Holland, C. H., 1982. The state of Silurian Stratigraphy. Episodes 5/3

Anuncio
THE STATE OF SI
LURI
AN
STRATI
GRAPHY
by
C.
H . Holl
and
Thi
s short arti
cle revi
ews recent deci
sions t
aken bv t
he IUGS Subcom mi
ssi
on on Si
l
uri
an St
rati
graphy,丈he
11 加ci
nq worker
s on t八e
pr
ocedures by which recom mendations are made and some o厂 t
he chal
l
enges sti
Sil
uri
an.
i
nt
roducti
on
Th
e g
eo
l
ogi
cal
s
ci
e
nc
es dema
nd cl
os
e i
n
t
er
na
t
i
o
nal
coop
er
-
at
i
o
n as
wel
l
a
s a r
i
g
or
ous
a
nd cl
e
ar
l
y u
nd
er
s
t
o
od l
ang
ua
ge of
wo
r
d
s
.
Nowher
e i
s t
hi
s mor
e ke
enl
y f
el
t
t
ha
n i
n s
t
r
a
t
i
gr
a
ph
y
wh
er
e
,
d
es
pi
t
e t
h
e l
u
xur
y of
l
o
ng p
hi
l
os
op
hi
c
al
di
s
cu
s
s
i
on
s on
r
o
ck
s v
er
s
u
s t
i
me,
man
y f
e
el
a s
en
s
e o
f u
r
ge
ncy a
bout
a
t
t
e
mp
t
s t
o achi
e
ve a s
t
and
ar
d gl
o
bal
ch
r
o
nos
t
r
a
t
i
g
r
a
phy.
For
s
t
a
g
es wi
t
h
i
n t
he
s
e t
wo s
er
i
es
,
t
h
e S
u
bc
ommi
s
s
i
on
a
gr
eed t
o us
e t
he "
S
he
i
nwo
odi
an"
a
nd "
Hor
r
i
er
i
an
" s
t
ag
es
f
o
r t
h
e We
nl
o
ck.
Th
es
e a
ga
i
n h
ad be
en d
ef
i
ne
d by Ba
s
s
e
t
t et
al
.
(
1
9
75
)
.
The bo
un
dar
y s
t
r
at
ot
y
pe f
or t
he b
as
e of
t
he f
ormer was to be the same as t
hat for the Wenl
ock Seri
es. A bo
un
dar
y s
t
r
a
t
ot
yp
e f
or
t
he b
as
e of t
he Homer
i
a
n S
t
a
ge The now wel
l
-
known pi
oneer work of t
he i
nter
nati
onal
com-
mi
t
tee on t
he Si
l
u
r
i
a
n-
Devoni
an Boundar
y t
ook 12 year
s to
co
mpl
et
e,
t
hou
gh this was a pioneering exercise. Correl-
nti
nns about thi
slevel were also found to have been in such gr
i
evous err
or thatmu
ch r
ea
dj
u
s
t
ment
an
d ev
en
t
ualco川 pro-
mi
s
e wer
e needed b
ef
ore agr
eement coul
d be r
eached
(
Boucek
,
of al
.
,
1966;
Hol
l
and,
1965;
Marti
ns
son, 1977)
.
Now
was accept
ed wi
t
hi
n t
he Wenl
ock area.
I
n t
he case of the Ludl
ow Seri
es,
Hol
l
and et al
.
(1963) had
p
r
e
vi
o
us
l
y de
f
i
n
ed f
o
ur s
t
age
s
,
bu
t t
h
e f
i
r
s
t and s
e
co
nd o
f
thes
e wer
e di
f
fi
cul
t to s
eparat
e out
si
de the Wel
sh Bor
der
l
and
a
nd t
h
e t
h
i
r
d (
Lei
nt
war
di
n
i
an
)
s
t
ag
e c
or
r
es
p
on
d
ed t
o onl
y on
e
gr
aptol
i
te bi
ozone, wi
despr
ead though that i
s.
Accor
di
ngl
y,
the Subcommi
ssi
on deci
ded that onl
y two s
tages were approp-
ri
ate f
or the Ludl
ow and,
as i
n t
he case of the Wenl
ock, t
hes
e
t
h
e l
UGS Commi
s
s
i
on on S
t
r
at
i
gr
aph
y,
t
han
ks
e
s
pe
ci
a
l
l
y t
o
t
h
e vi
s
i
o
n a
nd i
ni
t
i
a
t
i
v
e of
pa
s
t
ChaI
r
man Aca
de
mi
ci
a
n V.
