1 Holocene desert coasts and its topographical control,

2 analogues for the mid-Cretaceous of northern Iberia;

3 complex desert sedimentology and palaeohabitats

4 Juan Pedro Rodríguez-López1, Daniel Peyrot2,3, Eduardo Barrón4

5 1Calle Mascaraque, 48, 2ºA, 28044, Madrid.

6 2School of Earth and Environment, University of Western Australia. 6101 Crawley, Western Australia.

7 3Centre for Energy Geosciences, University of Western Australia. 6101 Crawley, Western Australia.

8 4Museo Geominero, Instituto Geológico y Minero de España (IGME), Ríos Rosas 23, E-28003 Madrid,

9 Spain.

10

11 Corresponding Author:

12 Dr. Eduardo Barrón

13 Museo Geominero, Instituto Geológico y Minero de España (IGME), Ríos Rosas 23, E-28003 Madrid,

14 Spain.

15 [email protected]

16

17

18 Abstract

19 Desert coasts in plate margins contain one of the most variable sedimentary records in

20 terms of facies and stacking patterns. Reliefs in these basins together with massif

21 palaeogeography and palaeotopography strongly control the spatial distribution of facies

22 belts and complex lateral facies changes between very different coeval sub-

23 environments, leading to mixtures of sedimentary particles with variable composition.

24 Palaeotopography and palaeogeography also control the distribution of flora

25 palaeohabitats in the desert basins depending on the spatial distribution of fresh water,

1

26 the basin geometry, the topographic variability and associated phreatic level, as well as

27 the effective distance from highlands to the coast. The Albian desert basin that

28 developed in northern Iberia presents similarities with the geomorphology of modern

29 Oman and Eritrea desert coasts. In both systems (Cretaceous and Holocene) the distance

30 between highlands and arid coastline determines the occurrence of extensive aeolian

31 sand seas (e.g. wide desert basin where distance between the highlands and the coastline

32 increases) or the development of wadi-fed alluvial fans that reach directly the desert

33 coast (e.g. narrow desert basin) leading to a variety of clastic and mixed carbonate

34 facies. Due to prevailing arid conditions, vegetation is restricted to highlands and water-

35 conditioned lowland environments such as wadis, (tidal) coastal marshes and lagoons.

36 Depending on sea influence and water availability, Cretaceous vegetation in Iberia were

37 characterized by montane communities including arboreal/shrubby gymnosperms

38 (mainly conifers) and lowland communities composed by a patchy mixture of ferns,

39 Cupressaceae (cypress family), Cheirolepidiaceae and early angiosperms and/or costal

40 woodlands incorporating Araucariaceae (monkey puzzle tree family). This distribution

41 matches with the ecosystems observed today in Eritrea mountains and other Holocene

42 desert coasts.

43

44 Keywords: desert basins, sediments, plate margin, palynology, vegetation.

45

46

47 1. Introduction; Desert basins and its palynological record.

48 Desert basins located close to the coast line represent complex depositional systems

49 hosting variable sedimentary successions and multifaceted vegetation types. In this

50 setting, the prevailing role of erosional processes and frequent occurrence of flash

2

51 floods generate facies with highly variable characteristics and usually low and

52 heterogeneous organic content (Stanistreet and Stollhofen, 2002). The spatial and

53 temporal variability of the operating depositional regimes and the poor representation of

54 plant debris hampers (bio-)stratigraphic inferences and paleoenvironmental

55 reconstructions (Rodríguez-López et al., 2014). As a result, the link between

56 palaeobotany and stratigraphic architecture and cyclicity of pre-Quaternary desert

57 systems have not been extensively studied. The early Albian–early Cenomanian desert

58 system recognized in eastern Iberia and represented by the Utrillas Group is a notable

59 exception (Rodríguez-López, 2008; Rodríguez-López et al., 2008, 2009, 2010, 2012a,

60 2013). The present work focuses on a desert system that developed in the Basque-

61 Cantabrian Basin (BCB), northern Spain, during the late Albian (Barrón et al., 2015)

62 representing the northern edge of widespread arid-desert zone recognized in the

63 Northern Hemisphere.

64 The location of the studied system in a relief-controlled basin and the proximity to the

65 coast led to complex interbedding of marine deposits and aeolian tongues similar to

66 Quaternary desert basins located nowadays in the Arab Gulf and Eritrea in the western

67 margin of the Red Sea where the distribution of vegetation is directly controlled by

68 desert basin topography altitude and distribution of water.

69 Palynological studies of ancient desert successions are very scarce as palynomorphs are

70 usually not preserved in coarse-grained lithologies constituting the bulk of the deposits.

71 Palynological assemblages integrate elements proceeding from different environments

72 and the varying proportions of terrestrial, freshwater and marine palynomorphs allow to

73 draw reliable inferences concerning the depositional setting. In marginal or open marine

74 depositional sequences, the relative proportion of terrestrially-produced palynomorphs

75 will depends on the distance from shoreline, the frequency and nature of fluvial

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76 discharges, and on proprieties directly related with the marine water masses such

77 salinity, water depth and levels of nutrients which are difficult to determine.

78 Additionally, distal pollen assemblages may be affected by complex taphonomic factors

79 involving turbulence and mixing processes generated by ocean currents (Matthiessen et

80 al., 2005). Notwithstanding, high proportion of dinocysts have been traditionally

81 regarded as indicative of open marine depositional settings (Davey and Rogers, 1975)

82 while abundant acritarchs have been previously used to infer stressful and/or high

83 energy, near-shore, marine Mesozoic environments (Schrank, 2003).

84 The correspondence between pollen assemblages and vegetation has been highlighted

85 for a long time (Von Post, 1916) and a careful examination of the pattern of dispersion

86 of their constituting elements allows to build robust inferences on depositional settings.

87 Albian assemblages with abundant pollen from flowering plants will characterize

88 depositional settings in close proximity from the source area as insect-pollinated grains

89 are not widely dispersed by water and wind (Taylor and Hu, 2010). Conversely,

90 abundant bisaccate pollen grains will characterize more distal assemblages and reflect a

91 more regional vegetation (Mudie and McCarthy, 1994, 2006).

92 The main objectives of this paper are (i) to review the complex processes and products

93 of relief-controlled narrow desert basins, from a multidisciplinary approach combining

94 sedimentology, stratigraphy and palaeobotany, (ii) to compare the Holocene analogues

95 here proposed with the Cretaceous example from Iberia, (iii) to propose a model that

96 will help to understand other Phanerozoic coastal desert systems and their

97 palaeohabitats.

98

99 2. Geological and palaeogeographic setting

4

100 The study area (Fig. 1A) is located in the Basque Cantabrian Basin (BCB), in the

101 Cantabrian Range, which is an E-W trending narrow range that constitutes the western

102 sector of the Southern Pyrenees (Capote et al., 2002), where the regional stratigraphy of

103 the studied area includes Mesozoic, Paleogene and, Neogene units (Martínez-Torres et

104 al., 2003; García-Mondéjar et al., 2004). The BCB developed on thinned continental

105 crust between the European and Iberian plates during the Cretaceous Period. The

106 evolution of this sedimentary basin is related to the kinematic relationship between both

107 plates and with the opening of the North Atlantic Ocean and the Bay of Biscay (Martín-

108 Chivelet et al., 2002). The mid-Cretaceous Iberian Desert System is represented by the

109 Utrillas Group widely outcropping in N and E Spain (Rodríguez-López, 2008). The

110 studied sections of the Utrillas Group are restricted between two main key supraregional

111 correlation datums (Fig. 1C) corresponding to (i) the stratigraphic contact between the

112 Escucha Formation and the Utrillas Group (Rodríguez-López, 2008; Rodriguez-Lopez

113 et al., 2013) and (ii) the early Cenomanian transgressive deposits that led to the

114 disappearance of the desert system in Iberia leading to the development of a broad and

115 extensive carbonate platform (Chivelet et al., 2002). The surface separating the coal-

116 bearing Escucha Formation from the Utrillas Group is a supraregional unconformity

117 that has been recognized in the eastern part of the Iberian Plate and marks the initiation

118 of the desert system (Rodríguez-López et al., 2009, 2013). The Iberian Desert System

119 accumulated in two main depositional areas: the northern part of the Iberian Plate

120 (Basque-Cantabrian Basin) and the eastern part of the plate (Iberian Basin) (Fig. 1A).

