The last interglacial in the Mediterranean as a model for the present interglacial

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<ul><li><p>Global and Planetary Change, 7 (1993) 109-117 109 Elsevier Science Publishers B V , Amste rdam </p><p>The Last Interglacial in the Mediterranean as a model for the present interglacial </p><p>C. Zazo a, J.L. Goy b, C.J. Dabrio c, T. Bardajl d, L. Somoza e and P.G. Silva b Departamento de Geologfa, Museo Nactonal de CLenctas Naturales, C S [ C Jos~ Guttgrrez Abascal 2, 28006-Madrid, Spam </p><p>b Departamento de Geologfa (Geodmdmlca), Facultad de Ctenetas, UnwersMad, 37008-Salamanca, Spam c Departamento de Estrattgraffa, Facultad de Geologfa, U C M and lnstituto de Geologfa Econdmlea C S I C, 28040-Madrid, Spare </p><p>a Departamento de Geologfa, UnwersMad de Alcald de Henares, 28871-Madrid, Spare e Instttuto Espahol de Oceanograf{a, Fuengtrola, Mdlaga, Spain </p><p>(Recewed August 30, 1991, revised and accepted July 30, 1992) </p><p>A B S T R A C T </p><p>Zazo, C , Goy, J_L, Dabrlo, C.J , Bardaj1, T , Somoza, L and Silva, P G., 1993 The Last Interglacial in the Mediterranean as a model for the present interglacial Global Planet Change, 7 109-117 </p><p>Deposits of the Last Interglacial on the south and southeastern coasts of Spain are shallow marine and coastal sediments, with a warm fauna of Strombus bubontus These units exhibit a diversity of morpho-sedimentary models controlled by the tectonic activity of the Mediterranean area, which is closely related to the approximation of Africa and Iberla during the Quaternary </p><p>There are three well-dated peaks of maximum sea level (T-I: isotopic substage 7a, T-II. isotopic substage 5e, T - I I I isotopic substage 5c) A younger episode, T-IV, probably corresponds to the isotopic substage 5a Episodes T-II, T-III and T-IV were laid down during Last Interglacial age. In addition, three Holocene peaks of maxamum sea level H 1 ca 5100 yr B P , H 2 ca_ 3500 yr B.P and H 3 ca. 2400 yr B P_ were found </p><p>The three mare peaks of the Last Interglacial correspond to the morpho-sedlmentary Tyrrhenlan units T-II, T-III and T-IV, deposited during a time span of some 45,000 years Several smaller oscillations can be distinguished within each of these units as subunlts separated by erosional surfaces At least three of such mapable subunlts were distinguished within the peak T-II (5e), each lasted ca 10,500 yr. </p><p>As the positive oscillations of sea level (HI, HE, and H 3) recorded during the present Interglacial (Holocene) are much shorter, we infer that they are smaller-scale fluctuations (2500-1100 yr cycles) within the first oscillation (duration ca 10,500 yr) of the first Holocene peak of sea level which has not yet been completed </p><p>In addition to changes of sea level, the vertical and lateral ar rangement of morpho-sed~mentary units, which can be designated as the stratIgraphlc architecture, depends on tectonics and oceanography, including geoidal and sterlc changes and coastal dynamics_ </p><p>The coastal dynamics factor largely depends on the exchange of waters between the Atlantic and the Mediterranean Maximum incursions of water coincides with warm periods (hlghstands) when the coastal accretion increases </p><p>The tectonic factor greatly influences and modifies the effects of sea-level changes in the coastal areas of tectonlcally-ac- tire regions such as the Mediterranean Areas with tectonic uplift will be characterized by a staircase of progradlng gravelly beaches, whereas sinking areas wdl favour