Ana Santos
Ana Santos is graduated in Marine Biology and has a MSc in Marine and Coastal Studies from the Algarve University (Portugal) in 2000. She carried out her pre-doctoral studies at Algarve University (2001-2005), obtaining her Ph.D. degree in Geosciences in the speciality of Paleontology. Her main research field concerns to the paleoichnological study of hard substrates and its taphonomy and paleoecology. Throughout the post-doctoral stage, her main research interests have broadened in scope from paleoichnology to its relations with past sea-level changes, ancient shoreline positions or the intensity of the physical disturbance of these past coastal environments.
From 2006 to 2008 she carried out her first postdoctoral research at University of Lisbon (Portugal) with a grant from the Portuguese FCT. From 2009 to 2011 Ana had a second postdoctoral contract from the Spanish Ministry of Science at the University of Huelva (Spain), during which she has been an Assistant Professor. Her postdoctoral experience covers 72 months. Currently she is a researcher in the GAIA Group at Huelva University.
Address: Departamento Geodinámica y Paleontología
Facultad Ciencias Experimentales
Universidad de Huelva
Campus del Carmen , Avda. 3 Marzo s/n
21071 Huelva, Spain
From 2006 to 2008 she carried out her first postdoctoral research at University of Lisbon (Portugal) with a grant from the Portuguese FCT. From 2009 to 2011 Ana had a second postdoctoral contract from the Spanish Ministry of Science at the University of Huelva (Spain), during which she has been an Assistant Professor. Her postdoctoral experience covers 72 months. Currently she is a researcher in the GAIA Group at Huelva University.
Address: Departamento Geodinámica y Paleontología
Facultad Ciencias Experimentales
Universidad de Huelva
Campus del Carmen , Avda. 3 Marzo s/n
21071 Huelva, Spain
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Papers by Ana Santos
outcrop and core research, to improve interpretations of depositional and paleoenvironmental conditions, with
special attention to sequence stratigraphy. Seven intervalswere differentiated in outcrops based on stratigraphic
and ichnological features, consisting of two ichnofabrics: Ophiomorpha-Thalassinoides-Spongeliomorpha
ichnofabric characterizes intervals 1, 2, 6, 7 and 8, while Palaeophycus-Planolites-Phycosiphon ichnofabric characterizes
intervals 3, 4 and 5. Fourteen ichnofabrics were differentiated in the core, mainly in view of lithological
features, including ferruginous material, grain size, mottled background, ichnotaxa, and Bioturbation Index. A
comparison between outcrop and core ichnofabrics through the upper 13.5 m, corresponding to the uppermost
Tortonian-lowermost Messinian interval, revealed certain similarities as well as some differences. A continuous
and relatively slow siliciclastic deposition with punctual variations in the sedimentation rate can be interpreted
that, associated with favorable paleoenvironmental parameters such as aerobic conditions and nutrient availability,
evidence that a well-developed and diverse macroinvertebrate trace maker community existed at that time.
Softgrounds are dominant, but occasionally loosegrounds and even firmgrounds could develop. The ichnofabric
distribution shows long-range patterns in outcrop and core, and short-range patterns exclusively in core. Longrange
patterns reflect the last phases of a transgressive systemtract, with a “maximumflooding zone” at the end,
and then a highstand normal regression. High-frequency, short-range, repetitive patterns in ichnofabrics from
core, mainly between ichnofabrics 6/8 to 9 from lower to upper part of the pattern, can be linked to “local
flooding surfaces”, subdividing the “maximumflooding zone” into parasequences. Our results reveals the usefulness
of the integrative ichnofabric analysis, including outcrop and core materials, in sedimentary basin analysis,
assessing paleoenvironmental conditions and improving sequence stratigraphy characterization.
cement-replacement textures originally hosted in shallowmarine
sandstones, were reworked into Lower Cretaceous
fluvio-deltaic conglomerates and shoreface sandstones
(External Zones, Betic Cordillera). A cycle of host sand
deposition, early diagenetic concretion formation and
concretion reworking is documented: (1) Well-sorted
shoreface sandstone deposited. (2) Spherical to ovoid,
non-ferroan calcite-cemented concretions formed below
flooding surfaces at shallow-burial depths during early
eodiagenesis. Non-ferroan calcite cements were precipitated
from the bicarbonate derived from seawater and from
dissolution of marine bioclasts, as shown by isotope analyses.