V.
c
or
r
es
pon
d b
r
oa
dl
y t
o t
wo b
r
ach
i
o
po
d f
au
n
as a
s wel
l
a
s b
ei
n
g
t
i
ed mor
e p
r
e
ci
s
el
y t
o t
he gr
a
p
t
ol
i
t
e bi
oz
on
al
s
eq
uen
ce (
Fi
g
.
2)
.
Ma
ny o
t
he
r g
r
ou
ps ar
e o
f co
ur
s
e r
ec
ogn
i
z
ed as
act
ual
l
y o
r
po
t
e
nt
i
al
l
y us
e
f
u
l
i
n c
or
r
el
a
t
i
o
n.
menner of t
he Sovi
et Uni
on,
act
s as an umbr
el
l
a to a whol
e
l
i
s
t o
f
S
ub
co
mmi
s
s
i
ons
f
or
t
he v
ar
i
o
us g
eo
l
o
gi
c
al
s
ys
t
ems an
d
o
f wo
r
k
i
n
g g
r
o
ups
c
onc
er
ne
d wi
t
h s
et
t
l
i
ng t
h
e b
ou
nda
r
i
e
s
.
Th
e S
ub
co
mmi
s
s
i
o
n on S
i
l
u
r
i
an S
t
r
at
i
gr
ap
hy was
co
ns
t
i
t
u
t
e
d
Those concerned most di
r
ect
l
y wi
t
h wor
k i
n the Ludl
ow area
fr
om an a生垫签 body at a meeti
ng hel
d i
n the Uni
versi
t
y of
wer
e a
s
k
ed t
o s
ug
ge
s
t n
ames
f
o
r t
h
es
e t
wo n
ew s
t
a
ge
s an
d
t
h
e S
ub
commi
s
s
i
o
n ap
pr
ov
ed t
h
ei
r
c
hoi
ce o
f "
Gor
s
t
i
a
n" an
d
"
Lud
f
o
r
di
an
" (
Hol
l
and et
al
.
1
980
)
.
Th
e b
ou
nd
ar
y s
t
r
a
t
o
t
yp
e
Bi
r
mi
ng
ha
m,
U.
K.
,
i
n 1
9
74.
At a f
or
ma
l
mee
t
i
n
g of
t
he
Subcommi
ss
i
on hel
d duri
ng the I
nt
ernati
onal
Geol
ogi
cal
Con-
g
r
es
s i
n S
yd
ney
,
Aus
t
r
a
l
i
a,
i
n Au
gu
s
t
1
9
76
,
i
t wa
s a
gr
eed t
o
p
r
o
c
eed wi
t
h an ei
g
ht
-
ye
ar p
r
o
gr
a
m de
s
i
g
n
ed t
o s
o
l
ve t
he
ma
j
or
p
r
o
bl
e
ms
o
f S
i
l
u
r
i
a
n ch
r
o
no
s
t
r
at
i
gr
ap
hy.Wo
r
k c
ont
i
n
-
u
ed us
i
ng q
u
es
t
i
on
nai
r
es
a
nd ev
e
nt
u
al
l
y t
h
er
e was al
mos
t
for t
he base of the Gor
st
i
an St
age i
s t
he same as that for the
base of the Ludl
ow Ser
i
es.
For t
he bas
e of the Ludf
or
di
an
St
ag
e,
al
s
o s
i
t
ed wi
t
h
i
n t
he Lud
l
o
w a
r
ea (
Fi
g.
I
)
,t
h
e d
eci
s
i
o
n
i
s t
o u
s
e t
he bou
nd
ar
y pr
opo
s
e
d b
y Hol
l
a
nd et
al
.(
1
96
3)
f
o
r
unani
mous support for a comprehensi
ve f
i
el
d meeti
ng i
n
t
h
e b
a
s
e o
f
t
he
i
r Lei
nt
wa
r
d
i
ni
an St
age
.
Br
i
t
a
i
n i
n 1
97
9.
Thi
s
me
et
i
ng r
an
ge
d f
r
o
r
n S
out
h Wal
es
,
Di
s
t
r
i
ct
,
t
o Mof
f
at
i
n t
he S
out
he
r
n Up
l
a
nds
of
Sc
ot
l
and.
Th
es
e d
eci
s
i
o
ns wer
e pr
es
en
t
ed t
o t
he Co
mmi
s
s
i
on o
n S
t
r
a
-
t
i
gr
aph
y at i
t
s meet
i
ng i
n Par
i
s i
n Au
gus
t 1
9
80.
Pr
o
f
e
s
s
o
r
Var
i
ous f
ormal
meeti
ngs of the Subcommi
s
si
on wer
e hel
d,
Anders Mar
ti
nsson and Dr. M.
G.
