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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Review of Palaeobotany and Palynology 162 (2010) 325–340 Contents lists available at ScienceDirect Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo Research paper Floristic and vegetational changes in the Iberian Peninsula during Jurassic and Cretaceous Carmen Diéguez a,⁎, Daniel Peyrot b, Eduardo Barrón c a Departamento de Paleobiología. Museo Nacional de Ciencias Naturales-CSIC. José Gutiérrez Abascal 2, 28006 Madrid, Spain b Departamento y UEI de Paleontología UCM-CSIC , José Antonio Novais 2, 28040 Madrid, Spain c Instituto Geológico y Minero de España, Ríos Rosas 23, 28003 Madrid, Spain article info abstract Article history: The successive vegetations inhabiting the Iberian Peninsula from the Triassic/Jurassic boundary to the Cretaceous/ Received 3 July 2009 Tertiary Boundary is reviewed based on published palynological and macrofloral data, and the vegetational changes Received in revised form 24 May 2010 set in a palaeogeographical and climate context. Xerophytic microphyllous coniferous forests and pteridophyte Accepted 4 June 2010 communities of arid environments dominated the Jurassic and earliest Cretaceous vegetation. This vegetation was Available online 17 June 2010 replaced in the mid Early Cretaceous by mixed forests of pteridophytes, gymnosperms and angiosperms. The composition of the successive plant assemblages suggests that a subtropical arid climate generally prevailed in the Keywords: – Jurassic Iberian Peninsula during Jurassic Cretaceous, although palaeobotanical and sedimentological evidences suggest that Cretaceous the climate was not uniform through the whole interval and that were two episodes in the Tithonian–Berriasian and palynoflora Aptian–Albian periods of pronounced dry and/or arid environmental conditions. The composition and structure of macroflora the vegetation was not only affected by evolutionary changes but also by successive global geographical and climate vegetation changes. Hence, significant changes in the distribution of continental areas during the Mesozoic resulted in the latitudinal or sublatitudinal extensions of the climatic belts. © 2010 Elsevier B.V. All rights reserved. 1. Introduction regularity that may be observed in the floras of the Jurassic and Cretaceous, involving the invasion of certain subtropical elements that The Iberian Block remained joined to Laurasia after the break-up of benefited from the rising temperatures of the warm belt. However, during Pangea, beginning of the Jurassic a system of shallow platforms (Gómez Uppermost Jurassic–Lowermost Cretaceous interval the subtropical and Goy, 2005). Throughout the Jurassic the Iberian Block was situated vegetation of this climate belt was never fully replaced. between 20° and 30° N paleolatitude, approximately at the level of the From the T/J (Triassic–Jurassic) to the K/T (Cretaceous–Tertiary), there current Tropic of Cancer (Smith et al., 1973). On the exposed landmasses is a successive change in vegetation structure correlated with a change in of these low palaeolatitudes deserts were formed. Later, in the Late systematic composition. Major floristic changes are particularly mani- Jurassic, the Iberian Block was displaced towards higher and more humid fested in two events that revolutionized terrestrial plant ecosystems: (i) a palaeolatitudes where seasonal dry or winterwet conditions prevailed global increased in abundance and systematic diversity of conifers, mainly (Hallam, 1984; Ziegler et al., 1993; Rees et al., 2000; Willis and McElwain, extinct conifers assignable to the Cheirolepidiaceae as well as other 2002). During the entire Jurassic–Cretaceous time interval, the lands that gymnospermssuchasCycadales,Bennettitales and Ginkgoales. This was today constitute the Iberian Peninsula were partially submerged and associated with a decrease in pteridophytes and pteridosperms diversity separated from the Laurasian continent by the Proatlantic and the Tethys (Willis and McElwain, 2002; Kenrick and Davis, 2004); (ii) the emergence Sea. The exposed land areas were islands with low relief. of angiosperms, their rapid diversification and colonisation of almost all The extensive changes in the distribution of exposed landmasses, continental environments (Hughes et al., 1979; Hughes and McDougall, gave rise to changes in the latitudinal or sublatitudinal extension