Julio Aguirre

Diversity of coralline red algae: Origination and extinction patterns from the Early Cretaceous to the Pleistocene

Abstract Data from a comprehensive literature survey for the first time provide stage-level resolution of Early Cretaceous through Pleistocene species diversity for nongeniculate coralline algae. Distributions of a total of 655 species in 23 genera were compiled from 222 publications. These represent three family-subfamily groupings each with distinctive present-day distributions: (1) Sporolithaceae, low latitude, mainly deep water; (2) Melobesioid corallinaceans, high latitude, shallow water, to low latitude, deep water; (3) Lithophylloid/mastophoroid corallinaceans, mid- to low latitude, shallow water. Raw data show overall Early Cretaceous–early Miocene increase to 245 species in the Aquitanian, followed by collapse to only 43 species in the late Pliocene. Rarefaction analysis confirms the pattern of increase but suggests that scarcity of publications exaggerates Neogene decline, which was actually relatively slight. Throughout the history of coralline species, species richness broadly correlates with published global paleotemperatures based on benthic foraminifer δ18O values. The warm-water Sporolithaceae were most species-abundant during the Cretaceous, but they declined and were rapidly overtaken by the Corallinaceae as Cenozoic temperatures declined. Trends within the Corallinaceae during the Cenozoic appear to reflect environmental change and disturbance. Cool- and deep-water melobesioids rapidly expanded during the latest Cretaceous and Paleocene. Warmer-water lithophylloid/mastophoroid species increased slowly during the same period but more quickly in the early Oligocene, possibly reflecting habitat partitioning as climatic belts differentiated and scleractinian reef development expanded near the Eocene/Oligocene boundary. Melobesioids abruptly declined in the late Pliocene–Pleistocene, while lithophylloid/mastophoroids increased again. Possibly, onset of glaciation in the Northern Hemisphere (∼2.4 Ma) sustained or accentuated latitudinal differentiation and global climatic deterioration, disrupting high-latitude melobesioid habitats. Simultaneously, this could have caused moderate environmental disturbance in mid- to low-latitude ecosystems, promoting diversification of lithophylloids/mastophoroids through the “fission effect.” Extinction events that eliminated >20% of coralline species were most severe (58–67% of species) during the Late Cretaceous and late Miocene–Pliocene. Each extinction was followed by substantial episodes of origination, particularly in the Danian and Pleistocene.

Coralline algal assemblages in upper Neogene reef and temperate carbonates in Southern Spain

Reef and temperate carbonate units alternate in the upper Miocene^Pliocene stratigraphic record of Betic basins palaeogeographically connected to the Mediterranean. Shallow-water coralline algal assemblages in temperate units differ in taxonomic composition from those in reef carbonate units. The difference attains the subfamily level since the temperate lithofacies are characterised by assemblages dominated by lithophylloids (Lithophyllum), whereas mastophoroids (Spongites and Neogoniolithon) predominate in the reef units. The proportion of lithophylloids, however, can be high in samples from shallow-reef palaeoenvironments. The distinction is less marked in deeper platform deposits since melobesioids (Lithothamnion, Mesophyllum and Phymatolithon) are the major elements in the assemblages from both reef and temperate units. Sporolithon, the only representative of the family Sporolithaceae, is frequent in reef-slope deposits but very rare in temperate lithofacies. The change in coralline algal assemblages from temperate to subtropical/tropical units is probably the result of the palaeophytogeography of the coralline red algae during the Late Neogene along climatic belts. Shallow-water floras were dominated by lithophylloids in cooler periods, during which the western Mediterranean was within the temperate belt, as in the present-day situation. In warmer episodes, subtropical/tropical conditions enveloped the region and the tropical coralline floras, in which mastophoroids predominate, together with reef corals and green algae inhabited the Betic basins. Similar, less pronounced, phytogeographic patterns can be roughly recognised in modern oceans. Fossil coralline algal assemblages can, therefore help to identify the palaeoclimatic context of sedimentation of the rocks in which they are recorded. They constitute a palaeontological tool supplemental to lithofacies and other fossil indicators for characterising such contexts in Cenozoic platform deposits. fl 2001 Elsevier Science B.V. All rights reserved.

