Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 N, 00 ), vesi- 10.18 0 46 ◦ in core MED- Lamellibrachia Lamellibrachia Discussions ). A callianassid 800 m in the Gela 822 m) provided a , and F. Trincardi Biogeosciences 3 − − E, 00 M. amorpha 636 yr cal BP ( 07.58 ± 0 , C. Froglia 1 moerchi 00 ◦ 40 ‰ PDB suggesting the occurrence − ). One shell of Lucinoma kazani, Myrtea amorpha , F. Foglini are two of the most significant chemosymbi- 1 968 967 N, Long 14 00 C dated to shed light on the historical evolution 14 L. kazani ), and gastropods ( 38.89 0 Lucinoma 45 ◦ , A. Ceregato C values as low as and 1 54 yr cal BP. These ages document that fluid seepage at this 13 calcified parts mixed with molluscs and subordinately miliolid ± δ 815 m) provided ages of 11 736 − E, 153.5 yr cal BP ( sp.) was consistently found alive in large numbers in the pockmark 00 ± , L. Angeletti 31.59 Lamellibrachia post-mortem 0 1,2 Calliax Isorropodon perplexum 01 ◦ This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. ISMAR-CNR Istituto di Scienze Marine,Woods Via Hole Gobetti Oceanographic 101, Institution, 40129, 266 Bologna,ISMAR-CNR Woods Italy Hole Istituto Rd, di Woods Scienze Hole, Marine, Ma. Largo 02543, Fiera USA della Pesca 2, 60125, Ancona, Italy otic taxa reported from variousern Mediterranean basin). cold seep Specimens sitesLong from (Alboran 14 Sea station and East- MEDCOR78sp.), (pockmark#1, and 9609.5 Lat 36 COR81 (pockmark#6, Lat 36 sub-modern age of 484 pockmark site has been episodicallysince sustaining the thiotrophic end macrobenthic of communities the Younger Dryas stadial up to sub-recent times. ate concretions display of light hydrocarbons inorganisms the was found seeping alive, fluids.some although Since specimens their have none skeletal been ofof parts AMS- this the appear site. truly at chemosymbiotic times very fresh, this key region, beforein documented its in eastern therecovered and Mediterranean from as westernmost this rather basins. areasp., disjunct loose The include and findings thiotrophic empty articulated shellscomyids chemosymbiotic tubes of ( of organisms lucinids ( thedecapod vestimentiferan ( mud. Their foraminifers form a distinct type of skeletal assemblage (named DECAMOL). Carbon- The geo-biological exploration ofbasin a (Strait pockmark of field Sicily, Central locatedbiotic Mediterranean) at provided community a ca. and relatively methane-imprinted diverserence chemosym- carbonates. of To such date, type this of is specialized the deep-water first cold-seep occur- communities recorded from Abstract Biogeosciences Discuss., 10, 967–1009, 2013 www.biogeosciences-discuss.net/10/967/2013/ doi:10.5194/bgd-10-967-2013 © Author(s) 2013. CC Attribution 3.0 License. 1 2 3 Received: 10 December 2012 – Accepted: 12Correspondence December to: 2012b M. – Taviani Published: ([email protected]) 22 January 2013 Published by Copernicus Publications on behalf of the European Geosciences Union. The Gela Basin pockmark fieldstrait in of the Sicily (Mediterranean Sea): chemosymbiotic faunal and carbonate signatures of postglacial to modernseepage cold M. Taviani 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . Swath- C) and a (Table 2). 13 δ 0.1 Urania ± 1.95 ‰ ( + shore constructions and ff ´ an Radiometric Laboratory, Poland (Ta- 970 969 the southern margin of Sicily (Fig. 1). Here we ff and 800 soundings per ping in dual mode. Chirp-sonar ◦ 1 × ◦ O) exactly to NBS 19 calcite; the analytical error is ect continental margins. During such exploration a field of pockmarks 18 ff 2.2 ‰ ( − , a beam width of 1 C-AMS dating was carried out at the Pozn ◦ Water-column attributes were measured with a Conductivity/Temperature/Depth pro- Stable isotope analyses were performed at the Mass Spectrometry Laboratory of 14 Bottom sampling were performed using a 1.2 ton gravity corer, large volume grab In the frame of the EU Hermes and Hermione projects, the Strait of Sicily in the ble 3). the CNR-IGG (Institutegan for MAT252 mass-spectrometer. Geosciences The carbonate and samples were Earththen cleansed, analysed powered Resources) following and standard Pisa, procedures byorthophosphoric using reacting carbonate a acid aliquots with under Finni- 100 % (Vienna-Pee vacuum. Dee Results Belemnite) are standard expressedvalue of by as assigning ‰ a relative value to of VPDB modulated 2–7 kHz outgoing signal equivalent to a 3.5 kHzand profile epibenthic hauls (Table 1). filer (CTD) using a Seabird SBE 11 PLUS employing the SEASAVE V5.33 software. 2 Material and methods The study areaand was DECORS December surveyed 2009bathymetry during and data August cruises were 2011 acquired HERMES05sounder respectively with using of (July a a R/V nominal 2005), Kongsberg sonar140 Simrad frequency MEDCOR of EM710 70–100 kHz multibeam anprofiles echo- angular were coverage obtained sector using of a hull-mounted sixteen-transducer source with a sweep present first data onmation deep about resident sea chemosymbiotic pockmarksauthigenic communities, in bio-sedimentological carbonates the processes, and Gela seepageranean basin temporal Sea variability resulting connecting its in in western this novel and sector infor- eastern of basins. the Mediter- was charted and sampled in detail o processes that a common compounds in fluids,(Cavanaugh i.e. et hydrogen sulphide al., and 2006;could hydrocarbons Dando, be like exploited 2001; methane by Duperron, specialized(see 2010). metazoans MacDonald through In et complex al., turn, symbiotic 1990;with such relationships Olu-Le references). communities Roy Pockmarks et are al.,ates also 2007; could sites Taviani, be 2001; were generated Duperron, (Hovland methane-relatedal., 2010, et 2007). authigenic al., carbon- 1987; Hovland and Judd, 1988; Gontharetcentral et Mediterranean was targeted as a key area where to study sediment instability failure along continental margins, in conjunction(Minisini with and sea Trincardi, level 2009). changes or Pockmarksresponse earthquakes are to known nature to of escaping hostdepth fluids, at (Hovland rate times of and peculiar emissions, Thomsen, biota seepageGas 1989; in resilience charged Hovland and sediments water and may in Judd, fact 1988; sustain Taviani, microbiological 2011, communities 2013). operating on and Knebel, 1989; Kelleyet et al., 2007). al., Pockmarks 1994; oftencommon Gay occur and et in widespread clusters feature al.,Judd, and on 2003; 1988). cover the They Trincardi wide continental receive et areas, much margins attention al., representinghydrocarbon-enriched worldwide especially a venues 2004; (Hovland because in and escaping Paull fluids theeruptions, are form often at of times slow representing seepage,navigation a (Newton vigorous et distinct venting al., geo-hazard or 1980;fluid for even Hovland, releases o 1987; are Curzi also et considered al., as 1988; a Curzi, potential 2012). co-actor Such in triggering mass-sediment Pockmarks are circular to sub-ellipticalmany crater-like hundreds depressions of of metersdegassing variable in size of diameter) (few fluids to and throughriety depth fine-grained unconsolidated (up of marine to geologic sediment few scenarios under tens (King a m) va- and typically McLean, due 1970; to Hovland, 1989, 1992; Scanlon 1 Introduction 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . The . The ◦ 2 anomalies. S - T reaching the maximum of 16 ◦ in mid-Pleistocene times (Trincardi and 3 to 13 . Width to depth ratio were calculated for 11 972 971 ◦ ◦ ected the northern margin of the basin mobilizing ff that litters the bottom by leaving behind scores of dead weights cannizzi shore the southern coast of Sicily in a depth range of 800–900 m (Fig. 1). Firstly de- Noticeably, acoustic signals relatable to the presence of gas entrapped in theThe sed- largest depression with an internal bulge, resulting from the coalescence of two The resulting detailed morpho-bathymetric map documents the existence of discrete The Gela basin pockmark field (GBPF) is located in the Strait of Sicily, ca. 20 nm Gela basin is the Plio-Quaternary foredeep of the Maghrebian fold-and-thrust belt ff by removing this litter. This goal was achieved by using a small modified haul that in iment (such as BSR)surveys or (Fig. 5). to Furthermore, active CTD degassing profiles (plumes) show no were notpockmarks, detected was during selected both is as a the fishing prime groundknown target subjected as for for bottom manywith years sampling. to long The a plastic entire peculiar threadscore area local sampling, attached fishing and (Taviani, (mal)practice 2010). CTD casting, Before it proceeding was with therefore grab necessary and to clear first the bottom their rim. Theregional side surrounding slope slope ranges ispockmarks from about form 7 bathymetric 2–3 profiles crossed neartween the 11 feature : centres. 1 The and ratiothis fell 40 : be- ratio 1 and with relative most size of near the 18 : pockmark. 1. There is not consistent relation between ied field are clusteredpockmarks in presents seven generally seafloor a sub-circular patches shape,1 for with a (Fig. the exception total 2) of area the whichmost pockmark of is about of elliptical-shape, 18 and km them rangeand are in 310 m. diameter between from The 40 40 bottomseafloor; and to of most 100 310 some however m m, of are although andbathymetric these less profile, only is then the 11 as 6 pockmarks m muchthem (Fig. in deep. as are 2) In most 20 V-shaped m are cross and case below section, (Fig. appear between the 2) extracted to 200 surrounding m from show be a the U-shaped; positive but relief four ranging of from 4 m to 7 m along summer 2011 during Hermione cruisewere DECORS acquired, when and high additional resolution pockmark multibeam fields data further west, identified. clusters of pockmarks in anot restricted show any sector clear of preferential the orientation Gela of basin these (Figs. features. All 1–4). pockmarks Our in data the do stud- data in 2005, the GBPF was then surveyed more in detail in winter 2009 and again in tected upon TOBI side scan sonar in 2003 and by low-resolution multibeam bathymetric that prograde with increasing slope anglePleistocene and outbuilding to the shelf Holocene seaward; muddy and upper- and contourite poorly deposits consolidated characterized sediment by (Verdicchiostacked water-saturated and MTD Trincardi, 2008). deposits In appear allunits sandwiched appear cases disrupted where within by basin-wide verticaltures features draped that from have units, been MTDs the ascribed thatTrincardi, to latter 2009). fluid-escape became fea- rapidly buried and perhaps pressurizedo (Minisini and Argnani, 1990). Following thisfailure major events basin-wide impacted event, therecurrence several area intervals smaller-scales in up mass- the to order(Minisini of the and few Trincardi, thousands Holocene 2009). of (Minisini The yearsious most between et mixes, recent successive al., two events mass-transport basic 2007) events involved, distinctive and in kinds var- with of slope sediments: the Pleistocene clinoforms also in various locations ofrelatively the shallow-water Strait (ca. of 70–200 Sicily, m)al., although 2010; occurrences most Micallef (Savini et published al., et studies 2011).