息.另外, 成土體系中也會新生成部分鐵礦物.自生的鐵礦物是反映成土期的濕度條件、溫度范圍的有效指標, 因此對當時的氣候演化歷史也有很好的指示意義.粘土礦物與鐵礦物在一定的條件下都可以作為獨立的重建古氣候的替代指標, 但是在使用時要充分考慮研究區(qū)域的地質(zhì)背景、物源供給、氣候類型、風化條件等客觀局限對這些風化指標的制約.另外, 對于區(qū)域內(nèi)風化程度及古氣候的重建, 通常多指標結(jié)合對比的方法更為可靠.
關(guān)鍵詞：成土作用; 化學風化; 粘土礦物; 鐵礦物; 第四紀氣候; 礦物學;
引言
硅酸鹽的化學風化過程直接影響著成土作用并控制著地表的演化過程 (Gislason et al., 2009;Dixon et al., 2016) , 而長尺度的碳循環(huán)與全球氣候變化也處于成土作用中的剝蝕與風化過程的潛在調(diào)控中 (Eiriksdottir et al., 2013) .因此, 評估控制成土風化過程中的因素對于更好地理解地球演化進程至關(guān)重要.復(fù)雜的成土過程受控于氣候主導(dǎo)下的溫度與降水變化, 經(jīng)過漫長的地質(zhì)時間積累后, 會在地表廣泛堆積成土作用的最終產(chǎn)物———土壤 (Dixon et al., 2009) .不同區(qū)域、氣候特點下的土壤具有相異的特性:不同的顏色、粒度、礦物組成等, 這些因素往往可以提取并作為反演風化強度與氣候改變的替代指標 (Sheldon and Tabor, 2009) .
目前我們在地表所見的土壤堆積基本屬于第四紀以來成土作用的產(chǎn)物, 這些土壤中提出來的指標可以反映第四紀的相關(guān)信息, 例如氣候演化、季風環(huán)流、環(huán)境變遷、構(gòu)造隆升、古人類繁盛等諸多第四紀以來地球表面的生命脈動過程 (Sun et al., 2015a;Wang et al., 2015) .第四紀是地球演化最新的階段, 也是改變?nèi)蛎婷沧钪匾碾A段.冰川數(shù)度盛衰, 構(gòu)造趨于活躍, 人類與文明的誕生都發(fā)生在第四紀, 對第四紀氣候演化的研究對于評估未來氣候走勢與環(huán)境發(fā)展有著極為重要的意義, 因此, 對成土體系中風化指標的提取與研究也同樣重要.
成土體系中常見的可以刻畫風化強度的指標有地球化學指標、粒度指標、礦物學指標等 (Buggle et al., 2011;Stuut et al., 2014;Hong et al., 2015) .其中成土體系中新生的礦物學指標是此次研究評述的重點.本文詳細闡述了成土體系中的自生礦物在表征氣候中所扮演的角色, 系統(tǒng)總結(jié)了其在古氣候重建中的研究方法、應(yīng)用及意義.另外, 本文還詳細探討了自生礦物作為古氣候替代指標的局限性, 并展望了光譜學分析自生礦物特征和應(yīng)用于風化重建中的可能.
1 成土作用
土壤是由多種風化過程相互作用下形成的復(fù)雜的系統(tǒng), 是存在于大氣圈、生物圈、水圈與巖石圈連接處的多元化界面 (Dixon et al., 2009) .在此界面發(fā)生的母巖降解與土壤生成的作用稱為成土作用, 成土作用發(fā)生的關(guān)鍵區(qū)域近年來受到更多的關(guān)注, 被稱為“關(guān)鍵帶”, 是巖石、空氣、水與生命交匯的地方 (Brantley et al., 2007) .在此處, 物理、化學與生物風化相互作用, 互為影響, 形成能量源源不斷的引擎將關(guān)鍵帶的基巖不斷地轉(zhuǎn)換成土壤, 改造著地球表面的面貌, 此過程可以通過圖1簡單概括 (Anderson et al., 2004;Brantley et al., 2007;曾方明等, 2014;曾方明, 2016) .
1.1 風化條件下的成土過程
在緩慢的成土過程中, 地表母巖在不斷的風化過程積累下, 組成巖石的礦物會逐漸降解, 不同的礦物風化降解的本質(zhì)與速率首先是由礦物本身決定的.Goldich (1938) 在1938年就指出, 地表主要造巖礦物的風化敏感性與巖漿結(jié)晶順序 (鮑文序列) 有直接的關(guān)系.所以橄欖石、輝石、角閃石等在巖漿冷卻過程中先結(jié)晶形成的礦物在風化開始后會更易于崩解蝕變.另外, 在近幾十年的研究中發(fā)現(xiàn), 礦物的抗風化能力與其晶體結(jié)構(gòu)與化學構(gòu)成有直接的關(guān)系, 礦物晶體結(jié)構(gòu)中的位錯與缺陷, 以及礦物在微區(qū)化學成分上的不均一性等, 都為風化作用提供了絕佳的起始位置 (Blumet al., 1990;White and Brantley, 2003;Wilson, 2004) .
隨著母巖礦物的不斷降解, 成土體系內(nèi)的元素組成也會隨之改變 (圖1) .可溶和易遷移的元素不斷流失耗盡, 難溶和不易遷移的元素逐漸富集.因此, 土壤中的Na, K, Ca等離子會不斷從成土體系中淋濾析出, 而較難溶的Mg, Fe, Al 等殘余組分會相對富集 (Buggle et al., 2011;Jiang et al., 2016) .與此同時, 成土作用會進入礦物蝕變與新礦物生成的階段.這個階段內(nèi)成土體系中顆粒粒度會不斷減小, 并生成大量的粘土礦物、三水鋁礦、鐵礦物等次生礦物 (Chadwick and Chorover, 2001) , 此類新礦物的不斷積累增加代表了成土作用進入了土壤生成的最終階段.
1.2 氣候條件對成土體系中礦物學的影響
風化過程作用下的成土作用受到很多因素的影響, 包括母巖、時間、地形、有機質(zhì)和氣候等 (Brady and Weil, 2004;Stockmann et al., 2011;圖1) .其中氣候變化起主要作用, 各個因素之間相互關(guān)聯(lián), 形成復(fù)雜的體系 (Jahn et al., 2001) .氣候變化通過以下方面直接地影響土壤的生成: (1) 控制成土期繁盛的動植物群, 使土壤發(fā)生物理遷移與混合, 并改變土壤的酸度; (2) 通過控制土壤溫度與含水量影響化學風化速率 (Dixon et al., 2009) .氣候通過溫度與降水影響成土過程的原理可闡述如下:首先, 溫度主要通過改變風化速率來影響風化程度, 隨著溫度的上升, 風化程度會隨之加強 (Sun et al., 2016a) .其次, 成土作用包含一系列的降解過程, 包括淋濾與淀積等遷移過程, 上述過程也可以被描述為流失/富集過程以及轉(zhuǎn)變過程 (Simonson, 1959;Huggett, 1998) .淋濾-淀積過程的動力來自于降水頻率與強度對巖石/土壤溶解力大小的影響, 不斷增加的淋濾過程增加了硅的活性并加劇了風化程度.
圖1 成土作用的影響因素、產(chǎn)物以及土壤形成的過程簡圖
據(jù)Brantley et al. (2007) 修改
在氣候較為干燥寒冷, 年降水量較低的地區(qū), 例如高緯度的極地地區(qū), 化學與生物風化不明顯, 通常以物理風化為主, 此時成土作用處于巖石崩解的最初階段, 其產(chǎn)物通常為巖石碎片以及風成堆積等外來堆積物 (Lee et al., 2004) .此時的成土體系中以原巖的礦物為主, 次生礦物極少或者沒有.但是在極其微弱的風化條件的不斷積累下, 原始成土體系中的橄欖石、輝石、角閃石等暗色礦物部分崩解殆盡, 并產(chǎn)生微量新生的粘土礦物、鐵礦物等, 原始巖層會出現(xiàn)數(shù)厘米的風化層 (Chevrier et al., 2006) .在氣候適宜, 降水量增多的中緯度溫帶地區(qū), 物理風化、化學風化與生物風化相互制約平衡, 成土作用進入由純粹的物理巖石崩解到化學性的元素遷移并逐漸形成新生礦物的階段 (Zhao et al., 2005) .成土體系中的顆粒開始變細, 暗色礦物基本瓦解消失, 礦物組成以伊利石、綠泥石等繁盛于弱化學風化條件下的粘土礦物以及石英、長石為主, 并開始出現(xiàn)部分磁赤鐵礦等磁性礦物.而在亞熱帶及熱帶, 氣候濕潤炎熱, 年降水量充沛的中低緯度地區(qū), 成土作用強烈且廣泛, 風化殼的厚度可以到幾米至二十幾米 (Liu et al., 2017;Zhao et al., 2017) .高溫以及潮濕的環(huán)境極大地促進了化學風化以及生物風化的進行, 這個時候的成土體系中的顆粒不斷變得更細, 長石等原巖中的礦物基本消失, 僅剩少量粒度極細的石英.粘土礦物組合由以伊利石、綠泥石為主轉(zhuǎn)變?yōu)橐悦擅撌案邘X石族礦物為主, 并且粘土礦物的結(jié)晶度會變差 (Sheldon and Tabor, 2009) .鐵礦物組合中以磁赤鐵礦為代表的磁性礦物逐漸減少, 而赤鐵礦占據(jù)了更大的比重 (Liu et al., 2017;Zhao et al., 2017) .另外, 在終年炎熱多雨的地區(qū), 成土體系中會出現(xiàn)大量三水鋁礦, 也是化學風化到達最終的產(chǎn)物 (Lu et al., 2015) .
2 成土體系中新生的礦物學風化指標
土壤中元素的遷移、粒度分布、新礦物的生成等與成土有關(guān)的特質(zhì)在風化過程中不斷改變并最終達到平衡 (Sun et al., 2016a;Zheng et al., 2016) .這些成土特質(zhì)的相對改變可以用來確定其風化程度.其中最具代表性的兩大類指標是離子遷移衍生的風化指標體系與自生礦物衍生的風化指標體系.與離子遷移有關(guān)的風化指標已有前人深入探討過 (Buggle et al., 2011) , 本次綜述不再評述;在接下來的篇幅中重點探討與自生礦物有關(guān)的風化指標.土壤體系中最典型的自生礦物是粘土礦物與鐵礦物.粘土礦物與鐵礦物的物相組成與含量變化可作為土壤剖面的風化程度以及成土時期的氣候演化歷史可靠的指標.
