In oduc ion
Geological eco ds om no he n Spain
show an a e age ela i e sea-le el ise a e
o 2 mm/y in he pas cen u y (Leo i
e al
.,
2008), in ag eemen wi h egional ide
gauge da a (Chus
e al
., 2009). This sup-
poses an impo an depa u e om back-
g ound Holocene alues (0.53 ± 0.48
mm/y ; Ga cía-A ola
e al
., 2018).
Unless sal ma shes a e able o keep pace
wi h sea le el, hese and o he in e idal a eas
a e a isk o subme gence. Sal ma sh en i-
onmen al egene a ion s udies in no he n
Spain showed ha he abundan sedimen
a ailable in he egional es ua ies allowed
apid sedimen a ion a es (up o 18 mm/y )
o ake place (Ga cía-A ola
e al
., 2016).
Consequen ly, in e idal a eas, such as sal
ma shes om no he n Spain, could po en-
ially adap o u u e sea-le el ise.
The su i al o in e idal en i onmen s
is de e mined by a complex equilib ium be -
ween bio ic and abio ic p ocesses. Sedimen
a ailabili y is a key ac o . Sedimen a ion in
sal ma shes occu s om deposi ion o sus-
pended de i ic sedimen and
in si u
plan
o ganic ma e (Cahoon, 2006; Allen, 2009;
Schile
e al
., 2014). Mo eo e , he sedimen
cap u e e iciency by ege a ion is an essen-
ial ac o in he de e mina ion o he d ow-
ning o adap a ion o a sal ma sh (Day
e
al
., 2011). This e iciency migh be a ec ed
by sea-le el ise ha inc eases inunda ion,
which in u n a ec s plan p oduc i i y (Ki -
wan and Gun enspe gen, 2012; Voss
e al
.,
2013). In ac , he ype o ege a ion in-
luences he adap a ion capaci y (Janousek
and Mayo, 2013).
Tidal la s lack halophy ic ege a ion
(P a olongo
e al
., 2019), which is known
o be o i al impo ance o he e olu ion
o sal ma shes in he cu en con ex o
sea-le el ise (Mo is
e al
., 2002; Ma ani
e al
., 2013). While nume ous egional
s udies ha e analysed he beha iou o
sal ma shes (see abo e), none has ocu-
sed on idal la s.
GEOGACETA, 66, 2019
79Copy igh ©2019 Sociedad Geológica de España / www.geogace a.com
Recepción: 1 de eb e o de 2019
Re isión: 25 de ab il de 2019
Acep ación: 24 de mayo de 2019
Geogace a, 66 (2019), 79-82
ISSN ( e sión imp esa): 0213-683X
ISSN (In e ne ): 2173-6545
Recen ans o ma ion o in e idal en i onmen s unde a sea-le el
ise scena io: examples om no he n Spain
T ans o mación ecien e de ambien es in e ma eales bajo un escena io de ascenso del ni el ma ino:
ejemplos del no e de España
Ane Ga cía-A ola1, Alejand o Cea e a1,2 and D. Reide Co be 3
1 Depa amen o de Es a ig a ía y Paleon ología, Facul ad de Ciencia y Tecnología, Uni e sidad del País Vasco UPV/EHU, Apa ado 644, 48080 Bilbao, Spain ane.ga [email protected];
alejand o.cea e [email protected]
2 Basque Cen e o Clima e Change-BC3, Leioa, Spain
3 Depa men o Coas al S udies, In eg a ed Coas al P og ams, Eas Ca olina Uni e si y, Wanchese, NC, 27981, USA. co be [email protected]
ABSTRACT
The ans o ma ion o wo in e idal en i onmen s om no he n Spain du -
ing he las 150 yea s shows an e olu ion om a idal la in o a sal ma sh en-
i onmen , wi h an in e media e ansi ional s age. The en i onmen o
deposi ion was econs uc ed based on ben hic o amini e a and sand con en .