Bass
ett
, r
espect
i
vel
y Chai
r
-
i
nc
l
u
di
ng s
ha
r
ed meet
i
ng
s wi
t
h t
he Wor
ki
n
g Gr
oup on t
h
e
Or
d
o
vi
ci
a
n-
S
i
l
u
r
i
a
n Bou
nda
r
y s
i
n
ce t
h
es
e t
wo gr
ou
ps had a
n
umb
er
o
f member
s i
n common.
Th
e t
ype ar
ea
s of
t
he
man and Se
cr
e
t
a
r
y o
f t
he Commi
s
s
i
o
n,
t
h
en ci
r
cu
l
at
ed d
ocu
-
thr
ough t
he Wel
s
h Bor
der
l
and,
Nort
h Wal
es,
and the Lake
ment
ati
on and arr
anged a pos
tal
vote by al
l members of the
Commi
ssi
on.
The deci
si
ons al
ready outl
i
ned above were
r
a
t
i
f
i
e
d wi
t
h
out
d
i
s
s
ent
(
s
ee Mar
t
i
n
s
s
on et al
.
,
1
981
)
.
I
-
l
andover
y,
Wenl
ock, and Ludl
ow seri
es were exami
ned,
as
was Charl
es Lapworth'
s famous l
ocal
i
ty f
or the Or
dovi
ci
an-
Cock
s
,
To
ghi
l
l
,
and Zi
eg
l
er (
1
97
0)
h
ad a
l
r
eady di
vi
de
d t
h
e
Ll
and
ov
er
y S
er
i
es
i
nt
o f
our
s
t
ag
es
,
e
qua
t
e
d r
e
s
p
ect
i
v
el
y wi
t
h
Si
l
uri
an tr
ansi
t
i
on at Dobb'
s Li
nn near Mof
fat.
The Subcomm i
ssi
on has 16 Ti
t
ul
ar Members and a con-
the much us
ed l
et
tered and number
ed di
vi
si
ons Al一A4,
BI-B3,
s
i
d
er
ab
l
y l
a
r
ge
r n
umb
er of
Cor
r
e
s
po
nd
i
ng Memb
er
s
.
Th
os
e
Cl-
C3
.
an
d C}
-
C6
.
The
s
e wer
e gi
v
en g
eo
gr
aphi
ca
l
name
s
based on l
ocal
i
ti
es wi
thi
n t
he t
ype area near Ll
andovery i
n
pres
ent at i
ndi
vi
dual meet
i
ngs t
ook part i
n di
s
cussi
ons and
S
o
ut
h Wal
e
s
.
As t
he l
owes
t Al
di
vi
s
i
on at
Li
and
o
ver
y p
r
o
ve
d
d
ec
i
s
i
o
n maki
ng,
but
f
or
mal
p
r
op
os
al
s
wer
e P
ut t
o po
s
t
al
v
ot
e
by t
he Ti
t
ul
ar Membe
r
s
.
De
ci
s
i
o
ns a
chi
ev
ed by a s
u
bs
t
ant
i
al
to be unf
oss
i
l
i
f
er
ous and of uncertai
n ext
ent, these aut
hors
chose Dobb'
s Li
nn f
or t
he def
i
ni
ti
on of t
he base of thei
r fi
r
st
,
ma)
ori
t
y were:
The second and t
hi
rd of the f
our seri
es i
nto whi
ch t
he
Rh
ud
da
ni
an St
ag
e.
Th
e b
as
a
l
b
oun
da
r
i
es o
f t
h
e r
emai
ni
n
g
dwi
a
n,
Fr
o
ni
a
n,
a
nd Tel
ych
i
a
n s
t
ag
es wer
e r
ef
er
r
ed t
o l
o
cal
-
Si
l
ur
i
an S
ys
t
em i
s
t
o b
e di
v
i
d
ed wer
e t
o be cal
l
ed”We
nl
ock I
Seri
es" and "Ludl
ow Ser
i
es",
and boundary st
rat
ot
ypes for i
ti
es wi
t
hi
n the Ll
andovery area.
Unf
ortunatel
y,
detai
l
ed
the base of each of t
hese were chosen i
n the Wel
sh f
au
na
l
ch
ang
es t
h
r
ou
gh c
o
nt
i
n
uo
us
bou
nd
ar
y s
t
r
at
ot
yp
e
e
ct
i
on
s wi
t
h ac
cu
r
at
el
y de
f
i
n
e
d mar
ker
p
oi
nt
s wer
e not
Borderl
and,
wher
e f
ul
l
y des
cri
bed st
andard ar
eas pr
ovi
de a s
l
abl
e and i
ndeed there was much di
scuss
i
on by Subcom-
s
e
t
t
i
ng f
or
t
he
s
e s
ec
t
i
o
ns
.