(3) Concretions were reworked and exposed on the
seafloor in a high-energy setting as indicated by the presence
of numerous bivalve borings (Entobia ichnofacies), laminated micritic microbial crusts around the concretions,
and epilithobionts (oysters, barnacles and corals) on the
concretion surface. Concretions also appear as erosional
remnants on the floor of channels which were incised into
the shoreline sandstone when sea-level fell. (4) The fluvio–
deltaic channels were filled with sediment during flooding
in the late lowstand of sea-level. (5) The concretions are
partly dolomitized, and the presence of siderite, pyrite and
barite in the outer part of the concretions precipitated
before the dolomite, suggests that the latter formed during
shallow burial.
Upper Tortonian site of Cacela, Algarve region, SE Portugal, revealed 24 different ichnotaxa and five systematic groups of encrusters
(Foraminifera, Annelida, Bryozoa, Balanomorpha and Bivalvia).
Despite a relatively high ichnodiversity, the percentage of bioerosion in the specimens analysed is quite low (10–12%). This is explained by
rapid sedimentation with only short periods of exposure on the sea-floor.
The dominant bioerosion structures were linked to the boring activity of nonpredatory organisms. Algal microborings are the most common,
followed by annelid borings (Caulostrepsis-Maeandropolydora), sponge borings (Entobia) and ctenostome bryozoans (Pinaceocladichnus).
Spatial distribution of bioerosion structures and encrusters allow the reconstruction of three successive stages. The first was restricted to the
biosubstrate lifetime, with structures showing a preferred orientation and situated exclusively on the outside of the shells. The second comprises the
period immediately after death, with structures that extend outwards and start with the colonization of the interior of the valves, losing their initial
orientation. The third stage relates to later postmortem colonisation, with structures on both sides of the valves and without a preferential
orientation.
of the families Saccamminidae (aff. Sagenina), Lituolidae
(Placopsilina), Cibicididae (Cibicides, Dyocibicides,
Cibicidella) and Planorbulinidae (Planorbulina and Planorbulinella)
that colonized epifaunal bivalves (ostreids and pectinids)
during the early Pliocene in southern Spain has led
to the recognition of two new boring ichnogenera: Camarichnus
ichnogen. nov., with two ichnospecies, C. subrectangularis
ichnosp. nov. and C. arcuatus ichnosp. nov., and
Canalichnus ichnogen. nov., with one ichnospecies, C. tenuis
ichnosp. nov. The first two ichnospecies were produced by
adnate lituolids and cibicidids, the last by saccamminids.
Their recognition is very important when quantifying populations of these organisms. Colonisation took place
after death of the host bivalves, when they acted as very
stable substrates whose topography probably controlled the
initial settlement pattern of the foraminifera. The colonisation
sequence started with the foraminifera (lituolidssaccamminids-
cibicidids-planorbulinids) and was followed
by vermetid gastropods, serpulids, spirorbids, cheilostome
bryozoans and ⁄ or ostreids. Preferred orientations and overgrowth
relationships between cheilostome bryozoans and
serpulids have been detected in this material.
Ceratoconcha aff. costata within the carbonate skeleton of a
colonial hermatypical coral (Tarbellastrea reussiana) is
described from a middle Miocene basaltic rocky palaeoshore
on a small north-eastern Atlantic islet of Porto Santo
(Madeira Archipelago, Portugal). The resulting structure is
named as a new trace fossil Imbutichnus igen. nov., characterized
by a small, funnel-like cavity, a circular to oval crosssection,
with a nearly cylindrical shape in the upper part and
a conical shape towards the base. Imbutichnus costatum isp.
nov. is defined as a bioclaustration structure produced by the overgrowth of a pyrgomatid barnacle by a coral. From
an ethologic point of view, Imbutichnus is attributed to the
Impedichnia category. In terms of palaeoecology, it is interpreted
as the result of a parasitic relationship. This is also
the oldest record of pyrgomatid barnacles in the eastern
Atlantic and clearly demonstrates that the Miocene palaeogeographic
range of Ceratoconcha was much wider than previously
assumed.
represented along the Mediterranean coast of Iberia. An outcrop
north of the Sierra Tejeda, named La Resinera, exposes
concentrations of pebbles and boulders of marble, comprising
an upper Miocene marine beach deposit. The high diversity
of bioerosion trace fossils present in these boulders
includes structures produced by polychaete annelids, demosponges,
echinoids and endolithic bivalves, which indicate a
shallow shoreface environment. The ichnotaxa represented
are Maeandropolydora sulcans, Caulostrepsis taeniola, Entobia geometrica, Entobia ovula, Circolites kotoncensis, Gastrochaenolites
torpedo, Gastrochaenolites lapidicus, Gastrochaenolites
ornatus and Gastrochaenolites turbinatus. The borings are
Tortonian (late Miocene) in age. Also present, and particularly
abundant, are large sponge borings that have a single
chamber from which radiating canals emerge. This trace
fossil is designated as Entobia resinensis isp. nov.