121 The latter, outcropping along the Iberian Range (eastern Spain, Fig. 1A) formed while

122 Iberia was located at a palaeolatitude of 25º–30º N in a northern subtropical high-

123 pressure system called the Northern-Hemisphere Hot Arid Belt (Fig. 1B; Chumacov et

124 al., 1995; Stampli and Borel, 2002; Spicer and Skelton, 2003; Rodríguez-López et al.,

5

125 2006, 2008). The desert system of the BCB was located further north at the junction

126 between the Northern-Hemisphere Hot Arid Belt and the Northern Mid-latitude Warm

127 Humid Belt (Fig. 1B) (Rodríguez-López et al., 2006, 2010). It received ephemeral

128 waters from the Variscan Massif and leading to the erosion of aeolian dunes, while wind

129 action formed desert pavements with well-developed ventifacts (Rodríguez-López et al.,

130 2010). The north-eastern part of the desert system received a more significant marine

131 influence (Rodríguez-López et al., 2012a) and the Tethys received large volumes of

132 windblown sand from the erg-margin system (Rodríguez-López et al., 2006). The close

133 proximity of the Tethys favoured a high water-table, which contributed to the

134 preservation of the aeolian facies, and to a variety of associated depositional

135 environments, including subtidal deposits, playa lakes, coastal lakes with tidal creeks

136 and marshes, and lagoonal embayments with tide-influenced delta deposits (Rodríguez-

137 López et al., 2012a). The presence of in situ, local, vegetation, probably growing along

138 wadis and in coastal areas has been previously inferred on the basis of indirect evidence

139 including root traces in interdune margins and coaly mudstones in coastal marshes

140 (Rodríguez-López et al., 2010, 2012a). Coetanous mid-Cretaceous desert systems have

141 been recorded in other locations of the Northern Hemisphere including China and

142 Northern Africa (Hasegawa et al., 2012; Newell et al., 2015). While similar in their

143 facies expression, the development of these systems is thought to have been initiated by

144 distinct palaeoenvironmental forcings. The expansion of desert systems in China has

145 been associated with a drastic shrinking of the Hadley cells (Hasegawa et al., 2012)

146 while the origin and evolution of the Iberian (Rodríguez-López et al., 2006) and

147 Northern African Albian desert systems (Newell et al., 2015) are currently interpreted to

148 result from a conjunction of allogenic controls acting at subtropical latitudes, and

149 including the expansion and northward shift of the Northern Hemisphere Hot Arid Belt

6

150 (Chumakov et al., 1995; Rodríguez-López et al., 2006, 2008; Hay and Floegel, 2012).

151 The position of the Iberian Basin and the BCB in the rain shadow of the Variscan

152 Massif may have probably enhanced the arid conditions of the Iberian Desert System

153 (Rodríguez-López et al., 2010) when compared to their Atlantic counterparts (e.g.

154 Horikx et al., 2016).

155

156 3. Materials and methods

157 About 260 m of stratigraphic series of the Utrillas Group have been logged in detail in

158 order to determine facies and facies associations as well as to carry out a systematic

159 sampling for palynological analysis (Fig. 2). The sections are located in four different

160 outcrops (Fig. 1A), where the recognition of major bounding surfaces (Sand-drift

161 surfaces [SDS] sensu Clemmensen and Tirsgaard, 1990) allow to establish a robust

162 stratigraphic framework. Facies associations have been described and interpreted based

163 on standard desert depositional systems nomenclature (see Rodríguez-López et al.,

164 2014).

165 The application of traditional sequence stratigraphic concepts in pure aeolian, mixed

166 aeolian-fluvial and mixed aeolian-marine systems is challenging (Rodríguez-López et

167 al., 2014). Although detailed attempts have been carried out (Mountney, 2006b; Bállico

168 et al., 2017) and new surfaces nomenclatures have been proposed (see Rodríguez-López

169 et al., 2013) sequence stratigraphy remains not robustly constrained in these

170 depositional systems and their application remains subject to caution. For this reason,

171 the word “sequence” has been preferentially used over “cycle" and is here used in a

172 general sense. Every sequence contains "intervals" (e.g. prograding and retrogradding

173 intervals) defined on the basis of facies stacking pattern and spatial distribution with

174 respect to the underlying and overlying sedimentary packages. The palynological

7

175 content of suitable (e.g. fine-grained) material has been characterized for 5 successions

176 distributed in the Peñacerrada (successions IP and IIP), Salinillas de Buradón

177 (successions SB and SF) and Pancorbo (PAN) outcrops (Figs. 1–2). The palynomorphs

178 constituted assemblages detailed in Barron et al. (2015). The palaeoecological and

179 botanical groupings of the palynological data followed Jolly et al. (1998), Abbink et al.

180 (2004) and Peyrot et al. (2007).

181

182 4. Palyno-sedimentary analysis of desert environments

183 The description and interpretation of main facies associations cropping out in the

184 Atlantic margin of the desert system are presented succinctly and follows the more

185 comprehensive treatment detailed in Rodríguez-López et al. (2006, 2007b, 2008, 2010,

186 2012a, 2013). Four Facies Associations (FA) have been recognised and summarized in

187 Table 1 and facies details can be observed in Figures 3, 4 and 5. We include here also

188 the description of the palynological record for every facies association in order to

189 integrate both approaches. The palynomorphs from the studied outcrops show diverse

190 assemblages mainly consisting of dinocysts (22 taxa identified), spores (101 taxa),

191 gymnosperm (40 taxa) and angiosperm pollen grains (66 taxa) and the most relevant

192 species are illustrated in Figure 6. The detail listing has been provided in a companion

193 paper (Barrón et al., 2015) and only the palynological data relevant for the present study

194 will be presented and discussed. Figures 7 and 8 show, sequence by sequence, the

195 stratigraphic correlation, facies distribution and palynological data discussed in detail in

196 chapter 5.

197

198

199 4.1. Facies Association 1: Aeolian Facies Association

8

200 This Facies Association is interpreted as an aeolian facies association, Facies 1A and 1B

201 (see Table 1) representing aeolian sandsheet and aeolian dune deposits, respectively

202 (Fig. 3A–D). This interpretation is based on the presence of subcritically climbing

203 translatent strata formed by wind ripple migration characterizing the aeolian sandsheets

204 (Fryberger et al., 1983; Veiga et al., 2002; Mountney 2004, 2006a, 2006b). Facies 1A

205 also show low-angle lamination that has been previously recognized as a component of

206 aeolian sandsheet strata (Fryberger et al., 1992; Kocurek and Nielson, 1986; Rodríguez-

207 López et al., 2012b). The inclined tabular and regular strata observed in aeolian Facies

208 1B formed aeolian dune foreset deposits consisting of grain flow sediments arranged in

209 strata packages 2–3 cm thick and several m-long suggesting sedimentation on well-

210 developed slip-faces and probably belonging to transverse/crescentic dunes (Stewart,

211 2005; Rodríguez-López et al., 2008). In these facies, the sharp surfaces separating large-

212 scale cross-bedding, slightly inclined to the stoss-side of the paleodunes are interpreted

213 as dry interdune bounding surfaces (e.g. Rodríguez-López et al., 2008). The absence of

214 conformable sediments with these surfaces suggests dry interdune sedimentation in a

215 climbing aeolian system (e.g. Kocurek, 1991; Fryberger, 1993; Mountney and

216 Thomspon, 2002).

217 The coarse grain nature of deposits characterizing Facies 1A and Facies 1B

218 represent adverse conditions for the preservation of organic matter. Pleistocene and

219 Holocene aeolian facies contain organic assemblages limited to small plant fragments

220 and are usually devoid of palynological material (Fægri and Iversen, 1975; Danielsen et

221 al., 2012).

222

223 4. 2. Facies Association 2: Wadi Facies Association

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224 This facies association is interpreted as representing sedimentation in wadi channels

225 (Figs. 3A, E and F). The occurrence of fine-grained sandstones with floating quartzite

226 pebbles and large euhedral feldspars grains (Fig. 3A) has been reported in deposits of

227 similar characteristics in the wadi channel deposits described from the same desert

228 system in eastern Iberia (Rodríguez-López et al., 2010). In these facies, cross-bedded

229 sets are formed by the migration of two- and three-dimensional subaqueous migrating

230 megaripples (Russel and Arnott, 2003). The planar surfaces separating it from

231 underlying aeolian deposits are interpreted as deflation surfaces (Glennie, 1970). The

232 frequent occurrence of angular mud intraclast pebbles and cobbles (Fig. 3F) observed

233 herein have been previously associated with wadi gravels deposited in ephemeral

234 streams (Karcz, 1969) and recognized in mud-cracked desert stream-bed floors

235 (Brookfield, 2008; Rodríguez-López et al., 2010). They are originated in the lee of the

236 clayey wadi banks by collapse due to mud-cracking being finally accumulated in wadi

237 mouths associated with desert flood deposits (Rodríguez-López et al., 2010). The

238 presence of sandy aeolian intraclasts (Fig. 3A) represents another common and

239 interesting process described in wadis and related with the erosion and rip-up of early

240 cemented aeolian sands by flash floods (Deynoux et al., 1989; Rodríguez-López et al.,

241 2012b).