of 1987; Lidgard and Crane, 1988, 1990; Crane and Lidgar, 1989). climatic belts, which induced large-scale climate perturbations that Palaeobotanical data for the Jurassic of NW areas of the Euro-Sinian modified both the composition of floras and the plant cover of vast areas. Region (sensu Vakhrameev, 1991) are much more abundant than for the Global climate changes had more pronounced effects on floras Iberian Peninsula (Batten, 1996; Batten and Koppelhus, 1996; Barale, inhabiting the bordering areas between the tropical and warm-temperate 1981; Thomas and Batten, 2001; Cleal et al., 2001; Cleal and Rees, 2003; climate belts (Krassilov, 1981). Meyen (1987) noted an interesting van Konijnenburg-van Cittert, 2008) due to the scarcity of macro and microfossils in most sediments dated as Early and Middle Jurassic. However, it is also true that the Mesozoic plant fossils of Spain or Portugal ⁎ Corresponding author. have not enjoyed the traditional interest shown in other European E-mail address: [email protected] (C. Diéguez). countries. 0034-6667/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2010.06.004 Author's personal copy 326 C. Diéguez et al. / Review of Palaeobotany and Palynology 162 (2010) 325–340 In the Iberian Peninsula the first palynological study about the SC515 and observed with SEM. The specimens were measured Cretaceous was carried out by Groot and Groot (1962) on sediments with a Measuroscope Nikon and with stereoscopic microscope from Estremadura (Portugal) and by Menéndez Amor and Esteras Leica MZ 16A and Nikon DS-FI1 with the program Nikon NIS- (1964) on Aptian–Albian lignites from the Utrillas Basin (Spain). The Elements. Photography and examination of specimens were made first Iberian Jurassic palynomorphs were studied by Riley (1974) from with an Olympus Zeiss stereomicroscope. In addition, some sediments of the Lusitanian Basin (Portugal). material was examined with a Quanta 200 scanning electron The first study of Portuguese Mesozoic macrofloras was performed by microscope at 25 kV. Hand samples were photographed with a Heer (1881). Later these macrofloras were revised and completed by Canon Eos 300D digital camera under low-angle incident light. Saporta (1894) and Teixeira (1948, 1950, 1952), lacking posterior revisions of Cretaceous macrofloras as a whole while Jurassic floras Geological ages and divisions follow the International Commission were revised by Pais (1974, 1998). Although the studies of Teixeira on Stratigraphy (ICS) and International Union of Geological Sciences provided a wide overview on Mesozoic Portuguese floras, the ages of most (IUGS) (Gradstein et al.,2004). The ages proposed by the authors of the Lusitanian outcrops remain uncertain. Early and Late Cretaceous meso- papers consulted were honoured. To facilitate the discussion of the plant floras from Lusitanian Basin has been extensively studied (Eriksson et al., fossils we grouped the fossil microfloras according to their stratigraphic 2000; Friis and Pedersen, 1996; Friis et al., 1992, 1994, 1997, 1999, 2000a, occurrence. Macrofloral data are presented according to their age and 2000b, 2003, 2004, 2009a, 2009b; Mendes et al., 2008a, 2008b; Pedersen, the different outcrops studied. We calculated the taxa richness by et al., 2007; Rydin et al., 2006; Schönenberger et al. 2001; von Balthazar et counting one organ per plant group of every outcrop and present this al., 2005). A thorough synthesis of Cretaceous mesofossils and pollen in variable according to the main suprageneric taxonomic groups. Out- situ from Lusitanian Basin was recently carried out by Friis et al. (2010). crops for which only a single species has been described were omitted. Macrofloras from Jurassic and Cretaceous of Spain are known from the pioneer work by Zeiller (1902) on few compressions from Montsec 3. Jurassic vegetation outcrops (Lérida province). More than fifty years later, Depape and Doubinger (1956–1960) described the first complete floral assemblage 3.1. Palaeogeographical remarks which compares with Wealden floras. From the seventies, studies of Spanish Cretaceous floras have been sparse and most of them focused on During Jurassic (Fig. 1A, B) large proportions of the central and the description of new taxa. Despite these studies, most of Iberia's western Iberian plate formed an emergent massif (the so-called Jurassic and Cretaceous floras are still not fully known, and most of them Iberian Massif),