The
s
e ar
e i
nd
i
ca
t
ed i
n Fi
g
ur
e I
avai
s
s
i
on membe
r
s o
n t
he di
f
f
i
c
ul
t
i
es
o
f di
s
cr
i
mi
na
t
i
n
g b
e-
a
n
d de
t
ai
l
s
of
t
he d
eci
s
i
o
ns wer
e r
e
po
r
t
e
d i
n 兰et
h
ai
a mi
(
Hol
l
an
d 1
9
80
)
.
Fu
l
l
d
es
c
r
i
p
t
i
on
s of
t
he a
r
ea
s a
nd s
e
ct
i
on
s t
we
e
n at
l
ea
s
t s
ome o
f t
he
s
e s
t
age
s el
s
ewhe
r
e i
n t
h
e wor
l
d
.
ar
e t
o be f
oun
d i
n Ba
s
s
et
t et a
l
.
(
1
975
)
f
or
t
he Wenl
ock,
A S
ub
co
mmi
s
s
i
on wor
k
i
n
g gr
ou
p i
s
now l
ook
i
ng c
ar
ef
u
l
l
y at
and Hol
l
and et al
. (1
963) f
or the Ludl
ow.
The secti
ons ar
e the so-
cal
l
ed "nort
hern ar
ea" of the Li
andovery di
s
tri
ct
,
e more graptol
i
tes may be avai
l
abl
e. But what
ever t
he
now cared f
or by the Nat
ure Conser
vancy.
wher
EPI
SODES, Vol
. 1982,
No. 3.
21
N‘.||-t-||||ee|
k
5
Dobb'
s Li
nn and Ant
i
costi
f
or thi
s purpose. They ar
e con-
10
c
er
ned al
s
o wi
t
h t
he d
i
f
f
i
c
ul
t q
u
es
t
i
on of
t
he b
i
os
t
r
at
i
gr
aph
i
-
cal
hori
zon best chos
en for the boundar
y.
a
The f
ou
r
t
h
.
p
os
t
-
Lud
l
ow p
r
e
-
Gedi
nn
i
an s
er
i
es of
t
he Si
l
ur
i
an
S
ys
t
em i
s
t
he di
vi
s
i
on whi
ch wa
s r
ec
og
ni
zed a
s a r
e
s
ul
t of
t
he
wor
k of
t
he Si
l
ur
i
an
-
De
von
i
an Bo
und
ar
y Commi
t
t
ee (
Mar
-
t
i
n
s
s
o
n,
1
97
7)
.
Er
r
or
s i
n pr
e
vi
ou
s co
r
r
e
l
a
t
i
ons
h
ad be
en s
u
ch
t
hat
t
he r
oc
ks dep
os
i
t
ed i
n t
h
i
s i
n
t
er
val
had ac
t
ua
l
l
y be
en
"l
ost",
mai
nl
y because of the ass
umpt
i
on that grapt
ol
oi
ds
mu
s
t i
n s
ome (
my
s
t
i
cal
)
s
e
ns
e b
e a
b
s
en
t f
r
om p
os
t
-
Si
l
ur
i
an
夕’
健
2
s
trata. The t
op of the fourt
h s
eri
es i
s al
r
eady defi
ned by the
n
ow a
gr
eed ba
s
e of
t
he Dev
oni
an at t
he b
a
s
e of
t
h
e Mo
no-
C HU RCH
STRETTO N
三 MUCH:
・
gr
a
pt
us
un
i
f
or
mi
s Bi
o
zon
e,
a
s r
ec
og
ni
z
ed i
n t
he bou
nd
ar
y
W ENLOCK
str
at
otype secti
on at Kl
onk i
n t
he Barrandi
an ar
ea of Czech-
o
s
l
ova
k
i
a.
Al
t
hou
gh t
her
e ha
s bee
n c
on
s
i
der
abl
e d
i
s
cus
s
i
on
and t
h
r
ee s
ub
mi
s
s
i
ons h
av
e al
r
e
ady b
e
en ci
r
cu
l
a
t
ed
,
t
he
bou
nd
ar
y s
t
r
a
t
ot
y
pe f
or t
he ba
s
e of
t
he f
our
t
h s
er
i
es
,
an
d
A
i
ndeed i
ts f
ormal name,
are sti
l
l
to be deci
ded by the
Subcom m i
ssi
on.
几
The t
h
r
e
e ca
nd
i
d
at
e
s f
or t
h
e s
e
ri
es (
Fi
g.
2)
ar
e t
he "
Downt
o
n
S
er
i
e
s
"
,
"
Pr
i
d
ol
i
S
er
i
e
s
" an
d "
Sk
al
a Se
r
i
es
"
,
or pe
r
ha
ps an
al
t
er
nat
i
v
e na
me.
