pp.277·288 Ciencias da Terra (UNL) Lisboa o ( N. 14 7 Figs. 2000 J The Neogene ofAlgarve (Portugal) J. Pals"-'', P. Legoinh a'':", H. Elderfi eld(b,3), L. 8 0 U53(8,4) & M.Estevensv-" Work supported by the Praxis XXI Project "Necgenicc e Quatemaric da margem aua nuce da Iberia e trans fonnao;&s globais" (FCT, MeT), a - Centro de Estudos Geol6gicos, Faculdade de Cienciase Tccnologia. Quinta da Torre, P·2825·114Caparica,Portugal. b - Department of Earth Sciences,University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK. t , [email protected]; 2 . [email protected];3 · helOl@csc,cam.ac.uk; 4 . 1S@ fct.urd,pt; S- eslevens@telcpac_pl A BSTRACT Key-word s: Neogene; Stratigraphy; Algarve; Portugal. A synthesis abou r rhe Neogene and Quaternary ofAlgarve (Southern Portugal) is presented. New isot opic ~ 7S rj86S r ages as well as biostratigraphic data about the Miocene deposits allow to present a new stratigraphic frame for the previously characterized units. The Lagos- Pcrtimao Formation corresponds to depo sits of "temperate carbonate platform " sedimentological type, develope d dur­ ing a long time span (Lower Burdigalian to Upper Serravallian). A major change in sed imentation conditions (carbonate to silic iclastic environments) occurred in the Lower Tortonian with the depos ition of yellowish sands. Spongoliths rich in microfossils are rep resented in Algarve inland. Their age is not well estab lished; calcareous nannofo ssils indicate the CN5a l one (Upper Serravall ian) whi le foraminifera point out at least Nl6 zone (Lo wer Tortonian). In the Upper Tortonian, the sedimentation is widespread in Easte rn Algarve, related with the Guada lqui vir Basin infill. The deposits begin with detrital limestones, locall y very rich in Heterostegina , passing to fossiliferous co nglomerates and siltstones (Cacela Fonnation). Coarse-grained conglomerates at Galvana (Faro) pose some age problems. K/Ar age on glauconite indicates 6.72±O. 17 Ma. However, glauconites may be reworked from older deposits (Cac ela Formation). The Galvana Con glomerate could be related to Pliocene deposits arc not well characterized. Olhos de Ague sands, with a thi n marin e intercalation rich in marine vertebrates (fishes, a crocodile, cetaceans, sircnians), may be Upper Pliocene; howeve r, the verte brates point out to a Serravallian to Tortonian age. " S r~S r ages on oysters from above the level with vertebrates point ou t to 3.0(+2.5-1. 0) Ma. Similar sand deposits occur at Morgadinho (Luz de Tavira). These sands are ove rlain by marls, lign ite clays, lacustrine limestones and a silty calca reous crust. A small mammals association indicate an age span between Upper Pliocene and Lower Middle Pleistocene (M N 17.MN20). A Biharian mammal fauna (Lower Pleistocene) was collect ed at Algoz in similar deposits. In the present stale of kno wledge, Mo rgadinho and Algoz deposits may be correlative. RESUMO Palavras-ch aver Neogenico; Bstratigrafia; Algarve; Portugal. Apresenta-se uma sintese sobre 0 Neoge nico do Algarve. Dataeccs de " S r~ 6 S r, bern como dad os biostratigrafico s de unidades miocenicas, pennitiram 0 estabelecimento de urn novo qua dro estratigrafico para as unidades liticas alg arvias. A Formacao de Lagos -Portimao corrcsponde a depositos sedimentares de tipo "plataforma carbonatada tempera da" que se dcscnvolveu durante urn longo intervalo de tempo (Burdigal iano inferior a Serravaliano superior). Uma mudanca maie r na scdirnentacao (ambie nres silici clasticos) deu-se no Tortonian o inferior com a deposicao de areias finas amarel adas . No interior do Algarve oco rrem espongolitos rieos de microfosseis. A idade nao este perfeitamente definida. Foraminiferos indieam a zon a N16 (Tortoniano inferior) e os Nanofosseis calce nos a zona CN5a (Serra valia no superior). No Tortoniano superior a sedimc ntacao foi mais significativa no Algarve Oriental, em retacac com 0 enchi me nto da bacia do Guadalquivir. Os depositos iniciam-se por calcarios detriticos, locahnentc multo ricos de Ileterostegina, que passam a conglomerados e silt itos muito foss ilifcros (Formacao de Caccia). 