Reflooding and repopulation of the Mediterranean Sea after the Messinian Salinity Crisis: Benthic foraminifera assemblages and stable isotopes of Spanish basins

Ma ine Mic opaleon ology 176 (2022) 102160 A ailable online 16 Augus 2022 0377-8398/© 2022 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY-NC-ND license (h p://c ea i ecommons.o g/licenses/by- nc-nd/4.0/). Re looding and epopula ion o he Medi e anean Sea a e he Messinian Salini y C isis: Ben hic o amini e a assemblages and s able iso opes o Spanish basins F. Bulian a , e , * , T.J. Kouwenho en b , N. Ande sen c , W. K ijgsman d , F.J. Sie o a a Dep . de Geología, Uni . de Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain b Facul y o Ea h Sciences, U ech Uni e si y, U ech , he Ne he lands c Leibniz-Labo a o y o Radiome ic Da ing and Iso ope Resea ch, Ch is ian-Alb ech s-Uni e si ¨ a Kiel, Max-Ey h-S .11-13, 24118 Kiel, Ge many d Palaeomagne ic Labo a o y Fo Hoo ddijk, U ech Uni e si y, Budapes laan 17, 3584 CD U ech , he Ne he lands e G oningen Ins i u e o A cheology, Uni e si y o G oningen, Pos s aa 6, 9712 ER G oningen, he Ne he lands ARTICLE INFO Keywo ds: Miocene-Pliocene bounda y Albo an Basin Spanish ma ginal basins Ben hic o amini e a ABSTRACT Ben hic o amini e al, sedimen ological, and s able iso ope analyses pe o med on ea ly Zanclean sedimen s om Albo an Basin ODP Si e 976 and sou he n Spanish land-based sec ions in he Malaga, Nija and So bas basins ha e enabled he econs uc ion o Medi e anean en i onmen al condi ions immedia ely a e he Messinian Salini y C isis. The p esence a he Miocene – Pliocene bounda y o da k laye s, o en en iched in o ganic ma e , sugges s ha he Zanclean e looding has c ea ed wa e column s a i ica ion, and educed bo om-wa e oxygen le els. Conside ing ha such da k laye s a e eco ded a bo h deep and ma ginal se ings a away om he Gib al a ga eway/s, a Medi e anean-scale wa e -mass s a i ica ion mus ha e occu ed. This s a i ica ion could be he esul o saline A lan ic wa e s sinking in o a less saline Medi e anean Basin s ill unde he in- luence o he Pa a e hys. Ou ea ly Zanclean ben hic δ 18 O da a show ha he Medi e anean wa e budge was indeed less nega i e han a p esen , explaining he lowe salini y o he basin. Howe e , he A lan ic alues o he ben hic δ 13 C egis e ed in he Albo an basin sugges ha bo om-wa e enewal a es we e qui e high du ing he ea ly Zanclean, p e en ing he educ ion o δ 13 C a he sea loo as obse ed in he Messinian eco ds. Zanclean ben hic o amini e al epopula ion sequences show simila i ies wi h eco e y om low-oxic episodes du ing sap opel deposi ion. These obse a ions, pai ed wi h he g adual deepening o he basins, sugges s ha he Zanclean e looding led o a p og essi e shi om s essed and uns able en i onmen s owa ds ben hic associa ions ypical o e icien ci cula ion and bo om wa e en ila ion. 1. In oduc ion Since he 1970s he e is an ongoing deba e ega ding he end o he Messinian Salini y C isis (MSC) o he Medi e anean Sea (Fig. 1A) and he exac dynamics o es o a ion o ma ine condi ions. Th ough ime h ee main e looding scena ios we e p oposed: (1) an ins an aneous inunda ion o an (almos ) desicca ed Medi e anean a 5.33 Ma, co e- sponding o he base o he Zanclean (Hsü, 1972; Blanc, 2002; Loge and Van Den D iessche, 2006; Ga cia-Cas ellanos e al., 2009; Ga cía-Alix e al., 2016); (2) high Medi e anean wa e le el du ing he la es Messinian wi h apid es o a ion o he A lan ic-Medi e anean connec ion cha ac e ised by a mino sea-le el ise ac oss he Messinian-Zanclean ansi ion (Loge e al., 2005; Pie e e al., 2006; Ro e i and Manzi, 2006; Co n´ ee e al., 2016; Ma zocchi e al., 2016; And ee o e al., 2021b) and (3) a wo-s age es o a ion o he connec- ion wi h he majo e looding aking place a 5.46 Ma, du ing he Messinian (Es ada e al., 2011; Bache e al., 2012; P´ e ez-Asensio e al., 2013; Bache e al., 2015). The h ee models di e no only in he dy- namics o he e looding i sel , bu also in he iming and he magni ude o he base le el luc ua ions. The Zanclean sedimen s in he Medi e anean we e deposi ed on op o shallow (Nija Basin: Basse i e al., 2006, his wo k; Malaga Basin: Gue a-Me ch´ an e al., 2008, his wo k; So bas Basin, his wo k; Fig. 1B) and deep, la e Messinian Lago-Ma e (LM) deposi s (E aclea Minoa: e.g., * Co esponding au ho a : Dep . de Geología, Uni . de Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain. E-mail add esses: [email p o ec ed] (F. Bulian), [email p o ec ed] (T.J. Kouwenho en), [email p o ec ed] (N. Ande sen), W.K ijgsman@uu. nl (W. K ijgsman), [email p o ec ed] (F.J. Sie o). Con en s lis s a ailable a ScienceDi ec Ma ine Mic opaleon ology jou nal homepage: www.else ie .com/loca e/ma mic o h ps://doi.o g/10.1016/j.ma mic o.2022.102160 Recei ed 9 Ma ch 2022; Recei ed in e ised o m 6 Augus 2022; Accep ed 9 Augus 2022 Ma ine Mic opaleon ology 176 (2022) 102160 2 B olsma, 1978; Si es 975 and 974: Iacca ino and Bossio, 1999; Iacca ino e al., 1999a). The con ac a he Miocene-Pliocene bounda y (MPB) is exp essed in di e en ways including con o mably abo e con inen al acies (So bas Basin, e.g., Ro e i e al., 2018), and e osional bo h in deep and shallow basins (e.g., Cheli Basin: Rouchy e al., 2007; Zakyn hos Island: Kon akio is e al., 2016 and Ka aki sios e al., 2017; Ve a Basin: Ca uso e al., 2020; Albo an Basin: Bulian e al., 2021). A some loca- ions conglome a es, b eccias o small clas s a e in e cala ed (Si e 975: Iacca ino e al., 1999b (Fig. 1E); Eas Albo an Basin: Ga cia-Cas ellanos e al., 2019; Le an Basin: Mado e al., 2019). In land sec ions and o sho e si es, he bounda y is ecognized h ough changes in li hology, ca bona e con en o s able iso opes o ca bona es (Iacca ino e al., 1999b; Pie e e al., 2006; Rouchy e al., 2007). A cha ac e is ic li hology iden i ied a he MPB (ma king he ea lies Pliocene sedimen s and/o la es Messinian ones) is a cm/dm- hick black laye deposi ed con o mably abo e he LM deposi s in he Piedmon Basin (Fig. 2G; T enkwalde e al., 2008; Dela Pie e e al., 2016), No he n Apennines (No he n Apennine; Genna i e al., 2008; G ossi Fig. 1. A) Ba hyme ic map o he Medi e anean egion ( om h ps://po al.emodne -ba hyme y.eu/) whe e he ec angle shows he s udied a ea and he Guadalqui i Basin. B) Ba hyme ic map o he Albo an Basin and Ri ian Co ido . The black do and ec angles indica e he s udied ODP Si e and onsho e sec ions (Rio Mendelin sec ion-Malaga basin; Zo e as sec ion-So bas Basin and Ba anco del Neg o sec ion-Nija Basin) espec i ely. The ha ched a eas show he ex ension o he Messinian ga eways (a e Ma ín e al., 2014). Fig. 2. Pho og aphs o he Miocene-Pliocene bounda y om some o he men ioned loca ions. A) Rio Mendelin sec ion ( his s udy); B) Zo e as sec ion ( his s udy); C) E aclea Minoa sec ion (pe sonal collec ion); D) ODP Si e 974 (Iacca ino e al., 1999b); E) ODP Si e 975 (Iacca ino e al., 1999b); F) Ba anco del Neg o sec ion ( his s udy); G) Moncucco qua y in Piedmon Basin (cou esy o . F. And ee o) and H) Zakyn hos island in G eece (cou esy o K. Agiadi). F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 3 e al., 2008), No he n I aly (Ri o gia o e al., 2011), Cyp us (Rouchy e al., 2001; Manzi e al., 2016), Sicily (B olsma, 1978; unpublished da a; Fig. 2C), DSDP Si e 376 (Ci a e al., 1978), ODP Si es 974 and 975 (Iacca ino e al., 1999b; Fig. 2D, E), Zakyn hos (Fig. 2H; K. Agiadi, pe s. comm.) and in sec ions in he Malaga, So bas and Nija Basins included in his s udy (Fig. 2A, B, F). A some loca ions (e.g., Malaga Basin) hese laye s a e deposi ed jus abo e he MPB. This black laye is usually ich in o ganic ma e (Genna i e al., 2008; T enkwalde e al., 2008; Manzi e al., 2016) and sca ce in o amini e a which a e usually ypical Plio- cene species, ewo ked Miocene o Eocene species, o in some cases bo h (Ci a and Zocchi, 1978; Genna i e al., 2008; Manzi e al., 2016). A some loca ions mic o ossils a e absen (e.g. Moncucco qua y: T enkwalde e al., 2008). The palaeoen i onmen al signi icance o such da k laye s emains s ill la gely unknown (e.g. Genna i e al., 2008). To es and alida e he mos p obable e looding scena io and explain he occu ence o da k laye s i is necessa y o inc ease ou unde s anding o he palaeoen i onmen al condi ions p esen a e he MSC and he e o e, o analyse he la e Messinian - ea ly Zanclean sedimen a y eco d a loca ions close o he Medi e anean – A lan ic ga eway. In his wo k, we s udied h ee onsho e ou c ops om Neogene basins in sou he n Spain which con ain well-p ese ed la e Miocene – ea ly Pliocene sedimen a y successions: he Rio Mendelin sec ion in he Malaga Basin, he Ba anco del Neg o sec ion in he Nija Basin and he Zo e as sec ion in he So bas Basin (Fig. 1B). In addi ion, we e- e alua ed he ea ly Zanclean sedimen s e ie ed a ODP Si e 976 in he Wes Albo an Basin, loca ed in on o he Gib al a ga eway (Fig. 1B). Du ing he la e Miocene, hese basins we e pa o he Medi- e anean