242 The granule-rich horizons, granule veneers and granule linings frequently observed in

243 the wadi facies have been previously observed in deposits associated with aeolian-

244 fluvial interactions in the Iberian Basin (Rodríguez-López et al., 2010) and are

245 interpreted to represent the end-product of deflation of dry aeolian sandsheet

246 depositional surfaces (Clemmensen and Abrahamsen, 1983; Kocurek and Nielson,

247 1986; Rodríguez-López et al., 2012b). The unfavorable lithologies constituting the

248 Wadi Facies Association affect negatively the preservation of organic matter and only

10

249 one palynological assemblage has been recovered from the interval (level Sb5). The

250 single palynoflora is dominated by pollen grains of conifers and includes c 10% of

251 angiosperm pollen (Fig. 6K) and twice as much spores of cryptogams (see C and D in

252 Figs. 7–8; Supplementary Material SM1-B).

253

254 4.3. Facies Association 3: Wadi-fed (fan) Delta Facies Association

255 This facies association is interpreted as representing sedimentation in a deltaic system

256 fed by the wadi channels of the coastal desert. The repetition and m-thick intervals of

257 this facies (Facies 3A and 3B in Table 1) suggests a long-lasting alternation of two main

258 coeval depositional sub-environments (lagoons and wadi fan deltas).

259 The palynological and sedimentological features observed in the grey heterolithic

260 siltstones (Facies 3A) indicate sedimentation under variable energy conditions in a

261 relatively restricted marine, tidally influenced environment (Reineck and Wunderlich,

262 1968; Howard and Frey, 1985). The associated fine-grained sandstones showing double

263 mud drapes also support a tidal modulation (Nio and Yang, 1991) and suggest

264 sedimentation in subtidal conditions under a semi-diurnal tidal regime with diurnal

265 inequality (Visser, 1980; de Boer, 1998). The presence of isolated carbonaceous clasts

266 and coal fragments and/or coal seams suggest the development of a perennial vegetation

267 in coastal settings (e.g. mangrove, salt marshes) and/or reworking of plant remains

268 living in upstream desert areas (e.g. interdunes and wadi levees) (Fig. 4E). The

269 occasional occurrence of preserved symmetrical ripples indicates wave-influenced

270 environments. The sporadic presence of conglomerates (Facies 3B in Table 1)

271 interpreted to be pebble-sand sheet-flood deposits (e.g. Wakelin-King and Webb, 2007)

272 allow to infer the episodic disruptions of tidal deposition by flash floods. The massive,

273 generally structureless, with crude local inverse grading conglomerates constituting the

11

274 Facies 3B are interpreted as pebble-sand sheet-flood deposits These sediments were

275 accumulated in tidal flats and associated tidal channels disrupted by flash floods.

276 Similar facies have been described in the Ab Dibdibba Formation ("Ab Dibdibba Fan or

277 Delta") outcropping in the NE corner of Saudi Arabia, the SE of Iraq and Kuwait

278 (Stewart, 2006) and associated with the Wadi ar Rimah-Wadi al Batin drainage system.

279 The corresponding palynological assemblages, recovered from the lower and middle

280 parts of the Salinillas de Buradón succession (C and D in Figs. 7–8; Supplementary

281 Material SM1-B) are dominated by pollen grains. While the assemblages from lower

282 part of the section (samples Sb3–Sb4) are characterized by abundant pollen of conifers

283 (Figs. 6L, 6O), the upper part of the succession includes substantially more angiosperms

284 (flowering plants, Figs. 6J–K). Spores (Figs. 6D–F) are observed in varying proportions

285 and exhibit a distribution pattern more or less similar to the one characterizing

286 Cheirolepidiaceae (Figs. 7–8). In conjunction, this facies association is interpreted as a

287 wadi-fed (fan) delta colonized by mixed vegetation.

288

289 4.4. Facies Association 4: Marine mixed-carbonates Facies Association.

290 This facies association is characterized by fossiliferous mixed carbonates and

291 interpreted to be deposited under marine conditions. It appears interbedded with the

292 Wadi and Aeolian Facies Associations (Figs. 5A and B). The lack of tractional

293 sedimentary structures and the occurrence of micrite in the matrix suggest low-energy

294 conditions probably below the fair-weather wave base. The textural variability of the

295 facies forming the association could indicate a proximal-distal trend; the

296 microconglomerates with micritic matrix representing the proximal depositional settings

297 (Fig. 5D) and the very coarse-grained sandstones with flattened orbitolinids the distal

12

298 ones (Fig. 5E). The coarse material is interpreted to be derived from delta fronts (i.e.,

299 Wadi-fed (fan) Delta Facies Association). More distal settings are also supported by the

300 flattened character of the orbitonids (Rahiminejad and Hassani, 2016). A similar

301 example in which alluvial fans merge laterally with a carbonate platform leading to

302 mixed facies has been described by Thrana and Talbot (2006) in the Miocene of the

303 Lorca Basin (southern Spain). In the BCB, the clastics delivered to the system were

304 most probably sourced from the western Variscan Iberian Massif.

305 Palynological samples in this facies association have been recovered in Peñacerrada (IP

306 and IIP), Pancorbo (PAN1, PAN2) and the uppermost part of the Salinillas de Buradón

307 succession (SFB, SFB, SFF) (Figs. 7–8). The palynofloras from the Peñacerrada

308 outcrop are particularly representative of the facies and present the highest number of

309 dinocysts (Fig. 6A–C) and marine palynomorphs of all fertile samples. In this outcrop,

310 spores and conifer pollen are well represented and display opposite abundance trends,

311 while Cupressaceous and Cheirolepidiaceous pollen (Fig. 6G, O) shows closely similar

312 abundance profiles (see E and F in Figs. 7–8; Supplementary Material SM1- A and C).

313

314 5. Discussion.

315 5.1. Stratigraphic correlation, desert system cyclicity and palynological evolution

316 The sedimentary record of the mid-Cretaceous Iberian Desert System is represented by

317 the early Albian-early Cenomanian Utrillas Group in Iberia (Rodríguez-López, 2008).

318 In the BCB this group is late Albian – early Cenomanian in age (Barrón et al., 2015).

319 The studied sections of the Utrillas Group are restricted between two main key

320 supraregional correlation datums (Fig. 7), (i) the stratigraphic contact between the

321 Escucha Formation and the Utrillas Group that constitutes a prominent stratigraphic

322 feature in Iberia (Rodríguez-López, 2008; Rodríguez-López et al., 2013) and (ii) the

13

323 early Cenomanian transgressive deposits that led to the disappearance of the desert

324 system in Iberia leading to the establishment of a broad and extensive carbonate

325 platform (Chivelet et al., 2002). The first surface separates the underlying upper Aptian

326 carbonate platforms (Figs. 2 and 7) from the Utrillas Group and represents a regional

327 unconformity surface (Fig. 1C) that has been recognized in the eastern part of the

328 Iberian Plate (Rodríguez-López et al., 2009, 2012a, 2013).

329 The separation of the overlying successions, constituting the desert system, into four

330 distinct sequences is based on the recognition of three successive and basin-wide

331 correlatable sand-drift surfaces (SDS sensu Clemmensen and Tirsgaard, 1990;

332 Rodríguez-López et al., 2013) and changes in composition of palynofloral assemblages

333 (Barrón et al., 2015). Each sequence consists of prograding deposits corresponding to

334 wadi and aeolian facies associations and transgressive/retrograding deposits represented

335 by fan delta and shallow marine mixed carbonates (Figs. 7–8).

336

337 5.1.1. Sequence 1.