(Minisini regard al., Pockmarks and do 2009; Trincardi, occur 2009, in Cangemi this the et paper). Gela basin at bathyal depths and is a site oftransport widespread and complex repeated in mass the transport. area,a Gela has volume Slide, a of the largest sediment mass- in the order of 1000 km Pockmarks are common featuresbasin at (Stefanon, 1981; many Stefanon et continental al.,1987; margins 1983; Hovland Curzi in and and the Veggiani, Curzi, 1985;et Mediterranean Mazzotti 1989; al., et 2012; Trincardi al., Curzi, et 2012; al., Somoza 2004; et Geletti al., 2012). et They al., have 2008; been recently Coleman documented 3 The pockmark field of Gela 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | sp.: Salas clams and Calliax Isorropodon Sturany, 1896 ) bivalves (Du- Taranis moerchi Lucinoma ), caprellid amphipods Lucinoma kazani ` ere, 1966). This species is ´ adiz. Myrtea amorpha Myrtea spinifera Southward, Andersen and Hourdez remains (threads and some weights), 974 973 ) and lucinid ( cannizzi , a recorded from deep water cold seep ) have been recently described by Dworschak and Lamellibrachia Lamellibrachia anaximandri er et al., 2005; Taylor et al., 2007; Taylor and Glover, 2010; Brissac et ffl ¨ o Sturany, 1896 (Fig. 7b), the sole species recorded that far from the recent Mendicula, Axinulus, Axinus , Vulcanocalliax arutyunovi ´ ario et al., 2011; Taviani, 2011), sunken wrecks (Hughes and Crawford, 2006; In addition to these well known deep-water chemosymbiotic metazoans, we can fur- Another remarkable megabenthic organism found in the GBPF is a siboglinid tube- The macrofaunal death assemblages recovered from the GBPF show a predomi- Thyasira Ennucula corbuloides, Cardiomya costellata, Kelliella miliaris tom outside the pockmarks (Appendix A). Furthermore, the more emblematic cold seep basin (references in Taviani, 2013). ther list few other( taxa preferentially copingfour, with 2005; reducing L environments i.e.al., thyasirid 2011; Rodrigues and(Fig. Duperron, 7d) that 2011), has and beenRoy observed the et to turrid be al., gastropod particularly 2004, commoncontain M. at spoils Taviani, of such unpublished truly seep data). seep sites communities Only (Olu-Le that some are instead pockmarks totally were absent from found the to seabot- 2010; Hil Gambi et al., 2011), andTubes hydrothermal might vents belong (Lott to and Zimmerman,(2011), 2012) described in the from basin. the(Southward Anaximander et mud al., volcano 2011), in and possibly the much eastern widespread Mediterranean in the entire Mediterranean tats in theOlu-Le Mediterranean Roy basin et (Corselli al., andIvanov 2004; et Basso, Werne al., 1996; et 2010a, Coselviani, al., b; 2011; and 2004; Ritt Rodrigues Duperron Salas, et et al., et al., 2001; 2012). al., 2010; Brissac 2007; et Duperron,worm al., 2010; of 2011; which Shank only et emptyof tubes al., the have 2011; been tube Ta- collected resembles sites by us (Olu-Le (Fig. Roy 7a). et The morphology al., 2004; Werne et al., 2004; Duperron et al., 2009; Ritt et al., are represented by theand Woodside large (2002) Mediterranean (Fig. endemic(Fig. 7c), taxon 7e). and Vesicomyidae subordinately are by perplexum represented by the MediterraneanMediterranean basin. endemic Such bivalves have been recorded from deep sea reducing habi- Lucinidae, and Vesicomyidae are at places noticeably abundant (Table 4). Lucinids molluscs, echinoids, serpulids andin octocorals, terms Non-seep of organisms number of are species more (Appendix diverse A) but chemosymbiotic bivalves in the families same shrimp have been alsoet found al., in 2010). active Members of pockmarks family inhabitats Callianassidae worldwide the are (summarized central known by Adriatic to Komai inhabit (Taviani sector and deep sea Fujiwara, close reducing 2012). to In the thespecies eastern ( Mediterranean, Atlantic a newCunha (2007) subfamily from (Vulcanocalliacinae) a and mud volcano a in new the deep Gulfnance of of C benthic molluscs over other components, predominantly decapods, pelagic and ghost shrimps. NumerousFig. specimens 7f, of Table a 4) callianassid weremorphologically ghost found close in shrimp to pockmark an ( elusive #in callianassid 6. taxon the This reported is Western from shallower likelyconsistently Mediterranean settings a associated (de still with Gaillande undescribed such species type and of Lagard environments since a few specimens of this ploration with CTD casts. Additional bottomoccasion samples other were pockmarks acquired were in also 2011 sampled. and on this 4 Fauna The living component inthe the time benthic of macro- and( sampling megafauna was inside rather the scarce pockmarks at and mostly represented by sparse bivalves the former intensely overgrown bytrajectory live intercepted cold the water bottom corals.tubeworms, collecting living A many ghost second dead shrimps trawl and shells onorganisms a of the few and carbonate same litter concretions (Fig. amidstpockmarks 7a). other benthic in Only at the this area stage, were this tested large with pockmark grab and sampling some and other coring, integrating the ex- fact successfully entangled some such 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C value of 13 δ use in the Ocean, ff which provided a sp.) are not co-occurring in all in- 2.66 ‰ PDB reflecting the seawa- + 976 975 40.77 ‰ PDB. A significantly carbon-depleted ects a predominantly silicoclastic-muddy sec- 1.23 and ff − − Lucinoma kazani C composition of chemosymbiotic bivalve shells display 13 . Besides shells of chemosymbiotic bivalves and tube- C value of δ 13 δ The pockmark field a L. kazani, I. perplexum, Lamellibrachia 37,57 ‰ PDB. Both very negative carbon signatures document unquestionably Authigenic carbonates worms, sampling from the GBPF produced also carbonate concretions, indurated (Table 2, Fig. 12). The isotopic values around between ter carbonate reservoir asThe stable expected carbon (Cobabe, composition 1998; ofprovided Lietard instead a a poorly and cemented Pierre, layercomposition 2009). in was core also MEDCOR 70, measuredshell for of concretioned the mudstone chemosymbiotic − encrusting a dead that at some timemark hydrocarbons field were in present the in Gelaproductive basin). the for On hydrocarbons seeping (Etiope the fluids et other of al., hand 2002; this this Holland region pock- et is al., known 2003). to be highly basin. Since deep-water coldmolluscs seep habitats and owing seep-related modern-typeCainozoic decapods chemosymbiotic to are present, geographically ittified di is at other predictable sites that beside DECAMOL the Strait sediment of would Sicily. be iden- burrows (Figs. 8pyrite and druses 9), were andbonates noticed cemented were on tested mudstones for small (Fig. the darker their 10). carbonate stable Microcrystalline carbon concretions. and Some oxygen isotopic car- composition (20–40 %). Secondary components in order(5–10 of %), abundance followed are by miliolid echinoids, foraminifers shells. serpulids, ostracods DECAMOL and sediment octocorals was and documented pelagic at various pockmarks in the Gela Sediments. tor of the southernbiogenic Sicilian carbonate margin. production Sampling in however theby reveals form calcified the of occurrence benthic skeletal of organisms componentscarbonate shed and biogenic primarily sediment subordinately is by producedform pelagics. here of A through medium cold distinct to coarse seep typebiotic skeletal factories bivalves of assemblages in (mainly enriched the vesicomyids), in and shells calcifiedThis of parts remarkable chemosym- of sediment callianassid decapods. representsschemes a of novelty skeletal not sediment classificationgeographic contemplated location (e.g., in of Hayton the the et current study al.,ment area here 1995). would among While heterozoan require the carbonates, placing theirrelated related genesis to skeletal climate is sedi- but in to fact chemical substantiallyname carbonate un- DECAMOL factories. (Fig. Therefore, we 7) introduce toin the highlight the sand the to two hash major fraction, i.e. forming DECApods skeletal (callianassid: components 30–50 %) and MOLluscs – – 2010a, b; Himmler et al., 2011;resent Capozzi a et legacy al., of 2012). sulphate The reduction presence in of the pyrite might formative rep- environment of such carbonates The stable carbon rangeincorporation is consistent of with carbon authigenic1987; carbonates derived Roberts formed et from al., through 1987; the anaerobic KulmRad and methane Suess, et 1990; al., oxidation Aharon, 1994; 1996; (Hovland KellyGreinert Aloisi et et al., et et 1995; al., al., von al., 2000,Campbell 2001; 2002a, et Peckmann b; al., et Elvert 2008; al., et Cangemi 2001; al., et Taviani, 2000; al., 2001; Naehr 2010; Gontharet et Feng al., et and 2000; al., Roberts, 2007; 2010; Ivanov et al., of such chemosymbiotic bivalves andtions siboglinids since relies their upon metabolic high pathwaydirect sulphide is fingerprints concentra- thiotrophic. of Thus, hydrocarbon they availability cannot in the be seeping considered fluids as at the GBPF. 5 Seep carbonates vestigated pockmarks in theother Gela hand, basin, spatio-temporal showing insteadthrough variability a time in and spatial analogue space variability. oftrait On habitats fluids’ at the responding composition modern to and and flowRoy variability past intensity et seepage is al., sites a 2007; (Olu well Lessard-Pilon et documented et al., al., 1997; 2010). Jenkins As et it al., is 2007; often Olu-Le the case, the sustainability species (e.g., 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C C 14 14 provided an AMS- produced an AMS- O values comprised be- 18 δ from sediment core MEDCOR (Figs. 1 and 3) and the overlying 2 Lamellibrachia Lucinoma kazani 978 977 54 yr cal BP. Although potentially somewhat in- Myrtea amorpha ± used in the Neogene Apennine chain (Taviani, 1994, 2001 and C age of 484 ff 14 611 yr cal BP, while a valve of 154 yr cal BP. A valve of ± ± 2.21–2.71 ‰ PDB) are interpretable as indicative of bottom cold temperatures + The genesis of the GBPF under study is thus not fully understood yet but a potential to have contiguity with such features, suggesting that no causative link between the stacked multiple submarine mass-transportet deposits al., of 2007). late These Pleistoceneat composite age present units (Minisini on are the bymulti-phase seabottom, large emplacement the buried best occurred and examples sinceMinisini only of and the a which Trincardi, 2009). last few are Pore are Post-Glacial the fluidtual gradients, exposed (Minisini “twin expulsion resulting onto slides” et in the whose fluid al., seabottom, migrationthough are 2007; and suggested not even- to necessarily be the a dominant,shape potential in this co-driving triggering region factor, episodic al- (Minisini mass-transport etscrutiny events al., that here 2007; Minisini lies and ca. Trincardi, 2009). 5 The nm GBPF away under to the west of the “twin slides” and do not appear than from it. link between defluidization (pockmarks)continental and margin (mass one sediment of failure)of the merits pockmarks to main in be the motif considered. Gela basin of In are fact, this just this located part cluster distally in of front the of a complex made up by at the base ofsuccession, slope with characterized a by positiveturbidites?) relief draped of thins and few toward onlapping km theperfect plain-parallel slope matching reflectors and of are (muddy thesuggestive breached pock of by a mark the possible field pockmarks causalthe with (Fig. relationship. pockmarks In 6). would the be this The slide-related fed viewcharged base-of-slope from the deposit. the bulge fluids However, MTD, emanating is in acoustically-transparent through andrule the possibly out lack gas- the of possibility deeper-penetration that MCS fluids profiles come, we at cannot least in part, from beneath the MTD rather The pockmark area investigatedslope in of this Gela studyMTD basin is at where located a Chirp-sonar at depthbidites. profile the of The detect base pockmarks few the of area tens are top the of not of northern meters randomly under the distributed a last but succession corresponds basin-wide of to a basin-floor bulge muddy tur- 7 Discussion age of 11 732 age of 9610 70 provided an AMS- fluenced by carbon sourced fromthat seeping seepage fluids, activity our in radiocarbonsince the ages the pockmarks clearly end is indicate of lasting, the albeit last not glacial necessarily epoch (Younger continuatively, Dryas stadial) up to sub-recent times. either dormant/episodic or ended.amined In the order core to record, unravelficial and this bottom carbon-dated fundamental samples faunas aspect and and we(respectively carbonate two ex- MEDCOR81 concretions. sedimentary Super- and cores MEDCOR70) wereseepage to taken at from reconstruct this pockmark the place 1 recent (see and history Fig. 6 of 11). fluid A tube of (cf. Sakai et al.,dating 1992), (see thus below). supporting the late glacial