the deposition of vertically stacked sequences with coastal onlap of barrier island and lagoon deposits. </p><p>Rates of sea-level rise for the coming years of 1 cm/yr , have been suggested by some authors These gradients greatly exceed those produced by any tectonic factor in the Spamsh coast during the last 100 kyr Shoreface erosion and transgression with landward migration of barrier islands and lagoons will occur in subsiding areas (Murcla-Allcante and Valencia), even with relatively low rates of sea-level rise (less than 0 5 cm/y r ) Higher rates of sea-level rise (0 5-1 cm/y r ) will increase the transgressive trend_ Areas with subsidence rates higher than 7_5 c m / k y r (Mar Menor and Oval of Valencia) are prone to transgression and erosion of barrier islands and lagoons both in the cases of stable and rising sea levels Risks are smaller m areas with lower rates of subsidence (La Mata, Santa Pola and Torrevleja lagoons) when a stable sea level is considered, however, any rise of sea level will trigger coastal erosion_ </p><p>0921-8181/93/$06 00 1993 - Elsevier Science Publishers B V All rights reserved </p></li><li><p>110 c ZAZO ET AL </p><p>Introduction </p><p>Deposits of the Last Interglacial have been recorded along the south and southeastern Span- lsh coast as three highstand sedimentary units. They consist of marine deposits, with a warm fauna of Strombus bubontus, commonly referred to as Tyrrhenian. </p><p>These three marine Tyrrheman umts exhibtt a diversity of morpho-sedimentary models con- trolled by the tectonic activity of the Mediter- ranean area, which is closely related to the ap- proximation of Africa and Iberia during the Qua- ternary. A compressional realm resulted from movements of the trans-Alboran fault (Fig. 1) which acted as a transmitter of smlstral stresses (Montenat et al , 1987) Compressional stresses decreased from south to north (Almerfa to Alt- cante, zones 4-1, Fig. 1) and generated a se- quence of variable tectonic uplift because of a reduction in the absorption of the deformation. Extensional regimes active during the Quaternary occur in Valencia and Balearic Islands (zones 6 and 7, Fig. 1) because of processes of the "Valencia Trough." Quaternary extensional pro- cesses in southwestern Spain induced strong sub- sidence in the Guadalquivlr and Cfidiz areas (zone 5, Fig. 1) (Zazo et al , 1985). These phenomena </p><p>EUROASIATIC PL / </p><p>, ~ IBERIAN PL~ </p><p>Fig 1 L o c a h o n m a p of the s tudy a r e a s ( 1 = A h c a n t e , 2 = </p><p>A h c a n t e - M u r c i a , 3 = C o p e , M u r c i a , 4 = Alrner~a, 5 = Cfidlz, </p><p>6 = Ova l o f V a l e n c m , 7 = B a l e a n c I s l ands ) as r e l a t ed to the </p><p>m a i n t ec ton ic s t r u c t u r e s a c t w e d u r i n g the Q u a t e r n a r y </p><p>are related to the Cfidiz-Alicante dextral frac- ture-line which is connected to the Azores trans- form fault </p><p>Thus there is a highly-variable geodynamic pattern during the Quaternary in south Spain (Zazo et al., 1990) from areas trending to uplift with a staircase of marine terraces in Almerla (Goy and Zazo, 1986) to subsiding areas both on the Atlantic side and the Oval of Valencia where large complexes of beach barriers and lagoons developed. </p><p>The studied area is important for understand- ing global and regional phenomena because of its proximity to the Gibraltar Strait Two important phenomena which occurred during glacial-inter- glacial periods affected the deposition of marine Quaternary deposits. Firstly, migrations through the