Joint RCMNS - RCANS Interim Colloquium, Salamanca. September 21st to 23rd, 2011 Climate changes, bioevents and geochronology in the Atlantic and Mediterranean over the last 23 Myr
A SINGULAR MIOCENE PALEOBOTANIC RECORD IN DELTAIC SEQUENCES OF NORD-BETIC CORRIDOR (GUADALQUIVIR BASIN, SOUTH OF SPAIN) M. Abad1, F. Ruiz1, C. Martin-Closas2, J. Tosquella1, A. Toscano1, M.L. González-Regalado1 1 Departamento de Geodinámica y Paleontología, Universidad de Huelva, 21071Huelva, Spain. e-mail:
[email protected] 2 Departamento de Estratigrafía, Paleontología y Geociencias Marinas, Universidad de Barcelona, 08028-Barcelona, Spain
In the central and western sectors of the Guadalquivir basin, the scarce paleobotanical record can be justified by the restricted presence of coastal and continental facies deposited under subaerial conditions. Previous researches highlight its presence in Early Pliocene units (Muñiz et al., 1999; Barrón et al., 2003) indicating high temperatures and subtropical palaeoclimatic conditions although not previous works have described macroflora fossils of Tortonian age. Along the northern margin the sedimentary fill includes very different facies grouped into the Tortonian Basal Transgressive Complex, or BTC (Abad, 2007). The BTC is composed of several internal sequences linked to 4th order cycles of sea-level change and provides a clear example of stacked high-frequency cycles of mixed carbonates and siliciclastics. Siliciclastic sedimentation took place in deltas, beaches and shallow marine zones. Deltaic systems migrated basinwards during stillstand phases whereas transgressive pulses provided better conditions for the production and accumulation of biogenic carbonates. Facies association of deltaic plain has been described in the central sector of this foreland margin (Arroyo Parroso section, Sevilla province). Facies are constituted mainly by conglomerates and gravely deposits, although sandy deposits are also common. They show massive to crudely horizontally stratified and lenticular channelized forms interpreted as migration of subaqueous dunes and infilling of scours inside mobile channel belts in a braided fluvial system (Hein and Walker, 1977). Gravel and pebbles bedload transport occurred under high flow regime. Subordinate muddy facies were deposited during lower flow regime although high proportions of fine sediments were winnowed out in suspension as turbidity plumes from plain delta to delta front and neighbouring shallow marine zones. These facies are yellowish, laminated silts and grey, massive clays and show tabular and lenticular geometry. Microfaunistic record is very poor but some specimens of benthic foraminifera (Ammonia beccari, A. inflata, Elphidium crispum and Nonion boueanum) have been
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Joint RCMNS - RCANS Interim Colloquium, Salamanca. September 21st to 23rd, 2011 Climate changes, bioevents and geochronology in the Atlantic and Mediterranean over the last 23 Myr
collected. They may also contain internal moulds of bivalve Modiolus sp. and burrows of crustacean decapods (Thalassinoides isp.). These facies contain fractured remains of plants, but their taxonomic classification is very difficult because they do not retain neither banks nor apices and veins are poorly preserved. Elongated forms similar to helophytes have been recognised as well as numerous spherical geometries interpreted as seeds. Seeds are abundant in transported associations of fluvial environments while as remains of plants transported by tractive and suspension processes often are broken into polygonal fragments following nervation pattern as can be observed in all the studied specimens (Martín Closas and Gómez, 2004). Due to the relationship with underlying and overlying deposits, and their sedimentary and paleontological characteristics, these facies are interpreted as rapid settling deposits of distal delta plain channels (topset) located in areas with limited marine influence.