ages obtained by radiocarbon 6 Age constraints The absence of distinctsediment signals close documenting to either surface active andwas degassing the taken or lack as of an gas indication live charged- that chemosymbiotic seepage macro- backing and the megafauna genesis of the GBPF is at present of incipient embedding ofgenic chemosymbiotic carbonates infaunal (Lalou and et epifaunalseep al., organisms rocks 1992), as in those eventually authi- di turning2011). into Finally, the macrofossiliferous stable cold- oxygentween composition of bivalves ( (e.g., Gontharet et al., 2007). Interestingly, the GBPF concretions represent a case 5 5 25 15 20 10 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) that ). It thus Calliax mise-en-place sediment that may ff MOLluscs) is here pro- Lamellibrachia or of the large vestimen- Lucinoma, Isorropodon, + and L. kazani tubeworms documents that these biota ) and callianassid decapods ( 980 979 Taranis Lucinoma, Isorropodon Lamellibrachia which are not recorded thus far from more than two pockmarks. ), gastropods ( ) is relevant as it is the first such site in this key-region of the erent ages provided by organisms from individual pockmarks suggest ff erences are equally observable at the GBPF such as for example the ff ers in space and time; ff Isorropodon Lamellibrachia Lamellibrachia Mediterranean Sea transitional to its eastern andthe western episodic basins; occurrence ofby hydrocarbons the in occurrence the ofstable seeping carbon carbonate isotopic fluids concretions composition; and is mudstones demonstrated withthe quite very di depleted that seepage activity inbut the di area is not a uniformly-distributed and steady event a new type of skeletal sedimentposed (DECAMOL: whose DECApods formation is noteral case controlled evoked by for most temperature biogenic regimes sediments,sustaining as but specialized by it cold biota; is seepage on the the gen- seafloor a possible causative linkmass-transport between processes seepage is tentatively with suggested related but pockmark still undemonstrated. genesis, and The Gela basinthiotrophic deep-water pockmark chemosymbiotic field macro- hosting and Mediterranean-emblematic megafauna ( dating of chemosymbiotic were thriving since theup end to of very the recent last times; glacial epoch (Younger Dryas stadial) and The GBPF is midway between the Eastern Mediterranean and Alboran basins where The GBPF shows a certain degree of homogeneity regarding the chemosymbiotic 2. 3. 5. 1. 4. 6. 8 Conclusions represents a relevant siteconnectivity to patterns be among considered geographicallysea disjunct in chemosynthetic but the sites compositionally (e.g., crucial similar Young, 2003;2007; and deep- Tyler and Marcus poorly-known Young, et 2003; issue al., Olu-Le 2009; of Roy et Mullineaux al., et al., 2010). those found in the study area (e.g., a variety of cold seep habitats is exploited by macro- and megabenthic organisms as consider the overall reduced variabilityto of larger cold and seepage heterogenous at(Olu et the seep al., GBPF sites 1997; when as Sibuet2010), compared and or those Olu-Le even observable in Roy, 2002; the elsewhere Olu-Leten Mediterranean in reflects Roy itself primarily et (Olu-Le the variations al., Roy in ocean et 2007; theminor al., fluid Cordes faunal 2004). regimes et di (Teichert Such al., et variability al., of- 2003).comparable Nevertheless, rarity of the largetiferan chemosymbiotic clam and Fontana, 2002; Lucente and Taviani, 2005). assemblages inhabiting individualcomyids pockmarks. ( This isare especially almost ubiquitous true in our for samples. small Such homogeneity vesi- is not at all surprising once we to those described by Minisiniprocess et of al. the (2007) slumping fromor, units this otherwise, may general in the area. theory The underpressuringbe cause conducive of squeezing to fluids out gas ofbeen related release invoked entrapped as to pockmarking fluids a sliding likely the mechanismmany o bottom. to others). trigger Release submarine On-land, of slumps similar (Carpenter, hydrocarbonsfor 1981 causative localized has and scenarios Miocene have chemosymbiotic beenates faunal assemblages suggested associated and/or to with authigenic account slumped carbon- bodies in the Apennine chain (Berti el al., 1994; Conti ries of still-unexplored pockmarks hasslides” been, (Minisini however, and identified at Trincardi,tain the 2009). similar toe It faunas of is and themap predictable carbonates “twin suggests that as the subsurface they their existence may counterparts. ofpockmarks, now-draped in The lobate that principle bodies multiswath in northwards topographic con- all of the likeness represent buried mass-transport deposits comparable two phenomena (twin-slide-slumping and pockmark-fluid expulsion) does exist. A se- 5 5 25 10 15 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) Waisiu- ´ e, J. S., , Vesicomya Ricerca italiana per mare sp. (Bivalvia: Thyasiridae) from a -consuming microorganisms and the 4 Thyasira cers, crew, and colleagues for their skilful co- 982 981 ffi in the eastern Atlantic and the Mediterranean, Sarsia, Callogonia and We are indebted to o sp. (Bivalvia: Lucinidae) and Myrtea Isorropodon , concha 86, 333–366, 2001. “L’Ateneo Parmense”, 21, 79–90 , 1985. cold seeps, Deep-Sea Res. Pt. II, 57, 1870–1881, 2010. the Napoli mud volcano (Eastern Mediterranean), Mar. Geol., 132, 227–239, 1996. carbonate deposits of the northern Apennines (Italy), Int. J. Earth Sci.,depth, 91, 1030–1040, and 2002. location on diversity and community composition at Gulf of Mexico lower-slope Aharon, P.: Hydrocarbon seep-carbonatesIsland, of New a Zealand, Miocene Sediment. Geol., forearc 204, (East 83–105, Coast 2008. Basin), North communities using isotope geochemistry, in:by: Isotope Norris, R. paleobiology D. and and paleoecology, Corfield, edited R. M., The Paleontologicalmarks, Society deepwater Papers, 4, corals, 255–285, and 1998. coldphy, seeps Suppl. along ,25, the 40–41, continental 2012. margin of Israel, Oceanogra- derived imprints in olistostromes ofmagna the Early Apennines Serravallian (Northern Marnoso-arenacea Italy), Formation, Geo-Mar. Ro- Lett., 14, 192–200, 1994. bioses in cold seep in the Eastern Mediterranean, Mar. Ecol., 32, 198–210, 2011. slope, Geo-Mar. Lett., 1, 29–32, 1981. in: The Prokaryotes,tions, 3 Biotechnology, Edn., Applied A Microbiology, editedE., Handbook Schleifer, by: K. on Dworkin, H., the M., and Stackebrandt, biology Falkow, E., S., of Springer Rosenberg, New Bacteria: York, 473–508, Symbiotic 2006. associa- ates (MDAC) in northern-central Adriaticseepages, Sea: Mar Relationships Geol., between reservoir 332–334, and 174–188, methane 2012. Gottschal, J. C., Forney, L.formation of J., carbonate and crusts Rouchy, J.-M.: at cold CH seeps, Earth Planet.diagenesis Sci. in Lett., the 203, mud 195–203,Res., 2002a. volcanic 22, sediments 2355–2372, of 2002b. the Barbados Accretionary Prism, Cont. Shelf istry and mineralogy ofof sediments Sicily and authigenic (Central carbonates Mediterranean):system, from Relationships Chem. the with Geol., Malta mud/fluid 276, Plateau, release 294–308, Strait 2010. from a mud volcano genic carbonates of easternto Mediterranean gas Sea hydrate destabilisation, mud Earth volcanoes Planet. and Sc. their Lett., possible 184, 1, relation 321–338, 2000. vents, Geo-Mar. Lett., 14, 69–230, 1994. Cosel, R. and Salas, C.: Vesicomyidae (: Bivalvia) of the genera Curzi, P. V.: Central Adriatic geologyCurzi, and fishing, P. Aracne V. Editrice and Bologna, 274 Veggiani, pp., A.: 2012. I Pockmarks nel mare Adriatico centrale, Acta Naturalia de Corselli, C. and Basso, D.: First evidence of benthic communities based on chemosynthesis on Cordes, E. E., Becker, E. L., Hourdez, S., and Fisher, C. R.: Influence of foundation species, Conti, S. and Fontana, D.: Sediment instability related to fluid venting in Miocene authigenic Coleman, D. F., Austin, J. A., Ben-Avraham, Z., Makowsky, Y., and Tchernov, D.: Seafloor pock- Campbell, K. A., Francis, D. A., Collins, M., Gregory, M. R., Nelson, C. S., Greinert, J., and Cobabe, E. A.: Chemosynthesis and chemosymbiosis in the fossil record: detecting unusual Brissac, T., Rodrigues, C. F., Gros, O., and Duperron, S.: Characterization of bacterial sym- Cavanaugh, C. M., McKiness, Z. P., and Newton, I. L. G.: Marine Chemosynthetic Symbioses, Berti, M., Cuzzani, M. G., Landuzzi, A., Taviani, M., Aharon, P., and Vai, G. B.: Hydrocarbon- Carpenter, G.: Coincident sediment slump/clathrate complexes on the U.S. Atlantic continental Capozzi, R., Guido, F. L., Oppo, D., and Gabbianelli, G.: Methane-derived authigenic carbon- Aloisi, G., Pierre, C., Rouchy, J.-M., and Faugres, J.-C.: Isotopic evidence of methane-related Aloisi, G., Bouloubassi, L., Heijs, S. K., Pancost, R., Pierre, C., Sinnighe Damst Cangemi, M., Di Leonardo, R., Bellanca, A., Cundy, A., Neri, R., and Angelone, M.: Geochem- Aloisi, G., Pierre, C., Rouchy, J.-M., Foucher, J.-P., and Woodside, J.: Methane-related authi- Aharon, P.: Geology and biology of modern and ancient submarine hydrocarbon seeps and both funded by thescientific Italian contribution Ministry no. 1778. of Research and Technology (MIUR). This is ISMAR-CNR References operation during theVI HERMES05, Integrated MEDCOR Projects andno: HERMES 226354). DECORS (GOCE-CT-2005-511234-1) The Cruises HERMIONE articleno: (grant supported 287844) is agreement of by also the a theduits European contribution linked FP- Community, to and to the to hydrocarbons the FP-VII-7 enriched national COCONET seepages” projects (Grant and PRIN agreement RITMARE “Carbonate ( con- Acknowledgements. 5 5 30 25 20 15 25 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Vul- nov. ects, ff , 2002. 001, 21 Lamelli- ´ adiz (Crustacea, shore construction, shore construction, Business Media BV, ff ff + sp. (Annelida: Siboglin- doi:10.1029/2001GL014340 Callianassa (Callichirus) lobata Lamellibrachia 984 983 ` ere, J.-P.: Description de n.gen., n.sp. from a mud volcano in the Gulf of C ´ edioni, A., Caprais, J.-C., Olu, K., and Sibuet, M.: Evidence for chemoau- shore Mar. Engin., 2, 5–15, 1988. ff sp., a siboglinid annelid from cold seeps in the eastern Mediterranean, FEMS Micro- shore Sicily, Mar. Geol., 199, 1–6, 2003. ff ´ ario, A., Comas, M. C., Azevedo, L., Pinheiro, L., Ivanov, M. K., and Cunha, M. R.: First record ered o Proc. JSCE, 388/III-8, Geotechnical Engineering, 13–22, 1987. Q. J. Eng. Geol., 22, 131–138, 1989. Palaios, 7, 376–382, 1992. carbonates from the eastern Mediterranean Sea, Terra Nova, 23, 206–212, 2011. and tubeworm-associated environments at AtwaterMexico, Deep-Sea Valley Res. lease Pt. block II, 340, 57, northern 2030–2039, Gulf 2010. of of a Vestimentifera (Polychaeta: Siboglinidae)Mediterranean Sea-Biogeographical from implications chemosynthetic and habitats futureI, in exploration, 58, the Deep-Sea 200–207, western Res. 2011. Pt. venting at hydrate ridge:Natural Classification, gas distribution, hydrates: andDillon, Occurrence, origin W. distribution, P., of American authigenic Geophysical and Union lithologies, detection Geophysical in: Monograph, edited 124, 99–113, by:tropical 2001. Paull, carbonate C. deposits based K,100, on and 123–141, New 1995. Zealand Cenozoic limestones, Sediment. Geol., Geochem., 31, 1175–1187, 2000. mud volcanoes of Sicily (Italy), Geophys. Res. Lett., 29, tures in the Central Adriatic Sea, Basin Res., 20,J. 473–487, P., 2008. Woodside, J., andgenetic Mascle, carbonate J.: crusts The anddeep-sea Nautinil fan concretions (eastern Scientific from Mediterranean Party: mud Sea), Nature Deep-Sea volcanoes Res. and and Pt. origin pockmarks II, of 54, of 1292–1311, dia- the 2007. Nile Decapoda, Callianassidae), Zootaxa, 1460, 35–46, 2007. tion in deep-sea sediments at cold seeps of the eastern Aleutian subduction zone, Organic belt as indicator of aWest shallow African buried Margin, turbiditic Geological channel on Society the London lower Special slope Publication, of 216, the 173–189, Congo 2003. Basin, ular characterization of bacteriabrachia associated with thebiol. Ecol., trophosome 69, and 395–409, 2009. the tube of canocalliax arutyunovi idae: Vestimentifera) from a deepBiodivers. Rec., shipwreck 4, in 1–6, the 2011. western Mediterranean Sea (Italy), Mar. sequence analysis of bacterialcrobiol. 