Strait of both warm fauna coming from the equatorial Atlantic Ocean and cold fauna. Sec- ondly, the differences in the exchange of Atlantic and Mediterranean water-masses during glacial and interglacial periods (Abrantes, 1988) greatly changed the coastal processes which, in one way or another, are related to the incoming current and the clock-wtse (anticyclonic) vortexes that it produces in the Alborfin Sea (Somoza et al., 1991) </p><p>Sea-level highstands in the last 200 ka in Spain, reference episodes and isotopic measurements </p><p>Four morpho-stratlgraphic m a r i e units bear- mg warm fauna including Strombus bubonius have been distinguished in the southeastern Spanish littoral Distinctive criteria were geomorphologi- cal mapping, sedimentological and neotectonlc studies (Goy and Zazo, 1986, 1988; Bardaji et al , 1986, Somoza, 1989) coupled with isotopic mea- surements (Bernat et al , 1982; Bruckner, 1986; Hillaire-Marcel et al., 1986, Goy et al., 1986), These episodes have been named T-I (Tyrrhenian I, age ca. 180 kyr), T-II (ca. 128 kyr), T-III (ca. 95 kyr) and T-IV. The youngest, fourth episode (T- IV) has not been dated so far (Zazo and Goy, 1989). </p><p>The same units crop out in the Balearic lit- toral, but S. bubomus is present in the deposits of the two older episodes (T-I and T-II) only In situ </p></li><li><p>LAST INTERGLACIAL IN THE MEDITERRANEAN AS A MODEL FOR THE PRESENT INTERGLACIAL 111 </p><p>S bubonius do not occur in T-III (although there are reworked remains); however, T-Il l bears the warm fauna, represented by in situ Conus testudt- nanus, which usually accompanies S. bubontus. The youngest episode (T-IV) yields abundant Acar plicata, a fossd that lacks chmatic slgmfl- cance. Thus, no climatic inference may be drawn about T-IV, but it is interesting to note that Acar phcata has not been found in the Holocene de- posits of the Balearlc Islands (Cuerda, 1989, Goy et al., m press) deposited under condmons some- what colder than the Tyrrhenian events </p><p>So, there are three well-dated peaks of maxi- mum sea level, or highstands (T-I" Isotopic sub- stage 7a, T-II: isotopic substage 5e, T-IIl: isotopic substage 5c). The episode equivalent to T-IV probably corresponds to the isotopic substage 5a (Hillalre-Marcel et al , 1986; Zazo et al., 1991) </p><p>In addition, there are three peaks of maximum sea level during Holocene time Hj ca 5100 yr B P., H z ca. 3500 yr B.P. and H 3 ca. 2400 yr B.P. (Somoza et al , 1991) </p><p>Factors controlling the geometry and three-di- mensional arrangement of marine and terrestrial deposits </p><p>Several factors (sea level changes, tectonics and oceanography, Including geoidal and steric changes and coastal dynamics) interacted during the generahon of these morphostratlgraphic units. Each factor shaped one or more particular as- pects of the resulting sediment (Zazo et al , 1990). </p><p>Sea-level changes cause sedimentation in a given locality to be discontinuous, because it is alternatively exposed or flooded during succeed- ing oscillations. This is true in both vertical and horizontal directions In our case study, only coastal and shallow marine sediments are ob- served because those of other stages including lowstands are under the present level of the Mediterranean Sea. And this, only in the situa- tions where no post-deposltional sinking has taken place. </p><p>Three main peaks indicative of three sea-level highs (hlghstands) are recorded on the Spanish coasts during the Last Interglacial. They corre- spond to the morpho-sedlmentary Tyrrhenian </p><p>Z C) &gt; uJ uJ </p><p>T H II III IV </p><p>5e </p><p>, ~a z / ~ ~12BKy 5 ~ 5100y 2400y TIME &lt; &gt; &lt; 3..