REFERENCES 1. Abad, M. (2007). La transgresión tortoniense en el margen pasivo de la Cuenca del Guadaquivir. Tesis doctoral. Universidad de Huelva. 510 pp. 2. Barrón, E., Muñiz, F. Mayoral. E. (2003). Aspectos macroflorísticos del Plioceno de Lepe (Cuenca del Guadalquivir, Huelva, España). Consideraciones paleocológicas. Boletín Real Sociedad Española de Historia Natural (Secc. Geol.), 98(1-4), 91-109. 3. Hein, F. J., Walker, R. G. (1977). Bar evolution and development of stratification in the gravely braided. Journal of Earth Sciences, 14, 562-570. 4. Muñiz, F., Mayoral, E., Barrón, E., Cachão, M. (1999). Nuevos datos sobre macroflora del Plioceno en el Suroeste de la Península Ibérica (Lepe, Huelva, España). Geogaceta, 25, 143-146. 5. Martín-Closas, C., Gomez, B. (2004). Plant taphonomy and palaeoecological interpretations. A synthesis. Geobios, 37, 65-88.
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THE GEOLOGICAL AND PALAEONTOLOGICAL RECORD OF GUADALQUIVIR BASIN ( SOUTHWESTERN SPAIN) Ruiz, F., Civis, J., González Delgado, J. A., Abad, M.,González-Regalado, M. L., Tosquella, J. Toscano, A., García, E. X. Corresponding-author:
[email protected]
unconformably on a Palaeozoic-Mesozoic substrate: FRAN
Iberian Massif
POR TUG
AL
CE
Madrid
Sevilla
Huelva
Córdoba
IBERI MASSAN IF
External Zones
I
1
IBERIAN RANGE
2,3,4 5
N
S
Granada
II
Volcanic Rocks
Betic Chain
CÁDIZ GULF
ACTIVE MARGIN
STUDY AREA
Tempestitic levels (Casa del Pino)
Internal Zones
Sevilla
Huelva
BETIC CHAIN
PASIVE MARGIN
Condensed section (Bonares)
BIVALVIA
'SANDS OF HUELVA' FM.
In the western sector of the Guadalquivir basin, four Neogene formations are defined, lying
GASTROPODA
THE NEOGENE OF THE GUADALQUIVIR BASIN
Cádiz
GUADALQUIVIR BASIN
MEDITERRANEAN SEA
0
50
IBERIAN MASSIF
BETIC CHAIN
100 Km
Intramountain Guadalquivir Basins Basin
BTC AND CALCARENITE OF NIEBLA FM
Tertiary Basins
TURBIDITES LOBES
380
POSTER 5 340
POSTER 4G G G
k
The lowermost part of this formation is formed by coarse sands, replaced by fluvial conglomerates near the top.
SAND OF HUELVA FM
360
k
SANDS OF HUELVA FM
G
320
POSTER 3 300
FOSSILS CLAYS OF GIBRALEÓN FM
250
200
100
90
70
POSTER 2 G
G
40 30 POSTER 1 20
10 0
G
BTC AND CALCARENITE OF NIEBLA FM
50
G
Bonares section
Gibraleón section
Amusium cristatum Pecten revolutus Macrochlamys latissima
CLAYS OF GIBRALEÓN FM
Ostreidae Bivalvia Gastropoda Dentalidae Clypeasterids
80
60
Amusiopecten koheni
The overlying deposits are composed of Pliocene silty sands enclosing a glauconitic layer near the base and several tempesti tempestitic layers towards the top.
OSTRACODS
k
Teeth of condrichtians and osteichtians Cetaceans Balanids Bryozoans Benthic foraminifera
This Tortonian-Messinian ortonian-Messinian formation comprises a very monotonous lithofacies consisting of greyish marls and clays, with a condensed, silty glauconitic layer near the base. CALCARENITE OF NIEBLA FM / TRANSGRESSIVE BASAL COMPLEX
Planktonic foraminifera Macroforaminifera
PALEOZOIC AND MESOZOIC SUSTRATE
These Tortonian units have a variable thickness (3-30 m) and consist of fluvial conglomerates, littoral sands and sandy calcarenites.
FORAMINIFERA
ECHINODERMS
k k
CALCARENITE OF NIEBLA FM TRANSGRESSIVE BASAL COMPLEX
k
SANDS OF BONARES FM
k
400
'CLAYS OF GIBRALEÓN' FM.