16S Ecol., 59, rRNA, 64–70, APS, 2007. reductase and rubisCO genes, FEMS Mi- and Seep Biota, Topics in137–167, Geobiology, 2010. Kiel, S., 33, Springer Science totrophic symbiosis in a Mediterranean cold seep clam (Bivalvia: Lucinidae): comparative to their biology, Strategic Environmental Assessment – SEA2 Technical Report TR sp. (Crustacead’Endoume, Decapoda 40, 259–265, Callianassidae), 1966. Recueil desBull., Travaux 208, de 200–212, 2005. la Station Marine Adriatic sea, O pp., 2001. Hovland, M.: Hydrocarbon Seeps in Northern Marine Waters – Their Occurrence and E Hovland, M.: The formation of pockmarks and their potential influence onHovland, o M.: The formation of pockmarks and their potential influence on o Holland, C. W., Etiope, G., Milkov, A. V., Michelozzi, E., and Favali, P.: Mud volcanoes discov- Himmler, T., Brinkmann, F., Bohrmann, G., and Peckmann, J.: Corrosion patterns of seep- Feng, D. and Roberts, H. H.: Initial results of comparing cold-seep carbonates from mussel- Hil Hayton, S., Nelson, C. S., and Hood, S. D.: A skeletal assemblage classification system for non- Greinert, J., Gerhard, B., and Suess, E.: Gas hydrate-associated carbonates and methane Gontharet, S., Pierre, C., Blanc-Valleron, M.-M., Rouchy, J. M., Fouquet, Y., Bayon, G., Foucher, Etiope, G., Caracausi, A., Favara, R., Italiano, F., and Baciu, C.: Methane emission from the Geletti, R., Del Ben, A., Busetti, M., Ramella, R., and Volpi, V.: Gas Seeps linked to salt struc- Elvert, M., Suess, E, Greinert, J, and Whiticar, M. J.: Archaea mediating anaerobic oxida- Gay, A., Lopez, M., Cochonat, P., Sultan, N., Cauquil, E., and Brigaud, F.: Sinuous pockmarks Dworschak, P. C. and Cunha, M.,: A new subfamily, Vulcanocalliacinae n.subfam., for Duperron, S., de Beer, D., Zbinden, M., Boetius, A., Schipani, V., Kahil, N., and Gaill, F.: Molec- Gambi, M. C., Schulze, A., and Amato, E.: Record of Duperron, S., Fiala-M Duperron, S.: The diversity of deep-sea mussels and their bacterial symbioses, in: The Vent Dufour, S. C.: Gill anatomy and the evolution of symbiosis in the bivalve family Thyasiridae, Biol. Dando, P. R.: A review of pockmarks in the UK part ofDe the Gaillande, North D. Sea, and with particular Lagard respect Curzi, P. V., Canu, M., Casini Ropa, D., and Rossi, S.: Geoengineering Hazard study in the 5 5 30 25 30 20 15 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | sp. (Poly- ? Sarsia, 74, , last access: Sowerby in the -cemented rocks shore Norway), Mar. , 2009. ff North Sea Axinus News.html Lamellibrachia Calyptogena C) of bivalve shells from cold seeps and Group forearc basin of Alexander Island, 13 ff δ O& doi:10.1029/2008JF001037 986 985 18 δ http://www.mpi-bremen.de/en/Recent ¨ urs, K. R., and Taviani, M.: The Genus e, V., and Butterfield, D. A.: Post-eruption succession of macrofaunal com- ff use flow hydrothermal vents on Axial Volcano, Juan de Fuca Ridge, Northeast ff er, S.-B., Janssen R., G ¨ ur Mikrobiologie, online at: ffl mass-transport deposits on the eastern217–240, slope 2007. of Gela Basin (Sicily channel), Basin Res., 19, Channel), J. Geophys. Res., 114, F03014, the Jabuka trough floor (Central Adriatic Sea), Boll. Oceanol. Teor. Appl.,Mediterranean 5, Sea, 237–250, Mar. 1987. Geol., 284, 74–85, 2011. and Bright, T. J.: ChemosyntheticMexico, mussels Science, at 248, a 1096–1099, brine-filled 1990 pockmark in the northernmunities Gulf at Of di Pacific, Deep-Sea Res. Pt. II, 56, 1586–1598, 2009. Axiidea) from reducing environments in Kyushu,2012. southwestern Japan, Zootaxa, 3271, 55–67, accretionary prism, J. Geophys. Res., 95, 8899–8915, 1990. worms at hydrothermal vents outsidef of the Pacific Ocean, Recent28 News, November Max-Plank-Institut 2012. linked fluid seepage, Miocenegeogr. Palaeocl., deep-sea 227, 176–190, strata 2005. of the Romagna Apennines, Italy, Palaeo- sic methane-seep limestone fromAntarctica, the J. Sediment. fossil Res., Blu A65, 274–282, 1995. 3148, 1970. hydrothermal vents, (controlla caratteri degli isotopi), Geobios, 42, 209–219,Mediterranean 2009. Basin (Bivalvia: Thyasiridae), J. Conchol., 38,5, 581–598, 2005. composition associated with Lophelia pertusaPt. colonies II, in 57, the Gulf 1882–1890, of 2010. Mexico, Deep-Sea Res. changes in a LateHokkaido, Japan, Cretaceous Geobiology, 5, chemosymbiontic 127–139, assemblage 2007. from the Nakagawapockmarks: area evidence for of gas escape from Belfast Bay, Maine, Geology, 22, 59–63, 1994. and concretions from the easternof uranium, part Earth of Planet. Nankai Sci. accretionary Lett., prism: 109, Age 419–429, and 1992. geochemisrty deep-water depositional systems of thetal Alboran Sea, margin, Gulf of Preliminary Cadiz resultsLogachev, and June–July Norwegian of 2008, continen- IOC investigations Techn. during Ser., 94, the 2010a. TTR-17 cruiseM., of and RV Kaskov, N.: Professor SeepPetrol. Geol., mounds 27, on 1235–1261, the 2010b. southern Vøring Plateau (o 29–40, 1989. ate cements in pockmarks of the North Sea, J.chaeta: Sediment. Siboglinidae) Petrol., 57, from 881–892, a 1987. Rec., deep 1, shipwreck 1–3, in 2006. the eastern Mediterranean, Mar. Biodivers. 293 pp., 1988. Adriatic Sea, Mar. Petrol. Geol., 6, 161–169, 1989. ¨ o Minisini, D., Trincardi, F., Asioli, A., Canu, M., and Foglini, F.: Morphologic variability of exposed Minisini, D. and Trincardi, F.: Frequent failure of the continental slope: The Gela Basin (Sicily Micallef, A., Berndt, C., and Debono, G.: Fluid flow systems of the Malta Plateau, Central Mazzotti, L., Segantini, S., Tramontana, M., and Wezel, F.-C.: Characteristics of pockmarks on Marcus, J., Tunnicli Macdonald, I. R., Reilly, J. F., Guinasso, N. L., Brooks, J. M., Carney, R. S., Bryant, W. A., Kulm, L. and Suess, E.: Relationship between carbonate deposits and fluid venting: Oregon Komai, T. and Fujiwara, Y.: New records of callianassid ghost shrimp (Crustacea: Decapoda: Lott, C. and Zimmerman, J.: Do Mediterranean tubeworms like it hot? First discovery of tube- Lucente, C. and Taviani, M.: Chemosynthetic communities as fingerprints of submarine sliding King, L. H. and Maclean, B.: Pockmarks on the Scotian Shelf, Geol. Soc. Am. Bull., 81, 3141– L Kelly, S. R. A., Ditchfield, P. W., Doubleday, P. A., and Marshall, J. D.: An Upper Juras- Lietard C., Pierre C.: Isotopic signatures ( Lessard-Pilon, S. A., Podowski, E. L., Cordes, E. E., and Fisher, C. R.: Megafauna community Kelley, J. T., Dickson, S. M., Belknap, D. F., Barnhardt, W. A., and Henderson, M.: Giant sea-bed Jenkins, R. G., Kaim A., Hikika, Y., and Tanabe, K.: Methane-flux-dependent lateral faunal Lalou, C., Fontugne, M., Lallemand, S. E., and Lauriat-Rage, A.: Ivanov, M. K., Kenyon, N. H., Laberg, J.-S., and Blinova, V. N.: Cold seeps, coral Mounds and Ivanov, M. K., Mazzini, A., Blinova, V. N., Kozlova, E., Laberg, J.-S., Matveeva, T., Taviani, Hughes, D. J. and Crawford, M.: A new record of the vestimentiferan Hovland, M., Talbot, M. R., Qvale, H., Olaussen, S., and Aasberg, L.: Methane-derived carbon- Hovland, M. and Thomsen, E.: Hydrocarbon-based communities in the Hovland, M. and Judd, A. G.: Seabed Pockmarks and Seepages, Graham & Trotman, London, Hovland, M. and Curzi, P.: Gas seepage and assumed mud diapirism in the Italian central 5 5 30 25 20 30 15 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ´ an ´ enach, K., n.sp., a new ¨ uter, M., and ´ andez-Molina, Bell, K. L.: Exploration of the Farran, M., Hern ´ ı ´ edioni, A.: Spatial distribution of shore Technology Conf., Hous- ff ff ´ eron, J., Budzinsky, H., Le M Lamellibrachia anaximandri shore Norway, Geo-Mar. Lett., 28, 43–51, ff ´ azquez, J. T., l 988 987 ¨ el, P., Gauthier, O., Pierre, C., Henry, P., and Des- ´ andez-Puga, M. C.: Structure of mud volcano systems ´ edioni, A., Gofas, S., Salas, C., Mariotti, A., Foucher, J.-P., (Bivalvia, Vesicomyidae, Pliocardiinae) also harbour chemoau- ´ on, R., Ercilla, G., V ´ egnies, F., Foucher, J.-P., and Fiala-M ´ eas, H., and Sibuet, M.: Cold-seep assemblages on a giant pockmark Isorropodon , A., Ondr ff ´ alez, J., Juan, C., and Fern ` eres, D., First insights into the structure and environmental setting of cold-seep com- West Africa: spatial patterns and environmental control, Mar. Ecol., 28, 115–130, 2007. shore Technology Conference, 27–30 April 1987, Houston, Texas, 373–382, 1987. ff ff J., Gonz and pockmarks in the regionSea), of Mar. the Geol., Ceuta 332–334, Contourite 4–26, Depositional 2012. System (Western Albor vestimentiferan tubeworm (Annelida) fromworms the from Mediterranean, the with same notes habitat, on Zoosystema, frenulate 33, tube- 245–279, 2011. quantitative distribution relative toSystems, geological edited by: and Wefer, fluidVan G., Weering, venting Billett, T., Springer-Verlag, patterns, D., Berlin, Hebbeln, in: Heidelberg, D., 235–251, Ocean Jørgensen, 2002. Margin B. B., Schl Lett., 9, 53–58, 1989. Anaximander mud volcanoes, Oceanography, 24, 22–23, 2011. and Oomori, T.: Ventingtrough of backarc carbon basin, dioxide-rich Science, 248, fluid 4959, and 1093–1096, hydrate 1992. formationseafloor in features mid-Okinawa along thegies Malta and Plateau geo-environmental (Sicily control channel2009 of – their Mediterranean distribution, Sea): Mar. Morpholo- Petrol. Geol., 26, 1831–1848, Geol., 177, 129–150, 2001. C., Buck, C. E.,Hajdas, Burr, G. I., S., Heaton, Edwards, T. J., R.F. G., Hogg, L., Manning, A. Friedrich, S. G., M., W., Reimer,S. Hughen, Grootes, R. M., K. P. W., M., van A., Richards, Guilderson, der D. Kaiser, T. A.,calibration Plicht, K. P., curves, Southon, J., F., 0–50,000 J. Kromer, and years R., B., Weyhenmeyer, cal C. Talamo, McCormac, S., BP, E.: Radiocarbon, Turney, C. IntCal09 51, 1111–1150, and 2009. Marine09 radiocarbon age valvia:Thyasiridae) from the eastern Atlantic98, 281–287, and 2011. Mediterranean Sea, Naturwissenschaften, in the genus totrophic symbionts, Symbiosis, 56, 129–137, 2012. 2007. Methane-derived carbonates and authigenic pyrite from the northwestern Black Sea, Mar. O Khripouno o Johnson, J. E., Winters,structures W. on J., the and flanks Lorenson, of T. the D.: Storegga Origin Slide, of o the pockmarks and chimney bruy munities in the Marmara Sea, Deep-Sea Res. Pt. I, 57, 1120–1136, 2010. and Woodside, J.: Cold seepsition, communities symbiosis in and the spatial deep distribution1936, on eastern 2004. mud Mediterranean volcanoes, Sea: Deep-Sea compo- Res. Pt. I, 51, 1915– seafloor engineering hazards orton, TX, geological May curiosities? 1980, Pap O OTC 3729, 1980 diverse cold seep communities livingprism, on various Prog. diapiric Oceanogr., 38, structures of 347–347, the 1997. southern Barbados authigenic carbonates associated withthe gas Blake hydrate Ridge decomposition diapir,K., and in: Matsumoto, Proceedings fluid R., Wallace, of venting P. J., the above and Ocean Dillon, Drilling W. P., Scientific Program, Results, edited 164, by: 285–300, Paull, 2000. C. deep-sea hydrothermal vents after7834, a 2010. catastrophic eruption, P. Natl. Acad. Sci., 107, 7829– Southward, E. C., Andersen, A. C., and Hourdez, A.: Somoza, L., Medialdea, T., Le Sibuet, M. and Olu-Le Roy, K.: Cold seep communities on continental margins: structure and Shank, T. M., Herrera, S., Cho, W., Roman, C. N., and Cro Scanlon, K. M. and Knebel, H. J.: Pockmarks in the floor of Penobscot Bay, Maine, Geo-Mar. Sakai, H., Gamo, T., Kim, E. S., Tsutsumi, M., Tanaka, T., Ishibashi, J., Wakita, H., Yamano, M., Savini, A., Malinverno, E., Etiope, G., Tessarolo, C., and Corselli, C.: Shallow seep-related Rodrigues, C. F., Cunha, M. R., Olu, K., and Duperron, S.: The smaller vesicomyid bivalves Reimer, P.J., Baillie, M. G. L., Bard, E., Bayliss, A., Beck, J. W., Blackwell, P.G., Bronk Ramsey, Peckmann, J., Reimer, A., Luth, U., Hansen, B. T., Heinicke, C., Hoefs, J., and Reitner, J.: Rodrigues, C. F. and Duperron S.: Distinct symbiont lineages in three thyasirid species (Bi- Roberts, H. H., Sassen, R., and Aharon, P.: Carbonates of the Louisiana Continental Slope, Paull, C. K., Ussler III, W., Holbrook, W. S., Hill, T. M., Keaten, R., Mienert, J., Haflidason, H., Olu-Le Roy, K., Caprais, J.