Sedimen s we e pu in o a empo al amewo k using sho -li ed adioiso ope
ac i i ies and hea y me al concen a ions. The obse ed na u al e olu ion e-
sponds o he a ailabili y o abundan sedimen and he cu en sea-le el ise
scena io, whe e in e idal en i onmen s a e ying o adap o inc easing lood-
ing pe iods by acc e ing sedimen apidly.
Key-wo ds:
o amini e a, in e idal en i onmen , na u al ans o ma ion,
sea-le el ise, San oña es ua y.
RESUMEN
La ans o mación de dos ambien es in e ma eales en el no e de España
du an e los úl imos 150 años mues a la e olución desde una llanu a in e ma-
eal a una ma isma, con una e apa de ansición in e media. El paleoambien e
se econs uyó median e el con enido en o aminí e os ben ónicos y en a ena.
Los sedimen os ue on da ados u ilizando adioisó opos de ida co a y con-
cen aciones de me ales pesados. La e olución na u al obse ada esponde a
la disponibilidad de abundan e sedimen o y al escena io ac ual de ascenso en
el ni el del ma , donde los ambien es in e ma eales es án a ando de adap a se
a los c ecien es pe íodos de inundación ac ecionando sedimen o ápidamen e.
Palab as cla e:
o aminí e os, ambien e in e ma eal, ans o mación
na u al, ascenso del ni el ma ino, es ua io de San oña.
This documen is he Accep ed Manusc ip e sion o a Published Wo k ha appea ed in inal o m in:
Ga ciá-A ola, A.; Cea e a, A.; Co be , D.R.S. 2019. Recen ans o ma ion o in e idal en i onmen s unde a sea-le el ise scena io:
Examples om no he n Spain. GEOGACETA.
© 2019 Sociedad Geologica de Espana. All igh s ese ed.
This manusc ip e sion is made a ailable unde he CC-BY-NC-ND 3.0 license h p://c ea i ecommons.o g/licenses/by-nc-nd/3.0/
He e, we s udy he e olu ion o wo
idal la en i onmen s om he San oña
es ua y (no he n Spain) o e he pas cen-
u y. These en i onmen s e ol ed ecen ly
in o sal ma shes as a esponse o he
20 h cen u y sea-le el ise. As o sal
ma shes, sedimen a ailabili y seems o
con ol he egional ans o ma ion o
hese lowe ele a ion en i onmen s ha
acc e e sedimen e y as o each equili-
b ium wi h he idal ame.
Ma e ials and Me hods
The San oña es ua y (no he n Spain)
is o med by he idal pa o he Asón
i e wi h an ex ension o 11 km leng h
and 0.5 km wid h in he uppe es ua y
and 3 km wid h in he lowe es ua y, co-
e ing a o al a ea o 200 ha (Ga cía-A -
ola
e al
., 2016).
The Jus eda (JU: X=461353.594;
Y=4807556.389; Z=2.737 m; wo 50-cm
long eplica es) and P imos o (PR: X=
462252.9; Y= 4804325.367; Z=2.683 m;
wo 46-cm long eplica es) co es we e ex-
ac ed by hand in oducing wo 50-cm long
and 12.5-cm diame e PVC ubes in each
sal ma sh cha ac e ized by
Spa ina ma i-
ima
(Cu is) Fe nald ege a ion (Fig. 1). P e-
cise loca ion and ele a ion o he co es
we e measu ed using a RTK-GPS, wi h a ho-
izon al p ecision o ±20 mm and a e ical
p ecision o ±35 mm. The Z coo dina e was
e e enced o he local o dnance da um
(LOD: lowes ide a he Bilbao Ha bou on
Sep embe 27, 1878; loca ed 1.73 m below
he Spanish na ional le elling da um o MSL
in Alican e). Sedimen compac ion du ing
sampling was negligible due o he mine o-
genic na u e o he sedimen and he la ge
diame e o he ube. In bo h cases, his o i-
cal ae ial pho og aphy does no show any
e idence o human impac in he ecen
pas (Fig. 1).
Each eplica e was longi udinally di i-
ded in o wo hal es. The i s hal was used
o analyse he g ain size and he o amini-
e al con en in o de o in e p e he pa-
laeoen i onmen (see Ga cía-A ola
e al.