ealm and consequen ly hei sedimen s could ha e egis e ed he i s in lux o A lan ic wa e s, oge he wi h Zanclean wa e le els and palaeoen i onmen al condi ions in he wes e n Medi e anean. We pe o med de ailed ben hic o amini e al and s able iso ope analyses o hese ou si es o be e unde s and he dynamics o he e looding oge he wi h he en i onmen al changes ha occu ed in he Medi e - anean a e he MSC. 2. Geological se ing and ma e ial s udied 2.1. Neogene Basins o he Be ic Co dille a The Malaga Basin (Fig. 1B) is an in e mon ane E-W o ien ed basin loca ed in he wes e nmos sec o o he Be ic Co dille a (Sanz De Gal- deano and Ve a, 1992). The basin is d ained by he Guadalho ce Ri e and bounded o he no h by he Malaga Moun ains, o he sou h by he Mijas Sie a and o he eas by he Albo an Basin. I s pos -o ogenic in illing is composed o uppe To onian o Qua e na y sedimen s (e.g. Gue a-Me ch´ an e al., 2008). The sec ion analysed in his s udy (Rio Fig. 3. Field pho og aph o he Miocene-Pliocene bounda y in he Malaga Basin (Rio Mendelin sec ion). Fig. 4. Field pho og aph o he Miocene-Pliocene bounda y in he So bas Basin (Zo e as sec ion). F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 4 Mendelín sec ion; 36◦45′2.53”N; 4◦25′57.26”W; Fig. 2A, 3, 6A) com- p ises la e Messinian deposi s ela ed o he inal s age o he MSC (Lago- Ma e uni ) and he lowe Zanclean. The Río Mendelín sec ion is loca ed in an ancien lu ial alley, incised du ing he la es To onian o du ing he MSC acme sea le el d op, which, based on he Pa a e hyan a ini y o i s aunal con en , was p og essi ely e illed du ing he dilu ion phase a he end o he Messinian (Gue a-Me ch´ an e al., 2010; Do Cou o e al., 2014). The Pliocene sedimen s a e deposi ed wi h an e osional con ac a he ma gins and a g adual con o mable con ac in he cen e o he basin on op o he LM uni . In his s udy, we analysed 23.5 m o he Rio Mendelin sec ion, including 2 uppe mos me es o he LM sequence ollowed, wi h a ansi ional con ac , by ea ly Pliocene sedimen s composed o 25 cm o yellow sil y sedimen s, 75 cm o g ey clays o e lain by 20.5 m o yellowish clays (Fig. 6A). The Nija and So bas basins a e in e mon ane basins de eloped abo e he me amo phic nappes o he sou he n Be ics (Fig. 1; Sanz De Galdeano and Ve a, 1992). The sedimen a y in illing o he basins occu ed du ing he la e Miocene (To onian and Messinian), Pliocene and Qua e na y (Dab io e al., 1981; Se ano, 1990; Omodeo Sal´ e e al., 2012). Du ing he Miocene, un il he end o MSC S age 1, he wo basins Fig. 5. Field pho og aph o he Miocene-Pliocene bounda y in he Nija Basin (Ba anco del Neg o sec ion). Fig. 6. S a ig aphic logs o he h ee sec ions s udied in Sou he n Spain. A) Rio Mendelin sec ion; B) Zo e as sec ion, C) Ba anco del Neg o sec ion. The black do s ep esen he analysed samples. The colou s e lec he colou s obse ed in he ield. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 5 we e connec ed o he Medi e anean, which en e ed he Nija Basin om he sou h and he So bas Basin h ough NW-SE ending co ido s no h o Nija (Fo uin and K ijgsman, 2003). In his wo k, he uppe Messinian-lowe Zanclean sedimen s om he Nija and So bas basins ha e been s udied (Figs. 4 and 5). In he So bas Basin, lowe Pliocene sedimen s (Gocha Fo ma ion) lie on op o he Zo e as Membe which mainly consis s o palaeosols, lu io-del aic eddish sil s and sands ones, g ey-colou ed sands ones and conglome - a es in e cala ed by up o 4 whi ish, massi e ca bona e beds (Manzi and Ro e i, 2009; Au gebaue and McCann, 2011; Ro e i e al., 2018; Ro e i e al., 2019b) con aining eu yhaline os acod specimens o Pa a e hyan a ini y like Cyp ideis sp. (e.g., Au gebaue and McCann, 2011). The Zo e as membe is conside ed as he equi alen o he LM acies (Rouchy and Ca uso, 2006). The ma ine ea ly Pliocene sands show 0.5 m abo e he bounda y a ossili e ous ho izon ich in bi al es (Fig. 6B) ha can be aced h oughou he basin (Ma he and S okes, 2001; Ro e i e al., 2019b). He e, we analysed 2 m o he Zo e as sec ion (37◦6′ 9.87′′ N; 2◦6’ 46.78′′ W) composed o 0.5 m o eddish LM deposi s, 0.3 m o g ey deposi s con aining ca bona e nodules and 1.2 m o Zanclean massi e sands including he in e cala ed bi al e ho izon (Fig. 4 and 6B). In he Nija Basin (Fig. 1B), he uppe Messinian is composed o al- e na ions o ma ly LM acies and conglome a e allu ial beds (Omodeo Sal´ e e al., 2012) o he Feos Fo ma ion, which a e o e lain by he lowe mos Zanclean wi h an uncon o mi y in he ma ginal pa s o he basin and a con o mable con ac a he cen e (Fo uin and K ijgsman, 2003; Agui e and S´ anchez-Almazo, 2004; Ro e i e al., 2019a). This s udy ocuses on he Ba anco del Neg o sec ion (Fig. 2F, 5, 6C; 37◦ 0′35.02′′ N; 1◦58’ 23.02′′ W) in he no h-eas e n pa o he Nija Basin. He e, he MPB can be clea ly iden i ied, wi h a sha p con ac o e up- pe mos Messinian sedimen s, a 5 cm- hick black and 5 cm- hick g ey laye opped by lowe Zanclean massi e yellow bioclas ic ma ine sands, cha ac e ised a he base by a 1 cm- hick laye wi h bi al e shell ag- men s (Fig. 2F, 6C). 2.2. Albo an Basin The Albo an Basin is a ansi ional a ea be ween he semi-enclosed Medi e anean Sea and he A lan ic Ocean (Fig. 1A, B) cha ac e ised by igo ous ci cula ion ha is s ongly ela ed wi h wa e exchange a he Gib al a S ai whe e he ela i ely low-salini y A lan ic wa e s en e he Medi e anean on op o high-salini y Medi e anean wa e masses. ODP Si e 976 (36◦12′18.78” N, 4◦18′45.78” W) is loca ed in he no he n sec o o he Wes Albo an Basin (WAB; Wes e n Medi e a- nean), ~100 km o he eas o he Gib al a S ai on op o a con inen al c us al ho s ha o med du ing ea ly- o mid-Miocene i ing (Comas e al., 1996). The ma ine lowe Pliocene sedimen s eco e ed a his si e a e mainly composed o homogeneous nanno ossil- ich clays one and sandy clays one (Comas e al., 1996) wi h no isible changes in colou . We analysed 32 samples om he lowe Pliocene o co e 61. F om he unde lying co e 62, only sec ion 62×-CC was eco e ed in which h ee samples we e collec ed. Because o hei unce ain s a ig aphic posi- ion, hese ha e been excluded om he mic opaleon ological in e - p e a ion (Bulian e al., 2021). The posi ion o he MPB was p e iously es ima ed wi h he aid o seismic in e p e a ion and egional bios a- ig aphy a he base o co e 61 (Bulian e al., 2021), co esponding wi h a isible e osional su ace. This e osion has been associa ed wi h he Zanclean e looding, when a e he b eaching o he Gib al a S ai , he A lan ic wa e would ha e ab up ly en e ed he Medi e anean (Ga cia- Cas ellanos e al., 2009; Es ada e al., 2011) and p oduced a ma ked incision (Es e as e al., 2000; Blanc, 2002). Al e na i ely, i a modes d awdown is conside ed, a hype pycnal subma ine cascading e osion (Ro e i e al., 2014b) could be he c ea ion mechanism. The ime slice ep esen ed by he hia us has been es ima ed a 1.67 Ma and includes he majo i y o he middle-uppe Messinian sedimen s (Bulian e al., 2021). 3. Me hodology 3.1. Mic opalaeon ological analyses Fo his s udy, a o al o 95 samples (33 om he Rio Mendelin sec ion, 32 om ODP Si e 976, 21 om he Ba anco del Neg o sec ion, 9 om he Zo e as sec ion) aken wi h a iable sampling s eps (10–20 cm o he Ba anco del Neg o and, Zo e as sec ions and Si e 976 and be- ween 10 cm and 1 m o he Rio Mendelin sec ion) we e selec ed o mic opalaeon ological analyses. The samples we e o en d ied a 40 ◦C and washed o e 63 μ m and 150 μ m sie es. Fo aunal analysis, aliquo s o he 150 μ m ac ion o on a e age 150–200 ben hic o amini e a we e coun ed. The coun s o ben hic o amini e a we e hen ans e ed o ela i e equencies. Samples yielding <50 specimens we e no included in he analyses and in e p e a ions. The ben hic o amini e al con en o he Zo e as sec ion has been s udied in a semi-quan i a i e way based on he p esence o absence o species conside ing ha e y ew speci- mens we e p esen . Simila ly, in he h ee land-based sec ions he p esence o os acods was eco ded, bu only he LM ma ke species (Cyp ideis sp.) was iden i ied om he assemblage. The di e si y o he ben hic o amini e al assemblages has been es ima ed h ough he Shannon index (H, Mu ay, 1991; Spelle be g and Fedo , 2003), exp essed by he o mula: H= − K∑ n i=1 piln(pi) whe e pi is he p opo ion o he i h species and K a posi i e cons an . Fo ODP Si e 976, o which he Messinian pa was deposi ed a slope dep h (Bulian e al., 2021) he sum o shallow-wa e ben hic o ami- ni e al species, Elphidium spp., Rosalina spp., disco bids and Cibicides loba ulus (Supp. 1) was calcula ed. Because a ela i ely high numbe o displaced specimens indica es downslope anspo (Fen imen e al., 2020 and e e ences he ein) his sum has been used as an indica o o cu en s in he basin. 