le cirque du creux du van

Primaire s'étant faites petit à petit usées et complètement arasées par l'érosion. Le ... continents voisins par les eaux de ruissellement, puis transportées par les ...
1MB taille 9 téléchargements 542 vues
LE CIRQUE DU CREUX DU VAN

Thierry Basset

    

          



 ! "!## $ !%!     !" #$  %&%'() *"+, -'().*) )) /0'&1 -

 % +2   '333% -

 % 

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

!"#$%&"'#$(#)*+,(#-(./0$12,(3#2)#4#1#!"#$%&''&()*$+,-))./*3#)1#5106%(#./77(0.(#8#9(# $29)/:"(,3#8#9*1;;1299(,3#;1#H*(9'#)(#;"'",#(7=)1.(7(0'#$"#I",1># E " ,/ = ( V " '" , # ( 7 = )1 . ( 7 ( 0 '#$ " # I " , 1

Q . % 1 0 # 1 )= 20 TG % '@ 4 9 U

! ; , 2: " (

J % = ? '9 # $ ( # 9 % $ 27 ( 0 ' 9 #7 1 , 20 9

!#.(''(#%=/:"(3#)*E",/=(#(9'#92'"%(#=,+9#$(#)*%:"1'(",#('#)(#.)271'#(9'#.@1"$3#$(#'4=(# ',/=2.1)> # J(9 # 9%$27(0'9 # 0( # .(99(0' # $( # 9*1.."7")(, # 9", # )( # ;/0$ # 71,203 # ;/,710' # $(9# ./".@(9#$(## A(9#71,0(9#,%9")'(0'#$"#$%=?'#$*"0#7%)106(#$(#&/"(9#.1).12,(9#('#$*1,62)(9>#A(9#1,62)(9# 9/0'#$(#',+9#=('2'9#720%,1"C#299"9#$(#)*1)'%,1'2/0#$(#,/.@(9#=,%(C29'10'(9>#!,,1.@%(9#1"C# K

!"#$%#&#$'()"%'%#'(*+,(-&'(&+./(0&(,.%''&--&1&#$2(*.%'($,+#'*",$3&'(*+,(-&'(4-&.)&'(&$(-&'( !".,+#$'(1+,%#'2(!&'(1%#.'!.-&'(*+,$%!.-&'(*&.)&#$('&(03*"'&,($,5'(-"%#(0&(-&.,(-%&.( 06",%7%#&8(9&'(1+,#&'('"#$(73#3,+-&1&#$('"1:,&'(&$(:&+.!".*(*-.'($�,&'(;.&(-&'( !+-!+%,&'8

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

!"#"$%&'()*++',),"&-)-.%,)#/.012',)3/&,)+/)4/.-5')".5'&-/+')'-)+/)4+1,)2+'62')31)71./8) 9:',-;/F"& ) .D-!#501'8 ) >".#/&- ) 1&' ) ,199',,5"& ) 3') 9.G-',)'-)3')324.',,5"&,)015),:2-5.'&-)4/./++%+'#'&-)/5++'

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

K

!"

!"#$%&'%()*+(,%$+*+-*-%./%.$&* !"#$%&'("#)(#*&"(+#)(#,-.#)/%0#0&12#3&/4-45"6".0#2/.#/&%7%."#8#59-&$:%0"$0(&"#6;6"#)"# 5-#6/.0-7."#-$0%?"#2(�/(2#5"2#&"5%"@2>#-#$&"(2=#2(&#(."#A/."#)"#@-%45"22"#)"# 5- # 6/.0-7."> # 8 # 59%.0"&2"$0%/. # ".0&" # 5" # 0/%0 # )" # 59-.0%$5%.-5 # "0# 5" # 3-22-7" # )9(." # @-%55" # ".# )=$&/$:"6".0#B?/%-7"#CD< E5(2%"(&2#3&/$"22(2#=&/2%@2#0&12#$/(&-.02#)-.2#5"#F(&-#2/.0#8#59/&%7%."#)(#*&"(+#)(#,-. 2 & 0 ? # - 0 # @ ( % # + H ( % ; & # 5 1 % # + 1 0 25 # & , - & 5 , ( / )*)5 & # ( )% 5 )# * 4& 5 + ( 2 6 & 3 & % , # - & # *( # > *0 5 & , , & "