2.1 粘土礦物
成土體系中自生的粘土礦物通常來自于母巖的風化蝕變殘余或者土壤溶解物的直接沉淀, 反映了成土作用中礦物連續(xù)遞進的演化過程 (Turpault et al., 2008) , 并直接受成土期盛行的環(huán)境狀態(tài)與氣候條件的影響 (Wilson, 2004) .因此, 粘土礦物的礦物學特征 (組成、粒度、含量、結(jié)晶度等) 充分記錄了成土期的氣候與環(huán)境信息 (Chamley, 1989) , 并廣泛應(yīng)用于湖泊、河流、海洋與陸地等各類沉積物的物源辨識與古氣候重建研究中 (Guyot et al., 2007;Liu et al., 2009, 2010;Hong et al., 2016) .
2.1.1 粘土礦物對古氣候信息的表征
粘土礦物對氣候的反映基于粘土礦物在巖石降解與成土過程中隨著氣候改變而演化的總體趨勢:當外部的氣候條件由干燥寒冷向潮濕炎熱轉(zhuǎn)變, 巖石/土壤中的粘土礦物會出現(xiàn)伊利石→綠泥石→蛭石→蒙脫石→高嶺石的總體演化趨勢 (Sheldon and Tabor, 2009;Nordt and Driese, 2010) .其中伊利石與綠泥石形成于成土風化過程的最初階段, 兩者在成土體系中的大量富集代表了源區(qū)物質(zhì)的快速物理侵蝕和相對干燥寒冷的環(huán)境 (Liu et al., 2010;Wang and Yang, 2013) .另外, 伊利石與綠泥石相對含量的變化與物源的變化或者原位氣候的振蕩改變密切相關(guān) (Sun et al., 2015b) .總體來說, 伊利石 (I) 與綠泥石 (Ch) 形成于弱風化的氣候環(huán)境, 隨著溫度與降水的增加, 易于向其他粘土礦物轉(zhuǎn)變 (Nesbitt and Young, 1989) .蛭石 (V) 與蒙脫石 (Sm) 形成于中等程度的風化條件下 (Zhao et al., 2017) .蒙脫石一般形成于季節(jié)性干濕交替的氣候下, 是伊利石、白云母或者其他碎屑成分在物源區(qū)或者沉積區(qū)中等風化程度下的原位產(chǎn)物.另外, 排水不暢的成土環(huán)境, 較低的地勢等都利于蒙脫石的生成 (Gylesj9and Arnold, 2006;Vargaet al., 2011;U'jvári et al., 2014) .高嶺石 (K) 是成土作用中原位風化的最終產(chǎn)物, 通常形成于濕熱氣候下排水順暢的陡坡環(huán)境中, 是強烈的化學風化與淋濾作用的結(jié)果, 其大量出現(xiàn)代表成土期經(jīng)歷了溫暖潮濕的氣候 (Dixon and Weed, 1989;Varga et al., 2011) .單獨的某種粘土礦物的含量特征或者某些粘土礦物的比值變化 (e.g., K/I, K+Sm/I, I/Ch) 以及粘土礦物與其他礦物的比值變化 (e.g., 伊利石/石英、綠泥石/石英) 都可以用來反映成土期的風化程度與氣候演化特征 (Zhao, 2005;Dou et al., 2010;Zeng et al., 2014;Sun et al., 2015b) .
另外, 當粘土礦物的物源來自排水盆地或物源混雜時, 粘土礦物搬運與沉積過程中會因為差異性的絮凝或者分選作用而發(fā)生一定程度的理化性質(zhì)的更改, 從而大大影響它們對氣候信息的解譯 (Wang and Yang, 2013) .某些晶體學指數(shù), 例如伊利石結(jié)晶度 (IC) 、綠泥石結(jié)晶度 (ChC) 和伊利石化學指數(shù) (CII) 等受沉積分異作用的影響較小, 可以更好地替代粘土組合含量指標來反映古氣候演化.其中IC是最為廣泛使用的結(jié)晶度指標 (Liu et al., 2007) .IC通常通過伊利石1nm衍射峰的半高寬 (Kübler指數(shù)) 來表征.當氣候干冷時, 環(huán)境中缺乏水分, 風化作用以物理風化為主, 伊利石保存完好, IC值相對較高;相反在濕熱的氣候條件下, 伊利石容易受到淋濾, 易于向其他粘土礦物轉(zhuǎn)變, 此時的IC值會逐漸降低 (Liu et al., 2010;季峻峰等, 2012) .CII值也可以有效反映氣候信息, 并且可以用于示蹤物源區(qū)和搬運路徑 (Liu et al., 2008) .當CII低于0.5時, 說明其為富鐵鋁的伊利石, 代表了較弱化學風化的環(huán)境;CII大于0.5時說明其為富鋁伊利石, 生成于強烈水解的環(huán)境中 (Chamley, 1989) .
2.1.2 中國南方紅土中粘土礦物的研究例析
中國南方 (秦嶺-淮河以南) 受東亞季風、印度季風等多股季風環(huán)流系統(tǒng)影響具有鮮明的熱帶季風氣候特征, 在地表形成了廣泛分布的紅土沉積物 (席承藩, 1991;Lu et al., 2015) .南方的紅土沉積物具有酸性、細粒性、強風化性、脫硅富鋁性等特征, 是地質(zhì)時期活躍的水-氣-生等因素共同參與下的產(chǎn)物, 其發(fā)育過程受控于全球氣候變化, 是研究第四紀氣候演化的良好載體 (李長安和顧延生, 1997;Hong et al., 2016) .近十年來, 眾多學者一直致力于尋找紅土沉積物中有效的氣候替代指標, 試圖建立紅土成土演化與環(huán)境氣候改變之間的關(guān)系, 并為全球變化提供依據(jù).其中出現(xiàn)了更多將紅土中的粘土礦物應(yīng)用于古氣候重建的例子, 并逐漸建立起一系列長江中下游典型的紅土剖面 (Yin et al., 2013;Hong et al., 2014, 2016;Lu et al., 2015;Zhao et al., 2017) .
粘土礦物的晶體形態(tài)和晶體結(jié)構(gòu)分別可以使用掃描電子顯微鏡 (SEM) 以及透射電子顯微鏡 (TEM) 進行推測與分析 (Xieetal., 2013a, 2013b;李金華和潘永信, 2015;洪漢烈等, 2017) .其中粘土礦物所特有的晶格條紋像的特點可以通過TEM照片較好的呈現(xiàn) (圖2) .隨著微觀成像技術(shù)的不斷發(fā)展, 粘土礦物之間的轉(zhuǎn)化過程可以直觀展示在高分辨率的TEM圖像中, 使得粘土礦物原位分析氣候轉(zhuǎn)變成為可能.圖2中蒙脫石與高嶺石之間的轉(zhuǎn)變, 蛭石與伊利石之間的轉(zhuǎn)變等都為紅土成土期的氣候轉(zhuǎn)變提供了直接的礦物學證據(jù).第四紀以來, 尤其是更新世以來, 中國南方區(qū)域內(nèi)的氣候波動性明顯, 在紅土剖面中下部出現(xiàn)部分混層粘土礦物, 以及偶爾可見的粘土礦物之間的微觀轉(zhuǎn)化, 正是氣候強烈波動、成土體系中強烈淋濾風化的直觀性證據(jù) (Hong et al., 2012, 2014, 2015;Yin et al., 2013) .
粘土礦物的物相測定與分析通常使用粉晶衍射分析 (XRD) 技術(shù).前人在安徽宣城、江西九江、四川成都、廣西百色、湖北梁子等地建立了一系列標準的紅土剖面, 以剖面中的紅土沉積物為載體, 對其中的粘土礦物進行提純與分析.其獲得的粘土含量變化數(shù)據(jù)與化學風化指標、粒度指標等都具有良好的對應(yīng)關(guān)系, 共同印證了南方紅土在更新世以來經(jīng)歷了比北方黃土更強烈的成土過程, 并且區(qū)域內(nèi)有逐漸干燥寒冷的趨勢, 與當時的季風環(huán)流、全球環(huán)境的變化相一致 (Hong et al., 2012, 2014, 2016;程峰等, 2014;趙璐璐等, 2015;Zhao et al., 2017) .
另外, 全球范圍內(nèi)其他中低緯度區(qū)域內(nèi)的土壤沉積物以及海相沉積物中, 粘土礦物也都有相一致的氣候環(huán)境指示意義, 可以作為輔助的指示環(huán)境與氣候的指標, 在指示古緯度、古海拔、古降水、洋流改變、動植物演化遷移過程中都有重要的應(yīng)用 (de Menocal, 2004;Liu et al., 2008;Sheldon and Tabor, 2009;Shen et al., 2011;Fang et al., 2017) .印度西南邊緣陸相巖心中粘土礦物的物相組合以及含量變化揭示了末次冰川時期以來相對微弱的夏季風作用, 并且在28ka與22ka有兩次不連續(xù)的氣候變濕潤的事件出現(xiàn).另外, 在15ka左右, 粘土礦物的沉淀增加與物源輸入都有明顯的提升, 證明在冰消期早期印度西南區(qū)域內(nèi)有顯著的氣候回暖的過程 (Thamban et al., 2002) .美國加利福尼亞州南部圣巴巴拉盆地內(nèi)的粘土礦物組合受控于第四紀晚期160ka的氣候環(huán)境, 更是與古降水的演化歷史密切相關(guān).盆地內(nèi)蒙脫石與其他粘土礦物的比值 (S/I與K/S) 被用作區(qū)域內(nèi)古降水變化的替代指標.當S/I較高或者K/S較低, 即蒙脫石含量較高的時期反映了區(qū)域內(nèi)強降水的階段, 這些階段與圣巴巴拉區(qū)域內(nèi)植被的繁盛期有很好的對應(yīng).另外, 由粘土礦物組合反映的強降水的階段與氧同位素的變化一致, 其中主要的強降水階段開始于冰期并持續(xù)至間冰期, 降水量的增加反映了周圍區(qū)域內(nèi)氣候的變暖, 也反映了同時期美國西南部周圍洋流中上升流的持續(xù)變?nèi)踹^程 (Robert, 2004) .愛琴海中部鉆孔中高精度的高嶺石與綠泥石組合變化可以重建北非沙漠中風成細粒物質(zhì)的匯集進度, 而這種物源輸入與湖泊的干旱消亡過程息息相關(guān).因此, K/Ch比值的變化可以作為物源區(qū)風力活性、干旱化程度與植被覆蓋面積的有效指示指標, 反映出105ka以來北非地區(qū)氣候環(huán)境的演化變遷史.末次冰期以來持續(xù)走低的K/Ch比值說明, 北非物源區(qū)的湖泊沉積物持續(xù)減少, 反映出末次冰期以來湖泊減少, 環(huán)境持續(xù)干旱的演化歷史 (Ehrmann et al., 2013) .