,
2016 o me hodology). The second hal
was employed o measu e he 137Cs ac i i y
and he Pb concen a ion o de elop a ch o-
nology o he eco e ed sedimen s (see
Co be
e al.
, 2006 and Ga cía-A ola
e
al.
, 2016 o me hodology).
Resul s and Discussion
The lowe hal o he JU co e is o med
o g ey sand (wi h abundan mollusc shells
in he lowe mos 8 cm) and he uppe hal
is made o g ey mud wi h plan oo s a he
op 15 cm (Fig. 2). Acco ding o he o a-
mini e al con en , h ee dep h in e als
(DIs) we e dis inguished in his co e. The lo-
we mos 22 cm (DI3) a e cha ac e ised by
high numbe s o o amini e al es s (mean
2846 es s/50 g). The assemblage is domi-
na ed by calca eous hyaline species (a e-
age 98%), whe e
Ammonia epida
(Cushman) (a e age 39%),
Haynesina ge -
manica
(Eh enbe g) (a e age 39%), and
C ib oelphidium williamsoni
(Haynes) (a e-
age 16%) a e dominan . This in e al is in-
e p e ed as a idal la en i onmen based
on i s simila i y wi h mode n assemblages
desc ibed by Cea e a (1988), Cea e a
e
al
. (2002) and Leo i
e al
. (2008). The
uppe 4 cm (DI2) con ain mode a e num-
be s o o amini e al es s (mean 1040
es s/50 g) cha ac e ised by a mix u e o
calca eous hyaline (a e age 65%) and up-
wa d inc easing agglu ina ed (a e age
35%) o ms. The assemblage is domina ed
GEOGACETA, 66, 2019 A. Ga cía-A ola, A. Cea e a and D.R. Co be
80 Paleon ología / Palaeon ology
Fig. 1.- On he le , geog aphical loca ion (g een squa e) o he San oña es ua y in no he n Spain and posi ion o he JU and PR co es ( ed do s). On
he igh , de ailed his o ical (1946: le ) and mode n (2011: igh ) ae ial pho og aphs wi h he posi ion o he JU and PR co es ( ed do s). See colo
igu e in he web.
Fig. 1.- A la izquie da, localización geog á ica (cuad ado e de) del es ua io de San oña en el no e de España y la posición de los sondeos JU y PR
(pun os ojos). A la de echa, o og a ías aé eas his ó ica (1946: izquie da) y mode na (2011: de echa) con la posición de los sondeos JU y PR (pun os
ojos). Ve igu a en colo en la web.
by
H. ge manica
(a e age 40%),
A. epida
(a e age 23%),
En zia mac escens
(B ady)
(a e age 23%) and
T ochammina in la a
(Mon agu) (a e age 11%). This in e al
migh ep esen a ansi ional en i onmen
om he lowe idal la en i onmen o-
wa ds he uppe DI1. In ac , he inc ease
o agglu ina ed species owa ds he op o
his in e al is in e p e ed as he shallowing
o he en i onmen . The uppe mos 24 cm
o med DI1 ha is di ided in o wo sec ions
based on di e ences in o amini e al den-
si ies. The lowe 16 cm (DI1b) a e ep esen-
ed by e y low numbe s o agglu ina ed
o amini e al es s (mean 62 es s/50 g). Fi-
nally, he uppe 8 cm (DI1a) a e domina ed
by agglu ina ed o ms (a e age 99%) and
a mode a e o amini e al densi y (mean
1584 es s/50 g), excep o he uppe mos
1 cm ha con ains abundan calca eous
axa.