338 This sequence is represented by the prograding aeolian sandstone constituting the upper

339 part of the section of Montoria la Mina and by the transgressive deposits of the lower

340 part of the Peñacerrada 1 (IP) succession (interval 1 in Figs. 7 and 8). In this section, the

341 distinctive change in facies occurs at c 8.8m, when carbonates are replaced by aeolian

342 sandstones in a sharp contact defining the SDS2. The palynofloras recovered from the

343 lower part of IP reflect particularly well the response of palynological elements to high-

344 order sea-level fluctuations. The gradual reduction in spores from IP1 to IP3, paralleled

345 by a simultaneous increase in bisaccate pollen grains represent typical palynological

346 signal of early transgressive deposits. The drowning and/or landward migration of

347 spore-producer habitats during transgressive intervals produced a characteristic

14

348 lowering of spore representation in distal assemblages. This pattern has been recognised

349 in Holocene (Chmura, 1994) and older deltaic environments (Turner et al., 1994; Holz

350 and Diaz, 1998; Holz et al., 2002). The opposite trend in bisaccate pollen is due to the

351 increasing representation of regional and extra-regional vegetation characterizing larger

352 depositional sites (Jacobson and Bradshaw, 1981) and the aerodynamic morpho-

353 functional characteristics of their pollen assumed to enhance dispersion by water and

354 wind (Crane 1986). In Pleistocene–Holocene successions, pelagic pollen assemblages

355 often include abundant bisaccate pollen grains issue from regional vegetation (Mudie

356 and McCarthy, 1994, 2006). An input driven by wind would be the more likely scenario

357 as terrestrial influxes are mainly dominated by aeolian transport (e.g. winds, dust

358 storms) and, to a less extent, by ephemeral discharges produced by wadis in modern

359 transitional depositional settings adjacent to arid or hyper-arid areas (Dupont et al.,

360 1998; Hooghiemstra et al., 2006). The increasing numbers of marine palynomorphs

361 characterizing the lower part of Peñacerrada 1 and terminating in IP4 would support the

362 existence of a high-order transgressive interval followed by highstand deposition (Fig.

363 8; Supplementary Material SM1-A). In a similar way, the correlated changes in

364 abundances of Araucariaceae and Cheirolepidiaceae and Cupressaceae may reflect

365 migration of the corresponding sources (vegetation belts) caused by a prograding

366 coastline (Poumot, 1989).

367

368 5.1.2. Sequence 2.

369 This sequence is represented by the inboard section of Salinillas de Buradón and the

370 outboard successions of Peñacerrada (IP and IIP successions; Figs. 7–8). The lowstand

371 is represented by the sandstone-dominated interval conforming the aeolian FA1 (Fig. 2,

372 Table 1) in the middle part of the IP succession and correspond to an offshore migration

15

373 of dunefields during a relative a possible sea-level fall although a progradation during

374 increasing aeolians sediment supply may occur under trangressive intervals (e.g.

375 Rodríguez-López et al., 2012a) (‘interval 3’ in Figs. 7 and 8). The overlying mixed

376 carbonates FA4 are separated from the aeolian deposits by a transgressive surface (TS2)

377 and are observed at Peñacerrada (upper part of IP1 and lower part of IIP successions).

378 The palynological assemblages of the IIP succession (see B in Figs. 7 and 8) have a

379 distinctive marine signature. The decreasing representation of spores suggests the

380 drowning of pteridophytic vegetation. This could indicate the absence/truncation of

381 highstand deposits at Peñacerrada. The lateral changes of facies induced by the rise of

382 sea-level are well reflected by the similar abundance profiles of Cupressaceae and

383 Cheirolepidiaceae. The lateral equivalent of the mixed carbonates (FA4) observed at

384 Peñacerrada are the deltaic sandstones and conglomerates (FA3) represented in the

385 lower part of the Salinillas de Buradón section. In this succession, the reduced number

386 of palynological samples (samples Sb-3 and Sb-4, see C in Fig. 8) does not allow robust

387 paleoenvironmental inferences but the variable nature of the assemblages may be linked

388 to the heterogeneity of local depositional settings in an inboard system.

389

390 5.1.3. Sequence 3.

391 This sequence is represented in Salinillas de Buradón and in the top of Peñacerrada 2

392 (Figs. 7–8). The lowstand intervals are represented by wadi channel deposits proximally

393 and aeolian facies basinward and are not hosting lithologies allowing preservation of

394 palynological material. The major increase in the representation of flowering plant

395 pollen recorded in the overlying deltaic deposits (middle and upper parts of Salinillas de

396 Buradón, Fig. 7 and sedimentary package D in Fig. 8; Supplementary Material SM1-B)

397 probably reflects the drastic transformation of the flora during the late Albian – early

16

398 Cenomanian interval documented in Iberia (Diéguez et al. 2010; Barrón et al. 2015) and

399 elsewhere (Crane and Lidgard, 1990). The contrasting abundance profile of

400 angiosperms compared with the ones exhibited by Cupressaceae and Cheirolepidiaceae

401 suggests the colonization of distinct habitats; the conifers presumably linked with driest

402 settings and flowering plants favouring moister environments.

403

404 5.1.4. Sequence 4.

405 Inboard, the SDS4 puts in stratigraphic contact overlying aeolian dunes with underlying

406 mud playa facies. The lowstand interval is represented at Pancorbo and Salinillas de

407 Buradón by wadi channel and aeolian deposits corresponding to the FA2 and FA1,

408 respectively. The aeolian dunefields developed between the wadi belt close to the

409 Iberian Massif to the west and the Atlantic coast to the east (Fig. 8). The occurrence of

410 granule leanings and deflation surfaces in the wadi deposits (Fig. 3) corroborates that

411 during dry periods wadi channels where intensively deflacted delivering windblown

412 sands that were ultimately accumulated in the aeolian dunefields (Fig. 8). The lower

413 part of the Pancorbo and upper part of Salinillas de Buradón successions (Fig. 8,

414 sedimentary packages E and F, respectively) present abundant angiosperms

415 (Supplementary Material SM1- B–C) and confirm the trend in vegetation observed in

416 the underlying sequence. The higher proportion of spores in Pancorbo when compared

417 to Salinillas de Buradón is consistent with its proximal location on the desert system.

418 The transgressive deposits of the last sequence led to the widespread development and

419 implantation of a broad carbonate platform in the northern and eastern Iberian Plate

420 previously dated as early Cenomanian (Martín-Chivelet et al., 2002) and marks the

421 complete disappearance of the desert System in Iberia.

422

17

423 5.2. Relief-controlled Holocene desert basins. Recent analogues for the Cretaceous of

424 northern Iberia

425

426 The narrow Eritrean desert coast and the coast of UAE and Oman, constitutes excellent

427 analogues of the Cretaceous desert system of northern Iberia (Figs. 9–10). The spatial

428 variability of desert depositional systems as well as the spatial relationship of these

429 environments with the desert highlands and the Albian desert coast (Fig. 9B–C) is

430 similar to that observed nowadays in the modern Oman coast where the border between

431 Oman and UAE is characterized by the basement rocks cropping out in the desert coast

432 leading to the direct interaction of wadi and alluvial fan facies with the marine realm in

433 a narrow desert basin (analogue of the Basque-Cantabrian Basin) (Fig. 9A–C). This

434 Quaternary narrow basin merges 100 km southwards to the Rub Al-Khali desert that

435 constitutes an expansive erg system (Figs. 9A–C) (Al-Farraj and Harvey, 2004). The

436 actual configuration of the Arabian Peninsula characterized by the narrow desert system

437 of the Oman coast widening into the broader desert basin of Rub Al-Khali is interpreted

438 to represent a modern analogue of the Spanish Cretaceous desert. The system

439 characterized by extensive erg fields, in the Iberian Basin, progressively tapering

440 northwards into a much narrower Basque-Cantabrian Basin controlled by the Iberian

441 Massif palaeotopography (Fig. 9A). The variable distance from highlands to coast

442 influences significantly the morphology of the erg system. While wadi-fed fan deltas

443 interbedding with shallow marine deposits and rare prograding aeolian dunes (Fig. 9B)

444 are characterizing the Basque-Cantabrian Basin (Rodríguez-López et al., 2012a), the

445 bulk of the deposits from the Iberian Basin are represented by aeolian dunes, with other

446 facies associations being subordinate (Fig. 9A).