3.2. S a is ical analyses O each da a se excep om he Zo e as and Ba anco del Neg o sec ions (Supp. 2), a hie a chical clus e analyses (Pea son co ela ion: Pas 4.02 so wa e; Hamme e al., 2001; Hamme e al., 2008) was pe o med on he mos abundan (≥3%) a iables ( axa) o iden i y he dis ibu ional pa e ns o ben hic o amini e al species assemblages occu ing in simila en i onmen s. Species wi h a e o single occu - ences we e emo ed om he da a whe eas species belonging o he same genus, when conside ed indica i e o analogous en i onmen al condi ions, we e g ouped oge he . Nodosa ia spp. comp ises unilocula spp., Nodosa ia spp., Pseudonodosa ia spp., Lagena spp. and P oce olagena spp., Canc is spp. con ains he species C. oblongus and C. au iculus. U i- ge ina pe eg ina includes bo h U ige ina pe eg ina and U. pygmea, and Bulimina s ia a is he sum o B. s ia a and B. s ia a mexicana. In Pullenia quinqueloba, bo h o ms wi h ou and i e chambe s we e included. 3.3. Palaeo – wa e dep h es ima es Palaeo-wa e dep h es ima es we e ini ially pe o med using he a io (P/(P +B))*100 (%P; Gibson, 1989; Van de Zwaan e al., 1990), which, al hough his e lec s gene al sea-le el ends, has disad an ages ela ed o sensi i i y o oxygen le els, ood a ailabili y and p e e en ial dissolu ion o he plank ic auna (e.g., Sen Gup a and Machain-Cas illo, 1993; Jo issen e al., 1995; Kuce a, 2007). To imp o e he eliabili y o palaeodep h es ima ions, we excluded om he a io he in aunal o a- mini e al species (e.g., buliminids, boli inids, u ige inids, Nonion spp.). This o ms he basis o calcula ion o he eg ession unc ion (Van de Zwaan e al., 1999; Van Hinsbe gen e al., 2005). Howe e , his app oach s ill does no accoun o dissolu ion o plank ic o amini e a. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 6 The e o e, o ob ain an independen quan i ica ion o he palae- oba hyme y we es ima ed he palaeo-wa e dep h using one o se e al mo e ecen ly de eloped equa ions (e.g. Hohenegge , 2005; Hohenegge e al., 2008; A naim-Ka a e al., 2016; Milke e al., 2017) based exclusi ely on he ben hic o amini e al auna. In his s udy we apply he ans e unc ion o Hohenegge (2005), since his is conside ed eliable in deepe en i onmen s and has been e alua ed by Baldi and Hohe- negge (2008) in he Vienna Basin and by P´ e ez-Asensio e al. (2012) in he Guadalqui i basin. The equa ion, he e used as modi ied by Hohe- negge e al. (2008) and Baldi and Hohenegge (2008) includes he ela i e abundances o each species and hei dep h anges (Table 1): Paleodep h (m) = ∑k j=1[(lj*nj)/dj]/∑k j=1(nj/dj) whe e n j is he ela i e abundance o he n h species, l j he mean species dep h, and d j he dispe sion. As sugges ed by Hohenegge (2005), o calcula e he mean species dep h o shallowe ma ginal basins (e.g., Rio Mendelin sec ion) we used he geome ic means, while o deepe basins (ODP Si e 976), we used he a i hme ic mean in o de o a oid unde - es ima ion. The o amini e a used in he calcula ion a e all au och ho- nous species and epo ed in Table 1. 3.4. Es ima ion o bo om-wa e oxygen le els The ben hic o amini e al dis ibu ion wi hin he sedimen depends on he o ganic lux and oxygena ion a he sea loo (Jo issen e al., 1995; Van de Zwaan e al., 1999). Consequen ly he mic ohabi a is used as an indica o o dissol ed oxygen (Kaiho, 1994), since species wi h deep in aunal (>3 cm below he sedimen -wa e in e ace; BSWI) and in e media e in aunal (>0.7 cm BSWI) mic ohabi a s h i e when oxygen le els a e educed, while epi aunal ones (0–0.7 cm BSWI) p e e be e oxygena ed bo om wa e s (e.g. Co liss and Chen, 1988; Jo issen e al., 1995; Schmiedl e al., 2000; Gooday, 2003). These mic ohabi a p e e ences, e lec ed by mo phological cha ac- e is ics (size, wall hickness, shape: e.g., Co liss and Chen, 1988) can be used o de ine h ee g oups o ben hic o amini e a (Table 2) indica ing espec i ely oxic (>1.5 ml/l O 2 ), suboxic (0.3–1.5 ml/l O 2 ) and dysoxic (0.1–0.3 ml/l O 2 ) en i onmen s (Kaiho, 1991; Kaiho, 1994; Kaiho, 1999). In addi ion, wi hin he dysoxic indica o s h ee di e en g oups (A, B, C) ha e been de ined (Kaiho, 1994) whe e g oup C includes species ha ha e in e media e cha ac e is ics be ween suboxic and dysoxic ma ke s. Using hese indica o s, he Ben hic Fo amini e al Ox- ygen Index is calcula ed (BFOI; Kaiho, 1991; Kaiho, 1994; Kaiho, 1999) ob aining i e di e en condi ions o dissol ed oxygen: anoxic (−55), dysoxic (−50 o −40), suboxic (−40–0), low oxic (0–50), and high oxic Table 1 The ba hyme ic anges, mean li ing dep h and s anda d de ia ion o he ben hic o amini e al species used o palaeo – wa e dep h econs uc ion. The species used o he Rio Mendelin sec ion a e unde lined, while he ones employed o ODP Si e 976 ha e an as e isk. Dep h anges a e based on p e i- ously published wo k o : 1 W igh (1979), 2 W igh (1978), 3 Lu ze and Coul- bou n (1984), 4 P lum e al. (1976), 5 Lu ze and We e (1980), 6 Haake (1982), 7 Ba bie i and Panie i (2004), 8 Van Hinsbe gen e al. (2005), 9 Violan i e al. (2011), 10 Co bí (2010), 11 Van Mo kho en e al. (1986), 12 De S ig e e al. (1998), 13 Baggley (2000), 14 Gebha d (1993), 15 Be gg en and Haq (1976), 16 P´ e ez-Asensio e al. (2012), 17 Poag and T essla (1981), 18 De S ig e e al. (1998), 19 Bandy and Chie ici (1966), 20 De Rijk e al. (2000), 21 De Rijk e al. (1999); 22 Sen Gup a and Machain-Cas illo (1993), 23 Mu ay (2006), 24 Bizon and Bizon (1984), 25 Mendes e al. (2012), 26 Ohga and Ki aza o (1997), 27 Milke and Schmiedl (2012), 28 Al e (2003), 29 Aus in and E ans (2000), 30 Schmiedl e al. (1997), 31 Suokh ie e al. (2021), 32 Russo e al. (2007) and 33 (Haywa d, 2004). Species min dep h max dep h SD Amphico yna spp.* 9 2860 1425.5 Anomalinoides helicinus* 600 2000 700 As e ige ina plano bis 200 400 1000 Boli ina dila a a 15 3000 1492.5 Boli ina spa hula a 30 3547 1758.5 Bulimina aculea a* 5 4000 1997.5 Bulimina elonga a 16 200 92 Bulimina mexicana 100 2000 950 Bulimina s ia a* 100 800 350 Canc is oblongus* 30 500 60 Chilos omella spp.* 700 1900 600 Cibicidoides b adyi* 200 3000 1400 Cibicidoides pseudounge ianus/unge ianus* 50 4000 1975 Cibicidoides kullenbe gi* 1000 4000 500 Cibicides loba ulus 20 1300 640 Cibicidoides pachyde ma* 30 4000 1985 Cibicides du emplei* 100 600 250 Den alina spp.* 30 1200 585 Fu senkoina acu a 0 600 300 Globobulimina spp.* 1000 1500 250 Globobulimina u gida 30 150 60 Globocassidulina subglobosa* 50 4000 1975 Gy oidina al i o mis* 30 600 285 Gy oidina soldanii* 100 5000 2450 Ka e iella b adyi* 100 3000 1450 Len iculina spp.* 600 1500 450 Ma ino iella communis* 200 3000 1400 Melonis ba leeanus* 13 3974 1980.5 Melonis pompilioides* 100 3000 1450 Melonis soldanii* 90 1000 455 Nodosa ia spp.* 30 1700 235 Nonion abum 0 200 100 O ido salis s ella us 250 1500 625 O ido salis umbona us* 65 4000 1967.5 Planulina a iminensis* 70 1300 615 Pullenia bulloides 60 4000 1970 Pullenia quinqueloba* 50 2000 975 Sigmoilopsis schlumbe ge i* 57 1500 721.5 Sphae oidina bulloides* 100 2000 950 S ain o hia usi o mis 0 2200 1080 Tex ula ia cal a 0 2000 1000 T i a ina b adyi 0 600 300 U ige ina pe eg ina* 100 4400 2150 U ige ina u ila* 200 1000 1400 Table 2 Mic ohabi a p e e ences o ben hic o amini e a om he Rio Mendelin sec ion and ODP Si e 976: epi auna (0–0.7 cm BSWI), in auna (>0.7 cm BSWI) and deep in auna (>3 cm BSWI). Oxic Suboxic (G oups A and B) Dysoxic Cibicidoides b ady Amphico yna spp. Boli ina dila a a Cibicides du emplei Anomalinoides helicinus Boli ina e icula a Cibicidoides kullenbe gi As e ige ina plano bis Boli ina seminuda Cibicides loba ulus Bulimina elonga a Boli ina spa hula a Cibicidoides pachyde ma Bulimina s ia a Chilos omella spp. Cibicidoides pseudounge ianus Canc is oblongus Fu senkoina acu a Cibicidoides unge ianus Den alina spp. Globobulimina spp. Sphae oidina bulloides Epis ominella inac ia Globobulimina u gida Globocassidulina subglobosa S ain o hia usi o mis Gy oidina al i o mis Gy oidina soldanii Ka e iella b adyi Len iculina spp. Ma ino iella communis Melonis ba leeanus Melonis pompilioides Melonis soldanii Nodosa ia spp. Nonion abum O ido salis s ella us O ido salis umbona us Planulina a iminensis Pullenia bulloides Pullenia quinqueloba Sigmoilopsis schlumbe ge i Tex ula ia cal a T i a ina b adyi U ige ina pe eg ina U ige ina u ila F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 7 (cap ion on nex page) F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 8 (50–100). The BFOI p o ed o accu a ely ep oduce long- e m dissol ed oxygen changes in he Ma ma a Sea (simila bo om-wa e condi ions as in he Medi e anean) and he e o e i can p obably be used o e alua e oxygen le els in he Medi e anean oo (Kaminski, 2012).The in e p e- a ion o he BFOI is p one o bias when e y low-di e si y assemblages a e s udied and consequen ly, his es ima e has no been applied o samples wi h a Shannon index ≤1 (Kaiho, 1994). Mo eo e , s udies on ecen ben hic o amini e a sugges ha quan i a i e econs uc ion o oxygen le els highe han 1 ml/l is p obably no easible (Mu ay, 2001; Jo issen e al., 2007 and e e ences he ein). The BFOI has been calcula ed ollowing he o mula (Kaiho, 1994): BFOI =(O (O+D))*100 whe e O and D (wi h O >0) a e he numbe s o oxic and dysoxic indi- ca o species, espec i ely. When O =0 and I >0, he equa ion: BFOI =(( I (I+D))−1)*100 is used ins ead, whe e I is he sum o suboxic indica o s. The suboxic indica o s in g oup C a e excluded om he o mula (Kaiho, 1994) al hough he species a e used o he paleoen i onmen al in e p e a ions. I is impo an o men ion ha oxygen es ima es based on any indices can be subjec o p oblems ela ed o, o example, exis ence o an ecosys em oxygen g adien , coexis ence o species wi h di e en mic ohabi a p e e ences, ime-a e aged samples o he in e play be- ween expo p oduc i i y and oxygena ion in de ining he p e e ed mic ohabi a (Jo issen e al., 2007). 