Th
es
e woul
d be r
ep
r
e
s
en
t
e
d b
y b
as
a
l
bo
un
dar
y s
t
r
at
ot
ype
s i
n,
r
es
pe
ct
i
v
el
y,
t
he We
l
s
h B
or
d
er
l
and,
the Bar
randi
an area, or Podol
i
a (
U.
S.
S.
R.
)
.
The Downton
飞
Ser
i
e
s oc
cur
s i
n cl
as
s
i
c cou
nt
r
y wh
er
e t
wo of
t
h
e Si
l
ur
i
an
s
er
i
e
s ar
e a
l
r
e
ad
y de
f
i
n
ed an
d i
t
s b
as
al
d
i
vi
s
i
on,
t
h
e Lu
dl
o
w
Bone Bed
,
i
s f
a
mi
l
i
ar
t
o ge
ol
ogi
s
t
s
.
Her
e,
howe
ver
,
t
h
e
f
a
ci
e
s i
s of mar
i
ne-
br
a
ck
i
s
h char
a
ct
e
r
.
Bas
s
et
t et a]
.
(
1
9
80
)
ha
ve r
ev
i
e
wed t
h
e co
ns
i
de
r
a
bl
e bi
o
s
t
r
at
i
gr
ap
hi
cal
d
at
a a
vai
l
-
abl
e,
t
o
get
her
wi
t
h t
h
e cor
r
e
l
at
i
o
n of
t
he s
er
i
es ac
r
os
s
Eu
r
o
pe an
d el
s
ewhe
r
e,
t
hr
ou
gh t
he u
s
e o
f a cha
i
n o
f evi
d
enc
e
i
n
vol
vi
ng os
t
r
ac
ode
s
,
s
por
es
,
ver
t
e
br
a
t
e
s
,
and gr
ap
t
ol
i
t
e
s
.
Ka
l
j
o (
1
9
78)
has al
s
o det
ai
l
ed t
h
i
s web of
co
r
r
e
l
a
t
i
ve ev
i
-
生三兰三
乞J 全
3兰争
于 二 ;干 石石 吕
冲们 I
t二二〔 拜
-
一一火
dence.
The Pri
dol
i rocks of Czechos
l
ovaki
a have been cl
assi
c si
nce
the work of Bar
rande.
The base of t
he Devoni
an i
s al
ready
LUDLOW
LLA N D O VERY
Dnestr Ri
ver and i
ts tri
butari
es i
n Podol
i
a wher
e r
i
ver cl
i
ffs
AND YO UNGER
[
口
< B
月霆吕
K E Y
DOW NTO NI
AN
W EN LO C K
巨
de
f
i
ne
d he
r
e.
Th
e s
t
r
a
t
a ar
e we
l
l
kn
own and wel
l
r
e
pr
es
e
nt
e
d
i
n mu
s
e
um co
l
l
e
ct
i
ons
.
Th
er
e ar
e b
ot
h g
r
ap
t
o
)
i
t
i
c and S
hel
l
y
f
aun
as
.
Th
e t
h
i
r
d p
ot
e
nt
i
al
s
t
r
a
t
o
t
y
pe i
s i
n t
he a
r
ea o
f
t
he
an
d ot
h
er
e
xp
os
u
r
es cl
ear
l
y di
s
pl
a
y a s
e
qu
en
ce o
f hi
gh
l
y
RO CKS
W ENL
OCK
LUD LO W
fossili
ferous Silurian to lowest Devoni
an rocks i
n m ari
ne
TYPE A REA
f
ac
i
es
an
d wi
t
h s
t
r
u
ct
ur
e of
ext
r
eme si
mpl
i
ci
t
y.
Br
ac
hi
o
po
ds
and os
tr
acodes are es
peci
al
l
y wel
l
repr
es
ent
ed i
n the Skal
a.
TYPE A REA
The S
ub
co
mmi
s
s
i
o
n i
s
gr
a
t
e
f
ul
t
o Aca
de
mi
ci
an B.
S.
So
k
ol
ov
and h
i
s co
l
l
e
agu
es wh
o ar
e ar
r
a
ngi
ng det
ai
l
ed ex
ami
n
at
i
on of
t
he Sk
al
a S
er
i
e
s i
n 1
983
,
wh
en i
t s
h
ou
l
d b
e p
os
s
i
bl
e t
o as
s
es
s
BOUNDARY STRATOTYPES
(I一A )
Fi
gu
r
e 1
;
Geol
ogi
cal
map o厂t
he Wel
s
h Bo
r
de
r
l
an
d s
howi
ng
t
he rel
ati
ve meri
t
s of al
l
three ar
eas under consi
der
ati
on.