18

447 The mid-Cretaceous Iberian system could also be related to the modern Eritrean coast

448 (Fig. 10). Both areas display highlands in close proximity to the sea (in a distance of 10s

449 of Km) forming a very narrow desert basin. Aeolian dunefields, wadi channels and fan

450 deltas interact in the basin and the spatial distribution of each subenvironment is

451 controlled by the proximity of the highlands to the coastline (Fig. 10A). In Eritrea, the

452 altitude gradient between the desert coast and the highlands associated with the Red Sea

453 rift generates a marked gradient in the distribution vegetation (Edwards et al., 1989–

454 2009). Rodríguez-López et al. (2010) suggested altitudes of 3000–5000 m for the

455 Iberian Massif which may probably have promoted orographic rains(/snowfall)

456 enhancing (melt)water runoff. Both systems are associated with active plate margins

457 and include a vegetation associated with tidal flats, lagoons, wadi levees and sand bars

458 as well as forested highlands (Fig. 10). The substantial proportion of bisaccate pollen

459 grains (e. g. Fig. 6M) recorded in Peñacerrada is interpreted to represent allochthonous

460 coniferous vegetation from montane and/or other upland locations (Fig. 11B). A

461 “mangrove”-type vegetation may have constituted the source of some of the bisaccate

462 grains recorded in Peñacerrada (seed fern producers of Alisporites and Vitreisporites

463 bisaccate pollen types). This hypothesis benefits from the relative support of modern

464 successions indicating a limited palynological representation of mangrove pollen in

465 marine environments represented by the Gulf of Aden (Fersi et al., 2016). The same

466 abundance pattern exhibited by cheirolepids and Cupressaceae suggest that

467 representatives of these families were incorporating the same open, xerophytic,

468 vegetation communities colonizing dry or water-stressed environments such as

469 interdunes, brackish and salty soils (Fig. 11B). The (scarce) record of polyplicate pollen

470 (Fig. 6P) would reflect the presence of drought-tolerant Gnetales which could

471 complement the arboreal tier composed by the conifers.

19

472 Modern Araucariaceae are trees constituting relict vegetation in disjunct areas with

473 moist and mesothermal climates restricted to the Southern Hemisphere (Kershaw and

474 Wagstaff, 2001). During the Cretaceous, the family presented a wider distribution and

475 probable broader physiologic tolerance allowing them to colonize a wide array of

476 habitats. This light demanding taxon may have constituted part of Montane vegetation,

477 coastal woodland or represent the arboreal element of early successional stages

478 following disturbance as described in modern settings from NW Australia (Kershaw,

479 1976). Fossil Araucariaceae, however, are known to produce pollen with limited

480 dispersal potential (de Jekhowsky, 1963; Siegl-Farkas, 1994; Peyrot et al., 2011, 2019).

481 The presence of their pollen (Fig. 6L) in significant amount in palynological

482 assemblages from Peñacerrada and Salinillas de Buradón (Figs. 7–8; Supplementary

483 Material SM1- A–B) is then interpreted to reflect a local, coastal vegetation.

484 The drastic increase in the proportion of angiosperms observed in the middle and upper

485 parts of Salinillas de Buradón and Pancorbo successions is accompanied by a significant

486 drop in spores (Fig. 8; Supplementary Material SM1- B–C). This could reflect a

487 vegetation turnover where angiosperms were replacing spore-producers in the desert

488 system. Among other habitats, they could have colonized ephemeral interdune swamps,

489 frequently disturbed habitats such as wadi banks and levee, sand bars and, potentially,

490 xeric settings such as the herbaceous tier of conifer-dominated woodland. Together with

491 the extreme ecological tolerance allowing them to successfully colonize the mentioned

492 environments, early angiosperms could also already have developed short life-cycles

493 permitting the flash flowering observed after rainfall in modern arid settings (Vidiella et

494 al., 1999; Field et al., 2004). The discontinuous nature of the suitable sedimentological

495 record in marginal-marine settings does not allow to confirm this hypothesis. The

496 increasing diversity of angiosperms through successions representing an arid system

20

497 may be linked with modern arid semi-arid systems with unexpected high diversity such

498 as the Southwest of Western Australia or the Cape region of South Africa. Although

499 still not explained, the link between arid settings and floristic biodiversity has been

500 highlighted for a long time (Stebbins, 1952; Hopper and Gioia, 2004).

501

502 5.3. A model for desert flora palaeohabitats and associated sedimentary environments

503 The modern vegetation of semi-arid to hyper-arid belt including the Eritrean region, the

504 main part of the Arabian Peninsula and most of the south-central latitudes of Northern

505 Africa are dominated by angiosperms adapted to subtropical/tropical desert conditions

506 (Hemming, 1961; Wood, 1997; Edwards et al., 1989–2009). The actual spatial

507 distribution of vegetation in Eritrea and arid settings from the same latitudinal belt

508 displays a clear control by both altitude and spatial distribution of humidity. Except for

509 water-conditioned environments such as coastal places, lagoons, lakes, oasis or

510 interdune swamps, modern plant life forms inhabiting semi-arid to hyperarid

511 environments are mainly represented by tropical xerophytic woods and succulents,

512 desert or steppe forb, shrubs and graminoids (including Poaceae).

513 In recent pollen spectra, the main ecological categories deposited in arid and hyper-arid

514 areas include i) long-distance wind-transported pollen produced by arboreal taxa

515 (usually conifers) inhabiting montane or warm temperate locations; ii) desert and steppe

516 pollen types produced by both arboreal sclerophylls and succulents; iii) herbaceous

517 local vegetation (pollen of Ephedra is included in this group); and iv) spores of ferns

518 and pollen grains from azonal (hygrophilous and aquatics) vegetation (Fig. 11A). The

519 assemblages are characterized by a low diversity of taxa and, generally, they are

520 numerically dominated by desert and steppe herbaceous pollen types except in areas

21

521 with ephemeral or semi-permanent lakes, swamps or wadis, which are characterized by

522 a higher number of Cyperaceae and Poaceae (see D in Fig. 11A).

523 In marine or marginal-marine depositional settings, palynological assemblages include

524 usually a higher proportion of long-distance wind-transported pollen (category i) and

525 may also include pollen produced by mangrove vegetation, although the latter rarely

526 reach quantitative significance (see H in Fig. 11A, Fersi et al., 2016). The assemblages

527 described in the Gulf of Aden (see H in Fig. 11A, Fersi et al., 2016) is interpreted to

528 represent a recent analogue s.l. of the successions recorded in Peñacerrada IP (Sequence

529 2, Figs. 7–8) and the lowermost part of Salinillas de Buradón (SB, Sequence 2, Figs. 7–

530 8), where the high numbers of bisaccate grains (Fig. 8; Supplementary Material SM1-

531 A–B) would reflect distant, presumably upland, vegetation.

532 A direct comparison between the modern and Cretaceous inland desert floras is more

533 difficult given the existing taxonomic and physiognomic differences. Modern

534 vegetation is mainly integrated by angiosperms whereas a mixture of early Cenophytic

535 and late Mesophytic floras including a higher content in ferns (Anemiaceae [Fig. 6E],

536 Cyatheaceae/Dicksoniaceae/Dipteridaceae, Gleicheniaceae, Lygodiaceae,

537 Osmundaceae, etc) and gymnosperms (conifers [Fig. 6G, L, M],

538 Cycadaceae/Bennetittales/Ginkgoales [Fig. 6H, N], Erdtmanithecales [Fig. 6I], Gnetales

539 [Fig. 6P]) characterized the Early Cretaceous ecosystems. The palynofloras from the

540 BCB suggest a vegetation dominated by arboreal or shrubby conifers (high proportions

541 of Araucariaceae, Cupressaceae and Cheirolepidiaceae), while the modern palynological

542 assemblages and the corresponding vegetation are usually dominated by non-arboreal

543 types (Fig. 11A). The presence of a stratified (i.e. tiered) arboreal formation with

544 conifers inferred by palynological data could explain the highest diversity (number of

545 taxa) recorded in the Cretaceous assemblages when compared with their modern

22

546 counterparts (average number of taxa c 80 in the studied palynofloras against 30+ in the

547 considered modern spectra, Figs. 11A). Conifers may occupy alpine locations in the

548 Iberian Massif that for the Albian times could have reached a palaeo-altitude between

549 3350 to 5500 m (Rodríguez-López et al., 2010) (Fig. 11B).

550

551 6. Conclusions.