3.5. S able iso ope measu emen s Epi aunal axa such as Cibicides spp. and Cibicidoides spp. we e obse ed o sec e e calci e close o equilib ium wi h he ambien sea wa e , displaying mino i al and minimal on ogene ic e ec s (Theodo e al., 2016a; Theodo e al., 2016b; J¨ ohnck e al., 2021 and e e ences he ein), and he e o e 2 o 10 specimens (based on he a ailabili y) o Cibicidoides pachyde ma we e picked om ODP Si e 976 (co e 61) sam- ples o s able iso ope analyses. The ac ual con ac be ween Miocene and Pliocene sedimen s was no eco e ed a his si e. None heless, ou new s able iso ope da a om h ee samples o 62×-CC sec ion con i ms hei Messinian age (see Sec ion 5.4) and consequen ly a ibu e, pai ed wi h s a ig aphic ma ke s (Bulian e al., 2021), an ea ly Pliocene age o co e 61. The analysis was only possible un il 571.18 m because specimens om he younge pa o he sequence we e a ec ed by seconda y calci e p ecipi a ion on he su ace and wi hin he ape u e, which pe sis ed e en a e ul asonic cleaning. Fo he Rio Mendelin sec ion, o he species we e chosen gi en he absence o C. pachyde ma. Epis o- minella inac ia was picked in he basal wo samples because he assemblage in he lowe mos le el is monospeci ic and in he nex le el nea ly so (88.6%). In he nex samples Cibicides du emplei was picked, while s a ing om 1 m and going upwa ds, Cibicidoides unge ianus was chosen. Mo e han one species was picked whe e possible, o ob ain in aspeci ic co ec ion ac o s. All measu emen s we e ans o med o C. unge ianus. This species has been epo ed o yield compa able alues as C. pachyde ma (Kabo h e al., 2017). Based on wo pai ed measu e- men s he E. inac ia alues we e co ec ed by adop ing a alue equal o he a e age o se om he C. du emplei alues (−0.21 o δ 13 C and 1.46 o δ 18 O alues). The C. du emplei eco d and he co ec ed E. inac ia da a poin s we e hen all adjus ed using he a e age o se es ablished om six pai ed measu emen s be ween C. du emplei and C. unge ianus (0.33 o δ 13 C and −0.03 o δ 18 O alues). Samples om he Ba anco del Neg o sec ion we e no picked o s able iso ope analyses because pa o he o amini e a a e no in si u. The s able oxygen and ca bon iso ope analyses we e pe o med wi h a Finnigan MAT 253 mass spec ome e connec ed o a Kiel IV ca bona e p epa a ion de ice a he Ch is ian-Alb ech Uni e si y in Kiel (Ge - many). Sample eac ion was induced by indi idual acid addi ion (99% H 3 PO 4 a 75 ◦C) unde acuum. The e ol ed ca bon dioxide was ana- lysed eigh imes o each indi idual sample. As documen ed by he pe o mance o in e na ional [NBS19: +1.95 ‰ VPDB ( 13 C), −2.20 ‰ VPDB ( 18 O); IAEA-603: +2.46 ‰ VPDB ( 13 C), −2.37 ‰ VPDB ( 18 O)] and labo a o y-in e nal ca bona e s anda ds [Hela1: +0.91 ‰ VPDB ( 13 C), +2.48 ‰ VPDB ( 18 O); HB1: -12.10 ‰ VPDB ( 13 C), −18.10 ‰ VPDB ( 18 O); SHK: +1.74 ‰ VPDB ( 13 C), −4.85 ‰ VPDB ( 18 O)], analy ical p ecision o s able iso ope analysis is be e han ±0.08 ‰ o δ 18 O and be e han ±0.05 ‰ o δ 13 C. The ob ained alues we e calib a ed ela i e o Vienna Pee Dee Belemni e (VPDB). 4. Resul s 4.1. Malaga Basin: Rio Mendelin sec ion 4.1.1. Mic opalaeon ology and s able iso opes The lowe mos 2 m o he Rio Mendelin sec ion (Lago-Ma e deposi s) a e ba en o o amini e a and con ain high abundances o os acods, mainly Cyp ideis sp. (Fig. 8). A he base o he Pliocene ben hic o a- mini e a appea and emain p esen h oughou he sec ion. Conside ing he dis ibu ion and he good p ese a ion o he specimens, which do no show any signs o anspo o al e a ion, he o amini e a can be conside ed in si u. Op ical mic oscope pic u es o he species a e shown in Pla es 1 and 2. The i s ben hic o amini e al species appea ing in he Zanclean is Epis ominella inac ia which cha ac e ises he lowe mos 60 cm o he sec ion (2.1–2.7 m) (Figs. 8, 9). This species disappea s almos comple ely a he base o he g ey laye when o he species appea : Fu senkoina acu a, Globobulimina u gida, and S ain o hia usi o mis (Fig. 8) which a e limi ed o his g ey in e al. A he same le el, se e al o he species appea which emain p esen h oughou he eco d (Fig. 9). The mos abundan a his le el is Nonion abum (~ 50%). Clus e analysis esul ed in wo main Clus e s 1 and 2 (Fig. 10A and B, op panel). Clus e 2 is composed o wo subclus e s, Clus e s 2.1 and 2.2, he i s composed o a o al o ou subclus e s (Fig. 10). These clus e s g oup ben hic o amini e al species based on hei dis ibu ion, enabling he dis inc ion o h ee s a ig aphic uni s (Uni s 1 o 3; Fig. 9). Clus e 1, de ining Uni 1, domina es om 2 o 2.5 m in he sec ion and is ep esen ed by only one species, E. inac ia. The ollowing 0.5 m (2.5–3 m, in he g ey laye ), Uni 2, is domina ed by F. acu a, G. u gida, B. dila a a and S. usi o mis o ming Clus e 2.2. O e lapping wi h Clus e 2.2 bu con inuing un il ~4 m, is Clus e 2.1.2 A. Highes abundances a e eached by N. abum (~50%), B. s ia a (~25%) and Len iculina spp. (up o ~20%). The o he species o Clus e 2.1.2 A show ela i e abundances anging be ween ~5 and 12% (Figs. 9 and 10). A ~4 m, Clus e 2.1.2 B becomes dominan (Fig. 10B). Cibicides du emplei, C. pseudounge ianus and C. unge ianus domina e he assemblage eaching abundances o ~15–16% (Figs. 9 and 10). Apa om Tex ula ia cal a (~10%), he emaining species a e subo dina e, and mos do no each 5% o abundance (Figs. 9 and 10). Clus e , 2.1.2C is composed o Pla e 1. Op ical mic oscope pho os o he mos abundan (>3%) ben hic o amini e species o Rio Mendelin sec ion. 1 Tex ula ia cal a; 2 Boli ina seminuda; 3 Boli ina spa hula a; 4 Boli ina dila a a; 5 Boli ina e icula a; 6 S ain o hia usi o mis; 7 a, b T i a ina b adyi; 8 a, b Fu senkoina acu a; 9 Bulimina s ia a a . mexicana; 10 a, b Bulimina s ia a; 11 Bulimina elonga a; 12 Bulimina aculea a; 6; 13 Globobulimina u gida; 14 Nonion abum; 15 a, b As e ige ina plano bis: a spi al iew, b umbilical iew; 16 Len iculina sp. Scale ba =100 μ m. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 9 (cap ion on nex page) F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 16 Pla e 6. Op ical mic oscope pho os o some o he mos abundan (>3%) ben hic o amini e species iden i ied a Si e 976. 1 Planulina a iminensis; 2 Canc is oblongis: a spi al iew, b umbilical iew; 3 Cibicidoides unge ianus: a spi al iew, b umbilical iew; 4 Cibicidoides b adyi: a spi al iew, b umbilical iew; 5 Pullenia bulloides: a ape u al iew, b la e al iew; 6 Pullenia quinqueloba; 7 Melonis soldanii; 8 Melonis ba leeanus; 9 Melonis pompilioides; 10 O ido salis umbona us: a spi al iew, b umbilical iew; 11 Gy oidina al i o mis: a spi al iew, b umbilical iew. Scale ba =100 μ m. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 17 deposi ed immedia ely a e he MPB we in e ha a he Los Ranchos sec ion no ini ial deepening a e he MPB is eco ded. 5.2.1.3. Zo e as sec ion (So bas Basin). The So bas Basin was cha ac- e ised by a con inen al en i onmen du ing he la es Messinian s age (Ro e i e al., 2018 and his wo k). The i s Pliocene sedimen s deposi ed a e g ey sands ich in ca bona e nodules and a e shallow- wa e ben hic o amini e a, sugges ing a e y shallow, a imes exposed en i onmen simila o a paleosol. On op o his mos ly eme ged, con inen al acies, coas al sandy sedimen s we e e en ually deposi ed because o he ising sea le el. The o amini e al da a a e only quali a i e; howe e , because o he absence o plank ic o amini e a and he p esence o shallow-wa e axa like N. abum and Elphidium spp. (Haywa d e al., 2001; Mu ay, 2006; Milke , 2010; Tulbu e e al., 2017) he Zanclean palaeodep h p obably did no exceed 10–20 m. In mos ma ginal basins, Zanclean sedimen s a e o e lying con i- nen al and/o shallow, b ackish LM acies (Fo uin e al., 2000; Gue a- Me ch´ an e al., 2010; Ca uso e al., 2020; And ee o e al., 2021a and e e ences he ein; And ee o e al., 2021b). In deepe ma ginal basins wi h age con ol based on plank ic o amini e a, whe e he MPB is con inuous and he MPl1 zone is comple e, o ins ance a E aclea Minoa (B olsma, 1978; Sga ella e al., 1997) and sec ions in Piemon e (T enkwalde e al., 2008; Violan i e al., 2009) ins an aneous e ill o uppe ba hyal dep h appea s o ha e occu ed immedia ely a e he MSC. This implies a apid deepening o a leas 500 m a he base o he