-C., Fifis, A., Fabri, M.-C., Gal Ritt, B., Sarrazin, J., Caprais, J.-C., No Olu-Le Roy, K., Sibuet, M., Fiala-M Olu, K., Sibuet, M., Harm Newton, R. S., Cunningham, R. C., and Schubert, C. E.: Mud volcanoes and pockmarks: Naehr, T. H., Rodriguez, N. M., Bohrmann, G., Paull, C. K., and Botz, R.: Methane-derived Mullineaux, L. S., Adams, D. K., Mills, S. W., and Beaulieu, S. E.: Larvae from afar colonize 5 5 30 25 20 15 10 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ´ ediconi, Pakistan, ff doi:10.1007/s00367-007- redo, S., Baader, H., and Dubinsky, Z., ff 990 989 ´ e, J. S., de Lange, G., Forney, L. J., Gottschal, J. C., ¨ osch, H., Berner, U., Geyh, M., Marchig, V., and Schulz, H.: Authigenic carbon- ´ eric, N.-V., and Arp, G., Lecture Notes in Earth Sciences, 131, 277–295, 2011. , 2008. Oceans, Ecosystems of the World, edited by: Tyler, P. A., Elsevier, 28, 381–384, 2003. ates derived from oxydized methane ventedMar. from Geol., the 136, Makran accretionary 55–77, prism 1996. o A., Pancost, R. D.,Foucher, Sinninghe J. P., Damst Mascle, J., andcal Woodside, and J.: ecological Life data at from cold205, Kazan seeps: 367–390, mud a 2004. volcano, synthesis eastern of Mediterranean biogeochemi- Sea, Chem. Geol., Gela and South0096-9 Adriatic Basins, Geo-Mar. Lett., 28, 137–151, munities from a pockmark field inHERMIONE, the 11–15 Strait April of Sicily 2011, (Mediterranean Malaga Sea) (Spain), 2nd 2011. Annual Meeting lusca: Bivalvia), monophyly and superfamily status, J. Mar. Assoc. UK,in 87, Geobiol 565–574, 33, 2007. edited by: Kiel, S., Springer Science-Business Media Dordrecht, 2010. tion, fluid escape, sediment failuredeposits and of regional the weak Adriatic layers Sea, within Mar. the Geol., late 213, Quaternary 91–119,Hydrobiologia, 2004. mud 503, 9–19, 2003. water cold seeps, IPC3 Chemosynthetic communitiesnities: symposium; palaeoecology, “Chemosynthetic systematics commu- and evolutionary history”, London, 28 June–3 July, 2010. Quaternary foredeep of Sicily, Geo-Mar. Lett., 10, 13–21, 1990. Its History and PresentSpringer, in Challenges, press, edited 2013. by: Go chemosynthetic assemblages from pockmark systemsatic in the their Strait of bearing Sicily on and Central composition, Adri- evolution and biogeography of the Mediterranean deep U/Th systematics and ages ofrecorders authigenic of carbonates fluid from flow Hydrate variations, Ridge, Geochim. Cascadia Cosmochim. Margin: Ac., 67, 3845–3857, 2003. central Mediterranean Sea, Hermione AnnualProgram Meeting and 2010, Abstract, Malta 32, 12–16 2010. April, Conference ranean Metazoans Through Time, in:ner, J., Advances Qu in Stromatolite Geobiology, edited by: Reit- from Miocene-age cold ventsVents in in Modern the and Romagna Ancient191 Apennine, Environments, 1994. Italy, edited in: by: Submarine Aharon, Hydrocarbon P., Geo-Mar. Lett., 14, 185– and Adjacent Mediterranean Basins, editedPublishers, by: Great Vai, G. Britain, B. 351–366, and 2001. Martini, I. P., Kluwer Academic Sea, Thalassia Jugoslavica, 19, 53–55, 1983. ternational Association of Sedimentologists, Bologna, Italy, 189–192, 1981. Young, C. M.: Reproduction, development and life-history traits, in: Ecosystems of the Deep Werne, J. P., Haese, R. R., Zitter, T., Aloisi, G., Bouloubassi, I., Heijfs, S., Fiala-M von Rad, U., R Verdicchio, G. and Trincardi, F.: Mediterranean shelf-edge muddy contourites: example from Tyler, P. A. and Young, C. M.: Dispersal at hydrothermal vents: a summary of recent progress, Taylor, J. D. and Glover, E. A.: Evolutionary relationships of theTaylor, bivalve J. family D. Thyasiridae and (Mol- Glover, E. A.: Chemosymbiotic bivalves, in: The Vent and Seep Biota, Topics Taviani, M., Angeletti, L., and Trincardi, F.: Postglacial to modern benthic chemosynthetic com- Trincardi, F., Cattaneo, A., Correggiari, A., and Ridente, D.: Evidence of soft sediment deforma- Trincardi, F. and Argnani, A.: Gela submarine slide: a major basin-wide event in the Plio- Taviani, M., Angeletti, L., Ceregato, A., Froglia, C., and Trincardi, F.: Recently discovered Taviani, M.: Marine chemosynthesis in the Mediterranean Sea, in: The Mediterranean Sea: Teichert, B. M. A., Eisenhauer, A., Bohrmann, G., Haase-Schramm, A., Bock, B., and Linke, P.: Taviani, M.: Abandoned and lost fishing devices as stepping-stones for deep water corals in the Taviani, M.: The Deep-Sea Chemoautotroph Microbial World as Experienced by the Mediter- Taviani, M.: Fluid venting and associated processes, in: Anatomy of an Orogen: the Apennines Taviani, M.: The “Calcari a Lucina” macrofauna reconsidered: Miocene deep-sea faunal oases Stefanon, A., Rabitti, A., and Boldrin, A.: Gas-charged sediments and pockmarks in Adriatic Stefanon, A.: Pockmarks in the Adriatic Sea? Abstracts, 2nd European Regional Meeting, In- 5 5 20 15 10 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 18 σ ± ± ± ± ± ± ± ± modified haul modified haul modified haul ‰ δ O 18 C 0.1 2.71 0.1 2.48 0.1 2.33 0.1 2.21 0.1 3.23 0.1 4.98 0.10.1 3.18 2.86 13 notation relative to the σ ± ± ± ± ± ± ± ± δ ‰ 10.82 840.0 820.0 Epibenthic 00.61 842.0 840.6 CTD (POM) 48.06 824.0 850.0 Epibenthic 31.59 815.0 811.0 Epibenthic 0 0 0 0 δ 00 01 58 01 ◦ ◦ ◦ ◦ 0.82 2.66 0.16 C 1.23 1.84 40.77 4.05 37.57 13 vs. PDB vs. PDB − − − − − 35.00 14 15.69 14 30.7 13 10.18 14 0 0 0 0 46 45 45 44 ◦ ◦ ◦ ◦ 992 991 sp. 09.0208.2001.0758.79 36 820.0 824.0 840,8 CTD Grab Gravity Core 01.18 36 10.35 36 15.29 833.0 Grab 24.85 820.2 Grab 52.79 831.7 Grab 08.90 36 09.03 828.0 CTD 08.21 832.0 Grab 01.08 840.9 Gravity Core 06.80 816.0 CTD 06.64 818.0 Grab 28.42 827.0 Grab 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 00 01 00 01 00 01 00 58 00 00 00 01 00 00 55 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Lucinoma kazani Isorropodon perplexum Myrtea amorpha Isorropodon perplexum Calliax Lucinoma kazani 38.2437.83 14 16.42 14 16.07 14 14 15.11 14 38.82 14 48.41 14 34.56 14 44.57 13 40.13 14 38.25 14 37.84 14 16.28 14 16.86 14 39.24 14 16.86 13 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 45 45 45 45 45 45 45 45 45 45 45 45 45 46 45 46 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ GGMMSS.XX GGMMSS.XX Depth Depth concretion on shell Stable Isotopes Analysis expressed in the conventional Sampling station list of Cruises MEDCOR and DECORS in the Gela Basin. SampleMEDCOR70 Material Shell Species MEDCOR78 Shell MEDCOR81 Shell MEDCOR81 Shell MEDCOR81 Claw MEDCOR70 Mudstone MEDCOR78 Lithified burrow MEDCOR78 Carbonate StationMEDCOR-68 DateMEDCOR-69 19 Dec 2009MEDCOR-70 19 Dec 36 2009MEDCOR-71 19 Dec 36 2009 19 Dec 36 2009 Start Lat. 36 Start Long. End Lat. End Long. Start End Gear MEDCOR-72 19 Dec 2009 36 MEDCOR-74 19 Dec 2009 36 MEDCOR-75 21 Dec 2009 36 MEDCOR-76 21 Dec 2009 36 MEDCOR-77 21 Dec 2009 36 MEDCOR-78 21 Dec 2009 36 MEDCOR-80 19 Dec 2009 36 MEDCOR-81 19 Dec 2009 36 MEDCOR-82 19 Dec 2009 36 DECORS-48 08 Aug 2011 36 DECORS-49 08 Aug 2011 36 DECORS-50 09 Aug 2011 36 Table 2. Vienna-Pee Dee Belemnite (VPDB) reference standard. Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 611 Marine09 154 Marine09 ± 54 Marine09 ± ± ´ an, Poland. Radio- Ranges Age cal BP Calibration σ 7 547–669 486 77 11 121–12 343 9456–9763 11 732 9610 ± ± ± x 200 41 994 993 30 41 60 41 ± ± ± C-yr BP) (yr) (yr cal BP) (yr cal BP) Data ´ an Radiocarbon Laboratory in Pozn 14 1090 ( 8960 sp 10 500 xxx x x x x x x x x x x x x 69 71 76 78 80 82 49 50 MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR DECORS DECORS Myrtea amorpha Lamellibrachia Lucinoma kazani -error) and were calculated with Calib6.0.1, using the surface marine σ C-yr) correspond to the true half-life. Calibrated age ranges reflect the 95.4 % 14 sp. x x x List of major established (chemosymbiotic bivalves, and tubeworm) and putative (gas- Radiocarbon data from the Pozn sp. x x x x x x Poz-37994 MEDCOR81 Code # SamplePoz-38025 MEDCOR78 Poz-37995 MEDCOR78 Species Radiocarbon Age Delta R Two- Calliax Salas and Woodside (2002) Myrtea amorpha (Sturany, 1896) Isorropodon perplexum Sturany (1896) Taranis moerchii (Malm, 1861) Lamellibrachia Lucinoma kazani tropods, callianassid) metazoans associated with pockmark cold seepage at the GBPF. Table 4. carbon years ( probability window (2 Table 3. calibration curve MARINE 09 by Reimer et al. (2009). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x 996 995 x x 69 71 76 78 80 82 49 50 MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR DECORS DECORS 69 71 76 78 80 82 49 50 MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR DECORS DECORS ´ en, 1997 x x ´ en,1980 x x x x x reys, 1847) x x ´ en & Carrozza in War ff (Scacchi, 1835) x x x x x x Sturany, 1896 x x x x x x x reys, 1876) x (Forbes, 1844) x ff (Je War ¨ reys, 1876) x x x uller, 1776) x x (Montagu, 1808) x x x x reys, 1883 (Seguenza, 1877) x x x x x x x ff (Sars, 1870) x x (Johnston, 1825) x x x (Montagu, 1803) (Deshayes, 1833) x x x x x x x ff (Je (Forbes, 1844) x x x (Philippi, 1844) (M ´ Bonfitto & Sabelli, 1995 x x x x x x x (Philippi, 1844) en, 1846) x ´ reys, 1869) x x x x x x x x en, 1846) x x x x x (Spengler, 1793) x x x (Philippi, 1844) x x x (Linnaeus, 1758) Salas and Woodside, 2002 x x x Je (Je ff Dautzenberg & H. Fischer, 1896 x x x x (Michaud, 1828) x (Sturany, 1896) x Bouchet & War (Forbes, 1844) x (Montagu, 1803) x x x (Monterosato, 1875) x x x x reys, 1870) x x x x (Verrill and Smith (in Verrill), 1885) x x x x x reys, 1877) x x x (Sykes, 1905) x (Malm, 1861) x x x (de Cristofori & Jan, 1832) x ff (Scacchi, 1835) x x x x x x x x sp. x (Philippi, 1844) x x x x x x (Lov (A. Adams, 1861) reys, 1883) (Pennant, 1777) (G.O. Sars, 1872) x (Sykes, 1903) x (Risso, 1826) x x x ff sp. x (Je (Bronn, 1831) x x (Lov sp. (Kiener, 1840) x x x x x x x (Forbes, 1844) x x x x x x x ff (Olivi, 1792) x x (Verrill and Bush, 1898) x (M. Sars, 1865) x (Seguenza, 1877) (Monterosato, 1872) x (Malm, 1861) x x x x x (Aradas, 1847) x x x x x x x sp. x x (Olivi, 1792) (Je ¨ uller, 1784) Smriglio & Mariottini, 1996 x x (Calcara, 1842) (Je sp. bidentata (Dall, 1881) x x (Je (Forbes, 1844) x sp. x x Benthic and pelagic molluscs recovered from the GBPF during cruises MEDCOR (Aradas and Maggiore, 1844) x (M sp. Continued. sp. x x x (Blainville, 1825) cf. sp. (Reeve, 1844) x sp. sp. sp. x sp. x sp. x sp. sp. sp. sp.1 sp.2 sp. x sp. Corbula gibba Xylophaga Myrtea amorpha Myrtea spinifera Axinulus croulinensis Axinulus eumyarius Axinus grandis Mendicula ferruginosa Thyasira Thyasira succisa Kelliella miliaris Isorropodon perplexum Waisiuconchia Tellimya tenella Venus Bathyspinula excisa Katadesmia cuneata Malletia obtusa Saccella commutata Microgloma Lucinoma kazani Myrtea Abra longicallus Timoclea ovata Yoldiella curta Yoldiella lucida Cardiomya costellata Cuspidaria rostrata Thracia Acanthocardia Parvicardium Kurtiella Yoldiella nana Yoldiella seguenzae Yoldia minima Ennucula Ennucula aegeensis Ennucula corbuloides Nucula sulcata Nucula tumidula Asperarca nodulosa Bathyarca pectunculoides Limatula gwyni Limatula subauriculata Notolimea crassa Parvamussium Pectinidae sp. Benthic Molluscs MOLLUSCA Bivalvia Putzeysia wiseri Dikoleps Galeodea echinophora Amphissa acutecostata Fusinus rostratus emendata (Calcara, 1841) Spirotropis modiolus Mangelia serga Pleurotomella gibbera Taranis moerchii Teretia teres Granulina gofasi Pagodula echinata Trophonopsis barvicensis Bathysciadium xylophagum Acteon pusillus Crenilabium exile Eulimella Syrnola Colpodaspis Diaphana lactea Philine Philine scabra Philine monterosatoi Roxania monterosatoi Fissurisepta granulosa Bittium Turritella communis Epitonium Haliella stenostoma Triphoridae sp.Aclis attenuans Melanella Naticidae sp.Lunatia fusca Alvania Alvania Alvania cimicoides Alvania elegantissima Alvania subsoluta Alvania testae Benthonella tenella Aporrhais serresianus x x x Table A1. Table A1. and DECORS: taxa of proven or putative chemosymbiotic type are bold. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ×