T ochammina in la a
(a e age 72%)
and
E. mac escens
(a e age 27%) a e do-
minan in DI1a. This in e al ep esen s a
high sal ma sh en i onmen because he
o amini e al assemblages a e almos ex-
clusi ely o med by agglu ina ed species,
excep o he op sample ha is indica i e
o a low sal ma sh en i onmen . The e y
low o amini e al densi y in he lowe DI1b
could be explained by he e y high sedi-
men a ion a es ha mus ha e occu ed
so ha he highe ele a ion sal ma sh in
DI1a could de elop. Sand con en dec ea-
ses om he co e bo om, whe e i is e y
high (mean 75% in DI3), o he op, whe e
i achie es e y low alues (3% in DI1a).
This pa e n sugges s ha as he en i on-
men was gaining ele a ion i became
mo e es ic ed and, he e o e, he en ance
o es ua ine and ma ine sand was mo e li-
mi ed. Sedimen con aining 137Cs is i s e-
co ded a 28 cm dep h (DI2). The 137Cs
eco d indica es he ansi ion be ween he
idal la and he sal ma sh occu ed a e
1954 when he a mosphe ic nuclea wea-
pon es ing eco d in sedimen s begun (Ri -
chie and McHen y, 1990). Addi ionally, he
Al-no malized Pb concen a ion peak a 24
cm dep h (DI1b) sugges s his ansi ion oc-
cu ed p io o he 1970s when maximum
emissions o Pb in Eu ope and he main e-
gional indus ializa ion pe iod coincide
(Pacyna
e al
., 2007; I abien
e al
., 2015).
The lowe 24 cm o he PR co e was
made o b own mud and he op 22 cm a e
composed o so black mud, wi h
Sc obi-
cula ia plana
(da Cos a) bi al e all o e and
Hedis e di e sicolo
(O.F. Mülle ) polychae e
in he op hal (Fig. 2). The co e was di ided
in o h ee DIs acco ding o he o amini e al
con en . The lowe mos 14 cm (DI3) con ain
a mode a e numbe o o amini e al es s
(mean 480 es s/50 g), almos exclusi ely
composed o hyaline species (a e age
99.7%).
Haynesina ge manica
(a e age
49%) and
A. epida
(a e age 46%) a e he
main species. This in e al is in e p e ed as
a idal la en i onmen because i was o -
med almos exclusi ely o calca eous hya-
line species. The uppe 7 cm (DI2) a e
cha ac e ized by a mix u e o upwa ds in-
c easing agglu ina ed (a e age 41%) and
dec easing calca eous hyaline (a e age
59%) o ms. The assemblage displays mo-
de a e numbe s o o amini e al es s (mean
GEOGACETA, 66, 2019
81Paleon ología / Palaeon ology
Recen ans o ma ion o in e idal en i onmen s unde a sea-le el ise scena io: examples om no he n Spain
Fig. 2.- Iden i ied dep h in e als (DIs) in he JU and PR co es based on he sand con en (%) and main o amini e al species (%). 137Cs ac i i y (Bq/kg)
and Al-no malised Pb dis ibu ion wi h dep h (cm) a e also shown o ch onological pu poses (see ex ).
Fig. 2.- In e alos de p o undidad iden i icados en los sondeos JU y PR en unción del con enido en a ena (%) y las especies de o aminí e os dominan es
(%). También se mues a la ac i idad de 137Cs (Bq/kg) y la dis ibución de Pb no malizado espec o a Al en unción de la p o undidad (cm) con ines c o-
nológicos ( e ex o).