圖2 中國南方紅土沉積物中粘土礦物的TEM照片
K.高嶺石;S.蒙脫石;V.蛭石;I.伊利石;HIV.羥基間層蛭石.a.高嶺石與蒙脫石的間層 (Hong et al., 2012) ;b.蛭石與伊利石的間層 (Hong et al., 2014) ;c.伊利石與蒙脫石、高嶺石的相互間層 (Hong et al., 2015) ;d.伊利石與羥基間層蛭石/蛭石的相互間層 (Yin et al., 2013)
2.2 鐵礦物
成土體系中新生成的鐵礦物是反映成土期的濕度條件、溫度范圍的有效指標, 因此對當時的氣候演化歷史也有很好的指示意義 (Schwertmann, 1993;Balsamet al., 2004;Inda et al., 2013) .成土作用中新生成的鐵礦物通常粒度極小, 結(jié)晶度差, 含量很低, 傳統(tǒng)分析測試手段 (e.g., XRD, SEM) 的分辨率經(jīng)常達不到實驗要求 (Ji et al., 2001;Ji, 2004;Zhao et al., 2017) .學者們都致力于尋找適宜的分析土壤中鐵礦物的測試技術(shù).根據(jù)成土體系中的鐵礦物的磁性強弱又可以將鐵礦物分為磁性鐵礦物 (磁鐵礦、磁赤鐵礦等) 與非/弱磁性鐵礦物 (赤鐵礦、針鐵礦等) .
2.2.1 磁鐵礦與磁赤鐵礦
成土體系中的磁性礦物一般通過間接的方法分析, 比如分析磁性參數(shù) (磁化率等) 、穆斯堡爾譜測試、化學抽取法等 (Chen et al., 2005;Liu et al., 2007;Hu et al., 2013;Long et al., 2016) .其中前人研究表明中國北方黃土-古土壤序列的低頻磁化率 (χlf) 變化與深海氧同位素波動有明顯的正相關(guān)關(guān)系, 證明磁化率可以幫助反演大陸古氣候特征, 并與東亞季風環(huán)流的演化有很好的對應(yīng)性 (Kukla et al., 1988;Deng et al., 2004) .磁化率的增加主要來自于成土體系中磁鐵礦與磁赤鐵礦的貢獻 (Torrent et al., 2007) .
2.2.2 黃土高原中磁化率的研究例析
中國北方的黃土-古土壤序列 (CLP) 被認為是大陸上第四紀以來最為完整詳盡的古氣候環(huán)境演化的記錄 (Liu and Ding, 1993;Liu et al., 1999;Clemens, 2015) .這些堆積序列由黃土與古土壤交疊構(gòu)成, 其中黃土與古土壤分別是風成堆積與成土風化的產(chǎn)物 (曾方明等, 2014) .黃土-古土壤中磁化率的研究將中國的黃土高原推向世界的面前, 使黃土-古土壤成為繼深海氧同位素、極地冰芯后又一個完整連續(xù)的研究古氣候演化歷史的載體 (Kukla et al., 1988;Liu et al., 1999;An et al., 2001) .黃土-古土壤序列中黃土層中的磁化率偏低, 證明黃土形成期經(jīng)歷了干燥寒冷的氣候, 在弱風化條件下來自西北的沙土持續(xù)加積;古土壤中的磁化率明顯增加, 證明了古土壤生成于溫暖濕潤的氣候條件, 風化成土作用強烈.此外, 黃土-古土壤序列中的磁化率與氧同位素以及同體系內(nèi)多種成土特性都有極好的對應(yīng)性.西風、薊縣、洛川等典型的黃土高原剖面中的黃土-古土壤序列的磁化率變化與Sr/Sr、Rb/Sr以及全球氧同位素的比值都有很好的對應(yīng)性, 反映出古土壤層形成期的氣候偏暖濕, 磁化率偏高, 而黃土層形成期的氣候偏冷干, 磁化率偏低 (圖3) .另外, 在世界其他范圍的中緯度的陸相沉積物中, 磁化率與其他風化指標都表現(xiàn)出了極高的對應(yīng)性, 說明其在一定的條件下可以作為普適性的風化指標 (Liu et al., 2007;Zhao et al., 2013;Ho2ek et al., 2015) .
2.2.3 洞穴石筍記錄土壤磁性礦物的研究例析
洞穴沉積物 (石筍等) 是保存重建過去氣候歷史的良好載體, 因為它們記錄的信息精度較高, 并且通常情況下是穩(wěn)定連續(xù)的 (Zhu et al., 2017) .成土體系中的部分磁性礦物會隨地下水轉(zhuǎn)移至洞穴系統(tǒng)中, 并隨著石筍等洞穴堆積物的生長不斷與之合成一體.石筍會即刻鎖住磁性, 不被后沉積作用所影響, 并提供穩(wěn)定可控的年齡數(shù)據(jù), 是極佳的記錄古地磁的載體.而隨著高精度高分辨率磁力儀的研制, 使得石筍中低濃度的磁性礦物可以被精確測得 (Osete et al., 2012;Zhu et al., 2012) .近年來, 對石筍等洞穴沉積物中共生的磁性礦物的研究在古地磁記錄方面取得了顯著的成果, 另外, 這些磁性記錄以及磁性礦物的礦物學特征都有諸多重建古氣候與古環(huán)境的潛能 (Fairchild et al., 2006;Lascu and Feinberg, 2011) .
圖3 中國北方典型黃土-古土壤剖面的低頻磁化率變化與其他風化指標的對比曲線
a.西風剖面磁化率變化曲線 (Chen et al., 2014) ;b.薊縣剖面磁化率變化曲線 (Jahn et al., 2001) ;c.洛川剖面磁化率變化曲線 (Guan et al., 2016) ;d.洛川剖面87Sr/86Sr比值變化 (Yang et al., 2000) ;e.洛川剖面Rb/Sr比值變化 (Chen et al., 1999) ;f.同時期全球冰芯氧同位素變化 (Railsback et al., 2015)
將石筍中的磁性礦物應(yīng)用于東亞季風區(qū)的古降水重建研究就是一個成功的例子 (Zhu et al., 2017) .前人研究表明長尺度的降水變化就可以記錄在石筍等洞穴堆積物的磁性礦物中 (Xie et al., 2013;Bourne et al., 2015) .降水量的增加會使成土體系中的磁鐵礦增加, 促進土壤內(nèi)的磁鐵礦通過滴水轉(zhuǎn)移至洞穴內(nèi).因此, 洞穴石筍中不連續(xù)的磁鐵礦及其他土壤衍生的微粒濃度的升高與間歇性的強降雨有密切的聯(lián)系 (Bourne et al., 2015;Zhu et al., 2017) .石筍中階段性成土磁鐵礦的增加記錄了與全新世厄爾尼諾現(xiàn)象相關(guān)的洪水的出現(xiàn), 并且其變化周期與厄爾尼諾500年的循環(huán)相一致.
2.2.4 赤鐵礦與針鐵礦
赤鐵礦 (Hm) 與針鐵礦 (Gt) 是成土體系中常見的鐵礦物, 會隨著氣候環(huán)境的改變而變化, 因此其組成與含量可以作為成土風化強度的指標 (Jordanova et al., 2010;Buggle et al., 2014) .溫暖的、年降水量充沛且季節(jié)性干旱的氣候利于土壤中赤鐵礦的形成.其中雨季間隔時成土體系中形成水鐵礦, 隨后的旱季間隔時會使水鐵礦轉(zhuǎn)換成赤鐵礦 (Cornell and Schwertmann, 2003;Balsamet al., 2004) .相反, 針鐵礦會直接形成于土壤溶液的沉淀, 持續(xù)的相對干燥涼爽的環(huán)境利于其形成 (Chen et al., 2010) .獨立的赤鐵礦和/或針鐵礦的含量變化, 或者赤鐵礦與針鐵礦的比值 (i.e.Hm/Gt, Hm/ (Hm+Gt) ) 都可以用作季風氣候演化的指標 (Torrent et al., 2007;Long et al., 2011;Clift et al., 2014) .
近年來, 漫反射光譜學技術(shù) (DRS) 的普及與應(yīng)用使赤鐵礦與針鐵礦快速、精準, 原位的測定分析成為可能, 因此出現(xiàn)了諸多嘗試將赤鐵礦與針鐵礦應(yīng)用于古氣候重建中的例子, 并取得了顯著的成果 (Zhang et al., 2009;Buggle et al., 2014;Clift et al., 2014) .
2.2.5 東亞季風氣候區(qū)內(nèi)赤鐵礦與針鐵礦
東亞地區(qū)第四紀以來一直受東亞季風、印度季風、南亞季風等多股季風環(huán)流的影響, 形成特色鮮明的季風氣候 (An, 2000;Guo et al., 2000;Anet al., 2001) .由于赤鐵礦與針鐵礦的形成與演化與季風息息相關(guān), 所以近十幾年來出現(xiàn)了更多使用赤鐵礦與針鐵礦研究東亞區(qū)域內(nèi)氣候與季風強度演化的研究, 取得了較為突出的成果 (Balsamet al., 2004;Torrent et al., 2007;Long et al., 2011;Buggle et al., 2014) .研究發(fā)現(xiàn), 在中國北方的黃土-古土壤序列中, 赤鐵礦與針鐵礦通常與成土體系中的磁性參數(shù)有很好的對應(yīng)性, 對研究土壤磁性的增長模式, 東亞夏季風強弱的變化等都有一定的輔助意義 (Ji et al., 2001;Hu et al., 2013) ;在中國南海海相沉積物中, 赤鐵礦與針鐵礦作為古氣候與夏季風的指標成功應(yīng)用于大陸風化歷史的指示中, 并與地球化學、同位素等指標有很好的對應(yīng)性 (Clift et al., 2014;Yang et al., 2016) .
另外, 值得一提的是, 赤鐵礦和針鐵礦是土壤的主要致色因子, 赤鐵礦使土壤顯紅色, 而針鐵礦使土壤顯黃色 (Torrent et al., 1983;Zhang et al., 2009) .中國南方廣布紅土沉積, 而北方則堆積了巨厚的黃土-古土壤序列, 可推測紅土中含有相比黃土更多的赤鐵礦, 這從另一方面論證了中國南方在第四紀以來經(jīng)歷了比北方更溫暖潮濕的季風性氣候 (Zhao et al., 2017) .