27 x x x x x ts major pockmarks); inset, the pockmarks); ts major Terrain Model (DTM of 20 m resolution with 10x Terrain Model (DTM of 998 997 ng the same area magnified in the figure. in the area magnified ng the same this article (red spots represen 69 71 76 78 80 82 49 50 MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR MEDCOR DECORS DECORS ˚ al, 1775) x x x x x x (d’Orbigny, 1834) x x x (d’Orbigny, 1834) x x (d’Orbigny, 1834) x x x x x (Forsk Blainville, 1817 x (Rang, 1829) x x x x x (Brocchi, 1814) x x (Blainville, 1821) x x x x (d’Orbigny, 1834) x x x (Rang, 1828) x x x x (Lesueur, 1813) x x x x x J. E. Gray, 1850 x x x (Linnaeus, 1767) x x x x x (Monterosato, 1875) x x x x x Lesueur, 1817 x x x x x x x x (Quoy and Gaimard, 1827) x x x x x x x x (Rang, 1828) x x x x x (M. Sars in G.O. Sars, 1872) x x x x x sp. sp. sp. sp. vertical exaggeration) of the Gela Basin in the Strait of Sicily. The figure illustrates the location the location illustrates Sicily. The figure of the Gela Basin in the Strait of vertical exaggeration) field discussed in of the pockmarks Mediterranean basin with rectangle showi Continued.