Si
l
uri
an s
ubdi
vi
si
ons and standar
d areas厂or t
he Wenl
ock and
Ludl
ow seri
es.
Boundar
y str
atotype sect
i
ons as shown i
n
Many members have al
ready seen t
he Downton and Barr
an-
Fi
g
ur
e 2 ar
e n
umbe
r
e
d as f
o
l
l
ows
:
1
.
Hu
ghZ
e
y Br
oo
k;
2.
por
tuni
t
i
es ar
e avai
l
abl
e for any necess
ar
y vi
si
ts to t
he two
for
mer ar
eas
. As yet t
here i
s no demand for the defi
ni
ti
on of
t
h
a
n ar
e
as
,
t
ho
ugh f
ew h
ave p
r
ev
i
ou
s
l
y v
i
s
i
t
ed Po
do
l
i
a.
Op-
Whi
twel
l
Coppi
ce;
3.
Pi
tch Coppi
ce;
4.
Sunnyhi
l
l Quarr
y.
s
t
a
ge
s wi
t
hi
n t
h
e f
ou
r
t
h S
i
l
u
r
i
an s
er
i
e
s,
t
ho
ugh t
h
es
e wi
l
l
doubt
l
ess become the concern of the Subcom mi
s
si
on i
n future
f
i
n
al
d
ec
i
s
i
on,
t
he or
i
gi
nal土
y匹 (
as di
s
t
i
nc
t f
r
om s
t
a
nd
ar
d)
ar
ea mu
st
co
nt
i
nue t
o b
e r
e
gar
d
ed as pr
ovi
di
ng s
i
gn
i
f
i
ca
nt
pa
r
a
s
t
r
al
ot
yp
es i
n Ll
a
nd
ov
er
y s
t
r
a
t
i
g
r
a
ph
y.
years.
On
ce de
ci
s
i
o
ns h
ave be
en mad
e t
hr
o
ug
h t
h
e p
r
op
er
us
e o
f t
h
e
i
nt
er
na
t
i
o
na
l
mac
hi
ner
y pr
ovi
d
ed b
y t
h
e Commi
s
s
i
on on S
t
r
a
-
t
i
gr
a
ph
y a
nd i
t
s s
ubs
i
di
ar
y bo
di
e
s
,
i
t
i
s ex
ce
edi
ngl
y i
mpor
t
an
t
t
h
at t
he
s
e s
ho
ul
d be i
mpl
eme
nt
ed na
t
i
ona
l
l
y a
nd i
n
t
er
na
t
i
on
-
al
l
y.
Pu
bl
i
ci
t
y f
or t
he dec
i
s
i
on
s i
s ne
ce
s
s
a
r
y:
he
nc
e t
he
pr
e
s
en
t
a
t
i
o
n of
t
h
i
s i
nt
er
i
m r
e
po
r
t on t
he a
ct
i
v
i
t
i
es of
t
h
e
Su
b
commi
s
s
i
on o
n S
i
l
ur
i
an S
t
r
at
i
g
r
ap
hy a
nd t
h
e p
ub
l
i
c
at
i
on of
v
ar
i
ou
s s
hor
t s
t
at
emen
t
s o
f dec
i
s
i
ons
al
r
e
ady r
e
ac
he
d as
I
n the meanti
me,
i
n t
he summer of 1981 t
he Subcommi
ssi
on
h
a
d t
h
e o
pp
or
t
u
n
i
t
y t
o e
xa
mi
ne a
n exc
eed
i
ngl
y f
os
s
i
l
i
f
er
ou
s
an
d b
eau
t
i
f
ul
l
y ex
pos
ed Ll
a
nd
ov
er
y s
eq
ue
nce on Ant
i
co
s
t
i
I
sl
and, Quebec, Canada,
where the st
ruct
ure i
s ext
remel
y
s
i
mpl
e (
Bar
nes
,
1
982
)
.
I
n Au
gu
s
t 1
98
2,
i
t
ex
ami
n
ed an
ot
h
er
p
r
omi
s
i
n
g s
e
que
nc
e i
n t
h
e Os
l
o di
s
t
r
i
ct
o
f Nor
way an
d,
ho
pef
ul
l
y i
n 1
983 i
t wi
l
l
be p
os
s
i
bl
e t
o make d
eci
s
i
ons on
bo
un
da
r
y s
t
r
at
o
t
y
pe
s f
or
t
h
e ch
r
o
no
s
t
r
at
i
g
r
ap
hy of
t
he f
i
r
s
t
vari
ousl
y r
ef
err
ed to above.
of t
he Si
l
uri
an ser
i
es. The base of t
he fi
rst of t
he two or
t
h
r
ee s
t
a
g
es i
nt
o wh
i
ch t
he "
Ll
a
ndo
ve
r
y (
or Ant
i
c
os
t
i
)
Se
r
i
e
s
"
i
s l
i
k
el
y t
o b
e d
i
vi
ded mu
s
t
be t
ha
t of
t
h
e S
i
l
ur
i
an S
ys
t
em,
an
d h
er
e t
h
e Wor
ki
n
g Gr
ou
p on t
h
e Or
do
vi
ci
an-
Si
l
u
r
i
an Bou
n-
da
r
y i
s
i
n t
he p
r
oce
s
s of
di
s
cu
s
s
i
ng t
h
e r
el
at
i
v
e mer
i
t
s
of
EPI
SODES,
Vol
.