Zanclean. A Ca a Se edi (Tuscany: Ri o gia o e al., 2011) he e ill seems o ha e been g adual; howe e , he ac ual base o he Zanclean may be missing since he MPB is epo ed o be con inuous, bu plank ic o amini e a o MPl1 and MPl2 (Sphae oidinellopsis spp., G. ma ga i ae) a e absen . Fo shallowe ma ginal basins, whe e age con ol is sub-op imal o absen , he pic u e is less clea and e osional su aces a e o en epo ed o be associa ed wi h he MPB. Despi e he e osional su ace in he Cue as del Almanzo a sec ion (Ve a Basin), he MPl1 zone is epo ed o be comple e. Ca uso e al. (2020) econs uc a wa e dep h o >250 m immedia ely a e he MPB, implying ha he e osional su ace has emo ed pa o he LM deposi s. This may be ela ed o base le el a ia ions du ing he la es Messinian, as sugges ed by Ga gani and Rigolle (2007), S oica e al. (2016) and And ee o e al. (2021b). A he Los Ranchos sec ion (Nija Basin) howe e , a palaeodep h o 274 m immedia ely a e he MPB (P´ e ez-Asensio e al., 2021) is mo e likely caused by absence o he basal Pliocene since only G. ma ga i ae and no Sphae oidinellopsis spp. appea , and no ben hic epopula ion sequence is epo ed. In he Rio Mendelin sec ion (Malaga Basin; his s udy) he con ac be ween Messinian and Zanclean is g adual. A ben hic epopu- la ion sequence is p esen and ew, bu qui e la ge G. ma ga i ae occu abo e he g ey laye . 5.2.2. Deep basin: ODP Si e 976 The palaeo-wa e dep h econs uc ed o ODP Si e 976 is ba hyal (≥1000 m). A simila dep h has been epo ed o he ea ly Messinian a he same si e (Bulian e al., 2022). Ba hyal Zanclean palaeodep hs ha e been econs uc ed o he E aclea Minoa and Capo Rossello sec ions in Sicily (Sga ella e al., 1997; Ba a e al., 1998: 600–800 m). In gene al, dep h econs uc ions o ea lies Zanclean DSDP and ODP Si es ha e been in he o de o uppe - o mesoba hyal (1000 m and mo e). DSDP Leg 42A, Si e 371 (Sou h Balea ic Basin) was es ima ed o be 1200–1400 m deep (W igh , 1978). Fo Leg 107, Si es 652–654 (Ty - henian Basin) and Leg 161, Si es 974 (Ty henian Sea) and 975 (Balea ic Basin), he dep h o MPl1 was also es ima ed o be ba hyal (McKenzie e al., 1990; Sp o ie i and Hasegawa, 1990; Iacca ino e al., 1999a). Based on plank ic o amini e bios a ig aphy, he MPl1 in Si e 975 (Iacca ino e al., 1999a) is comple e. This would imply ha he Pliocene e ill o his – and o he - deep basins happened ins an aneously on a geological ime sale, o al e na i ely, he basins we e no d y a ha ime (e.g., Ma zocchi e al., 2016; S oica e al., 2016). 5.3. Ben hic en i onmen s and epopula ion Lago-Ma e deposi s we e ei he ba en o con aining b ackish o esh/con inen al aunas, including ewo ked ossils. Zanclean epopu- la ion by ben hic o amini e a shows simila i ies wi h epopula ion ollowing sap opel deposi ion. Jo issen (1999 and e e ences he ein) disce ns gene al pa e ns when mo phog oups a e conside ed a he han indi idual species and de ines mo phog oups gene ally ecognized in epopula ion sequences: deep in auna ole a ing ex eme hypoxia in ela i ely s able en i onmen s (g oup A, e.g., Chilos omella and Globo- bulimina spp.); in e media e in auna, less ole an o hypoxia (g oup B, elonga ed bi- and ise ial axa, e.g., boli inids, buliminids, Cassiduli- noides spp.); so-called ‘phy ode i us species’, small, bicon ex and o- chospi al axa ole a ing oxic o hypoxic, uns able en i onmen s and ep oducing as a e seasonal inpu o esh phy ode i us (g oup C, e. g., small Epis ominella, Eponides and Gy oidina spp.). Depending on local en i onmen al condi ions, ei he g oup A o g oup C will p ecede g oup B in a epopula ion e en . 5.3.1. Ma ginal basins 5.3.1.1. Rio Mendelin sec ion (Malaga Basin). In he Rio Mendelin sec- ion, he ben hic o amini e al assemblage immedia ely abo e he LM consis s o monospeci ic Epis ominella inac ia (Fig. 8; Pla e 2). This species was desc ibed in Pliocene sap opels by Ve hallen (1991) wi hou u he de ails; i s occu ence is explained by analogy wi h o he Epis- ominella species (men ioned in G oup C c . Jo issen, 1999). In ecen en i onmen s Epis ominella species ha e been associa ed wi h seasonal (sp ing/ea ly summe episodes) deposi ion o esh phy ode i us in oxic o sub-oxic (bu no anoxic), o he wise oligo ophic en i onmen s (E. exigua: Gooday, 1988; Gooday, 1993; Sma e al., 1994; E. i ea: Gooday and Hughes, 2002; Pla on e al., 2005; Langezaal e al., 2006). In he ossil eco d Epis ominella species we e obse ed in Zanclean epo- pula ion sequences (e.g., Sga ella e al., 1997 (Sicily); Iacca ino e al., 1999b (Ty henian Sea); Rouchy e al., 2001 (Cyp us); Agui e e al., 2006 (Nija Basin, Spain); Cipolla i e al., 2013 (Adana Basin, Tu key); Kon akio is e al., 2016 (Zakyn hos, G eece); Ca uso e al., 2020 (Ve a Basin, Spain)) Thei occu ence sugges s ha hese en i onmen s we e oxic o sub-oxic, oligo ophic bu p one o seasonal a ia ions in o ganic ma e inpu . The abundance o E. inac ia declines in he Rio Mendelin sec ion a e he lowe mos , monospeci ic sample and he abundance o Nonion abum inc eases o nea ly 50% a he op o Uni 1 (Figs. 8, 9). Nonion spp. a e e sa ile species, ypical o high o ganic ca bon con en , phy- ode i us and low oxygen condi ions (Fon anie e al., 2002; Diz e al., 2004; Mendes e al., 2004; Moj ahid e al., 2006). Subo dina e S ain- o hia usi o mis, Fu senkoina acu a and Globobulimina u gida (G oup A c . Jo issen, 1999; Clus e 2.2) sugges a ansi ion om a ela i ely oxic en i onmen cha ac e ised by E. inac ia owa ds a mo e di e en ia ed bu mo e hypoxic en i onmen owa ds Uni 2, he g ey laye . A he same ime, Bulimina aculea a, B. elonga a, and Boli ina dila a a appea , axa less ole an o hypoxia (G oup B c . Jo issen, 1999). Towa ds he op o Uni 2, B. seminuda and O ido salis s ella us inc ease in abundance (clus e 2.1.2A, Fig. 10), sugges ing con inued epopula ion in mo e oxic and less s able condi ions owa ds he yellowish s a a o Uni 3. This epopula ion sequence is compa able o he one iden i ied a e Qua- e na y sap opels (S1, S5, S6) (Jo issen, 1999). Uni 3 e lec s a no mal ma ine assemblage unde ela i ely s able, oxic condi ions: he di e si y (H) inc eases o 3, he BFOI, minimal in he g ey laye suppo ing hypoxia, inc eases o 80% in Uni 3 (Fig. 10) and he hypoxia- ole an species o clus e 2 dec ease in abundance o disappea . In he Rio Mendelin sec ion, he Clus e 2.1.2 A assemblage p e ails in he eco d un il 4 m (Figs. 9 and 10), when Clus e 2.1.2 B F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 18 (C. du emplei, C. pseudounge ianus, C. unge ianus and Tex ula ia cal a) becomes dominan . Al hough Tex ula ia spp. a e ole an o ood- en iched and oxygen-de icien condi ions (Naehe e al., 2012), he mo e common Cibicides/Cibicidoides, epi aunal o shallow in aunal and wi h low ole ance o oxygen de iciency (Van de Zwaan, 1982; Jo issen e al., 2007), sugges ela i ely well‑oxygena ed wa e s and mode a e p oduc i i y up o 6.4 m, in ag eemen wi h he BFOI, wi h alues close o high-oxic en i onmen s (BFOI =~90%; Fig. 10). Beginning in Uni 3, he ben hic o amini e al assemblages show a clea al e na ion be ween Clus e 2.1.2 A and Clus e 2.1.2 B (Fig. 10), hence be ween a mos ly in aunal assemblage (buliminids, boli inids, N. abum, Len iculina spp.) associa ed wi h high p oduc i i y and educed oxygena ion, and an epi aunal one, cha ac e ised by Cibicides/Cibicidoides species, indica ing mo e oxic condi ions. We sugges hese cycles e lec an al e na ion o phases o lowe e sus highe nu ien inpu and i e ine discha ge associa ed wi h cyclical changes in he eshwa e budge (see 5.4). The ben hic and plank ic δ 18 O (Fig. 10 and Supp. 3) show hea ies alues concomi an wi h Clus e 2.1.2 B peaks, sugges ing as onomical con ol o e he cyclici y. In summa y, in he Rio Mendelin sec ion monospeci ic E. inac ia ma ks he s a o ben hic epopula ion ollowing he incu sion o ma- ine wa e s. The g ey clays (Uni 2) mo e likely e lec wa e s a i i- ca ion ela ed o u he sea-le el ise han in lux o o ganic ma e . Con inued sea-le el ise amelio a ed ci cula ion and en ila ion, e en- ually suppo ing a di e se open ma ine ben hic o amini e al assem- blage. Compa able epopula ion sequences we e desc ibed elsewhe e in he Medi e anean (see abo e). 