3 局限與展望
3.1 不同區(qū)域內(nèi)粘土礦物的古氣候表征
粘土礦物對當?shù)貧夂蜓莼姆从持饕芪镌摧斎搿⒊赏磷饔玫纫蛩氐挠绊? 當風化條件下的成土作用影響大于物源輸入時, 粘土礦物的組成可以一定程度上重建當?shù)氐臍夂蜓莼?例如在風化程度強烈 (CIA≥80;Hong et al., 2010;Lu et al., 2015) 的中國南方紅土中, 成土作用對體系內(nèi)粘土礦物組合的影響大于物源輸入的影響, 所以在此區(qū)域內(nèi)粘土礦物是優(yōu)良的古風化與古氣候替代指標 (Wang and Yang, 2013) .在風化程度中等 (60≤CIA<80;Jahn et al., 2001) 的黃土-古土壤序列中, 來自西北源源不斷的巨厚物源輸入一定程度上降低了成土作用對體系中粘土礦物組合的影響, 因此在風化程度偏低的黃土層中, 伊利石含量偏低, 而高嶺石含量偏高;而在風化程度偏高的古土壤層中粘土含量結(jié)果恰恰相反 (Gylesj9and Arnold, 2006) .這與粘土礦物生成與演化本身所代表的氣候含義截然相反.這是因為在中等程度風化的成土體系中, 將粘土礦物作為古氣候指標時, 需要充分考慮到物源對粘土礦物組合的影響, 否則得到的結(jié)果是不可靠的.另外, 在中國南海的海相沉積物中, 粘土礦物對季風氣候的指示主要通過物源供給與當代的洋流運輸來實現(xiàn), 洋流運輸在決定粘土礦物組合上起到了舉足輕重的作用 (Liu et al., 2007, 2010;Dou et al., 2010, 2014;Yu et al., 2016) ;中國黃河與長江的河流沉積物中主導(dǎo)的粘土礦物有鮮明的差別, 其中長江盆地含有較多高嶺石, 反映了較強烈的化學風化過程, 黃河盆地含有較多蒙脫石, 與較強的物理風化作用有關(guān).這種粘土組合的分布除了與氣候密切相關(guān)外, 還與河流盆地內(nèi)構(gòu)造有關(guān) (Yang et al., 2004;Wang and Yang, 2013) .在澳大利亞境內(nèi)河流相沉積物中, 粘土礦物的組合與河流運輸、儲存的關(guān)聯(lián)性更密切, 而與第四紀氣候的快速演化無明顯相關(guān)性 (Gingele and de Deckker, 2004;Gingele et al., 2007) .以上兩個例子也說明河海沉積物中水體的運輸力以及構(gòu)造因素對粘土礦物組合也有巨大的影響.
以上實例充分說明, 粘土礦物在表征古氣候與古風化信息時有一定的地域性與局限性, 在考慮使用粘土礦物組合作為古氣候替代指標之前, 需要充分考慮當?shù)氐膮^(qū)域地質(zhì)背景、風化強烈程度、物源輸入等因素的影響, 并將結(jié)果與其他指標相對比以確保其可靠性.
3.2 不同氣候特征下鐵礦物的古氣候表征
3.2.1 風化程度決定磁化率的適用性
磁化率對過去氣候變化的表征有諸多客觀條件的制約, 這一屬性在世界各地的成土體系中都有表現(xiàn).例如, 在中緯度中等風化的黃土-古土壤序列中, 例如中國黃土高原、中東地區(qū)、歐洲中部等地, 成土體系中的磁化率與風化強烈的強度有一定的正相關(guān)關(guān)系 (Maher, 1998;Ho2ek et al., 2015) .而在高緯度弱風化的西伯利亞、阿拉斯加等地, 以及中低緯度風化強烈的中國南方、南亞、阿根廷等地, 成土體系中的磁化率與其他指標并無太多相關(guān)性 (Maher, 1998;Hu et al., 2009) .這種差異性可以通過以下假說來闡明:與磁化率相關(guān)的磁赤鐵礦是水鐵礦氧化轉(zhuǎn)變?yōu)槌噼F礦的中間產(chǎn)物, 在較強的氧化環(huán)境下不穩(wěn)定, 極易轉(zhuǎn)變?yōu)槌噼F礦, 此轉(zhuǎn)化過程可以簡單表述為水鐵礦→磁赤鐵礦→赤鐵礦 (Cornell and Schwertmann, 2003;Torrent et al., 2007) .所以在極弱風化條件下, 成土體系中的磁化率可能大部分來自于原巖的磁性礦物, 來自成土作用新生的極少;而在強烈的風化過程中, 成土體系中的磁赤鐵礦大量地轉(zhuǎn)變?yōu)槌噼F礦, 所以磁化率也就失去了表征古氣候的意義.因此, 中緯度風化程度中等的土壤中, 磁化率的增加大部分來自于成土作用及風化強度的增加, 此時的磁化率是良好的古氣候替代指標.
另外, 近年來, 學者們傾向于將土壤的磁化率 (χ) 、非滯剩磁特性 (ARM) 、等溫剩磁特性 (IRM) 等磁性特征結(jié)合研究, 探討了成土體系中各種鐵礦物的轉(zhuǎn)換閾值與過程, 以期得到成土作用下磁性增強的模式規(guī)律, 并取得了越來越多的成果 (Deng et al., 2004;Torrent et al., 2007;Hu et al., 2015;Rupp et al., 2016) .
3.2.2 氣候類型決定赤鐵礦與針鐵礦的適用性
由于大量地形成赤鐵礦的最佳條件是干濕交替的氣候與較為豐富的年降水量, 因此溫暖潮濕的季風氣候下赤鐵礦與針鐵礦是適用性上佳的氣候指標.第四紀以來, 在夏季, 東亞季風、印度季風、南亞季風等多股夏季風為亞洲東部帶來熱量與豐沛的降水;到了冬季, 又主要受到東亞冬季風與亞洲西風所帶來的強烈的干冷空氣的影響 (An, 2000;Guo et al., 2000;An et al., 2001) .因此亞洲東部形成了利于赤鐵礦與針鐵礦共同生成的環(huán)境.例如中國的北方與南方的土壤沉積物 (Ji et al., 2001;Balsamet al., 2004;Zhang et al., 2009) 、中國南海的海相沉積物中 (Clift et al., 2014) , 赤鐵礦與針鐵礦作為輔助重建同時期第四紀氣候的演化與反映不同季風系統(tǒng)的此消彼長的指標得到了很好的應(yīng)用.然而, 當氣候類型中沒有旱季間隔時, 比如終年潮濕多雨的雨林氣候, 赤鐵礦與針鐵礦的組成與含量就無法反演當?shù)氐墓艢夂蜃兓?(Harris and Mix, 1999;Abrajevitch et al., 2009;Zhao et al., 2017) .因此, 在干濕交替的季風性氣候類型下, 赤鐵礦與針鐵礦可以作為獨立的、可靠的古氣候重建指標.
3.3 新型風化指標的尋找與展望
在當今的地質(zhì)學研究中, 對某區(qū)域內(nèi)過去氣候歷史與環(huán)境變遷史的解譯通常需要多指標對比驗證的方法 (Clift et al., 2014;Sun et al., 2015a;Zhao et al., 2017) .隨著近年來地質(zhì)學各領(lǐng)域內(nèi)越來越先進的測試儀器的出現(xiàn), 學者們一般通過兩種手段來加深原有的研究, 一是不斷提高風化指標的精度, 增加研究區(qū)的數(shù)據(jù)量 (Chen et al., 2014;Sun et al., 2016b;Yu et al., 2016) ;二是積極尋找新的地質(zhì)學方法, 創(chuàng)建新型的風化指標 (Balsamet al., 2004;Buggle et al., 2011;Cudahy et al., 2016) .下文內(nèi)容以光譜學為例, 展望了其作為新型風化指標的可能.
近年來, 光譜學在研究土壤的各種性能方面得到了越來越多的關(guān)注.光譜學是一種快速、無損、無需繁瑣樣品前期處理并且性價比極高的技術(shù)手段, 廣泛應(yīng)用于土壤pH、濕度、活性、離子轉(zhuǎn)換能力、有機碳、碳酸鹽、總氮量等的分析檢測 (Soriano-Disla et al., 2013;Nocita et al., 2014) .風化成土過程中典型的產(chǎn)物 (粘土礦物與鐵礦物) 的特征峰位于可見光至短波紅外光譜范圍 (VSWIR;350~2 500nm;圖4) .其中土壤中自生鐵礦物 (赤鐵礦與針鐵礦) 的最重要的特征峰位于可見光至短波紅外區(qū)域 (圖4a;350~1 000nm;VNIR) , 粘土礦物最重要的特征峰位于短波紅外區(qū)域 (圖4b;1 000~2 500nm;SWIR) (da Cruz et al., 2015;Zheng et al., 2016) .隨著風化程度的不同, 土壤體系中自生礦物的含量不斷變化, VSWIR圖譜特征峰的幾何學參數(shù) (峰位、峰強、峰寬、半高寬、對稱性等) 都會隨之改變.以針鐵礦與伊利石為例:針鐵礦在~500 nm, ~700 nm與~900nm左右都有典型的特征峰, 當風化程度降低, 氣候變冷時, 位于~900nm的峰位會右移, 位于~700nm的峰強會增大 (圖4a;Murphy et al., 2013, 2014) ;伊利石在~1 400nm, ~1 900nm與~2 200nm存在顯著的特征峰, 當氣候由暖濕向干冷轉(zhuǎn)變時, 位于~1 400nm與~2 200nm峰的對稱性增大, ~2 200nm峰的峰位左移, 峰強變?nèi)?(圖4b;da Cruz et al., 2015) .更重要的是, VSWIR范圍內(nèi)粘土礦物與鐵礦物的特征峰值、峰位等幾何學特征所反映的信息與XRD分析所得的結(jié)果相一致 (Cudahy et al., 2016;Leask and Ehlmann, 2016) .這種一致性使得VSWIR光譜學特征對古風化以及古氣候過程信息的反演成為可能.
圖4 部分常見粘土礦物與鐵礦物在VSWIR光譜區(qū)域內(nèi)的特征峰
4 結(jié)論
地球表層的土壤是在物理、生物、化學風化過程綜合作用下形成的產(chǎn)物, 記錄了第四紀以來與氣候、環(huán)境、人類等有關(guān)的地球演化信息, 是重要的研究全球變化的載體.風化過程下的成土作用一般經(jīng)歷了原始母巖礦物的分解、體系內(nèi)離子的遷移以及新礦物的形成等一系列的進程.成土體系中元素的遷移、粒度分布、新礦物的生成等與成土有關(guān)的特質(zhì)可以用來確定其風化程度, 進而反映成土期的氣候變化.其中, 成土體系中自生的粘土礦物與鐵礦物等自生礦物的礦物學信息可以提取并作為可靠的反演第四紀古氣候的風化指標.