552 The Albian desert basin developed in northern Iberia has similarities with Holocene

553 desert coasts (e.g. UAE, Oman and Eritrea). The geomorphology of the coast and the

554 variable relief and topography of the highlands dominated the distribution of vegetation

555 in the desert basin and surrounding reliefs. The temporal evolution of Albian desert sub-

556 environments led to progradational and retrogradational sequences in which wind-laid

557 and water-laid facies alternate through time. The relevant percentages of dinocysts and

558 acritarchs in Peñacerrada, Pancorbo and the upper part of Salinillas de Buradón

559 successions indicate the existence of various episodes of sedimentation with a

560 substantial marine influence. This palynological signal is expected in organic-rich

561 mudstones associated with shallow marine carbonate platform facies interpreted to have

562 been deposited in coastal lagoons. In Pancorbo and the upper part of Salinillas de

563 Buradón successions, the increase of marine elements characterizing the assemblages

564 can be related with the major regional transgression dated as late Albian/?early

565 Cenomanian and expressed across northern and eastern of Iberia by a wide carbonate

566 platform. The slightly lower representation of dinocysts observed in Pancorbo with

567 respect to Salinillas de Buradón would be related to the more distal position of the latter

568 inferred by the characteristics of the underlying facies (proximal wadi-aeolian sand

569 sheet facies in PAN compared to prograding climbing aeolian dune facies towards the

570 Atlantic Ocean in SB). In the underlying deposits, the higher abundances of marine

23

571 palynomorphs are associated with transgressive facies recorded between aeolian

572 tongues. An example of this transition is provided by the Peñacerrada IP and IIP

573 successions, where aeolian dune facies are overlying a dinocyst-rich fan-delta-shallow

574 marine interval (lower part of Peñacerrada IP) and are sharply covered by transgressive

575 marine facies with similar palynological characteristic (Peñacerrada IIP). Conversely,

576 the facies integrating the lower and middle part of the Salinillas de Buradón successions

577 interpreted as wadi, aeolian and fan delta facies (Facies Associations 1–3) yielded

578 palynological assemblages with poor and inconsistent marine palynomorphs suggesting

579 more proximal settings. The palynological data recovered from these facies allow to

580 speculatively interpret the Early Cretaceous vegetation of the southern margin of the

581 Basque-Cantabrian Basin as being determined by various types of formations: (1)

582 xerophilous arboreal, coastal communities with Araucariaceae, (2) hygrophilous, mostly

583 non-arboreal communities including (probably fast growing) ferns and angiosperms (r

584 reproductive strategy) related to ephemeral interdune swamps or wadis, (3) xerophilous

585 arboreal or shrubby communities incorporating cheirolepids, Cupressaceae and scarce

586 Gnetales (the latter arguably still represented in modern arid vegetation), (4) distant

587 (regional or extra-regional) upland forested formations including conifers. “Mangrove”-

588 like communities may have been present but did probably not covered extensive areas.

589 The main differences with the actual vegetation being explained by differential

590 ecological conditions, taxonomical compositions, later physiological adaptations and/or

591 resilience of remnants (Mesophytic representatives) with no modern analogues.

592

593

594 ACKNOWLEDGEMENTS

24

595 We are grateful to Editor Prof. Chris Fielding and two anonymous reviewers for their

596 valuable comments and suggestions that help us to present results and integration of

597 seidmentology and palynology in a more comprehensive manner. Our gratitude to Dr.

598 Nieves Meléndez from the Complutense University of Madrid and Dr. Wiem Fersi who

599 kindly provided her raw palynological data from the Gulf of Aden. This work is a

600 contribution from the Centre for Energy Geoscience (UWA) and has been possible

601 thanks to the support of the Spanish research projects AMBERIA (CGL2014-52163)

602 and CRE (CGL2017-84419).

603

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959 from Swedish by K. Faegri and MB Davis, 1967. Pollen Spores 9, 375–402.

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963 the Agrio Formation (Lower Cretaceous), central Neuquén Basin, Argentina.

964 Sedimentology 49, 1001–1019.

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967 flowering after rain in the southern Atacama Desert. J. Arid Environ. 43, 449–458.

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973 flow-regime sand channels: sediment transport and deposition in a drylands mud-

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975

976 White, H.H., 1842. On fossil Xanthidia. Microsc. J. London 11, 35–40.

977

978 Wood, J.R.I., 1997. A handbook of the Yemen Flora. Royal Botanic Gardens, Kew.

979

980 Wortmann, U.G., Hesse, R., Zacher, W., 1999. Major-element analysis of cyclic black

981 shales: palaeoceanographic implications for the early Cretaceous western Tethys.

982 Palaeoceanography 14, 525–541.

983

984 985 FIGURE CAPTIONS

986

987 Figure 1. A) Geographical location of the study area and geological map of the Basque-

988 Cantabrian Basin. Note the location of the study area with respect to the previously

40

989 published worked on the Iberian Desert System in the Iberian Range. The location of

990 the studied stratigraphic sections is pointed out. Modified after Martín-Chivelet et al.,

991 2001 and Barrón et al., 2015. B) Palaeogeography and palaeoclimate belts after

992 Chumacov et al. (1995) and Spicer and Skelton (2003). Palaeowinds simplified from

993 Poulsen et al. (1998) and Latta et al. (2006). ‘NHA’ (Northern Hemisphere Hot Arid

994 Belt), ‘NMW’ (Northern Hemisphere Mid-latitude Warm humid Belt), ‘STH’

995 (Subtropical High-pressure system) and ‘TL’(Tropical Low-pressure system) zonation

996 from Wortmann et al. (1999) and Herrle et al. (2003). ‘EH’ Equatorial Humid Belt.

997 Modified after Rodríguez-López et al. (2010). C) General stratigraphy showing the

998 location of the Iberian Desert system (Utrillas Gp.) the underlying Escucha Fm. and the

999 overlying transgressive Cenomanian Carbonate platforms. See text for discussion.

1000

1001 Figure 2. Studied stratigraphic sections showing the location of the studied samples and

1002 the distribution of facies associations in color. The succession of Montoria-La Mina, not

1003 covered in detail in the present work, has been inserted for stratigraphic reference as it

1004 includes the lower boundary of the BCB desert system. See legend in the figure.

1005 Thickness bar is 5 m.

1006

1007 Figure 3. A). Wind-water interaction stratigraphy showing intraclast conglomerate

1008 eroding an underlying aeolian sandsheet. Wadi conglomerate is sharply covered by an

1009 aeolian sandsheet that rests over a flat-lying deflation surface with ventifacts. B).

1010 Aeolian dune facies formed by white color friable fine-grained and very well sorted

1011 sands. C). Field photograph and D). Line-drawing of large-scale cross-bedding

1012 developed in the aeolian dune foreset organized in decametric-thick inclined tabular

1013 strata. E). Sheet flood facies formed by reworked aeolian sands and floating pebbles.

41

1014 Arrows pointing out to a set of water-lain cross-bedding sharply covered by a deflation

1015 surface. F). Stratigraphic contact between aeolian sandsheet facies below and sheet

1016 flood gravelly sandstones above. Note the erosional surface that contains an armored

1017 intraclast. Pancorbo outcrop.

1018

1019 Figure 4. A). Tabular and massive level of conglomerates sharply covered by

1020 heterolithic facies. B). Sandy matrix pebbly conglomerate. C). Preserved wave ripples

1021 crests in a tabular sandy level interbedded in heterolithic muddy facies. D). Double mud

1022 drapes on tidal facies showing flaser bedding. E). Heterolithic facies showing mud

1023 drapes rich in organic matter. F). Black shales sharply covered white sandstones.

1024 Salinillas de Buradón outcrop.

1025

1026 Figure 5. A). Field photograph showing the distribution of the fan-delta shallow marine

1027 facies of Cycle 2 and the overlying aeolian dune, wadi and lagoonal facies of Sequence

1028 3. B). Close up view of the friable very well sorted aeolian dune sands sharply covering

1029 underlying lagoonal heterolithics. C). Lagoonal heterolithic facies. D). Mixed

1030 carbonates with floating quartzite granules of the fan delta facies association and E).

1031 Packstone of orbitolinids in the same facies association. Peñacerrada outcrop.

1032

1033 Fig. 6. Light photomicrographs of selected palynomorphs, scale bar: A–C = 10 µm, D–P

1034 = 5 µm. (A–C) Dinoflagellate cysts: A. Oligosphaeridium complex (White 1842) Davey

1035 and Williams 1966, Peñacerrada 1 outcrop, level IP1, B. Criboperidinium sp.,

1036 Peñacerrada 2 outcrop, level IIP2, C. Cyclonephelium chabacca Below 1981, the

1037 Pancorbo site, level PAN1. (D–F) Spores of ferns: D. Patellasporites tavaredensis

1038 Groot and Groot 1962, Peñacerrada 1 outcrop, level IP4, E. Costatoperforosporites

42

1039 foveolatus Deák 1962, Peñacerrada 1 outcrop, level IP3, F. Acritosporites cf. kyrtomus

1040 Juhász 1979, Peñacerrada 1 outcrop, level IP8. (G) Inaperturate pollen grain of

1041 Inaperturopollenites dubius (Potonié and Venitz 1932) Thomson and Pflug 1953

1042 (Cupressaceae taxodioid), Salinillas de Buradón outcrop, level Sb-1. (H) Monosulcate

1043 pollen of Cycadopites sp. (Cycadales/Bennettitales/Ginkgoales), Salinillas de Buradón

1044 outcrop, level Sb-6. (I) Eucommiidites troedsonii Erdtman 1948 (Erdtmanithecales),

1045 Peñacerrada 1 outcrop, level IP8. (J–K) Pollen grains of Angiosperms: J. Tricolpate

1046 pollen of Tricolpites cf. parvus Stanley 1965, Peñacerrada 2 outcrop, level IIP2, K.