5.3.1.2. Ba anco del Neg o sec ion (Nija Basin). The calca eni es abo e he black and g ey laye in he Ba anco del Neg o sec ion sugges a nea sho e, high-ene gy en i onmen (see Sec ion 5.3.1), bu he econs uc ion o palaeoen i onmen and epopula ion by ben hic o amini e a is complica ed by ewo king (see 4.2; Table 3). The numbe o ben hic o amini e a pe g am o sedimen (BF/g; Fig. 12), which is e y low in he black and g ey laye , ises s eadily sugges ing ha he numbe o ewo ked o amini e a is ela i ely low, and mo e indigenous ben hic o amini e a s a occu ing abo e he black-g ey laye . In he i s sample abo e he g ey le el Chilos omella and Globobulimina species appea which, i in si u, may be pa o a epopula ion sequence in an ini ially s able, hypoxic-anoxic en i onmen (G oup A o Jo issen, 1999). The ben hic o amini e al species expec ed o h i e in a del aic o sho e ace palaeoen i onmen is C. loba ulus (Hald and Ko sun, 1997). Cibicides loba ulus is absen in he sample wi h Chilos omella and Globo- bulimina spp. and i s abundance hen ises (~30%), sugges ing ha i could be in si u. No expec ed o h i e in del aic o sho e ace en i- onmen s a e C. kullenbe gi, P. a iminensis, U. u ila, C. pseudounge ianus, C. unge ianus and S. bulloides; his would imply ha oge he wi h he Miocene plank ic o amini e a, hese ou e ne i ic o ba hyal ben hic o amini e a a e ewo ked. Assuming ha o he species (e.g., S. depe di a, Elphidium spp., P. bulloides, P. quinqueloba, Len iculina spp., Cassidulina spp.) may be in si u, his ben hic o amini e assemblage is in ag eemen wi h shallow, high-ene gy en i onmen s. Se e al oppo unis ic axa eeding on esh phy ode i us indica e episodes o in e mi en , seasonal supply o o ganic ma e . Among hese a e Val uline ia spp. including V. b adyana (Amo osi e al., 2013; Goineau e al., 2015 and e e ences he ein). A maximum abundance o 30% E. inacia occu s a ±1.5 m and is he e appa en ly no associa ed wi h epopula ion. Apa om C. e ulgens and C. loba ulus, li ing a ached o ha d subs a es, he axa assumed o be in si u a e epi aunal and shallow in aunal and indica e a gene ally mo e oligo- o meso ophic, hypoxic en i onmen owa ds he op o he sampled sec ion (e.g., Jo issen, 1987; Kaiho, 1999; Mu ay, 2006). In such an en i onmen , specimens o he os acod Cyp ideis sp., usually ega ded as a b ackish species (Benson, 1978), a e also conside ed ewo ked. 5.3.1.3. Zo e as sec ion (So bas Basin). In he Zo e as sec ion, whe e he uppe Messinian is con inen al, he lowe mos Pliocene sedimen s consis o clas ic sands wi h sca ce low-di e se ben hic o amini e a and no epopula ion sequence is ound. The i s species appea ing in he g ey laye is monospeci ic N. abum, included in he shallow in auna g oup, which is in he Rio Mendelin sec ion he dominan species immedia ely ollowing he le el wi h monospeci ic E. inac ia. He e, he p esence o nume ous calca eous nodules, oge he wi h N. abum known o ole a e shallow inne shel en i onmen s and eu ophic condi ions (Fon anie e al., 2002; Mu ay, 2006; Duchemin e al., 2008), indica e ha he palaeoen i onmen was no pe manen ly sub- me ged, bu ma ine wa e could ha e in e mi en ly en e ed he basin h ough a local geological ba ie . While N. abum domina es he en i e sec ion, a 1.1 and 1.2 m abo e he base o he Pliocene some Elphidium spp. and a e C. loba ulus appea . Toge he his sugges s a g adual ing ession o ma ine wa e s and a nea sho e ma ine en i onmen which was pe manen ly es ablished a e he ansg essi e pulse ha deposi ed he 5-cm hick bi al e- ich ho izon. Fig. 7. Ea ly Pliocene co e sec ions om ODP Si e 976 wi h co esponding co e pho og aphs. The black do s ep esen he analysed samples. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 19 5.3.2. Deep basin: ODP Si e 976 (Albo an Basin) The lowe mos Pliocene Uni 1 a ODP Si e 976 may no co e he MPB because he e is an in e al o non- eco e y in co e 62, igh below he i s Pliocene sedimen s (Fig. 7) and a black o g ey laye is absen . Howe e , a ela i ely di e se plank ic assemblage is p esen om he base o he s udied in e al (co e 61×-CC, 573.5 mbs : Fig. 7), wi h G. ma ga i ae and Sphae oidinellopsis spp. appea ing a 572.6 m and 572.3 m espec i ely (Supp. 1). In addi ion, an in e al wi h high abundances o U. pe eg ina (Fig. 13) was also iden i ied in o he deep si es ( om cycle 6 o 10 in Sicily, and om cycle 4 o 12 in he Ty - henian Sea). I is e e ed o as he U ige ina pygmea-U. pe eg ina e en (Sga ella e al., 1997; Ba a e al., 1998; Iacca ino e al., 1999b) and has Fig. 8. Base o he Rio Mendelin sec ion. F om le o igh : he pho o o he Miocene-Pliocene bounda y ( ed line), he s a ig aphic sec ion and he i s ben hic o amini e al species ha epopula e ea ly Pliocene en i onmen s. In addi ion, a pho o o he p edominan la e Messinian os acod species Cyp ideis sp. is shown. (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed o he web e sion o his a icle.) Fig. 9. Va ia ions in ela i e abundances o majo ben hic o amini e al axa o he Rio Mendelin sec ion. Colou bands co espond o o amini e al assemblages cha ac e izing he sample clus e ing in Fig. 10 which was he basis o he de ini ion o mic opaleon ological uni s. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 20 been used o con i m he ea ly Pliocene age o he sedimen s. A ben hic epopula ion sequence compa able o he Rio Mendelin sec ion is no de eloped a Si e 976. Phy ode i us species (epis o- minellids, G. subglobosa, small Gy oidina spp.) and deep in aunal axa (e. g., Chilos omella and Globobulimina spp.; Jo issen, 1999) each amoun o no >5%. Ins ead, Uni 1 is cha ac e ised by a single peak o B. aculea a (>35%), wi h C. du emplei (6%) o ming Clus e 1 (Figs. 13 and 14). Bulimina aculea a is one o he mos oppo unis ic axa in he Medi e - anean (De Rijk e al., 2000), eeding on esh phy ode i us and ole a ing suboxic en i onmen s (Schni ke , 1993; Gebha d , 1999). Cibicides du emplei is gene ally assumed o ole a e li le oxygen de i- ciency, al hough Cibicides spp. ha e been obse ed in oxygen-de icien en i onmen s as well bu hey may be mo e sensi i e o esh (unde- g aded) ood pa icles han o hypoxia (Jo issen e al., 2007). Consid- e ing ha he abundance peak o B. aculea a co-occu s wi h s ess- ole an species such as M. ba leeanum, M. soldanii (Ca alp, 1989; Koho e al., 2008), and Len iculina spp. (Sen Gup a and Machain-Cas illo, 1993; Kaiho, 1994) he basal Pliocene bo om-wa e en i onmen o Si e Fig. 10. A) Dend og am esul ing om he hie a chical clus e ing in he Rio Mendelin sec ion. The clus e s ha e been highligh ed wi h colou s. Fo explana ion see ex . B) om le o igh : Clus e s 1, 2.2, 2.1.2 A, 2.1.2 B and 2.1.2C plo ed agains s a ig aphic posi ion; Mic ohabi a dis ibu ion o he mos abundan ben hic o amini e species; The BFOI es ima ion (Kaiho, 1994); Shannon di e si y index; % o plank ic o amini e a; Ben hic δ 13 C and δ 18 O iso opic eco d (C. unge ianus); The column o he igh shows he mic opalaeon ologically de ined s a ig aphic uni s based on he clus e analysis. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 21 976 was p obably cha ac e ised by seasonal o ganic ca bon supply and educed oxygen le els, in ag eemen wi h he BFOI alues indica i e o low-oxic en i onmen s (~20, Fig. 14). Uni 2 is s ill domina ed by in aunal, low-oxic axa. The appea ance o he ben hic o amini e al assemblage o Uni 3 (Figs. 13 and 14) and he decline in abundances o axa p esen in Uni s 1 and 2 e lec s a change in en i onmen al condi ions. Taxa inc easing in abundance include G. subglobosa (up o 40%) and la e U. pe eg ina (up o 30%; Clus e 2.2.1; Fig. 14). Al hough shallow in aunal axa a e s ill domi- na ing he assemblage and he di e si y (H index) does no inc ease, he BFOI ises om a mean o 40 o a mean o 80 (Fig. 14), sugges ing he p esence o well oxygena ed wa e s. Dominance o G. subglobosa (in size ac ions >150 μ m and 63–150 μ m) has been eco ded in he oxygen minimum zone (OMZ) o he Sulu Sea, unde high luxes o o ganic ma e (e.g., Miao and Thunell, 1993), bu G. subglobosa is also a phy- ode i us eede in he gene ally oxic and oligo ophic en i onmen s o he Po cupine Abyssal Plain whe e he sp ing bloom deli e s pulsed supply o esh o ganic ma e (Gooday, 1993). I is also p esen in mode a ely dysae obic en i onmen s cha ac e ised by e icien p ese - a ion o o ganic ma e (Loub` e e e al., 1988) as well as in ea ly Plio- cene ecoloniza ion successions (Ba a e al., 1998). U ige ina pe eg ina is a shallow in aunal species associa ed wi h upwelling and labile ( esh) o ganic ma e ial, and gene ally no associa ed wi h low-oxygen condi- ions (Mo igi e al., 2001; Fon anie e al., 2002; Koho e al., 2008; Schmiedl e al., 2010). O he species in his assemblage include S. bulloides and B. s ia a, indica ing upwelling and an ele a ed o ganic ca bon con en (Sen Gup a and Machain-Cas illo, 1993; Lica i and Mackensen, 2005). Cibicidoides pachyde ma and P. a iminensis gene ally li e in well-oxygena ed en i- onmen s (Schmiedl e al., 2000; Schmiedl e al., 2003), al hough hey also ole a e oxygen de iciency and sus ained o ganic ma e luxes (Be nha d and Gup a, 1999). The ben hic o amini e al assemblage e- lec s be e ci cula ion and ins alla ion o an upwelling egime. The change owa ds highe and mo e s able BFOI (~80–95) sugges a p o- g essi e inc ease in oxygen le els. F om 569 mbs , he Clus e 2.2.2 assemblage e u ns (Fig. 14 and Supp. 2), wi h a maximum abundance o M. ba leeanus (25%) a he base and wi h addi ional p esence o C. oblongus and A. helicinus (Clus e 2.1). Anomalinoides helicinus indica es inc eased p oduc i i y and/o p ese - a ion o o ganic ma e (Ba a e al., 1998) and C. oblongus can also be