~y </p><p>LAST INTERGLACIAL PRESENT INTERGLACIAL </p><p>Fig 2 Hlghstand peaks of the Last Interglacial and Holocene w~th the posltwe oscdlatlons ms,de the isotopic substage 5e, and the Holocene (Spanish httoral) T = Tyrrheman (II, III, IV), H = Holocene (1, 2, 3) </p><p>units T-II, T-III and T-IV, deposited during a tlme span of some 45,000 yr. Several smaller oscillations can be distinguished inside each of these units (Zazo and Goy, 1989) which can be mapped in the area of Almerfa (locality 4, Fig 1). There are at least three such oscillations, with an presumed average duration of some 10,500 yr each, within the peak T-II (5e, Fig. 2). </p><p>As the positive variations of sea level (H 1, H2, and H 3) recorded during the present Interglacial (Holocene) are much shorter than these of the Last Interglacial, we infer that they are actually smaller-scale fluctuations (2500-1100 yr cycles) within the first oscillation (duration: ca 10,500 years) of the first Holocene peak of sea level which, if we take the Last Interglacial as a refer- ence, has not yet been completed (Fig. 2). </p><p>The tectomc factor, visualized as rates of uphft and (or) subsidence, has a longer-lasting effect (but this does not imply that it will retain the same value with time) which is superimposed upon those previously cited. </p><p>Its main effect is to control the vertical and lateral arrangement of morpho-sedimentary units, which can be termed the stratigraphlc architec- ture. As discussed later, variable rates of vertical movements will induce dramatic changes of archi- tecture. </p><p>Areas with tectonic uplift will be characterized by staircased, progradlng gravelly beaches (high- stands) separated by subaerlal or fluvial erosional </p></li><li><p>TA</p><p>BL</p><p>E 1</p><p>Geo</p><p>met</p><p>ries</p><p> an</p><p>d s</p><p>edim</p><p>enta</p><p>ry m</p><p>od</p><p>els </p><p>of </p><p>Ty</p><p>rrh</p><p>eman</p><p> mar</p><p>ine </p><p>un</p><p>its </p><p>as r</p><p>elat</p><p>ed t</p><p>o te</p><p>cto</p><p>mcs</p><p> an</p><p>d d</p><p>ista</p><p>nce</p><p> to </p><p>the </p><p>sou</p><p>rce </p><p>of </p><p>sed</p><p>imen</p><p>t (m</p><p>od</p><p>ifie</p><p>d a</p><p>fter</p><p> Zaz</p><p>o e</p><p>t a</p><p>l, </p><p>1990</p><p>) </p><p>MED</p><p>ITER</p><p>RA</p><p>NEA</p><p>N (</p><p>m~c</p><p>rotid</p><p>al) </p><p>ATL</p><p>AN</p><p>TIC</p><p> B</p><p>AS</p><p>INS</p><p>/SU</p><p>BB</p><p>AS</p><p>INS</p><p> (m</p><p>esot</p><p>idal</p><p>) E</p><p>xter</p><p>nal b</p><p>ound</p><p>ary </p><p>(mar</p><p>me-</p><p>terr</p><p>estn</p><p>al </p><p>ALI</p><p>CA</p><p>NTE</p><p> - M</p><p>UR</p><p>CIA</p><p> M</p><p>UR</p><p>CIA</p><p> A</p><p>LME</p><p>RIA</p><p>- N</p><p>IJA</p><p>R </p><p>lrans</p><p>ltlon</p><p>) </p><p>SE</p><p>DIM</p><p>EN</p><p>TAR</p><p>Y </p><p>MO</p><p>DE</p><p>LS </p><p>MA</p><p>R M</p><p>EN</p><p>OR</p><p> (2)</p><p>BA</p><p>RR</p><p>IER</p><p> IS</p><p>LA</p><p>ND</p><p>- L</p><p>AG</p><p>OO</p><p>N </p><p>LA M</p><p>ATA</p><p> (1) </p><p>BA</p><p>RR</p><p>IER</p><p> IS</p><p>LAN</p><p>D- </p><p>LAG</p><p>OO</p><p>N </p><p>I r </p><p>AS</p><p>SO</p><p>CIA</p><p>TED</p><p> B</p><p>EA</p><p>CH</p><p>ES</p><p>CO</p><p>PE</p><p> (3)</p><p>FAN</p><p> DE</p><p>LTA</p><p>S </p><p>~r </p><p>ALL</p><p>UV</p><p>IAL </p><p>FAN</p><p>S </p><p>DA</p><p>LLA</p><p>S (4</p><p>) </p><p>GR</p><p>AV</p><p>EL </p><p>BE</p><p>AC</p><p>HE</p><p>S </p><p>BA</p><p>Y O</p><p>F