成土作用中新生成的粘土礦物直接受成土期盛行的環(huán)境狀態(tài)與氣候條件的影響, 所以其組成、粒度、含量、結(jié)晶度等礦物學特征充分記錄了成土期的氣候與環(huán)境信息.其中伊利石、綠泥石、蛭石、蒙脫石、高嶺石等土壤中常見的粘土礦物具有極其鮮明的氣候反演意義, 單獨的某種粘土礦物的含量特征或者某些粘土礦物的比值變化都可以用來反映成土期的風化程度與氣候演化特征.另外, 隨著微觀分析技術(shù)的不斷進步, 粘土礦物的微觀轉(zhuǎn)換特征更是為成土期的氣候轉(zhuǎn)變提供了直接的證據(jù).
除了粘土礦物, 成土體系中也會新生成部分磁鐵礦、磁赤鐵礦等磁性鐵礦物與赤鐵礦、針鐵礦等非/弱磁性鐵礦物.自生的鐵礦物是反映成土期的濕度條件、溫度范圍的有效指標, 因此對當時的氣候演化歷史也與很好的指示意義.磁鐵礦與磁赤鐵礦的含量與磁化率息息相關(guān), 黃土-古土壤序列中的磁化率與深海氧同位素波動有明顯的正相關(guān)關(guān)系, 證明磁化率可以幫助反演大陸古氣候特征.另一方面, 赤鐵礦與針鐵礦在成土體系中的此消彼長與季風性的氣候變化相對應(yīng), 獨立的赤鐵礦和/或針鐵礦的含量變化, 或者赤鐵礦與針鐵礦的比值都可以用作季風氣候演化的指標.
成土體系中新生的粘土礦物與鐵礦物的礦物學特征在一定條件下都可以作為獨立的反映氣候信息的良好指標.但是在真正將其應(yīng)用在某研究區(qū)域中時, 還要充分考慮當?shù)氐牡刭|(zhì)背景、物源供給、氣候類型、成土條件等因素的制約.在將某古氣候指標應(yīng)用于實際研究中時, 要注意結(jié)合主量元素、微量元素、粒度分布、同位素等指標共同印證, 使得得到的結(jié)論清晰可靠.另外, 在今后的研究中, 應(yīng)該積極探尋光譜學等新的風化指標, 在多指標的共同重建下力求對區(qū)域內(nèi)的古氣候歷史完整、精準的表達.
參考文獻
[]Abrajevitch, A., van der Voo, R.V.D., Rea, D.K., 2009.Variations in Relative Abundances of Goethite and Hematite in Bengal Fan Sediments:Climatic vs.Diagenetic Signals.Marine Geology, 267 (3-4) :191-206.https://doi.org/10.1016/j.margeo.2009.10.010
[]An, Z., Kutzbach, J.E., Prell, W.L., et al., 2001.Evolution of Asian Monsoons and Phased Uplift of the HimalayaTibetan Plateau since Late Miocene Times.Nature, 411 (6833) :62-66.
[]An, Z.S., 2000.The History and Variability of the East Asian Paleomonsoon Climate.Quaternary Science Reviews, 19 (1-5) :171-187.https://doi.org/10.1016/s0277-3791 (99) 00060-8
[]Anderson, S.P., Blum, J., Brantley, S.L., et al., 2004.Proposed Initiative Would Study Earth's Weathering Engine.EOS, Transactions American Geophysical Union, 85 (28) :265.https://doi.org/10.1029/2004eo280001
[]Balsam, W., Ji, J.F., Chen, J., 2004.Climatic Interpretation of the Luochuan and Lingtai Loess Sections, China, Based on Changing Iron Oxide Mineralogy and Magnetic Susceptibility.Earth and Planetary Science Letters, 223 (3-4) :335-348.https://doi.org/10.1016/j.epsl.2004.04.023
[]Blum, A.E., Yund, R.A., Lasaga, A.C., 1990.The Effect of Dislocation Density on the Dissolution Rate of Quartz.Geochimica et Cosmochimica Acta, 54 (2) :283-297.https://doi.org/10.1016/0016-7037 (90) 90318-f
[]Bourne, M.D., Feinberg, J.M., Strauss, B.E., et al., 2015.Long-Term Changes in Precipitation Recorded by Magnetic Minerals in Speleothems.Geology, 43 (7) :595-598.https://doi.org/10.1130/g36695.1
[]Brady, N.C., Weil, R.R., 2004.Elements of the Nature and Properties of Soils.Upper Saddle River, New Jersey, Prentice-Hall, 960.
[]Brantley, S.L., Goldhaber, M.B., Ragnarsdottir, K.V., 2007.Crossing Disciplines and Scales to Understand the Critical Zone.Elements, 3 (5) :307-314.https://doi.org/10.2113/gselements.3.5.307
[]Buggle, B., Glaser, B., Hambach, U., et al., 2011.An Evaluation of Geochemical Weathering Indices in LoessPaleosol Studies.Quaternary International, 240 (1-2) :12-21.https://doi.org/10.1016/j.quaint.2010.07.019
[]Buggle, B., Hambach, U., Müller, K., et al., 2014.Iron Mineralogical Proxies and Quaternary Climate Change in SE-European Loess-Paleosol Sequences.Catena, 117:4-22.https://doi.org/10.1016/j.catena.2013.06.012
[]Chadwick, O.A., Chorover, J., 2001.The Chemistry of Pedogenic Thresholds.Geoderma, 100 (3-4) :321-353.https://doi.org/10.1016/s0016-7061 (01) 00027-1
[]Chamley, H., 1989, Clay Sedimentology.Springer, Berlin, 623.
[]Chen, J., An, Z.S., Head, J., 1999.Variation of Rb/Sr Ratios in the Loess-Paleosol Sequences of Central China during the Last 130 000 Years and Their Implications for Monsoon Paleoclimatology.Quaternary Research, 51 (3) :215-219.https://doi.org/10.1006/qres.1999.2038
[]Chen, J.S., Liu, X.M., Kravchinsky, V.A., 2014.Response of the High-Resolution Chinese Loess Grain Size Record to the50°N Integrated Winter Insolation during the Last 500 000Years.Geophysical Research Letters, 41 (17) :6244-6251.https://doi.org/10.1002/2014gl060239
[]Chen, T., Xu, H., Xie, Q., et al., 2005.Characteristics and Genesis of Maghemite in Chinese Loess and Paleosols:Mechanism for Magnetic Susceptibility Enhancement in Paleosols.Earth and Planetary Science Letters, 240 (3-4) :790-802.https://doi.org/10.1016/j.epsl.2005.09.026
[]Chen, T.H., Xie, Q.Q., Xu, H.F., et al., 2010.Characteristics and Formation Mechanism of Pedogenic Hematite in Quaternary Chinese Loess and Paleosols.Catena, 81 (3) :217-225.https://doi.org/10.1016/j.catena.2010.04.001
[]Cheng, F., Hong, H.L., Gu, Y.S., et al., 2014.Clay Mineralogy and Its Paleoclimate Interpretation of the Pleistocene Sediments in Baise Basin, Southern China.Quaternary Sciences, 34 (3) :560-569 (in Chinese with English abstract) .
[]Chevrier, V., Mathé, P.E., Rochette, P., et al., 2006.Magnetic Study of an Antarctic Weathering Profile on Basalt:Implications for Recent Weathering on Mars.Earth and Planetary Science Letters, 244 (3-4) :501-514.https://doi.org/10.1016/j.epsl.2006.02.033
[]Clark, R.N., Swayze, G.A., Wise, R., et al., 2007.USGS Digital Spectral Library Splib06a.US Geological Survey, Digital Data Series, 231.
[]Clemens, S.C., 2015.Late Cenozoic Climate Change in Asia:Loess, Monsoon and Monsoon-Arid Environment E-volution.Quaternary Science Reviews, 107:274-275.https://doi.org/10.1016/j.quascirev.2014.10.026
[]Clift, P.D., Wan, S.M., Blusztajn, J., 2014.Reconstructing Chemical Weathering, Physical Erosion and Monsoon Intensity since 25Ma in the Northern South China Sea:A Review of Competing Proxies.Earth-Science Reviews, 130:86-102.https://doi.org/10.1016/j.earscirev.2014.01.002
[]Cornell, R.M., Schwertmann, U., 2003, The Iron Oxides:Structure, Properties, Reactions, Occurrences and Uses.Wiley VCH, Weinheim
[]Cudahy, T., Caccetta, M., Thomas, M., et al., 2016.SatelliteDerived Mineral Mapping and Monitoring of Weathering, Deposition and Erosion.Scientific Reports, 6 (1) :1-12.https://doi.org/10.1038/srep23702
[]da Cruz, R.S.D., Fernandes, C.M.D., Villas, R.N.N., et al., 2015.A Study of the Hydrothermal Alteration in Paleoproterozoic Volcanic Centers, S2o Félix do Xingu Region, Amazonian Craton, Brazil, Using Short-Wave Infrared Spectroscopy.Journal of Volcanology and Geothermal Research, 304:324-335.https://doi.org/10.1016/j.jvolgeores.2015.09.005
[]de Menocal, P.B., 2004.African Climate Change and Faunal Evolution during the Pliocene-Pleistocene.Earth and Planetary Science Letters, 220 (1-2) :3-24.https://doi.org/10.1016/s0012-821x (04) 00003-2
[]Deng, C.L., Zhu, R.X., Verosub, K.L., et al., 2004.Mineral Magnetic Properties of Loess/Paleosol Couplets of the Central Loess Plateau of China over the Last 1.2 Myr.Journal of Geophysical Research:Solid Earth, 109 (B1) :241-262.https://doi.org/10.1029/2003jb002532
[]Dixon, J.L., Chadwick, O.A., Vitousek, P.M., 2016.ClimateDriven Thresholds for Chemical Weathering in Postglacial Soils of New Zealand.Journal of Geophysical Research:Earth Surface, 121 (9) :1619-1634.https://doi.org/10.1002/2016jf003864
[]Dixon, J.L., Heimsath, A.M., Kaste, J., et al., 2009.ClimateDriven Processes of Hillslope Weathering.Geology, 37 (11) :975-978.https://doi.org/10.1130/g30045a.1
[]Dixon, J.B., Weed, S.B., 1989.Minerals in Soil Environments (2nd ed.) .Soil Science Society of America, Madison, WI.