SANDS OF BONARES FM
420
BENTHIC FORAMINIFERA
NEOGENE LITOSTRATIGRAPHIC FORMATIONS
Niebla section
CORALLINE RED ALGAE
Lora del Río section
A SINGULAR MIOCENE PALEOBOTANIC RECORD IN DELTAIC SEQUENCES OF NORD-BETIC CORRIDOR (GUADALQUIVIR BASIN, SOUTH OF SPAIN) POSTER 1 Abad, M., Ruiz, F., Martin-Closas, C., Tosquella, J., Toscano, A., González-Regalado, M.L. Corresponding-author::
[email protected]
INTRODUCTION
REGIONAL SETTING
In the central and western sectors of the Guadalquivir basin, the the scarce paleobot paleobotanical anical record can be justified by the restricted presence of coastal coastal and continental continental facies deposited under subaerial conditions. Previous researches highlight its its presence in Lower Pliocene units units indicating high temperatures and subtropical palaeoclimatic palaeoclimatic conditions although not previous works have described macroflora fossils for Tortonian. In this work we describe for first time a relatively complete paleobot p aleobotanic anic record for Upper Miocene in this basin.
SEDIMENTARY ENVIRONMENT
Estuary-Bay
Le
WSW
Gi
Beachs and carbonate shelf
Prodelta Prodelt a / Siliciclastic Shelf
Deltas, beachs and shallow Deltas, marine shelf (mixed sedim.)
Coastal Coast al plain ,deltaic ,deltaic front and beachs
Ni
Az
Pa
Ge Vv
Vn
Carbonate shelf Shallow marine carbonate platform plat form and beachs
Lo
Ho
ENE
Ay This work
25 m
FACIES ASSOCIA ASSOCIATION TION Facies association of deltaic deltaic plain has been describe in the central sector of this foreland margin (Arroyo Parroso section, Sevilla province). Facies are constituted mainly by conglomerates and gravely deposits, deposits, but sandy deposits deposits are also common. They have been interpreted as migration of subaqueous dunes and infilling of scours inside mobile channel belts belts in a braided fluvial system. Gravel and pebbles bedload transport occurred under high flow regime.
SW
0
NE
?
? ZSP
Fluvial system
Sea-level
Prodelta
o Fr
lta
e td
during lower flow regime although high proportions of fine sediment sedimentss were winnowed out in suspension as turbidity plumes from plain delta delta to delta delta front and neighbouring shallow marine zones. These facies are yellowish, laminated silts silts and grey, grey, massive clays and show tabular tabular and lenticular geometry (LS-2 Facies). Microfaunistic record record is very poor but some specimens of benthic foraminifera (Ammonia (Ammonia beccari, A. inflata, inflata, Elphidium crispum and Nonion boueanum) boueanum) have been collected. They may also contain contain internal moulds of bivalve Modiolus, burrows burrows of crustacean crustacean decapods (Thalassinoides (Thalassinoides isp.) and fractured remains of plants. plants.
Silt and clay facies rich in plant remains
0
50 Km
Along the northern margin the sedimentary fill includes very different facies grouped into the Tortonian Basal Transgressive Complex, or BTC. The BTC is composed of several internal sequences linked to 4th order cycles of sea-level change and provides a clear example of stacked stacked high-frequency cycles of mixed carbonates and siliciclastics. Siliciclastic sedimentation took place in deltas, beaches and shallow marine zones. Deltaic systems migrated basinwards during stillstand phases whereas transgressive pulses provided better conditions for the production and accumulation of biogenic carbonates.
Deltaic Plain
n
Subordinate muddy facies were deposited
?
RESULTS RESUL TS AND CONCLUSIONS Taxonomic classification of this paleobotanic record is very ain neither banks nor apices and veins difficult because not retain are poorly preserved. Elongated forms similar to helophytes have been recognised as well as numerous spherical geometries interpreted as seeds. Seeds are abundant in transported associations of fluvial environments while as remains of plants transported by tractive and suspension processes often are broken into polygonal fragments following nervation pattern as can be observed in all the studied specimens. Due to the relationship with underlying and overlying s, and their sedimentary sediment and paleontological deposits, characteristics, these facies are interpreted as rapid settling deposits of distal al delta delta plain channels (topset) (topset) located in areas with limited marine influence.