1982,
No.
3.
References
Bar
nes
,
C.
R.
,
1982, Ordovi
ci
an-
Si
l
uri
an Boundary Studi
ed:
EPI
S
ODES
,
t
982
/t
,
p
.
33
.
22
CHRO NO STRATI
G RAPHY │ │
LO CATI
ON OF │
BO UNDARY STRATOT│ YPES │
│
uni
form i
s │
tr
ans
gr
edi
│ns │
e
S!LURI
AN │
Do
wn
t
on Ser
i
es ? │
(
di
v
i
s
i
o
n i
n
t
o
│
We
l
s
h B
o
r
d
e
r
l
a
n
d ? │
│
SYSTEM │ o
r
│ s
t
a
g
e
s
t
o c
.a
i
t
│ B
a
r
r
a
n
d
i
a
n a
r
e
a ? │
│ Ph'
dol
l
Ser
i
es ? │ ne
ces
s
i
t
y)
│
Po
do
l
i
a ? │ │
or │ │ │
│ │ Skal
a S│ │ er
i
es ? │ │ 2 │
│ 2 │
│ Ludl
ow Seri
es │
│ │
Ludf
ordi
an St
age │L
udl
o
w di
s
t
r
i
c
t {Su
n
ny
b
i
l
l
Qu
ar
r
y}
│
l
ei
nt
ward
│i
nensi
s│
tum escens, │
│
(
=i
n
c加i
ens
│
) │
Gor
st
i
an St
age │
L
u
dl
ow d
i
s
t
r
i
c
t (
Pi
t
c
h Co
pp
i
c
e} │
│ │ ni
l
ssoni s
.
l
. │
│
ludensi
s │
│
Wenl
ock Seri
es │
Homeri
an St
age │
Wen
l
o
c
k d
i
s
t
r
i
ct
(
Wh
i
t
we
l
l
C
o
pp
i
c
│ │
e) │
lundgreni
│ │
el
l
esae │
│
She
i
n
wo
odi
an St
a
ge│ We
n
l
o
c
k
d
i
s
t
r
i
c
t
(
H
u
g
h
l
e
y
Br
o
o
k
)
│
│ │ ce
nt
r
i
f
u
│
gus │
crenul
at
a │
│
Anti
cost
i
Seri
es? │
s
t
ages (
pr
obabl
y │ An
t
i
co
s
ti ? │
│ │
or │
three) to 一be │
Liandowery di
│ │ strict ? │
Li
an
do
ver
y Ser
i
es? │
d
e
f
i
n
e
d │
O
s
l
o
d
i
s
t
r
i
c
t? │
│ │
户 │
│ , │
│
F4
W e 2;
St
at
e of Si
l
ur
i
an ch
r
o
no
st
r
at
i
gr
a
phy
.
Cr
i
t
i
c
al
qr
a
pt
ol
i
t
e bi
o
zon
es ar
e al
s
o i
ndi
cat
e
d.
Bas
set
t, M.
G.
, Cocks,
L.
R.
M.
,
Hol
l
and, C.
H.
,
Ri
ckards, R.
B.
nat
i
on
al
Un
i
on of Geol
ogi
ca
l
S
ci
en
ces Se
r
i
es A,
No.,)
,
Bas
set
t, M.
G.
,
Laws
on,
J.
D.
and Whi
t
e, D.
E.
,
1982, The
i
f
i
c
a
t
i
o
n
o
f
S
t
a
n
d
a
r
d
C
h
r
o
n
o
s
t
r
a
t
i
g
r
a
p
h
i
c
a
l
D
i
v
i
s
i
o
n
s
1
,
a
n
d
345 p.
and Wa
r
r
e
n,
P.
T.
,
1
975
,
Th
e t
ype Wenl
oc
k S
er
i
es
:
Re
p.
I
ns
t
.
Geol
.
S
ci
.
,
No.
75
八3
,
1
9
p.
Mar
t
i
n
s
s
o
n,
A.
,
Bas
s
et
t
,
M.
G.
a
nd Hol
l
and
,
C.