[]Dou, Y., Li, J., Zhao, J., et al., 2014.Clay Mineral Distributions in Surface Sediments of the Liaodong Bay, Bohai Sea and Surrounding River Sediments:Sources and Transport Patterns.Continental Shelf Research, 73:72-82.https://doi.org/10.1016/j.csr.2013.11.023
[]Dou, Y., Yang, S., Liu, Z., et al., 2010.Clay Mineral Evolution in the Central Okinawa trough since 28ka:Implications for Sediment Provenance and Paleoenvironmental Change.Palaeogeography, Palaeoclimatology, Palaeoecology, 288 (1-4) :108-117.https://doi.org/10.1016/j.palaeo.2010.01.040
[]Ehrmann, W., Seidel, M., Schmiedl, G., 2013.Dynamics of Late Quaternary North African Humid Periods Documented in the Clay Mineral Record of Central Aegean Sea Sediments.Global and Planetary Change, 107:186-195.https://doi.org/10.1016/j.gloplacha.2013.05.010
[]Eiriksdottir, E.S., Gislason, S.R., Oelkers, E.H., 2013.Does Temperature or Runoff Control the Feedback between Chemical Denudation and Climate?Insights from NEIceland.Geochimica et Cosmochimica Acta, 107:65-81.https://doi.org/10.1016/j.gca.2012.12.034
[]Fairchild, I.J., Smith, C.L., Baker, A., et al., 2006.Modification and Preservation of Environmental Signals in Speleothems.Earth-Science Reviews, 75 (1-4) :105-153.https://doi.org/10.1016/j.earscirev.2005.08.003
[]Fang, Q., Hong, H.L., Chen, Z.Q., et al., 2017.Microbial Proliferation Coinciding with Volcanism during the Permian-Triassic Transition:New, Direct Evidence from Volcanic Ashes, South China.Palaeogeography, Palaeoclimatology, Palaeoecology, 474:164-186.https://doi.org/10.1016/j.palaeo.2016.06.026
[]Gingele, F.X., de Deckker, P., 2004.Fingerprinting Australia's Rivers with Clay Minerals and the Application for the Marine Record of Climate Change.Australian Journal of Earth Sciences, 51 (3) :339-348.https://doi.org/10.1111/j.1400-0952.2004.01061.x
[]Gingele, F., de Deckker, P., Norman, M., 2007.Late Pleistocene and Holocene Climate of SE Australia Reconstructed from Dust and River Loads Deposited Offshore the River Murray Mouth.Earth and Planetary Science Letters, 255 (3-4) :257-272.https://doi.org/10.1016/j.epsl.2006.12.019
[]Gislason, S.R., Oelkers, E.H., Eiriksdottir, E.S., et al., 2009.Direct Evidence of the Feedback between Climate and Weathering.Earth and Planetary Science Letters, 277 (1-2) :213-222.https://doi.org/10.1016/j.epsl.2008.10.018
[]Goldich, S.S., 1938.A Study in Rock-Weathering.The Journal of Geology, 46 (1) :17-58.https://doi.org/10.1086/624619
[]Guan, H., Zhu, C., Zhu, T., et al., 2016.Grain Size, Magnetic Susceptibility and Geochemical Characteristics of the Loess in the Chaohu Lake Basin:Implications for the Origin, Palaeoclimatic Change and Provenance.Journal of Asian Earth Sciences, 117:170-183.https://doi.org/10.1016/j.jseaes.2015.12.013
[]Guo, Z., Biscaye, P., Wei, L., et al., 2000.Summer Monsoon Variations over the Last 1.2Ma from the Weathering of Loess-Soil Sequences in China.Geophysical Research Letters, 27 (12) :1751-1754.https://doi.org/10.1029/1999gl008419
[]Guyot, J.L., Jouanneau, J.M., Soares, L., et al., 2007.Clay Mineral Composition of River Sediments in the Amazon Basin.Catena, 71 (2) :340-356.https://doi.org/10.1016/j.catena.2007.02.002
[]Gylesj9, S., Arnold, E., 2006.Clay Mineralogy of a Red Clay-Loess Sequence from Lingtai, the Chinese Loess Plateau.Global and Planetary Change, 51 (3-4) :181-194.https://doi.org/10.1016/j.gloplacha.2006.03.002
[]Hamann, Y., Ehrmann, W., Schmiedl, G., et al., 2009.Modern and Late Quaternary Clay Mineral Distribution in the Area of the SE Mediterranean Sea.Quaternary Research, 71 (3) :453-464.https://doi.org/10.1016/j.yqres.2009.01.001
[]Harper, R.J., Gilkes, R.J., 2004.Aeolian Influences on the Soils and Landforms of the Southern Yilgarn Craton of Semi-Arid, Southwestern Australia.Geomorphology, 59 (1-4) :215-235.https://doi.org/10.1016/j.geomorph.2003.07.018
[]Harris, S.E., Mix, A.C., 1999.Pleistocene Precipitation Balance in the Amazon Basin Recorded in Deep Sea Sediments.Quaternary Research, 51 (1) :14-26.https://doi.org/10.1006/qres.1998.2008
[]Hong, H.L., Fang, Q., Wang, C.W., et al., 2017.Constraints of Parent Magma on Altered Clay Minerals:A Case Study on the Ashes near the Permian-Triassic Boundary in Xinmin Section, Guizhou Province.Earth Science, 42 (2) :161-172 (in Chinese with English abstract) .
[]Hong, H., Cheng, F., Yin, K., et al., 2015.Three-Component Mixed-Layer Illite/Smectite/Kaolinite (I/S/K) Minerals in Hydromorphic Soils, South China.American Mineralogist, 100 (8-9) :1883-1891.https://doi.org/10.2138/am-2015-5170
[]Hong, H., Churchman, G.J., Gu, Y., et al., 2012.KaoliniteSmectite Mixed-Layer Clays in the Jiujiang Red Soils and Their Climate Significance.Geoderma, 173-174:75-83.https://doi.org/10.1016/j.geoderma.2011.12.006
[]Hong, H., Churchman, G.J., Yin, K., et al., 2014.Randomly Interstratified Illite-Vermiculite from Weathering of Illite in Red Earth Sediments in Xuancheng, Southeastern China.Geoderma, 214-215:42-49.https://doi.org/10.1016/j.geoderma.2013.10.004
[]Hong, H., Fang, Q., Cheng, L., et al., 2016.MicroorganismInduced Weathering of Clay Minerals in a Hydromorphic Soil.Geochimica et Cosmochimica Acta, 184:272-288.https://doi.org/10.1016/j.gca.2016.04.015
[]Hong, H., Fang, Q., Wang, C., et al., 2017.Constraints of Parent Magma on Altered Clay Minerals:A Case Study on the Ashes near the Permin-Triassic Boundary in Xinmin Section, Guizhou Province.Earth Science, 42 (2) :161-172 (in Chinese with English abstract) .
[]Hong, H., Gu, Y., Yin, K., et al., 2010.Red Soils with White Net-Like Veins and Their Climate Significance in South China.Geoderma, 160 (2) :197-207.https://doi.org/10.1016/j.geoderma.2010.09.019
[]Ho2ek, J., Hambach, U., Lisá, L., et al., 2015.An Integrated Rock-Magnetic and Geochemical Approach to Loess/Paleosol Sequences from Bohemia and Moravia (Czech Republic) :Implications for the Upper Pleistocene Paleoenvironment in Central Europe.Palaeogeography, Palaeoclimatology, Palaeoecology, 418:344-358.https://doi.org/10.1016/j.palaeo.2014.11.024
[]Hu, P., Liu, Q., Heslop, D., et al., 2015.Soil Moisture Balance and Magnetic Enhancement in Loess-Paleosol Sequences from the Tibetan Plateau and Chinese Loess Plateau.Earth and Planetary Science Letters, 409:120-132.
[]Hu, P., Liu, Q., Torrent, J., et al., 2013.Characterizing and Quantifying Iron Oxides in Chinese Loess/Paleosols:Implications for Pedogenesis.Eath and Planetary Science Letters, 369:271-283.
[]Hu, X., Wei, J., Xu, L., et al., 2009.Magnetic Susceptibility of the Quaternary Red Clay in Subtropical China and Its Paleoenvironmental Implications.Palaeogeography, Palaeoclimatology, Palaeoecology, 279 (3-4) :216-232.
[]Huggett, R.J., 1998.Soil Chronosequences, Soil Development, and Soil Evolution:A Critical Review.Catena, 32 (3-4) :155-172.
[]Inda, A.V., Torrent, J., Barrón, V., et al., 2013.Iron Oxides Dynamics in a Subtropical Brazilian Paleudult under Long-Term No-Tillage Management.Scientia Agricola, 70 (1) :48-54.https://doi.org/10.1590/s0103-90162013000100008
[]Jahn, B.M., Gallet, S., Han, J.M., 2001.Geochemistry of the Xining, Xifeng and Jixian Sections, Loess Plateau of China:Eolian Dust Provenance and Paleosol Evolution during the Last 140ka.Chemical Geology, 178 (1-4) :71-94.https://doi.org/10.1016/s0009-2541 (00) 00430-7
[]Ji, J.F., 2004.High Resolution Hematite/Goethite Records from Chinese Loess Sequences for the Last GlacialInterglacial Cycle:Rapid Climatic Response of the East Asian Monsoon to the Tropical Pacific.Geophysical Research Letters, 31 (3) :1-4.https://doi.org/10.1029/2003gl018975
[]Ji, J.F., Balsam, W., Chen, J., 2001.Mineralogic and Climatic Interpretations of the Luochuan Loess Section (China) Based on Diffuse Reflectance Spectrophotometry.Quaternary Research, 56 (1) :23-30.https://doi.org/10.1006/qres.2001.2238
[]Ji, J.F., Chen, J., Wang, H.T., 2012.Crystallinity of Illite from the Luochuan Loess-Paleosol Sequence, Shanxi Provice-Indicators Origin and Paleoclimate of Loess.Geological Review, 43 (2) :181-185 (in Chinese with English abstract) .
[]Jiang, H., Guo, G., Cai, X., et al., 2016.Geochemical Evidence of Windblown Origin of the Late Cenozoic Lacustrine Sediments in Beijing and Implications for Weathering and Climate Change.Palaeogeography, Palaeoclimatology, Palaeoecology, 446:32-43.https://doi.org/10.1016/j.palaeo.2016.01.017
[]Jordanova, D., Jordanova, N., Petrov, P., et al., 2010.Soil Development of Three Chernozem-Like Profiles from North Bulgaria Revealed by Magnetic Studies.Catena, 83 (2-3) :158-169.https://doi.org/10.1016/j.catena.2010.08.008
[]Kukla, G., Heller, F., Ming, L.X., et al., 1988.Pleistocene Climates in China Dated by Magnetic Susceptibility.Geology, 16 (9) :811.https://doi.org/10.1130/0091-7613 (1988) 016<0811:pcicdb>2.3.co;2
[]Lascu, I., Feinberg, J.M., 2011.Speleothem Magnetism.Quaternary Science Reviews, 30 (23-24) :3306-3320.https://doi.org/10.1016/j.quascirev.2011.08.004
[]Leask, E.K., Ehlmann, B.L., 2016.Identifying and Quantifying Mineral Abundance through VSWIR Microimaging Spectroscopy:A Comparison to XRD and SEM.The Workshop on Hyperspectral Image&Signal Processing:Evolution in Remote Sensing.