1047 Trichotomosulcate pollen of Asteropollis trichotomosulcatus (Singh 1971) Singh 1983,

1048 Salinillas de Buradón outcrop, level Sb-5. (L) Inaperturate pollen of Araucariacites

1049 australis Cookson 1947 (Araucariaceae), Salinillas de Buradón outcrop, level Sb-1. (M)

1050 Bisaccate pollen grain of Podocarpidites sp. (Podocarpaceae), Peñacerrada 1 outcrop,

1051 level IP3. (N) Porate pollen of Exesipollenites tumulus Balme 1957 (Taxodioids?,

1052 Bennettitales?), the Pancorbo site, level PAN1. O) Tetrad of circunsulcate pollen of

1053 Classopollis major Groot and Groot 1962 (Cheirolepidiaceae), Peñacerrada 2 outcrop,

1054 level IIP6. P) Polyplicate pollen of Equisetosporites sp. (gnetophytes), Peñacerrada 1

1055 outcrop, level IP8.

1056

1057 Figure 7. Stratigraphic architecture and facies distribution in the studied continental-

1058 shallow marine system of the desert basin. The stratigraphic location of the studied

1059 samples is indicated. Montoria La mina outcrop (MN) studied in Barrón et al. (2015) as

1060 a stratigraphic reference for the correlation panel.

1061 Figure 8. Synthetical percentual pollen diagrams organized by stratigraphic architecture,

1062 cyclicity and facies distribution. See labelling (A to H) indicated in Fig. 7.

1063 Palaeogeographic maps for key intervals are indicated.

43

1064

1065

1066 Figure 9. A). Iberian Desert System cyclicity variability. B–C). Coeval narrow and

1067 broad desert basins in Oman and the United Arab Emirates as an analogue of the Iberian

1068 Desert Basin variability. Google Earth. See text for discussion.

1069

1070 Figure 10. Holocene desert basin analogue for the Albian of northern Iberia. A).

1071 Distribution of sedimentary environments and associated vegetation in Eritrea and its

1072 spatial and altitudinal distribution compared with the topographic profiles of the desert

1073 basin. B). Vegetation colonizing the interdunes from wadi channel levees. C). Plants

1074 colonizing wadi channels located between intradesert scarpments. D) and E). Vegetation

1075 colonizing interdunes from wadi channel levees and crevasse splays. F). Vegetation

1076 located in the margins of a wadi delta. G). Vegetation in mangroves and tidal channels.

1077

1078 Figure 11. A). Abundance in the number of taxa of the main miospore groups recovered

1079 from selected Holocene and recent semi-arid to hyper-arid sites (A–C, H = Lézine et al.,

1080 1990, 1998; D–E = Maley, 1972; I = Fersi et al., 2016). The circular percentual

1081 diagrams reveal the representation of the different miospore groups. The miospore

1082 ecological groups have been grouped according to Jolly et al. (1998). B). Sedimentary

1083 model and vegetation distribution in the desert system. Main sources of palynomorphs

1084 are indicated. See text for discussion.

1085

1086 Table 1. Continental and marine facies associations in the northern sector of the

1087 Cretaceous Iberian Desert Basin.

1088

44

1089 Supplementary Material SM1. Percentual pollen diagrams of A) Peñacerrada 1 (IP) and

1090 2 (IIP) outcrops, B) Salinillas de Buradón outcrop (Sb); and C) The Pancorbo site

1091 (PAN).

1092

45

N A this paper Basque-Cantabrian Basin Santander European Plate BCBBCB San Sebastián NPZ SB BT C Bilbao BM IBIB NPFZ Iberian AM IM Peninsula previous papers on the Vitoria P Mid-Cretaceous Iberian Desert System Pamplona IP/IIPIP/IIP

PANPAN SBSB MINMIN BCBBCB Basque-CantabrianBasque-Cantabrian BasinBasin Iberian Plate Burgos Logroño 50 km IBIB IberianIberian BasinBasin

Axial zones of the basin Cenozoic occupied by Cretaceous flysch troughs

Mesozoic Continental and shelf domains StudiedStudied ooutcrops:utcrops: Palaeozoic outcrops of the Cretaceous Iberian Margin PANPAN PPancorboancorbo SBSB SSalinillasalinillas AM Asturian Massif BT Basque Trough IM Iberian Margin IP/IIPIP/IIP PeñacerradaPeñacerrada I / NPFZ C Cabuérniga Fault SB Santander coastal domain BM Basque Trough PPeñacerradaeñacerrada IIII MINMIN MontoriaMontoria P Pamplona Fault NPZ North Pyrenean Zone North Pyrenean Fault Zone (plate boundary)

B MID-CRETACEOUS PALAEOCLIMATE AND WIND PATTERNS NHT NHT Northern High-latitude Temperate humid belt Prevailing westerly belt NMW Northern Mid-latitude Warm humid belt NMW NHA Northern Hot Arid belt EH Equatorial Humid belt STH STH Subtropical High-pressure system

NHA TL Tropical Low-pressure system TL Prevailing trade belt Mid-Cretaceous Iberian Desert System EH Iberian Massif Atlantic realm C SupraregionalSupraregional ttransgressionransgression Cenomanian UtrillaUtrillas GGpp DesertDesert eexpansionxpansion & pprogradationrogradation

Albian easterneastern aandnd nnorthernorthern IIberiaberia

CRETACEOUS Escucha Fm supraregional unconformity Aptian PAN SB IIP MIN

Sf Sg Sf Sg Sg Sf Sg Sg A L A L Sf A L Sf A B C D Sm Cgl A B C D Sm Cgl A B C D A L Sm Cgl A B C D Sm Cgl A B C D A L Sm Cgl

IIP6 PAN 2 PAN 1 SFF SFD SFB PAN 0 IIP2 Sb-6

DL Sb-5 IP

Sf Sg A B C D A L Sm Cgl Sb-7 Sb-8 Sb-9 IP.6 Sb-10

Sb-4 IP.5

Sb-11 IP.4 1011g IP.3 1011e Sb-3 IP.2 1011d IP.1 1011b 1011a Sb-1

Upper Cretaceous marine carbonates bivalves aeolian sandstones root traces 1009 wadi sandstones and conglomerates bioturbation fan-delta conglomerate and sandstones leaf carbonaceous p shallow marine mixed carbonates lant remain Lower Cretaceous marine carbonates Fe crust sandstones mudstones cross-bedding limestones ripple 1005 cross-lamination siltstones

pebbly sandstones and conglomerates lenticular bedding 1003 fine-grained deposits erosional surface A B intraclast in aeolian sandsheet conglomerateco tr n ac gl la om st e ra te

aeolian ae sandsheetsa o n li d an sh e et 1010 cmcm 2020 cmcm

C D

5050 cmcm 5050 cmcm

top E top F

aeolian

sandsheets a a e n o d li s a h n e e base t base 2525 cmcm 1010 cmcm baseb a A s B e

greyg heterolithic and r laminatedla e silstones conglomeratesc m y o h n i e g n l a te o t m e ro d l e s it r i h a ls i t t c e topt o a s o n n p e d s 3030 ccmm 3030 ccmm

baseb a C s D e

5 cmcm

topto p 2 cmcm

E F 1010 cmcm

2020 ccmm 2 m A

B C E WADI-AEOLIANWADI-AEOLIAN DDUNEFIELDSUNEFIELDS 3 FANFAN DDELTA-SHALLOWELTA-SHALLOW MMARINEARINE 2

B 1m1m C

5 ccmm

D E

5 cmcm 4 ccmm

correlation line correlation coastal lakes and lagoons lakes and coastal shallow marine shallow carbonates mixed wadi belt outcrop vegetation playa lake playa aeolian belt fan delta aelian dunefields 10 km 4

legend l a v r e t n I

. 2

E N I R A M

W O L L A Palaeogeographical maps Palaeogeographical H S - A T L E D

N A FAN DELTA-SHALLOW MARINE 2. Interval MARINE 4 DELTA-SHALLOW FAN F 4 10 km 10 km 10 km 10 km 6 7 8

1

3 2

l

l

l l l l a a a a a a v v v v r v v r r r r r e e e e t e e t t t t t n n n n I I n n I

I

I I

.