as a tool to solve stratigraphic and tectonic issues is
beginning to bear fruits. The occurrence of an extensive
intra-Miocene marine abrasion platform in southern Portugal
at Oura (Albufeira) has been identiWed on the basis of
bioerosion trace fossils analysis. The observed ichnodiversity
is rather low, with bivalve boring Gastrochaenolites
being dominant. Nevertheless, the ichnoassemblage may be
assigned to the Entobia ichnofacies. The palaeoichnological
study of the Oura hardground conWrmed the existence
of an important intra-Miocene stratigraphic gap (ca. 3 Ma
hiatus), represented by a razor-sharp erosional contact that
separates the two main Neogene units in the Algarvian
region: the lower carbonate sequence of Lagos–Portimão
Formation (Langhian/Serravallian) and the upper siliciclastic
sequence of the Cacela Formation (Upper Tortonian).
outcrop and core research, to improve interpretations of depositional and paleoenvironmental conditions, with
special attention to sequence stratigraphy. Seven intervalswere differentiated in outcrops based on stratigraphic
and ichnological features, consisting of two ichnofabrics: Ophiomorpha-Thalassinoides-Spongeliomorpha
ichnofabric characterizes intervals 1, 2, 6, 7 and 8, while Palaeophycus-Planolites-Phycosiphon ichnofabric characterizes
intervals 3, 4 and 5. Fourteen ichnofabrics were differentiated in the core, mainly in view of lithological
features, including ferruginous material, grain size, mottled background, ichnotaxa, and Bioturbation Index. A
comparison between outcrop and core ichnofabrics through the upper 13.5 m, corresponding to the uppermost
Tortonian-lowermost Messinian interval, revealed certain similarities as well as some differences. A continuous
and relatively slow siliciclastic deposition with punctual variations in the sedimentation rate can be interpreted
that, associated with favorable paleoenvironmental parameters such as aerobic conditions and nutrient availability,
evidence that a well-developed and diverse macroinvertebrate trace maker community existed at that time.
Softgrounds are dominant, but occasionally loosegrounds and even firmgrounds could develop. The ichnofabric
distribution shows long-range patterns in outcrop and core, and short-range patterns exclusively in core. Longrange
patterns reflect the last phases of a transgressive systemtract, with a “maximumflooding zone” at the end,
and then a highstand normal regression. High-frequency, short-range, repetitive patterns in ichnofabrics from
core, mainly between ichnofabrics 6/8 to 9 from lower to upper part of the pattern, can be linked to “local
flooding surfaces”, subdividing the “maximumflooding zone” into parasequences. Our results reveals the usefulness
of the integrative ichnofabric analysis, including outcrop and core materials, in sedimentary basin analysis,
assessing paleoenvironmental conditions and improving sequence stratigraphy characterization.
cement-replacement textures originally hosted in shallowmarine
sandstones, were reworked into Lower Cretaceous
fluvio-deltaic conglomerates and shoreface sandstones
(External Zones, Betic Cordillera). A cycle of host sand
deposition, early diagenetic concretion formation and
concretion reworking is documented: (1) Well-sorted
shoreface sandstone deposited. (2) Spherical to ovoid,
non-ferroan calcite-cemented concretions formed below
flooding surfaces at shallow-burial depths during early
eodiagenesis. Non-ferroan calcite cements were precipitated
from the bicarbonate derived from seawater and from
dissolution of marine bioclasts, as shown by isotope analyses.
(3) Concretions were reworked and exposed on the
seafloor in a high-energy setting as indicated by the presence
of numerous bivalve borings (Entobia ichnofacies), laminated micritic microbial crusts around the concretions,
and epilithobionts (oysters, barnacles and corals) on the
concretion surface. Concretions also appear as erosional
remnants on the floor of channels which were incised into
the shoreline sandstone when sea-level fell. (4) The fluvio–
deltaic channels were filled with sediment during flooding
in the late lowstand of sea-level. (5) The concretions are
partly dolomitized, and the presence of siderite, pyrite and
barite in the outer part of the concretions precipitated
before the dolomite, suggests that the latter formed during
shallow burial.
Upper Tortonian site of Cacela, Algarve region, SE Portugal, revealed 24 different ichnotaxa and five systematic groups of encrusters
(Foraminifera, Annelida, Bryozoa, Balanomorpha and Bivalvia).
Despite a relatively high ichnodiversity, the percentage of bioerosion in the specimens analysed is quite low (10–12%). This is explained by
rapid sedimentation with only short periods of exposure on the sea-floor.