[]Lee, Y.I., Lim, H.S., Yoon, H.I., 2004.Geochemistry of Soils of King George Island, South Shetland Islands, West Antarctica:Implications for Pedogenesis in Cold Polar Regions.Geochimica et Cosmochimica Acta, 68 (21) :4319-4333.https://doi.org/10.1016/j.gca.2004.01.020
[]Li, C.A., Gu, Y.S., 1997.A Priliminary Study on Phytolith Assemblages and Its Paleoenvironmental Indication of the Vermicular Red Earth.Earth Science, 22 (2) :195-198 (in Chinese with English abstract) .
[]Li, J.H., Pan, Y.X., 2015.Application of Transmission Electron Microscopy in Earth Science.Earth Science, 45 (9) :1359-1382 (in Chinese) .
[]Liu, Q.S., Deng, C.L., Torrent, J., et al., 2007.Review of Recent Developments in Mineral Magnetism of the Chinese Loess.Quaternary Science Reviews, 26 (3-4) :368-385.https://doi.org/10.1016/j.quascirev.2006.08.004
[]Liu, T., Ding Z.L., Rutter, N., 1999.Comparison of Milankovitch Periods between Continental Loess and Deep Sea Records over the Last 2.5Ma.Quaternary Science Reviews, 18 (10-11) :1205-1212.https://doi.org/10.1016/s0277-3791 (98) 00110-3
[]Liu, T., Ding, Z., 1993.Stepwise Coupling of Monsoon Circulations to Global Ice Volume Variations during the Late Cenozoic.Global and Planetary Change, 7 (1-3) :119-130.https://doi.org/10.1016/0921-8181 (93) 90044-o
[]Liu, Z., Ma, J., Wei, G., et al., 2017.Magnetism of a Red Soil Core Derived from Basalt, Northern Hainan Island, China:Volcanic Ash versus Pedogenesis.Journal of Geophisical Research-Solid Earth, 122 (3) :1677-1696.
[]Liu, Z.F., Colin, C., Huang, W., et al., 2007.Climatic and Tectonic Controls on Weathering in South China and Indochina Peninsula:Clay Mineralogical and Geochemical Investigations from the Pearl, Red, and Mekong Drainage Basins.Geochemistry, Geophysics, Geosystems, 8 (5) :1-18.https://doi.org/10.1029/2006gc001490
[]Liu, Z.F., Colin, C., Li, X.J., et al., 2010.Clay Mineral Distribution in Surface Sediments of the Northeastern South China Sea and Surrounding Fluvial Drainage Basins:Source and Transport.Marine Geology, 277 (1-4) :48-60.https://doi.org/10.1016/j.margeo.2010.08.010
[]Liu, Z.F., Tuo, S.T., Colin, C., et al., 2008.Detrital FineGrained Sediment Contribution from Taiwan to the Northern South China Sea and Its Relation to Regional Ocean Circulation.Marine Geology, 255 (3-4) :149-155.https://doi.org/10.1016/j.margeo.2008.08.003
[]Liu, Z.F., Zhao, Y.L., Colin, C., et al., 2009.Chemical Weathering in Luzon, Philippines from Clay Mineralogy and Major-Element Geochemistry of River Sediments.Applied Geochemistry, 24 (11) :2195-2205.https://doi.org/10.1016/j.apgeochem.2009.09.025
[]Long, X.Y., Ji, J.F., Balsam, W., 2011.Rainfall-Dependent Transformations of Iron Oxides in a Tropical Saprolite Transect of Hainan Island, South China:Spectral and Magnetic Measurements.Journal of Geophysical Research-Earth Surface, 116:1-15.
[]Long, X.Y., Ji, J.F., Barrón, V., et al., 2016.Climatic Thresholds for Pedogenic Iron Oxides under Aerobic Conditions:Processes and Their Significance in Paleoclimate Reconstruction.Quaternary Science Reviews, 150:264-277.https://doi.org/10.1016/j.quascirev.2016.08.031
[]Lu, S., Wang, S., Chen, Y., 2015.Palaeopedogenesis of Red Palaeosols in Yunnan Plateau, Southwestern China:Pedogenical, Geochemical and Mineralogical Evidences and Palaeoenvironmental Implication.Palaeogeography, Palaeoclimatology, Palaeoecology, 420:35-48.https://doi.org/10.1016/j.palaeo.2014.12.004
[]Maher, B.A., 1998.Magnetic Properties of Modern Soils and Quaternary Loessic Paleosols:Paleoclimatic Implications.Palaeogeography, Palaeoclimatology, Palaeoecology, 137 (1-2) :25-54.https://doi.org/10.1016/s0031-0182 (97) 00103-x
[]Martinson, D.G., Pisias, N.G., Hays, J.D., et al., 1987.Age Dating and the Orbital Theory of the Ice Ages:Development of a High-Resolution 0to 300 000-Year Chronostratigraphy.Quaternary Research, 27 (1) :1-29.https://doi.org/10.1016/0033-5894 (87) 90046-9
[]Murphy, R.J., Schneider, S., Monteiro, S.T., 2014.Consistency of Measurements of Wavelength Position from Hyperspectral Imagery:Use of the Ferric Iron Crystal Field Absorption at~900nm as an Indicator of Mineralogy.IEEE Transactions on Geoscience and Remote Sensing, 52 (5) :2843-2857.https://doi.org/10.1109/tgrs.2013.2266672
[]Nesbitt, H.W., Young, G.M., 1989.Formation and Diagenesis of Weathering Profiles.The Journal of Geology, 97 (2) :129-147.https://doi.org/10.1086/629290
[]Nocita, M., Stevens, A., van Wesemael, B.V., et al., 2014.Soil Spectroscopy:An Opportunity to be Seized.Global ChangeBiology, 21 (1) :10-11.https://doi.org/10.1111/gcb.12632
[]Nordt, L.C., Driese, S.D., 2010.New Weathering Index Improves Paleorainfall Estimates from Vertisols.Geology, 38 (5) :407-410.https://doi.org/10.1130/g30689.1
[]Osete, M.L., Martín-Chivelet, J., Rossi, C., et al., 2012.The Blake Geomagnetic Excursion Recorded in a Radiometrically Dated Speleothem.Earth and Planetary Science Letters, 353-354:173-181.https://doi.org/10.1016/j.epsl.2012.07.041
[]Railsback, L.B., Gibbard, P.L., Head, M.J., et al., 2015.An Optimized Scheme of Lettered Marine Isotope Substages for the Last 1.0Million Years, and the Climatostratigraphic Nature of Isotope Stages and Substages.Quaternary Science Reviews, 111:94-106.https://doi.org/10.1016/j.quascirev.2015.01.012
[]Robert, C., 2004.Late Quaternary Variability of Precipitation in Southern California and Climatic Implications:Clay Mineral Evidence from the Santa Barbara Basin, ODP Site 893.QuaternaryScienceReviews, 23 (9-10) :1029-1040.https://doi.org/10.1016/j.quascirev.2003.11.005
[]Rupp, K., Jungemann, C., Hong, S.M., et al., 2016.A Review of Recent Advances in the Spherical Harmonics Expansion Method for Semiconductor Device Simulation.Journal of Computational Electronics, 15 (3) :939-958.https://doi.org/10.1007/s10825-016-0828-z
[]Schwertmann, U., 1993, Relations between Iron Oxides, Soil Color, and Soil Formation.In:Bigham, J.M., Ciolkosz, E.J., Luxmoore, R.J., eds., Soil Color SSSA Special Publication, 31:51-70.
