Clay mineral formation and transformation in non-marine environments and implications for Early Cretaceous palaeoclimatic evolution:The Weald Basin,Southeast England  

作　　者：Oladapo O.Akinlotan Ogechukwu A.Moghalu Stuart J.Hatter Sunday Okunuwadje Lorna Anquilano Uche Onwukwe Safiyeh Haghani Okwudiri A.Anyiam Byami A.Jolly 

机构地区：[1]Department of Geography,University of Sussex,Falmer,Brighton,BN19SJ,United Kingdom [2]Department of Geology,University of Nigeria,Nsukka Road,410001,Nsukka,Nigeria [3]Badley Ashton and Associates Ltd,Winceby House,Winceby,Horncastle,Lincolnshire,LN96PB,United Kingdom [4]Department of Geology and Geophysics,School of Geosciences,Kings’College,University of Aberdeen,Scotland,AB243UE,United Kingdom [5]Experimental Techniques Centre,Brunel University London,Bragg 16,Brunel University London,Uxbridge,UB83PH,United Kingdom [6]Department of Geology,Ahmadu Bello University,Zaria,Nigeria

出　　处：《Journal of Palaeogeography》2022年第3期387-409,共23页古地理学报（英文版）

基　　金：CGG Robertson provided collaborative funding by conducting QEMSCAN?,SEM and thin section analyses for the project。

摘　　要：Analyses of clay minerals within the Early Cretaceous Weald Basin,Southeast England reveal kaolinite,illite and chlorite as the main detrital clay minerals while glauconite and smectite are subordinates.A kaolinite-rich assemblage which characterized the sand-dominated Ashdown and Tunbridge Wells Sand formations and an illite-dominated assemblage associated mostly with the Wadhurst Clay and Weald Clay formations are recognized.Kaolinite was enriched in the Ashdown and Tunbridge Wells Sand formations during warm and humid climate with high precipitation that encouraged chemical weathering and leaching,while cold and dry conditions favoured the concentration of illite in the Wadhurst Clay and Weald Clay formations.Rainfall patterns associated with warm climate were drastically reduced during the drier climatic conditions.Most clay minerals are detrital in origin,with chlorite being more prominent than previously recognized.Contrary to previous studies and assumptions,this study revealed that authigenic clay minerals are present in the Hastings Beds,with vermiform and mica-replacive kaolinite being the most common,consistent with humid depositional environments.Isolated authigenic illite is also present,along with a chloritized grain,providing evidence for mesodiagenesis.The absence of dickite and occurrence of kaolinite,suggest that authigenic illite formed in relatively shallow burial conditions,indicating a maximum burial depth of2500 m-3000 m,about 1000 m deeper than previous estimates of 1500 m-2000 m.Authigenic clay minerals are absent in the Weald Clay Formation possibly because of hindered flow of meteoric water and limited growth space for authigenic minerals.This study is significant in:1)reinforcing multiple methods to facilitate a robust and balanced knowledge of formation and transformation of clay minerals;2)investigating detrital and authigenic clay mineral assemblages when assessing the palaeoenvironments of sedimentary basins.

关 键 词：Clay minerals Clay mineral transformation PALAEOCLIMATE Early Cretaceous Weald Basin WEALDEN Southeast England 

分 类 号：P618.13[天文地球—矿床学]