GEOGACETA, 66, 2019 A. Ga cía-A ola, A. Cea e a and D.R. Co be
82 Paleon ología / Palaeon ology
410 es s/50 g), domina ed by
A. epida
(a e age 33%),
H. ge manica
(a e age
24%),
Sche ocho ella monili o mis
(Sid-
dall) (a e age 19%) and
E. mac escens
(a e age 16%). As in he JU co e, his in-
e media e in e al ep esen s a ansi io-
nal en i onmen om he lowe idal la
en i onmen owa ds he uppe sal
ma sh se ing. The op 25 cm (DI1) a e
cha ac e ised by a mode a e o amini e al
densi y (mean 379 es s/50 g), whe e cal-
ca eous hyaline species inc eases up-
wa ds (a e age 61%). This uppe pa is
domina ed by
H. ge manica
(a e age
42%),
S. monili o mis
(a e age 23%) and
A. epida
(a e age 19%). This in e al e-
p esen s a low sal ma sh en i onmen
ha is losing ele a ion h ough ime as
he inc ease o calca eous hyaline species
in de imen o agglu ina ed species o-
wa ds he co e op indica es. Sand con-
en is a he cons an h oughou
(a e age 11%) excep o he op 10 cm
whe e i inc eases up o 30%. This e olu-
ion o he sand con en suppo s he idea
o a opog aphically lowe sal ma sh en-
i onmen owa ds he op, which makes
i mo e p one o idal inunda ion. In P i-
mos o, he bo om idal la e ol ed in o
a high sal ma sh bu , unlike Jus eda, he
sal ma sh appa en ly did no ecei e
enough sedimen o main ain he inc ea-
sing ele a ion and quickly u ned in o a
low ma sh. This could be ela ed o a ia-
ions in local hyd odynamic condi ions o
di e en ial i e low inpu s o he Jus-
eda and P imos o sal ma shes. The Jus-
eda sal ma sh ecei es sedimen om
he main Asón i e h ough he Limpias
channel as well as om he Cla ín s eam,
a ibu a y o he o me , h ough he
Rada channel (Fig. 1). The loca ion o he
P imos o sal ma sh, sepa a ed om he
Limpias channel by he Ca asa sal ma sh
(Fig. 1), which has ecen ly been egene-
a ed (Ga cía-A ola
e al
., 2016), could
es ic sedimen inpu o he smalle Cla-
ín s eam. Fu he mo e, he limi ed space
a ailable o sal ma sh mig a ion o
changes in plan p oduc i i y could ha e
also been esponsible o he obse ed
e olu ion (Schile
e al
., 2014). The PR co e
p esen s a simila empo al e olu ion o
he JU co e, wi h he ansi ional zone be-
ginning p io o 1954 (137Cs is i s eco -
ded a 27 cm dep h) and ending be ween
1954 and he 1970s ( he Al-no malized
Pb maximum is a 21 cm dep h).
Conclusions
The sedimen eco ds ex ac ed om
wo in e idal a eas om no he n Spain
showed he na u al ans o ma ion o a
idal la en i onmen in o a sal ma sh
se ing, loca ed highe in he idal ame.
The o me idal la s acc e ed sedimen
aiming o each equilib ium wi h he new
idal ame as sea le el was ising. This
was indica ed by he upwa ds inc ease o
agglu ina ed species, sugges ing ha he
en i onmen was gaining ele a ion. Bo h
hese eco ds show he impo ance o
abundan sedimen a ailabili y o hese
en i onmen s o keep pace wi h inc ea-
sing sea le el. When sedimen inpu was
no su icien , he o he wise high ma sh
en i onmen was ans o med in o a low
ma sh en i onmen , domina ed by a mix-
u e o calca eous and agglu ina ed o-
amini e a. These conclusions a e o
in e es o he de elopmen o p edic-
ions ega ding he adap i e esponse o
hese coas al ecosys ems and hei po-
en ial use as na u al de ences o on-
going sea-le el ise.
Acknowledgmen s
This esea ch was unded by he Mi-
nis y o Economy and Compe i i eness o
Spain (CGL2013-41083-P), he Uni e si y
o he Basque Coun y UPV/EHU
(UFI11/09), and he Basque Go e nmen
(IT976-16). Ane Ga cía-A ola was unded
by he Basque Go e nmen (BFI08.180).
Mi iam To on egui Aguado ca ied ou
he mic opalaeon ological analysis o he
PR co e and Edua do Leo i (Eas Ca olina
Uni e si y, USA) helped in he ield. We
hank Juan Use a (Uni e si a de Valèn-
cia), an anonymous e iewe , and Manuel
Díaz Azpi oz (Assis an Edi o ) o hei a-
luable commen s. This wo k ep esen s
con ibu ion #29 o he Geo-Q Zen oa
Resea ch Uni (Joaquín Gómez de Lla ena
Labo a o y).
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