277 I" Ccogressc sobre 0 Cenozcico de Portugal o conglomerado grossciro de Galvana (Faro) poe alguns problemas. uatecees KJAr de glauconite indicam 6.72±O. 17 Ma. Todavia, a glauconi te podc tcr sido remobilizada a partir de niveis mais antigos (Formacao de Cacela). Parecem ester relacionados com memento de forte instabilidade tectcruca como 0 da instalacao do olistostroma do Guadalquivir. o Pliocenico nao csta bern caracrcrizado .As areias de Olhos de Ague com uma intcrcalacao marinha pouco espcssa, rica de vertebrados marinhos (peixes, urn crocodile. cetaceos, sircnidoos) possivelmcntc redepositados, pede corrcs pondcr ac inicio do Pfiocenico superior; eontudo , os pcixcs, marnlferos marinhos e 0 crocodile apontam para 0 Serravaliano a Tortoniano inferior. Datacces 17SrJ1"Sr cfecruadas em ostras e em dentes de pcixc fomcccram vatores de 3.0(+2.5-1.0) Ma. Arcias do mesmo tipo ocorrem em Morgadinho {Luz de Tavira). Sao sobrepostasper margas, argilites lignitosos, calcarios lacustres e uma crcsta carbonatada. Os argilites lignitoscs fomeceram fauna de pcqucnos mamiferos corrcspondcnte eo intervale Plioccnico superior a parte inferior do Plisroccnico medic (tvrN 17-MN20). Em Algoz foi recolhida uma fauna datada do Pllstocenlco inferior (Bihariano) em depositos sernelhantes. Epossivcl que as jazidas de Morgadinho e de Algoz sejam correlatives. FOREWORD compression (only locally? - at the Albufeira salt dome); Lower and Middle Miocene N-S and E-W distension; The first studies about the Cenozoic ofAlgarve dealt Tortonian N-S co mpression; post-Messinian E·W only with some fossil localities and deposits (Pereira da compression; N-S compression during the Quaternary. Costa, 1866 ; Dollfus et at., 1903·1904; Bourcan & Zbyszcwski, 1940; Chavan, 1940; Zbyszewski, 1948; 1950). Table I • nSrJ1"Sr results. In 1979, M.T. Ant unes and 1. Pais, carried out stratigraphic studies on the Neogene ofAlgarve (Research line n" I of the former "Centro de Estratigrafia c Loulil. Lnra liti.. Sam p. .\ h "S rrSr .,. Paleobiologia da Universidade Nova de Lisboa"}, Some o· , 9.g('d.5) 0,708903 0.000024 synthetic interpretations have been published (Antunes et , Alje,u' , 12.6(+0.9·0.g) 0,70n50 0.000020 aI., 1981; Antunes et aI., 1990; Antunes et al., 1992). New Fu,oa Ama,ela , 11.9(t{l,8) 0 ,70 g ~67 0.0000t 8 developments have been achieved concerning mainly 87Srl a AljJ lgreja Nc.'a 16.9(-'0.3) 0.708701 0.000018 !IIISr isotopic dating at the Department of Earth Sciences a Alje,u' , 18.5(-'0,3) 0.70860S 0.000017 of Cambridge University (Table 1, Fig. 1). A revision is IG;mnodesponivo , 19.5(+0.3.0,2) 0,70gSn 0,000017 OO21סס. under way taking into account all the available data, and • Sag'.. 12.0(+1.3·1.3) 0 ,70 g ~~6 0 specially isotopic ages, micropaleontology and sequence 12.5(+0.S·0.7) 0,70gS50 0.000047 stratigraphy analysis. 5 Za,;.1 16.2(+0.5'0.5) 0.708734 0.00002 1 At the present status ofknowledge, the Neogene units , 17.S(+0.7_0.7) 0,708653 0.000026 characterized so far are mainly of Miocene age and mostly , 16.3(+0.S-0.3) 0,708737 0.000020 marine. They range from Lower to Uppermost Miocene. 6 Praia do C.o",;al • 14.3(+0,S·0.5) 0.708 ~04 0.000017 OO1 8סס. However, there are lithological differences. Olhos de Agua s 15.l(+0.S.0.5) 0,108771 0 OO1 8סס.sands could be ascribed to the Pliocene based on ~ 7Srfl6Sr , Alb"de;ra 5.5(+4,1'0.1) 0,708959 0 dating, bu t this needs to be confir med . T hose of a 12.2(+1.2.1.3) O,708S60 0.000018 Morgadinho (Antunes et at.; 1986e) may (at least in part) a P,aia d. Roeh , 11.5(+0.8·0.5) 0,708815 0.000026 be Pliocene in age. " 10.1(+0.8.1.2) 0,708SS6 0.000018 The Neogene units so far recognized in Algarve are 9 Albaodei.. W, 15.5(-'0.4) 0.108763 0.000017 shown in the Fig. 7, and will be discussed by chronologi­ W. 16.3{+0.4·0,5) 0,108799 0.000017 cal order. rc Gal'; 11.J{+0.9.1.3) 0.108n O 0.000024 Pereira de Sousa (1917; 1918; 1922) admitted the pres­ P,.i. do C."elo , 15.5{+0.8·0 ,3) 0.108759 0,000017 ence ofMiocene igneous rocks in Algarve although these " i9.5{+0.2-0,3) 0.70851S 0.000017 An iflo , 19.2(+0.2_0,4) 0.108553 0.000018 were not found later. In 1971, a small basanite outcrop " , 14.2{+0.6-0.4) 0 .10 ~801 0,000020 enclosed by Miocene biocalcarcnites was detected, show­ 8.3(+2.2-3.3) 0.708922 0,000021 ing clear evidence of low grade thermal effects on the sedi­ • , 14.4(+0.5-0,6) 0.108804 0.000017 mentary rocks along the contact with the igneous dike. u S'o,.Eul.lli. z 14.6(+0.5·0,6) 0.708799 0,000017 This rock represents the latest volcanic activity in Portugal , 15,5(-'0.4) 0.70876l 0,000017 (Pinto Coelho & Bravo, 1983). However, Cenozoic 110,el Au"m" z 9.S(+1.O.0.5) 0.708907 0.000016 volcanic activity is well known in Southern Spain, since " Olho, de Asu' 14.6(_0,4+1.4) 0.708797 0,000020 Langhian-Scrravallian till the Quaternary. " Arei.,lOlhos 3,0(+2,S_1.0) 0.709044 0,000048 Tectonic structures concerning the Mesozoic and " A . , , 5.2(+4,('{l.6) 0.708961 0.000014 Cenozoic deposits ofthe Algarve basin allow to recog­ Quclfe, , 5.2(+4.4.