[]Sheldon, N.D., Tabor, N.J., 2009.Quantitative Paleoenvironmental and Paleoclimatic Reconstruction Using Paleosols.Earth-Science Reviews, 95 (1-2) :1-52.https://doi.org/10.1016/j.earscirev.2009.03.004
[]Shen, J., Algeo, T.J., Zhou, L., et al., 2011.Volcanic Perturbations of the Marine Environment in South China Preceding the Latest Permian Mass Extinction and Their Biotic Effects.Geobiology, 10 (1) :82-103.https://doi.org/10.1111/j.1472-4669.2011.00306.x
[]Simonson, R.W., 1959.Outline of a Generalized Theory of Soil Genesis 1.Soil Science Society of America Journal, 23 (2) :152.https://doi.org/10.2136/sssaj1959.03615995002300020021x
[]Soriano-Disla, J.M., Janik, L.J., Rossel, R.A.V., et al., 2013.The Performance of Visible, Near-, and Mid-Infrared Reflectance Spectroscopy for Prediction of Soil Physical, Chemical, and Biological Properties.Applied Spectroscopy Reviews, 49 (2) :139-186.https://doi.org/10.1080/05704928.2013.811081
[]Stockmann, U., Minasny, B., McBratney, A., 2011.Advances in Agronomy Quantifying Processes of Pedogenesis.Advances in Agronomy, 150:1-74.https://doi.org/10.1016/b978-0-12-386473-4.00001-4
[]Stuut, J.B.W., Temmesfeld, F., de Deckker, P., 2014.A 550ka Record of Aeolian Activity near North West Cape, Australia:Inferences from Grain-Size Distributions and Bulk Chemistry of SE Indian Ocean Deep-Sea Sediments.Quaternary Science Reviews, 83:83-94.https://doi.org/10.1016/j.quascirev.2013.11.003
[]Sun, Y., Kutzbach, J., An, Z., et al., 2015a.Astronomical and Glacial Forcing of East Asian Summer Monsoon Variability.Quaternary Science Reviews, 115:132-142.https://doi.org/10.1016/j.quascirev.2015.03.009
[]Sun, Y., Ma, L., Bloemendal, J., et al., 2015b.Miocene Climate Change on the Chinese Loess Plateau:Possible Links to the Growth of the Northern Tibetan Plateau and Global Cooling.Geochemistry, Geophysics, Geosystems, 16 (7) :2097-2108.https://doi.org/10.1002/2015gc005750
[]Sun, Z., Owens, P.R., Han, C., et al., 2016a.A Quantitative Reconstruction of a Loess-Paleosol Sequence Focused on Paleosol Genesis:An Example from a Section at Chaoyang, China.Geoderma, 266:25-39.https://doi.org/10.1016/j.geoderma.2015.12.012
[]Sun, Y., Liang, L., Bloemendal, J., et al., 2016b.HighResolution Scanning XRF Investigation of Chinese Loess and Its Implications for Millennial-Scale Monsoon Variability.Journal of Quaternary Science, 31 (3) :191-202.https://doi.org/10.1002/jqs.2856
[]Thamban, M., Rao, V.P., Schneider, R.R., 2002.Reconstruction of Late Quaternary Monsoon Oscillations Based on Clay Mineral Proxies Using Sediment Cores from the Western Margin of India.Marine Geology, 186 (3-4) :527-539.https://doi.org/10.1016/s0025-3227 (02) 00268-2
[]Torrent, J., Liu, Q.S., Bloemendal, J., et al., 2007.Magnetic Enhancement and Iron Oxides in the Upper Luochuan Loess-Paleosol Sequence, Chinese Loess Plateau.Soil Science Society of America Journal, 71 (5) :1570.https://doi.org/10.2136/sssaj2006.0328
[]Torrent, J., Schwertmann, U., Fechter, H., et al., 1983.Quantitative Relationships between Soil Color and Hematite Content.Soil Science, 136 (6) :354-358.https://doi.org/10.1097/00010694-198312000-00004
[]Turpault, M.P., Righi, D., Utérano, C., 2008.Clay Minerals:Precise Markers of the Spatial and Temporal Variability of the Biogeochemical Soil Environment.Geoderma, 147 (3-4) :108-115.https://doi.org/10.1016/j.geoderma.2008.07.012
[]U'jvári, G., Varga, A., Raucsik, B., et al., 2014.The Paks Loess-Paleosol Sequence:A Record of Chemical Weathering and Provenance for the Last 800ka in the Mid-Carpathian Basin.Quaternary International, 319:22-37.https://doi.org/10.1016/j.quaint.2012.04.004
[]Varga, A., U'jvári, G., Raucsik, B., 2011.Tectonic versus Climatic Control on the Evolution of a Loess-Paleosol Sequence at Beremend, Hungary:An Integrated Approach Based on Paleoecological, Clay Mineralogical, and Geochemical Data.Quaternary International, 240 (1-2) :71-86.https://doi.org/10.1016/j.quaint.2010.10.032
[]Wang, C., Hong, H., Abels, H.A., et al., 2015.Early Middle Miocene Tectonic Uplift of the Northwestern Part of the Qinghai-Tibetan Plateau Evidenced by Geochemical and Mineralogical Records in the Western Tarim Basin.International Journal of Earth Sciences, 105 (3) :1021-1037.https://doi.org/10.1007/s00531-015-1212-0
[]Wang, Q., Yang.S.Y., 2013.Clay Mineralogy Indicates the Holocene Monsoon Climate in the Changjiang (Yangtze River) Catchment, China.Applied Clay Science, 74:28-36.https://doi.org/10.1016/j.clay.2012.08.011
[]White, A.F., Brantley, S.L., 2003.The Effect of Time on the Weathering of Silicate Minerals:Why do Weathering Rates Differ in the Laboratory and Field?Chemical Geology, 202 (3-4) :479-506.https://doi.org/10.1016/j.chemgeo.2003.03.001
[]Wilson, M.J., 2004.Weathering of the Primary Rock-Forming Minerals:Processes, Products and Rates.Clay Minerals, 39 (3) :233-266.https://doi.org/10.1180/0009855043930133
[]Xi, C.F., 1991.On the Red Weathering Crusts of Southern China.Quaternary Sciences, (1) :1-8 (in Chinese with English abstract) .
[]Xie, Q., Chen, T., Zhou, H., et al., 2013a.Mechanism of Palygorskite Formation in the Red Clay Formation on the Chinese Loess Plateau, Northwest China.Geoderma, 192:39-49.https://doi.org/10.1016/j.geoderma.2012.07.021
[]Xie, S., Evershed, R.P., Huang, X., et al., 2013b.Concordant Monsoon-Driven Postglacial Hydrological Changes in Peat and Stalagmite Records and Their Impacts on Prehistoric Cultures in Central China.Geology, 41 (8) :827-830.https://doi.org/10.1130/g34318.1
[]Yang, J.D., Chen, J., An, Z.S., et al., 2000.Variations in87Sr/86Sr Ratios of Calcites in Chinese Loess:A Proxy for Chemical Weathering Associated with the East Asian Summer Monsoon.Palaeogeography, Palaeoclimatology, Palaeoecology, 157 (1-2) :151-159.https://doi.org/10.1016/s0031-0182 (99) 00159-5
[]Yang, S., Jung, H., Li, C., 2004.Two Unique Weathering Regimes in the Changjiang and Huanghe Drainage Basins:Geochemical Evidence from River Sediments.Sedimentary Geology, 164 (1-2) :19-34.https://doi.org/10.1016/j.sedgeo.2003.08.001
[]Yang, X., Peng, X., Qiang, X., et al., 2016.Chemical Weathering Intensity and Terrigenous Flux in South China during the Last 90 000 Years-Evidence from Magnetic Signals in Marine Sediments.Frontiers in Earth Science, 4:1-9.https://doi.org/10.3389/feart.2016.00047
[]Yin, K., Hong, H., Churchman, G.J., et al., 2013.HydroxyInterlayered Vermiculite Genesis in Jiujiang LatePleistocene Red Earth Sediments and Significance to Climate.Applied Clay Science, 74:20-27.https://doi.org/10.1016/j.clay.2012.09.017
[]Yu, Z., Wan, S., Colin, C., et al., 2016.Co-Evolution of Monsoonal Precipitation in East Asia and the Tropical Pacific ENSO System since 2.36 Ma:New Insights from HighResolution Clay Mineral Records in the West Philippine Sea.Earth and Planetary Science Letters, 446:45-55.https://doi.org/10.1016/j.epsl.2016.04.022
[]Zeng, F.M., 2016.Provenance of the Late Quaternary Loess Deposit in the Qinghai Lake Region.Earth Science, 41 (1) :131-138 (in Chinese with English abstract) .
[]Zeng, F.M., Xiang, S.Y., Liu, X.J., et al., 2014.Progress in Tracing Provenance of Eolian Deposits in Chinese Loess Plateau.Earth Science, 39 (2) :125-140 (in Chinese with English abstract) .
[]Zeng, M., Song, Y., An, Z., et al., 2014.Clay Mineral Records of the Erlangjian Drill Core Sediments from the Lake Qinghai Basin, China.Science China Earth Sciences, 57 (8) :1846-1859.https://doi.org/10.1007/s11430-013-4817-9
[]Zhang, W., Yu, L., Lu, M., et al., 2009.East Asian Summer Monsoon Intensity Inferred from Iron Oxide Mineralogy in the Xiashu Loess in Southern China.Quaternary Science Reviews, 28 (3-4) :345-353.https://doi.org/10.1016/j.quascirev.2008.10.002
[]Zhao, G., Mu, X., Wen, Z., et al., 2013.Soil Erosion, Conservation, and Eco-Environment Changes in the Loess Plateau of China.Land Degradation&Development, 15:499-510.https://doi.org/10.1002/ldr.2246
[]Zhao, L., 2005.Variations of Illite/Chlorite Ratio in Chinese Loess Sections during the Last Glacial and Interglacial Cycle:Implications for Monsoon Reconstruction.Geophysical Research Letters, 32 (20) :1-4.https://doi.org/10.1029/2005gl024145
[]Zhao, L., Hong, H., Fang, Q., et al., 2017.Monsoonal Climate Evolution in Southern China since 1.2 Ma:New Constraints from Fe-Oxide Records in Red Earth Sediments from the Shengli Section, Chengdu Basin.Palaeogeography, Palaeoclimatology, Palaeoecology, 473:1-15.https://doi.org/10.1016/j.palaeo.2017.02.027
[]Zhao, L.L., Hong, H.L., Yin, K., et al., 2015.Characteristics and Palaeoclimate Significance of Clay Minerals in the Red Earth Sediment in Chengdu Basin.Geological Science and Technology Information, 34 (3) :80-86 (in Chinese with English abstract) .
[]Zheng, G., Jiao, C., Zhou, S., et al., 2016.Analysis of Soil Chronosequence Studies Using Reflectance Spectroscopy.International Journal of Remote Sensing, 37 (8) :1881-1901.https://doi.org/10.1080/01431161.2016.1163751
[]Zhu, Z., Feinberg, J.M., Xie, S., et al., 2017.Holocene ENSO-Related Cyclic Storms Recorded by Magnetic Minerals in Speleothems of Central China.Proceedings of the National Academy of Sciences, 114 (5) :852-857.https://doi.org/10.1073/pnas.1610930114
[]Zhu, Z., Zhang, S., Tang, C., et al., 2012.Magnetic Fabric of Stalagmites and Its Formation Mechanism.Geochemistry, Geophysics, Geosystems, 13 (6) :1-12.https://doi.org/10.1029/2011gc003869
[]程峰, 洪漢烈, 顧延生, 等, 2014.廣西百色盆地更新世沉積物中粘土礦物特征及其古氣候指示意義.第四紀研究, 34 (3) :560-569.
[]洪漢烈, 方謙, 王朝文, 等, 2017.巖漿母質(zhì)對蝕變粘土礦物的約束:以貴州新民剖面P-T界線附近火山灰層為例.地球科學, 42 (2) :161-172.
[]季峻峰, 陳駿, 王洪濤, 2012.陜西洛川黃土-古土壤剖面中伊利石結(jié)晶度---黃土物質(zhì)來源和古氣候環(huán)境的指示.地質(zhì)論評, 43 (2) :181-185.
[]李長安, 顧延生, 1997.網(wǎng)紋紅土中的植硅石組合及其環(huán)境意義的初步研究.地球科學, 22 (2) :195-198.
[]李金華, 潘永信, 2015, 透射電子顯微鏡在地球科學研究中的應(yīng)用.地球科學, 45 (9) :1359-1382.
[]席承藩, 1991, 論華南紅色風化殼.第四紀研究, (1) :1-8.
[]曾方明, 2016.青海湖地區(qū)晚第四紀黃土的物質(zhì)來源.地球科學, 41 (1) :131-138.
[]曾方明, 向樹元, 劉向軍, 等, 2014.黃土高原風塵堆積物源研究進展.地球科學, 39 (2) :125-140.
[]趙璐璐, 洪漢烈, 殷科, 等, 2015.成都盆地紅土沉積物中黏土礦物的特征及其古氣候指示意義.地質(zhì)科技情報, 34 (3) :80-86.