The dominant bioerosion structures were linked to the boring activity of nonpredatory organisms. Algal microborings are the most common,
followed by annelid borings (Caulostrepsis-Maeandropolydora), sponge borings (Entobia) and ctenostome bryozoans (Pinaceocladichnus).
Spatial distribution of bioerosion structures and encrusters allow the reconstruction of three successive stages. The first was restricted to the
biosubstrate lifetime, with structures showing a preferred orientation and situated exclusively on the outside of the shells. The second comprises the
period immediately after death, with structures that extend outwards and start with the colonization of the interior of the valves, losing their initial
orientation. The third stage relates to later postmortem colonisation, with structures on both sides of the valves and without a preferential
orientation.
of the families Saccamminidae (aff. Sagenina), Lituolidae
(Placopsilina), Cibicididae (Cibicides, Dyocibicides,
Cibicidella) and Planorbulinidae (Planorbulina and Planorbulinella)
that colonized epifaunal bivalves (ostreids and pectinids)
during the early Pliocene in southern Spain has led
to the recognition of two new boring ichnogenera: Camarichnus
ichnogen. nov., with two ichnospecies, C. subrectangularis
ichnosp. nov. and C. arcuatus ichnosp. nov., and
Canalichnus ichnogen. nov., with one ichnospecies, C. tenuis
ichnosp. nov. The first two ichnospecies were produced by
adnate lituolids and cibicidids, the last by saccamminids.
Their recognition is very important when quantifying populations of these organisms. Colonisation took place
after death of the host bivalves, when they acted as very
stable substrates whose topography probably controlled the
initial settlement pattern of the foraminifera. The colonisation
sequence started with the foraminifera (lituolidssaccamminids-
cibicidids-planorbulinids) and was followed
by vermetid gastropods, serpulids, spirorbids, cheilostome
bryozoans and ⁄ or ostreids. Preferred orientations and overgrowth
relationships between cheilostome bryozoans and
serpulids have been detected in this material.
Ceratoconcha aff. costata within the carbonate skeleton of a
colonial hermatypical coral (Tarbellastrea reussiana) is
described from a middle Miocene basaltic rocky palaeoshore
on a small north-eastern Atlantic islet of Porto Santo
(Madeira Archipelago, Portugal). The resulting structure is
named as a new trace fossil Imbutichnus igen. nov., characterized
by a small, funnel-like cavity, a circular to oval crosssection,
with a nearly cylindrical shape in the upper part and
a conical shape towards the base. Imbutichnus costatum isp.
nov. is defined as a bioclaustration structure produced by the overgrowth of a pyrgomatid barnacle by a coral. From
an ethologic point of view, Imbutichnus is attributed to the
Impedichnia category. In terms of palaeoecology, it is interpreted
as the result of a parasitic relationship. This is also
the oldest record of pyrgomatid barnacles in the eastern
Atlantic and clearly demonstrates that the Miocene palaeogeographic
range of Ceratoconcha was much wider than previously
assumed.
represented along the Mediterranean coast of Iberia. An outcrop
north of the Sierra Tejeda, named La Resinera, exposes
concentrations of pebbles and boulders of marble, comprising
an upper Miocene marine beach deposit. The high diversity
of bioerosion trace fossils present in these boulders
includes structures produced by polychaete annelids, demosponges,
echinoids and endolithic bivalves, which indicate a
shallow shoreface environment. The ichnotaxa represented
are Maeandropolydora sulcans, Caulostrepsis taeniola, Entobia geometrica, Entobia ovula, Circolites kotoncensis, Gastrochaenolites
torpedo, Gastrochaenolites lapidicus, Gastrochaenolites
ornatus and Gastrochaenolites turbinatus. The borings are
Tortonian (late Miocene) in age. Also present, and particularly
abundant, are large sponge borings that have a single
chamber from which radiating canals emerge. This trace
fossil is designated as Entobia resinensis isp. nov.
as a tool to solve stratigraphic and tectonic issues is
beginning to bear fruits. The occurrence of an extensive
intra-Miocene marine abrasion platform in southern Portugal
at Oura (Albufeira) has been identiWed on the basis of
bioerosion trace fossils analysis. The observed ichnodiversity
is rather low, with bivalve boring Gastrochaenolites
being dominant. Nevertheless, the ichnoassemblage may be
assigned to the Entobia ichnofacies. The palaeoichnological
study of the Oura hardground conWrmed the existence
of an important intra-Miocene stratigraphic gap (ca. 3 Ma
hiatus), represented by a razor-sharp erosional contact that
separates the two main Neogene units in the Algarvian
region: the lower carbonate sequence of Lagos–Portimão
Formation (Langhian/Serravallian) and the upper siliciclastic
sequence of the Cacela Formation (Upper Tortonian).