ela ed o high o ganic lux and lowe oxygen (Mu ay, 2006). Consid- e ing he high BFOI alues (~ 50–60), bo om wa e oxygen le els mus ha e been qui e high, e en i sligh ly dec easing om his poin onwa d owa ds low oxic condi ions. Despi e di e ences, epopula ion o he ea ly Pliocene bo om-wa e en i onmen s a deep Medi e anean si es has elemen s in common. The ea lies Pliocene is cha ac e ised by he p esence o phy ode i us eede s a Si e 975 and E aclea Minoa (e.g., Eponides pusillus and Epis- ominella exigua) and con ains shallow in aunal species a Si es 976 and 975 (e.g., Bulimina spp. and Boli ina spp.). All si es a e cha ac e ised in he ea ly Zanclean by educed oxygen and high o ganic lux. A e his i s in e al, all si es a e cha ac e ised by a g adual amelio a ion o ci cula ion leading o be e oxygena ed, and in E aclea Minoa o ully Fig. 11. Calcula ed palaeodep hs o he Rio Mendelin sec ion. The g ey line is he palaeodep h es ima ed by g adien analysis (Hohenegge , 2005; Hoheneg- ge e al., 2008). The blue line is he palaeodep h es ima ed by using he %P (Van de Zwaan e al., 1990). (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed o he web e sion o his a icle.) Fig. 12. The Ba anco del Neg o sec ion wi h om le o igh : he Shannon di e si y index, he % o plank ic o amini e a, ben hic o amini e pe g am and he a ia ions in ela i e abundances o mos abundan ben hic o amini e al axa a e shown. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 22 open ma ine condi ions. 5.4. E iciency o he ea ly Pliocene Medi e anean – A lan ic connec ions In o de o be e unde s and Medi e anean-A lan ic connec i i y changes a he onse o he Pliocene as well as salini y and empe a u e di e ences be ween he Medi e anean and A lan ic, he newly acqui ed ea ly Pliocene ben hic δ 13 C and δ 18 O iso opic eco ds om Si e 976 and he Rio Mendelin sec ion ha e been compa ed wi h ODP Si e 982 (Hodell e al., 2001; D u y e al., 2018) and IODP Si e U1387 (He n´ andez-Molina e al., 2013; Van De Schee e al., 2016; Figs. 16 and 17). Si e U1387 is loca ed in he Gul o Cadiz, on he A lan ic side o he S ai o Gib al a a 559 m wa e dep h (He n´ andez-Molina e al., 2013), which is ba hed oday by Medi e anean Ou low Wa e (MOW). This wa e mass is composed mainly o Le an ine In e media e Wa e and a small componen o Wes Medi e anean Deep Wa e (WMDW) a e aging 13 ◦C and 38.4 psu (B yden and S ommel, 1984; B yden e al., 1994; He nandez-Molina e al., 2014). Si e 982 is loca ed in he no h A lan ic a a wa e dep h o 1135.3 m (Jansen e al., 1996) and ba hed cu en ly by he cold (3–8 ◦C) and less saline (34.95–35.2 ‰) No h A lan ic Deep Wa e (NADW; Ochoa and B ay, 1991; Venz e al., 1999; He n´ andez-Molina e al., 2016). In he a eas o deep-wa e o ma ion, deep-wa e δ 13 C is con olled by he δ 13 C o he su ace. Du ing pho osyn hesis, he phy oplank on p e e en ially ex ac 13 C-deple ed CO 2 , en iching su ace wa e s wi h he hea y 13 C iso ope. In con as , he deg ada ion o sinking o ganic ma e du ing deep-wa e enewal eleases 13 C deple ed CO 2 leading o a p og essi e dec ease o δ 13 C in deep-wa e masses. This dec ease de- pends on he quan i y o CO 2 added by emine aliza ion o o ganic ma e , and so, on he deep-wa e esidence ime and bo om-wa e en ila ion (Laube-Len an and Pie e, 1994; Pie e, 1999). The ea ly Pliocene ben hic δ 13 C alues a Si e 976 a e ini ially analogous o he ones egis e ed a he Gul o Cadiz (Fig. 16; Si e 1387) and become inc easingly hea ie up co e when hey each he A lan ic cu e (Si e 982), which e lec s he well en ila ed high δ 13 C o he NADW. In con as , he mo e deple ed Messinian δ 13 C alues om Si e 976 (a e age alue a ound −1 pe mil) e lec he longe bo om-wa e esidence ime o Medi e anean caused by he educed Medi e anean – A lan ic exchange (Bulian e al., 2022). In he Pliocene, wi h he ees- ablishmen o an e icien Medi e anean – A lan ic wa e exchange, Si e 976 ben hic δ 13 C ises o A lan ic alues. None heless, ben hic species p esen a he base o he Pliocene sugges bo h educed oxygen le els and high o ganic ca bon con en which is no isible om he ben hic δ 13 C. This disc epancy can be explained by assuming ha he high bo om-wa e enewal a e and DIC (Dissol ed Ino ganic Ca bon) cha ac e ised by high δ 13 C was no la ge enough o d ama ically educe he δ 13 C a he sea loo , despi e high emine alisa ion a es. Ea ly Pliocene ben hic δ 13 C alues om he ma ginal Rio Mendelin sec ion a e gene ally lowe han A lan ic and Medi e anean alues showing a ~ 2 ‰ o se . This sugges s ha while he deep Medi e anean was e i- cien ly connec ed wi h he A lan ic, his ma ginal basin could ha e s ill been isola ed om he Medi e anean. The δ 18 O alues o he ea ly Pliocene in he ma ginal Rio Mendelin sec ion and deep ODP Si e 976 a e e y simila and mos p obably e lec a compa able empe a u e and salini y (Fig. 17). A he same ime, ligh e Medi e anean, and hea ie Gul o Cadiz (Si e 1387) alues show an o se o almos 2 ‰, which is he opposi e si ua ion in com- pa ison wi h he p esen one (Fig. 17). As a e e ence o he la es Holocene da a, we used he Cibicidoides pachyde ma ben hic δ 18 O alues eco ded in he Albo an Sea (P´ e ez-Asensio e al., 2020) and Gul o Cadiz Si e 1387 (Singh e al., 2015). To hese da a we applied a co ec ion o −0.25 ‰ accoun ing o he di e ence in ice olume be- ween he ea ly Pliocene and he la e Holocene (Raymo e al., 2018). F om his compa ison i eme ged ha he p esen day δ 18 O di e ence be ween IODP si e U1387 in he Gul o Cadiz and ODP si e 976 in he Albo an Sea is −0.75 ‰ (Fig. 17, dashed lines). This di e ence is p obably due o he highe δ 18 O o Medi e anean wa e s due o i s nega i e wa e budge and highe salini ies compa ed o hose o he A lan ic. Howe e , in he ea ly Pliocene we obse e an opposi e ben hic δ 18 O o se be ween he Gul o Cadiz and Albo an, which was ~ +1.75 ‰. I he la ge posi i e Pliocene o se was due o empe a u e alone, he e would ha e been an 8 ◦C di e ence be ween Medi e anean and A lan ic deep wa e s on bo h sides o he S ai (0.23 ‰ =1 ◦C), while his di e ence oday is only 1–3 ◦C (MEDARG oup, 2002). This sugges s ha a he dep h o Si e U1387 he he mal in luence o he MOW was low du ing he ea ly Pliocene, which could be explained i he low o wa m Medi e anean wa e s o he A lan ic was lowe han oday. A lowe low o hea om he Medi e anean o he A lan ic would ha e inc eased he empe a u e di e ence be ween he wo basins and consequen ly he oxygen iso ope di e ence. Ano he scena io ha could jus i y such Pliocene o se be ween he ben hic δ 18 O in he Albo an Sea and he Gul o Cadiz is ha Medi e anean seawa e salini y and δ 18 O Fig. 13. ODP Si e 976: Va ia ions in ela i e abundances o majo ben hic o amini e al axa. Colou bands co espond o o amini e al assemblages associa ed wi h he clus e s o he dend og am (Fig. 14) and Uni s 1–4. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 23 we e lowe han oday and/o ha he S ai was much wide han oday. This would imply ha in he ea lies Pliocene he Medi e anean wa e budge would ha e been less nega i e han oday, o e en posi- i e. Lowe salini ies ag ee wi h he la es Messinian scena io, whe e he Medi e anean wa e would con ain a s ong Pa a e hyan signal which was pa ly main ained h ough he ea ly Pliocene as well. A much wide s ai in he ea ly Pliocene compa ed o he p esen would ha e exposed he Medi e anean wa e o a sho e ime o a nega i e wa e budge , esul ing in lowe δ 18 O and salini ies o Medi e anean wa e . E en mo e ex eme is he o se be ween he Medi e anean ben hic δ 18 O and A lan ic Si e 982 eco d. This o se is p obably due o he di e ence in empe a u e be ween hese wo wa e masses. Today, he Medi e anean deep-wa e empe a u e is in he o de o 13 ◦C, while deep wa e empe a u e a he loca ion o si e 982 is close o 4–5 ◦C (MEDARG oup, 2002). This di e en wa e empe a u e would esul in a δ 18 O o se o 2 ‰, which is s ill lowe han he obse ed δ 18 O di - e ence in he ea ly Pliocene be ween si e 976 and 982. This could be explained again by he occu ence o ligh e δ 18 O wa e s in he deep Medi e anean p obably due o a less nega i e wa e budge du ing he ea ly Pliocene. Fig. 14. ODP Si e 976: A) Dend og am esul ing om he hie a chical clus e ing ha di ided he ben hic o amini e species in wo main species clus e s (Clus e 1, Clus e 2) and wo subclus e s (Clus e s 2.1 and 2.2). Clus e 2.2 in u n b anches o wo subo dina e b anches as well (Clus e 2.2.1 and 2.2.2). The used clus e s ha e been highligh ed wi h speci ic colou s. B) F om le o igh : Clus e s 1, 2.1, 2.2.1 and 2.2.2 plo ed agains s a ig aphic posi ion; Mic ohabi a dis ibu ion o he mos abundan ben hic o amini e species; The BFOI es ima ion (Kaiho, 1994); Shannon di e si y index; % o plank ic o amini e s; Ben hic δ 13 C and δ 18 O iso opic eco d (C. pachyde ma); The column o he igh con ains he mic opaleon ologically de ined s a ig aphic uni s based on he clus e analysis. F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 