.

. . . . 3 4 4

1

2 1

E S S S S E N D D I D D N L I L L R L E E R E I E A I I I A F F F F M E

E E E M

N N N N W U W U U U O D O L D D

D

L L N L N N N A 10 km A A A A 10 km I A I H I I L H L S L L - S O O O - O A E E E A E T A

L Ebro River T A A A -

- Ebro River - L I E - I I I E D D D D

D D A

A A N A N WADI-AEOLIAN DUNEFIELDS 4. Interval 7 WADI-AEOLIAN W A WADI-AEOLIAN DUNEFIELDS 4. Interval DUNEFIELDS 8 WADI-AEOLIAN W WADI-AEOLIAN DUNEFIELDS 1. Interval 1 WADI-AEOLIAN W 6 WADI-AEOLIAN DUNEFIELDS 2. Interval 3 WADI-AEOLIAN W 7 2 A FAN DELTA-SHALLOW MARINE 3. Interval MARINE 6 DELTA-SHALLOW FAN F 5 3 FAN DELTA-SHALLOW MARINE 1. Interval MARINE 2 DELTA-SHALLOW FAN F 1

Cycle 4 Cycle 3 Cycle 2 Cycle 1 CYCLE 4 CYCLE 3 CYCLE 2 CYCLE 1 B A ENE Interval 2 Interval 4 TS TS TS SDS TS SDS SDS SDS Interval 8 Interval 7 Interval 6 Interval 5 Interval 4 Interval 3 Interval 2 Interval 1 CARBONATE PLATFORMS CARBONATE COASTAL/SHALLOW MARINE COASTAL/SHALLOW FAN DELTA-SHALLOW MARINE 1 MARINE DELTA-SHALLOW FAN FAN DELTA-SHALLOW MARINE MARINE DELTA-SHALLOW FAN 3 MIXED CARBONATES WADI-AEOLIAN DUNEFIELDS 3 WADI-AEOLIAN WADI-AEOLIAN DUNEFIELDS 2 WADI-AEOLIAN FAN DELTA-SHALLOW MARINE 2 MARINE DELTA-SHALLOW FAN WADI-AEOLIAN DUNEFIELDS 4 WADI-AEOLIAN WADI-AEOLIAN DUNEFIELDS 1 WADI-AEOLIAN APTIAN CARBONATE PLATFORM APTIAN CARBONATE B F IIP6 Interval 7 IIP2 ENE C A Cgl D Sg Sm Sf L A P D I C H IIPI B Interval 3 Interval 4 A Interval 6 PEÑACERRADA 2 PEÑACERRADA (IIP) Interval 8 IP.6 IP.4 IP.5 IP.3 IP.2 IP.1 Cgl Sg Sm Sf L A P D I IP C B WSW A PEÑACERRADA 1 PEÑACERRADA (IP) E Cgl Sg Sm Sf L A D C B A MIN WSW F E D C H Sb-11 Sb-10 Sb-9 Sb-8 Sb-7 Cgl Sg Sm Sf L A D C B A SALINILLAS 2 Sb-4 Sb-3 Sb-1 Sb-6 Sb-5 Cgl Sg Sm SB Sf E L A D C B A SALINILLAS 1 G Interval 8 Interval 7 G E Palynology, cyclicity sedimentology and Palynology, (Taxodioids?/Bennettitales?) aeolian sandstones (dunes and sandsheets) aeolian sandstones carbonate platforms carbonate wadi channel sandstones and conglomerates wadi channel sandstones playa lake mudstones playa fan delta sandstones and conglomerates fan delta sandstones shallow marine mixed carbonates and coastal and coastal carbonates marine mixed shallow lagoons

DL PAN 1 PAN 2 PAN 0 Cgl Sg Sm Sf L A D

C

B A PAN facies belts

d : Salinillas de Buradón outcrop : Salinillas de Buradón outcrop

n P U O R G S A L L I R T U Marine depostis GROUP UTRILLAS Wadi-fed delta deposits Wadi-fed Lagoonal deposits Spores of ferns and allied of ferns Spores Marine palynomorphs Pollen grains of Gymnosperms grains Pollen Pollen grains of Angiosperms grains Pollen

W

e Peñacerrada 1 and 2 outcrops Peñacerrada

: the Pancorbo site : the Pancorbo : W Angiosperms Angiosperms Gnetophyta

Exesipollenites tumulus tumulus Exesipollenites Bisaccate pollen grains (Pinaceae + Podocarpaceae) (Pinaceae pollen grains Bisaccate

Cycadales/Bennettitales/Ginkgoales + Erdmanithecales Cycadales/Bennettitales/Ginkgoales g Cupressaceae (Taxodioids) Cupressaceae Bryophyta + Lycophyta + Pteridophyta Bryophyta + Lycophyta Acritarchs + Dinoflagellate cysts + Prasinophytes + Dinoflagellate + cysts Acritarchs Araucariaceae Cheirolepidiaceae

e

E, G

C-D, F, H F, C-D, A-B

Legend L

10

9

8

7

6

5

4

3

2 1 A ATLANTICATLANTIC OOCEANCEAN MMARINEARINE EERGRG MMARGINARGIN ERITREA-LIKEERITREA-LIKE DDESERTESERT CCOASTOAST B

Iberian Massif mixed carbonates NARROW DESERT BASIN and coastal facies CYCLE C Arab Gulf Atlantic Ocean wadi facies and aeolian sandsheets Oman aeolian dunefields Iberian Massif NARROW DESERT BASIN NARROW DESERT BASIN wadi-fed fan delta Atlantic Ocean CYCLE B wadi facies

mixed carbonates and coastal facies wadi facies fan delta facies CYCLE A aeolian facies marine facies aeolian dunefields

Atlantic Ocean AtlanticAtlantic OceanOcean BROAD DESERT BASIN EBRO EBRO MASSIF MASSIF

IBERIAN MASSIF IBERIAN United Arab Emirates Tethys Ocean MASSIF TethysTethys OceanOcean Rub Al-Khali

mud playas TETHYSTETHYS OOCEANCEAN MMARINEARINE EERGRG MMARGINARGINQATAR-LIKEQATAR-LIKE DESERTDESERT CCOASTOAST lagoon CYCLE C 20 km Rodríguez-López et al. (2012a) aeolian dunefields Oman mud playas IBERIAN MASSIF lagoons, tidal deltas BROAD DESERT BASIN CYCLE B aeolian dunefields Sabkha and playas

mud playas and Erg (aeolian dunes) aeolian dunefields IBERIAN MASSIF BROAD DESERT BASIN CYCLE A Wadi & alluvial fans coastal lakes, lagoons, marshes and tidal channels Basement rocks

wadi facies aeolian facies (Modified after Al Farraj & Harvey, 2004) aeolian dunefields alluvial fan facies marine facies

C n i

wadi s a b

t r e s

wadi e d

w Indian o r r Ocean a Arab Gulf 2727 kmkm desertnarrow n basin t r e s e n i d

s d 7070 kmkm a a b

o

r

broad desertbroad b basin B B’ A Precambrian relief alluvial fans C’ narrownarrow desertdesert basinbasin intradesert escarpment alluvial fans & wadis gullies, terminal fans & wadis aeolian deposits coastal/tidal ERITREAERITREA & alluvial fans aeolian dunefield Red Sea REDRED SEASEA B’ C A’ wadi-fedwadi-fed ffanan ddeltaelta

MASSAWAMASSAWA PrecambrianPrecambrian B rreliefseliefs

mountainmountain vvegetationegetation

C C’ AsmaraAsmara ccityity 22,325,325 m aaltitudeltitude A ASMARAASMARA A A’ Precambrian relief alluvial fans Precambrian relief & wadis alluvial fans & wadi channels between delta wadi channels intradesert escarpments aeolian dunefield wadi (delta feeder channel) aeolian dunefield Red Sea

B colonizationcolonization ooff wwadiadi ssandand bbarsars C wadi-derived deltas

aeolian dunefield vegetation entering the erg from wadi levees CenozoicCenozoic rreliefseliefs

srtaightsrtaight wadiwadi channelschannels throughthrough desertdesert aaeolianeolian dunesdunes wadi basinbasin

D E

aeolian dunefield

E interdune colonization from wadi channel

F close up view of a wadi delta. G Note vegetation distribution in mangoves wadi distributary channels tidaltidal ccreeksreeks

aeolianaeolian ddunefieldunefield

aeolianaeolian ddunefieldunefield tidaltidal flatsflats tidaltidal flatsflats