C</p><p>AD</p><p>IZ (5</p><p>) </p><p>BA</p><p>RR</p><p>IER</p><p> IS</p><p>LA</p><p>ND</p><p>- L</p><p>AG</p><p>OO</p><p>N </p><p>CO</p><p>LLU</p><p>VlU</p><p>M </p><p>DIS</p><p>TAN</p><p>CE</p><p> TO</p><p> S</p><p>OU</p><p>RC</p><p>E A</p><p>RE</p><p>A </p><p>(ALO</p><p>NG</p><p> SH</p><p>OR</p><p>E) </p><p>LON</p><p>G </p><p>ME</p><p>DIU</p><p>M </p><p>SH</p><p>OR</p><p>T LO</p><p>NG</p><p> LO</p><p>NG</p><p>TEC</p><p>TON</p><p>IC </p><p>LOW</p><p> SU</p><p>BS</p><p>IDE</p><p>NC</p><p>E </p><p>VE</p><p>RY</p><p> LOW</p><p> SU</p><p>BS</p><p>IDE</p><p>NC</p><p>E </p><p>VE</p><p>RY</p><p> LO</p><p>W U</p><p>PLI</p><p>FT, </p><p>LOW</p><p> UP</p><p>LIFT</p><p> LO</p><p>W S</p><p>UB</p><p>SID</p><p>EN</p><p>CE</p><p> TR</p><p>EN</p><p>D </p><p>TILT</p><p>ING</p><p>CO</p><p>AS</p><p>TAL O</p><p>N LA</p><p>P </p><p>GE</p><p>OM</p><p>ETR</p><p>Y </p><p>RA</p><p>TE O</p><p>F V</p><p>ER</p><p>TIC</p><p>AL </p><p>MO</p><p>VE</p><p>ME</p><p>NT </p><p>(Ple</p><p>isto</p><p>cene</p><p>) D</p><p>educ</p><p>ed fr</p><p>om </p><p>Tyrrh</p><p>en~a</p><p>n T-</p><p>Ill le</p><p>vels</p><p>OFF</p><p>LAP</p><p>@,, </p><p>CO</p><p>AS</p><p>TAL </p><p>ON</p><p>LAP</p><p>T-Ill</p><p> " T</p><p>-I~</p><p> ~ </p><p>STA</p><p>CK</p><p> T-Ill</p><p>:~</p><p>~ </p><p>T-II </p><p>T-I </p><p> S</p><p>UB</p><p>SID</p><p>EN</p><p>CE</p><p>STA</p><p>IRC</p><p>AS</p><p>E </p><p>T-I </p><p>UP</p><p>LIF</p><p>T </p><p>+2</p><p>.25</p><p> cm</p><p>/Ky </p><p>(La</p><p>te P</p><p>leis</p><p>toce</p><p>ne</p><p>) +</p><p>7 cm</p><p>/Ky </p><p>(Lat</p><p>e P</p><p>leis</p><p>toce</p><p>ne</p><p>) -8</p><p> cm</p><p>/Ky </p><p>(Lat</p><p>e P</p><p>leis</p><p>toce</p><p>ne</p><p>) -1</p><p> 2 c</p><p>m/K</p><p>y (L</p><p>ate </p><p>Ple</p><p>isto</p><p>cen</p><p>e) </p><p>Mid</p><p>dle </p><p>Ou/</p><p>l~en</p><p> P</p><p>le~s</p><p>loce</p><p>ne </p><p>-I- </p><p>W </p><p>E </p><p>SU</p><p>BS</p><p>IDE</p><p>NC</p><p>E </p><p>~I~ </p><p>Oul</p><p>jien </p><p>(100</p><p> Ky </p><p>=T</p><p>-Ill)</p><p> -1</p><p> m</p><p>/Ky </p><p>(Lat</p><p>e P</p><p>leis</p><p>toce</p><p>ne</p><p>) </p></li><li><p>L A S T I N T E R G L A C I A L IN T H E M E D I T E R R A N E A N A S A M O D E L F O R T H E P R E S E N T I N T E R G L A C I A L 113 </p><p>surfaces (lowstands), whereas sinking areas will favour the deposition of vertically stacked se- quences with coastal onlap of beach-barrier sys- tems deposits (Table l) </p><p>The coastal dynamics factor largely depends on global sea-level changes which greatly influ- ence the exchange of waters between the Atlantic and the Mediterranean At present, a rapid cur- rent of surface Atlantic waters enters the Mediterranean forming anticyclonic vortexes which reach both the African and the Spanish coasts (Parrilla and Kinder, 1987). Maximum in- cursion of water coincides with periods of maxi- mum insolation in the Mediterranean Sea, when increased evaporation produces differences in sea level on both sides of the Strait of Gibraltar </p><p>The places in which the present circulation pattern reaches the coasts of the Albor~in Sea closely coincide (Somoza et al., 1991) with those yielding the largest number of species of the warm fauna (S. bubonius) and with those where they persisted longest (Almeria and Alicante, lo- calities 4 and 1, respectively in Fig. l) during the Pleistocene. </p><p>The major point about this factor is that it defines and modifies the sedimentological fea- tures and organization of any unit being de- </p><p>posi...</p></li></ul>


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