24 6. Conclusions The s udied uppe Messinian–lowe Pliocene sec ions in he Spanish basins e lec he sedimen ological changes linked wi h he ees ab- lishmen o no mal ma ine condi ions a e he MSC and gi e impo an in o ma ion abou he wa e le el ac oss he Miocene-Pliocene bounda y. In he ma ginal sec ions (Rio Mendelin, Ba anco del Neg o, Zo e- as), he ea lies Pliocene sedimen s show as a da k laye , usually g ey o black, o en en iched in o ganic ma e . This laye , iden i ied in deep and ma ginal basins all o e he Medi e anean, could imply wa e column s a i ica ion, and educed bo om-wa e oxygen le els, which is in ag eemen wi h he ben hic o amini e al assemblages. Such condi- ions could de elop in a scena io whe e he A lan ic in low eaching he Medi e anean was mo e saline han he Medi e anean wa e s s ill unde he in luence o he Pa a e hys, causing A lan ic wa e s o sink and s a i y he wa e column. The ea ly Pliocene o ODP Si e 976 loca ed in he Albo an Basin does no show a da k laye , p obably because o i s p oximi y o he S ai o Gib al a and he in lowing A lan ic wa e s ha could ha e e oded he basal Pliocene laye s. The analyses pe o med on ben hic o amini e al assemblages enable a mo e de ailed econs uc ion o he ea ly Pliocene Medi e anean en i onmen s and e lec ben hic o amini e al epopula ion o he sea loo . The i s ben hic aunas ha appea a e in line wi h educed bo om-wa e oxygen le els and a s a i ied wa e column in ag eemen wi h he deposi ion o he da k laye s a he MPB. Du ing he ea ly Pliocene, he sea-le el ise e-es ablished no mal ma ine condi ions in he Medi e anean as can be deduced om he ben hic o amini e al assemblages cha ac e izing his in e al. The ben hic o amini e al epopula ion iden i ied in he s udied basins is compa able wi h o he Medi e anean sec ions and co es and shows simila i ies wi h epopu- la ion ollowing sap opel deposi ion. The gene al epopula ion end shows a shi om s essed and uns able en i onmen s o ben hic as- semblages indica ing an amelio a ion o he ci cula ion and bo om- wa e oxygena ion. In he s udied ma ginal Spanish basins, he es ima ed palae- oba hyme y o he ea ly Pliocene was simila anging be ween 50 and 150 m. In he Malaga Basin, he ea lies Pliocene palaeodep h does no exceed 50 m, and e en ually eaches alues o 150 m. In he Nija Basin, he p esence o mac o ossils and ossil aces sugges s high-ene gy shallow en i onmen s jus a e he MPB, while owa ds he op o he sec ions deepe , less high-ene gy en i onmen s we e p obably es ab- lished. These obse a ions imply a p og essi e deepening o he Medi- e anean ma ginal basins as he Medi e anean – A lan ic connec i i y was becoming mo e e icien . A Si e 976, he ea ly Pliocene is cha ac- e ised by a ba hyal en i onmen (>1000 m), which is wi hin he ange we ind oday. Al hough he wa e column may ha e been s a i ied and o ganic ma e accumula ing, he high δ 13 C alues om Si e 976 es i y ha Fig. 15. Calcula ed palaeodep hs o ODP Si e 976. The g ey line is he palaeodep h es ima ed by g adien analysis (Hohenegge , 2005; Hohenegge e al., 2008). The blue line is he palaeodep h es ima ed by using he %P (Van de Zwaan e al., 1990). (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed o he web e sion o his a icle.) Fig. 16. Compa ison be ween ben hic δ 13 C eco ds o Si e 976 and he Rio Mendelin sec ion ( his s udy) wi h A lan ic Ocean ODP Si e 982 (Hodell e al., 2001; D u y e al., 2018) and IODP Si e 1387 (Van De Schee e al., 2016). The blue dashed line shows mode n Medi e anean ben hic δ 18 O alues (P´ e ez-Asensio e al., 2020). The map shows he loca ions o he si es. (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed o he web e sion o his a icle.) F. Bulian e al. Ma ine Mic opaleon ology 176 (2022) 102160 25 bo om-wa e enewal in he deep basins was e icien immedia ely a e he e looding and ha an e icien basin-scale ci cula ion was e- es ablished. The alues a e in ac almos 2‰ highe han he ones egis e ed in concomi ance wi h he i s ga eway es ic ion a 7.17 Ma. The signi ican o se be ween he Albo an Basin and Gul o Cadiz ben hic δ 18 O alues o he ea ly Pliocene can be ela ed ei he o a empe a u e o salini y di e ence among he wo basins. Howe e , because o he opposi e iso opic o se be ween he ben hic δ 18 O in he ea ly Pliocene and la e Holocene we belie e ha he Pliocene wa e budge was less nega i e han oday, ende ing he di e ence in salini y be ween he wo basins he p e ailing ac o de e mining he δ 18 O. A less saline ea ly Pliocene Medi e anean is in line wi h con inua ion o he Pa a e hyan in luence p esen in he la es Messinian, and conse- quen ly wi h s a i ica ion o he wa e column once he A lan ic wa e s in aded he basin. CRediT au ho ship con ibu ion s a emen F. Bulian: Concep ualiza ion, In es iga ion, Me hodology, Da a cu a ion, W i ing – o iginal d a . T.J. Kouwenho en: Me hodology, Da a cu a ion, Supe ision, W i ing – e iew & edi ing. N. Ande sen: Fo mal analysis, W i ing - e iew & edi ing. W. K ijgsman: Resou ces, Concep ualiza ion, Supe ision, W i ing – e iew & edi ing. F.J. Sie o: Resou ces, Concep ualiza ion, Supe ision, W i ing – e iew & edi ing. Decla a ion o Compe ing In e es The au ho s decla e ha hey ha e no known compe ing inancial in e es s o pe sonal ela ionships ha could ha e appea ed o in luence he wo k epo ed in his pape . Acknowledgmen s The au ho s app ecia e he wo k o Jose Ignacio Ma in C uz in sample p ocessing and p epa a ion. Robe Speije is hanked o his inpu when classi ying ben hic o amini e al species and Fede ico And ee o o his ad ice ega ding os acod iden i ica ion. We also app ecia e he use ul in o ma ion on ou c op loca ion p o ided by F i s Hilgen. Mo eo e , all ellow ESRs and supe iso s om he SALTGIANT p ojec a e hanked o hei aluable sugges ions and discussions. A pa o he samples used in his esea ch we e collec ed h ough ODP Expedi ion 161 aboa d he Joides Resolu ion. This esea ch has ecei ed unding om he Eu opean Union's Ho izon 2020 esea ch and inno- a ion p og am unde he Ma ie Skłodowska-Cu ie g an ag eemen n◦ 765256 SALTGIANT. Appendix A. Supplemen a y da a Supplemen a y da a o his a icle can be ound online a h ps://doi. o g/10.1016/j.ma mic o.2022.102160. Re e ences Agui e, J., 1998. El Plioceno del SE de la Península Ib´ e ica (p o incia de Alme ía). Sín esis es a ig ´ a ica, sedimen a ia, bioes a ig ´ a ica y paleogeog ´ a ica. Re . Soc. Geol. Esp. 11 (3), 297–316. Agui e, J., S´ anchez-Almazo, I.M., 2004. The Messinian pos -e apo i ic deposi s o he Ga a es a ea (Alme ıa-Nıja basin, SE Spain). A new iew o he “Lago-Ma e” acies. Sedimen . Geol. 168 (1–2), 71–95. Agui e, J., P´ e ez-Mu˜ noz, A., Sanchez-Almazo, I., 2006. Ben hic o amini e assemblages in he lowe Pliocene deposi s o he Alme ia-Níja Basin (SE Spain). Re . Esp. Mic opaleon ol. 38 (2), 411–428. Al e, E., 2003. A common oppo unis ic o amini e al species as an indica o o apidly changing condi ions in a ange o en i onmen s. Es ua . Coas . Shel Sci. 57 (3), 501–514. Amo osi, A., Rossi, V., Vella, C., 2013. S epwise pos -glacial ansg ession in he Rhˆ one Del a a ea as e ealed by high- esolu ion co e da a. Palaeogeog . Palaeoclima ol. Palaeoecol. 374, 314–326. And ee o, F., Aloisi, G., Raad, F., Heida, H., Flecke , R., Agiadi, K., Lo i, J., Blondel, S., Bulian, F., Came lenghi, A., 2021a. F eshening o he Medi e anean Sal Gian : con o e sies and ce ain ies a ound he e minal (Uppe Gypsum and Lago-Ma e) phases o he Messinian Salini y C isis. Ea h Sci. Re . 103577. And ee o, F., Ma suba a, K., Bee s, C., Fo uin, A., Flecke , R., K ijgsman, W., 2021b. High Medi e anean wa e -le el du ing he Lago-Ma e phase o he Messinian Salini y C isis: insigh s om he S iso ope eco ds o Spanish ma ginal basins (SE Spain). Palaeogeog . Palaeoclima ol. Palaeoecol. 562, 110139. An hony, E.J., Aagaa d, T., 2020. The lowe sho e ace: Mo phodynamics and sedimen connec i i y wi h he uppe sho e ace and beach. Ea h Sci. Re . 103334. Au gebaue , A., McCann, T., 2011. Messinian o Pliocene ansi ion in he deep pa o he So bas Basin, SE Spain—A new desc ip ion o he deposi ional en i onmen du ing he Messinian Salini y C isis.(Wi h 8 igu es and 1 able). Neues Jah. Geol. Palaon ol. Abh. 259 (2), 177. Aus in, W., E ans, J., 2000. NE A lan ic ben hic o amini e a: mode n dis ibu ion pa e ns and palaeoecological signi icance. J. Geol. Soc. 157 (3), 679–691. Fig. 17. Compa ison be ween ben hic δ 18 O eco ds o Si e 976 and he Rio Mendelin sec ion ( his s udy) wi h A lan ic Ocean ODP Si e 982 (D u y e al., 2018) and IODP Si e 1387 (Van De Schee e al., 2016). The blue dashed line shows mode n Medi e anean ben hic δ 18 O alues (P´ e ez-Asensio e al., 2020). The o ange dashed line e e s o he mode n Gul o Cadiz alues (Singh e al., 2015). Bo h a e co ec ed wi h espec o he Raymo e al. (2018) global cu e. (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed o he web e sion o his a icle.) F. Bulian e al.