Fig. 1. Map showing the shaded relief Digital Cavolinia uncinata Diacria trispinosa Clio pyramidata Creseis clava Hyalocylis striata Styliola subula Limacina bulimoides Limacina trochiformis Peracle diversa Peracle reticulata Hanleya Antalis agilis Dentalium Janthina Carinaria lamarckii Atlanta brunnea Atlanta peronii Heterobranchia Cavolinia inflexa Cavolinia tridentata Heliconoides inflata Limacina Entalina tetragona Map showing the shaded relief Digital Terrain Model (DTM of 20 m resolution with 10 Polyplacophora Scaphopoda Pelagic Molluscs 1 2 3 4 5 6 Fig. 1. vertical exaggeration) of the Gelaof Basin the in pockmarks the field Straitthe discussed of Mediterranean in Sicily. basin this The with article figure rectangle illustrates (red showing the spots the location represents same major area pockmarks); magnified in inset, the figure. Table A1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 29

28 tical exaggeration) of vertical exaggeration) vertical exaggeration) × × ric characteristics are listed in the table; sub-circular depressions interpreted as ea with more then 40 pockmarks with variable with variable then 40 pockmarks ea with more two main pockmarks showing the different pockmarks two main (resolution 5m and 10x ver (resolution 5m ckmark (Number 1) is formed by two partly 1) is formed (Number ckmark nd V-shaped with internal positive relief. relief. positive nd V-shaped with internal solution and 10 x vertical exaggeration) showing 999 1000 tion of the pockmarks and their geometries; the inset shows a tion of the pockmarks e cross sections of of the shaded relief DTM of the shaded relief DTM magnification of the highest density pockmarks ar of the highest density pockmarks magnification features). ones and up to 30 minor (8 of the major dimensions the study area showing the distribu the complex, rough topography punctuated by many rough topography punctuated by many the complex, greater then 200m, are numbered from with diameter The 11 major pockmarks, pockmarks. Their geo-morphomet dimension, to minimum maximum the bathymetric profiles show th internal geometry, respectively U-shaped a respectively geometry, internal po reveal that the major the image Furthermore, coalescent depressions. depressions. coalescent