!-#@/&6-0%/.#)(#*&"(+#)(#,-.>#0"5#'("#2"#59%6-7%."#5"2#7=/5/7("2#B*/55"$0%@>#JLLLD

!- #2#1'3$4,-'%(> # 59-$0%/. # )( # 7"5 # "0 # )( # )=7"5 # )-.2 # 5"2 # @%22(&"2 # )"2 # &/$:"2> # 2-3" # 5"2# @-5-%2"2#".#5"2#@-%2-.0#3"0%0#8#3"0%0#&"$(5"&-1)$+4&6!'#$$)"17+X,+'"1'#-+'#0$#+).!D*56+,)+,#31)+ 6*2",).)0-+4)$+)'"@+4)+,&R1)"$)+()1$+,)+A,'-)'"+)-+*166+"0+,'*+4)+3'11':)+0'-"1),+)-+ 6!56.>1) + M9 + ,&6*5),,) + :62,2:#%")O/ + ,) + ,'* + 4" + C', + 4) + _1'()1$/ + ,20: + 4) + !,"$ + 4) + N]+ b#,2.>-1)$7 + $+;'#3,)+4)+,&2141)+4)+N]c]]7+ d0)+'"-1)+5=!2-5>$)+!2"1+)@!,#%")1+,'+!16$)0*)+4"+,'*+4"+C',+4)+_1'()1$+;'#-+'!!),+'" + :,'*#)1+4"+Q5G0)7+B),"#?*#+'"1'#-+)0('5#+"0)+!'1-#)+4"+C',+4)+_1'()1$+,21$+4)+,'+4)10#>1) + :1'04)+:,'*#'-#207+1)+ ,)%"),+$)+$)1'#-+;21.6+,)+,'*7

NS

#" ! " #$ " %& '

! 0# ,

'# (

)C $

.7

'. '0

+

- " &. ' ,

!"

$"

! 0 # , '# ( ) 7 G '@ 'A % + ) 3 * ' , , # $ % & ' # ( ;

! 0 # , '# ( ) @ ? 7 . ( 'A % + 3 C ? $'-0 . 7 & '# ( ;

! " #$ " %& '

( ) * + #%, - " &. ' ,

( ) * + #%,

!"#$%&'#()*+,)-.$.',+,)*%)/0+%1)*%)2.()30+*+,,'(+0)*4.506,)/#$$+7&'-8)9:::; 4?0#,'#()@?7.('A%+)70??)%()&.B$'+0)*4?B#%$',=)9=)>+)&.B$'+0)*4?B#%$',),+)*?"+$#55+)+&)-'(')5.0)50#&?C+0)$. ) -.$.',+)A%')(4?"#$%+)5$%,)A%+)&06,)$+(&+@+(&=)D=)>.)-#0@.&'#()*+)C$.7'+0,)*.(,)$+)/0+%1)*%)2.()$#0,)*+,) C0.(*+,)5?0'#*+,)-0#'*+,)5+0@+&)*4?".7%+0)$+,)?B#%$',)"+0,)$4.".$=)+)$.7 ) ,+),?5.0+).$#0,)+()&0#',)B.,,'(,)*',&'(7&,)+&),#().,,67G+@+(&)*?-'('&'-)*.&+0.'&)*+)L4KMM) .(,)+("'0#(=

9
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email protected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

C\

!"#$%&'#()#*+,%-'#$.&* !"#$%& ' ()* ' #+,-. ' ,)! "#$$%& ! ' ! ()*+,-*./ ! 01 ! 213,4 ! 56)7)-8. ! .+ ! 9,:/,-./' ! ;!9?? !/+0&',)! "#$$@&!'!A.!213,?!J@!9?? !122"',)! "@K%L&!'!A./!M)CD./?!N)77.C+8)*!N)**,O+3. !7,!;,+13.!.*!P,7,8/4!.0?!Q877.+4! (,3+8-*:4!@JK!9?? #$+23//+"4'5)*'!+6317'$)'"@KK$&!'!R18//.!76S,*8I1.4!9,:/!0.!5.*HT.!.+!ND,G7,8/?!