H.
,
1
981
,
Rat
-
Downton Seri
es as the Four
th Ser
i
es of the Si
l
uri
an 3TraToTypes ior Ihe M uri
an 3YSleM : r
-t
-1JU L)
r
-3q 17OLILIF.
Sy
s
t
e
m:
Let
hai
a,
1
5,
1
-
74.
,
36
Bou
ce
k,
B.
,
Hor
ny,
R.
a
nd Ch
l
up
ac
,
1
.
,
1
966
,
Si
l
ur
i
an Ve
r
s
us
De
von
i
a
n:
Act
a Nu
s
.
n
at
I
.
Pr
a
ga
e,
2
2B,
4
9-
66.
Co
cks
,
L.
R.
M.
,
To
ghi
l
l
,
P.
an
d Zi
e
gl
e
r
,
A.
M.
,
1
970
,
St
ag
e
name
s wi
t
hi
n t
h
e Ll
and
ov
er
y S
er
i
es
:
Geol
.
Mag.
1
07
,
79
- 87.
Hol
l
an
d,
C.
H.
,
1
965
,
The Si
l
ur
o-
De
vo
ni
an Bo
und
ar
y:
Geo
l
.
Ma
g.
1
02,
21
3
-
2
21
.
Hol
l
an
d,
C.
H.
,
1
98
0,
Si
l
ur
i
a
n s
er
i
e
s an
d s
t
a
ges
:
de
ci
s
i
on
s
co
nc
er
ni
ng c
hr
ono-
s
t
r
at
i
g
r
ap
hy
:
Let
hai
a,
1
3,
23
8.
Hol
l
and, C.
H.
,
Lawson, J.
D.
and Wal
msl
ey, V.
G.
, 1963,
The
Si
l
ur
i
an r
o
cks of
t
he Ludl
ow di
s
t
r
i
ct
,
S
hr
op
s
h
i
r
e:
Bul
l
.
Br
.
八BOUT THE AUTHOR:
Mu
s
.
Na
t
.
Hi
s
t
.
,
S
er
.
Geol
.
8
,
p.
93-
1
71
.
Pr
o
f
.
Ch
ar
l
es Hep
wor
t
h Hol
l
an
d i
s Pr
of
es
s
o
r of Geo
l
o
gy an
d
Hol
l
an
d,
C.
H.
,
Laws
on
,
J.
D.
,
Wal
ms
l
ey,
V.
G.
a
nd Whi
t
e,
D.
E.
,
Mi
n
er
a
l
o
gy at t
h
e Dep
t
.
of Ge
ol
o
gy
,
Tr
i
ni
t
y Co
l
l
eg
e,
Du
bl
i
n
1
98
0,
Ludl
ow s
t
age
s
:
Let
hai
a 1
3,
26
8.
2
,
I
r
e
l
a
nd.
He i
s a pas
t Pr
es
i
de
nt of
t
he Pa
l
a
eon
t
o
l
o
gi
c
al
As
s
oci
at
i
on a
nd pa
s
t Chai
r
man of t
h
e S
t
r
at
i
gr
aph
y Com-
Kal
j
o,
D.
,
1
978
,
Th
e Do
wnt
o
ni
a
n or Pr
i
do
l
i
an f
r
o
m t
he p
oi
n
t
mi
t
t
ee of t
he Geo
l
og
i
ca
l
S
o
ci
et
y o
f Lon
do
n.
Hi
s r
e
s
e
ar
ch
of vi
ew of the Bal
t
i
c Si
l
ur
i
an: Eest
i NSV Tead. Akad. i
n
t
e
r
e
s
t
s ce
nt
er mai
nl
y o
n Lower Pal
a
eoz
oi
c s
t
r
at
i
gr
a
ph
y a
nd
Toi
m.
27, Geol
. Ser
i
es No. 1,
5-10.
pa
l
a
eo
nt
ol
o
gy.
S
i
n
ce h
i
s ea
r
l
i
er
r
es
ea
r
c
h on S
i
l
u
r
i
an r
oc
ks of
t
he Wel
s
h Bor
derl
and and Central
Wal
es,
he has exami
ned
Mar
t
i
n
s
s
o
n,
A.
(
ed.
)
,
1
97
7
,
The Si
l
ur
i
an
-
D
ev
oni
an Bou
nd
ar
y:
S
c
hwe
i
z
er
bar
t
'
s
che Ver
l
ags
b
uc
hh
and
l
un
g,
S
t
ut
t
g
ar
d (
I
n
t
er
- t
h
ei
r cou
nt
er
p
ar
t
s i
n man
y pa
r
t
s of
t
he wor
l
d.
EPI
SODES, Vol
. 1982, No.
3.
23
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