Fig. 3 Perspective view

Fig. 2. Shaded relief DTM of the study area (5 m re Shaded relief DTM of the study area (5 m resolution and 10 Perspective view of the shaded relief DTM (resolution 5 m and 10 erent internal geometry, respectively U-shaped and V-shaped with internal positive re- 1 2 3 4 5 6 ff 1 2 3 4 5 6 7 8 9 10 of the studyshows area a showing magnification the ofwith distribution variable the of dimensions highest (8 the density of pockmarks the pockmarks and major area ones their with and geometries; up more to the then 30 inset 40 minor features) pockmarks Fig. 3. lief. Furthermore, the image revealcoalescent that depressions. the major pockmark (Number 1) is formed by two partly Fig. 2. showing the complex, roughpreted topography as punctuated pockmarks. by Thebered many 11 from maximum sub-circular major to depressions minimum pockmarks, dimension.in inter- with Their the geo-morphometric diameter table; characteristics greater the are then listed the bathymetric 200 profiles di m, show are the num- cross sections of two main pockmarks showing Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- 3-D ff

31 (B)

30 and the regional ◦ kmark area; (B) 3D kmark stratigraphy of the poc from the DTM, showing clearly the difference from aching the maximum of 16° and the regional aching the maximum 1002 1001 hows the location of the chirp profile and the sample locations; locations; the sample and profile the chirp of hows the location . ◦ Chirp profile showing the subsurface stratigraphy of the pockmark area; perspective view of the DTM s red. DECORS samples yellow, MEDCOR samples between the side slope of the pockmarks re between the side slope of the pockmarks surrounding slope about 2°-3°.

Slope map of the study areas, calculated from the DTM, showing clearly the di the subsurface showing Fig. 5. (A) Chirp profile

study areas, calculated of the Fig. 4. Slope map 1 2 3 4 5 1 2 3 4 5 perspective view of the DTMMEDCOR shows samples the yellow, DECORS location samples of red. the chirp profile and the sample locations.; Fig. 5. (A) Fig. 4. ence between the side slopesurrounding slope of about the 2–3 pockmarks reaching the maximum of 16 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

sp. 33 Tara- (D) Calliax 32 Isorropodon (F)

Isorropodon perplexum haul whole catch of station Myrtea amorpha from st. (B) (A) , theratological shell from st. from shell , theratological from st. MEDCOR78, ng morphologic bulge at the base of the slope turbidites and hemipelagites) toward the bulge. by the ascending fluids than in other areas. by the ascending ansport event (Gela slide?) and the thinning of the GBPF: (A) haul whole catch of station eep fauna and anthropogenic litter; (B) Lucinoma kazani 1004 1003 , theratological shell from st. MEDCOR78, Myrtea amorpha from st. MEDCOR69, (E) from (E) sp. from st. MEDCOR71. sp. from Lucinoma kazani showing the top of the last basin-wide mass-tr showing the top of the last basin-wide plane-parallel reflectors (basin-plain fine-grained (basin-plain reflectors plane-parallel to breach unit is likely easier this Where thinner, Taranis moerchi (C)

Fig. 6. Chirp sonar profiles across the pockmark-hosti Calliax 1 2 3 4 5 6 from st. MEDCOR71, (C) from from st. MEDCOR69, Chemosymbiotic metazoans recovered from the GBPF: Chirp sonar profiles across the pockmark-hosting morphologic bulge at the base of the otic bivalves (L), tubeworms (S), and tubeworms otic bivalves (L), MEDCOR 78 (pockmark 1) showing chemosymbi with non-s mixed carbonate concretions (m) perplexum MEDCOR78, (D) MEDCOR78, (F)

recovered from metazoans Fig. 7. Chemosymbiotic from st. MEDCOR71 , nis moerchi from st. MEDCOR71. Fig. 7. MEDCOR 78 (pockmarkconcretions #1) mixed showing with chemosymbiotic non-seep bivalves, fauna tubeworms, and anthropogenic and litter; carbonate slope showing the top of theof last basin-wide plane-parallel mass-transport reflectors event (Gela (basin-plainbulge. slide?) and Where fine-grained the thinner, thinning turbidites this andareas. unit hemipelagites) is toward likely the easier to breach by the ascending fluids than in other Fig. 6. 1 2 3 4 5 6 7 8 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 35

(C– 34 , , (C-D) , (C-D) Calliax Calliax ted matrix) embedding embedding ted matrix) (A–B)

hash fraction, all from st. (B) (B) hash fraction, from st. moured with chemosymbiotic-organism with chemosymbiotic-organism moured at 210-230 cm in core MEDCOR70. at 210-230 cm rked black-stained shallow-water foraminifer ic concretions (cemen concretions ic azoans, all from st. MEDCOR78: (A-B) azoans, all from 1006 1005 coarse sand fraction; authigenic concretions (cemented matrix) embed- anassid decapod; M = mollusc. anassid decapod; M = mollusc. (A) ); (G) cemented mudstone layer mudstone ); (G) cemented (A–D) ; (E) indurated callianassid? burrow, ar cemented mudstone layer at 210–230 cm in core MEDCOR70. Elphidium crispum Isorropodon bioclasts; (F) cemented matrix embedding a rewo embedding matrix bioclasts; (F) cemented ( skeletal biosomes of seep-related met skeletal biosomes (G)

the GBPF: (A-D) Authigen Fig. 9. Carbonates from indurated callianassid? burrow, armoured with chemosymbiotic-organisms ); 1 2 3 4 5 6 7 (E) ; cemented matrix embedding a reworked black-stained shallow-water foraminifer (F) Carbonates from the GBPF: DECAMOL skeletal assemblage; DECORS50 and MEDCOR69. D = calli Isorropodon

Fig. 8. DECAMOL skeletal assemblage; (A) coarse sand fraction; Elphidium crispum D) ( bioclasts; Fig. 9. ding skeletal biosomes of seep-related metazoans, all from st. MEDCOR78: MEDCOR69. Fig. 8. 1 2 3 4 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

36 37 carbon-depleted

, almost completely em- ,. encrusted by encrusted by carbon-depleted ark 1), and MEDCOR70 (pockmark 6): ark 1), and MEDCOR70 (pockmark trix on valves of chemosymbiotic bivalves trix on valves of chemosymbiotic Lucinoma kazani tratigraphic logs reporting main chronological, isotopic and main logs reporting tratigraphic Isorropodon perplexum Lucinoma kazani Isorropodon perplexum 1008 1007 (A) (B) seep-limestones: (A) seep-limestones: photographic (left) and (right) lithos photographic faunal features.

(pockm cores MEDCOR81 Fig. 11. Sedimentary 1 2 3 4 5 13C -37,57‰PDB, see text), (B) δ 13C–37.57 ‰ PDB, see text), δ Incipient methane-driven cementation of matrix on valves of chemosymbiotic bivalves Sedimentary cores MEDCOR81 (pockmark #1), and MEDCOR70 (pockmark #6): pho- from GBPF, precursors of GBPF, from concretion (

of ma cementation Fig. 10. Incipient methane-driven Fig. 11. tographic (left) andisotopic (right) and lithostratigraphic faunal features. logs reporting main chronological, petrographic, Fig. 10. concretion ( from GBPF, precursors of seep-limestones: bedded. 1 2 3 4 5 6 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1009 Stable isotope compositions of bivalve shells (core MEDCOR 81), callianassid claw and notation relative to the PDB reference standard. Fig. 12. authigenic carbonates all from st.δ MEDCOR70 and MEDCOR78 expressed in the conventional