Taxonomy of fossil coralline algal species: Neogene Lithophylloideae (Rhodophyta, Corallinaceae) from southern Spain

The anatomy of coralline algae is relatively simple. This, together with high intraspecific variability, reduces characters used as diagnostic criteria in delimiting species in present-day coralline algae to a very few, most of which can be recognized in fossil representatives of this family. Similar taxonomic procedures may thus be used at the species level both in modern and fossil coralline algae. Extant species of this subfamily can be recognized in fossil material. This study of Lithophylloideae from the Neogene of southern Spain describes five species (Lithophyllum dentatum, L. incrustans, L. nitorum, L. orbiculatum, and L. pustulatum), which are all found in the present-day Atlantic and western Mediterranean. Palaeontological studies on coralline algae, at least those from the late Cenozoic, have to take into account modern species and their current taxonomy, as coralline algal species have long stratigraphic ranges and many extant species were presumably already present in the Neogene.

The Mediterranean coral Cladocora caespitosa: a proxy for past climate fluctuations?

Sclerochronology was applied to recent, Holocene and Pleistocene samples of Cladocora caespitosa. Late Pliocene samples were recrystallised and thus unsuitable for sclerochronology. Quaternary samples showed a clear, alternating banding pattern as in the living coral, confirming a marked seasonality of past climate. The computed mean annual growth rates ranged from 2.1 to 6.9 mm year 1 , with highest growth rates during the warmer phase (isotope stage 5e) of the first climate cycle. It is hypothesised that the largest fossil banks of C. caespitosa grew in a coastal environment with considerable alluvial inputs and warmer temperatures than today. D 2003 Elsevier B.V. All rights reserved.

Contrasting models of temperate carbonate sedimentation in a small Mediterranean embayment: the Pliocene Carboneras Basin, SE Spain

Temperate carbonates consisting of bioclastic (bryozoan–bivalve–coralline algal) packstones to rudstones formed in the Carboneras Basin, a small embayment of the Mediterranean Sea in SE Spain, during the early Pliocene. Transgressive systems tract carbonate deposits exhibit three distinct sedimentary styles, with contrasting lithofacies patterns and stratal-geometry arrangements. Palaeotopography and local hydrodynamic conditions were the major factors controlling sedimentation. On the steep northern margin, affected by southeasterly wind-driven storms, a prograding platform (distally steepened ramp) with well-marked, platform-slope clinoforms developed. Bivalves extensively colonized the outer platform, and rhodolith pavements covered its edge. Coarse-grained, bioclastic sediments were frequently removed from the platform by storms and redeposited on the platform slope. On the southern margin of the basin, longshore currents driven by southeasterly winds hydrodynamically accumulated carbonate particles to form a spit-platform, on top of which some shoals developed. These shoals were dismantled from time to time by the northern storms, and the sediment was redeposited on the lee-side slope of the spit-platform. On the gentle and protected western margin, oyster banks and rhodolith pavements colonized the inner-ramp environment whereas coralline algal–bryozoan–bivalve bioconstructions formed on the outer ramp. This example shows that several sedimentary styles of temperate carbonate deposition can coexist in a single basin.

Dasycladalean Algal Biodiversity Compared with Global Variations in Temperature and Sea Level over the Past 350 Myr

Abstract Dasycladalean green algae show marked fluctuation in genus and species biodiversity from the Carboniferous to the Pliocene. Diversity lows (<10 species) alternate with peaks (>70 species) over periods of ∼20–50 Myr. Relatively few taxa are recorded for the earliest Carboniferous, Early Triassic, Early to Mid-Jurassic, Late Cretaceous, and Pliocene. Diversity maxima occur in the Permian, Early Cretaceous, and Paleocene. With the exception of the Late Cretaceous, biodiversity broadly tracked temperature from the Carboniferous to the Pliocene. Diversity minima generally correspond with low sea level, and diversity maxima with periods of intermediate sea level. Dasycladaleans were most diverse when their main habitats—warm shallow seas—were most extensive. This observation does not preclude the influence of additional important factors on dasycladalean evolutionary history, but it suggests a strong link between long-term patterns of dasycladalean diversity and global fluctuations in temperature and sea level.

Integrating phylogeny, molecular clocks, and the fossil record in the evolution of coralline algae (Corallinales and Sporolithales, Rhodophyta)

Abstract When assessing the timing of branching events in a phylogeny, the most important tools currently recognized are a reliable molecular phylogeny and a continuous, relatively complete fossil record. Coralline algae (Rhodophyta, Corallinales, and Sporolithales) constitute an ideal group for this endeavor because of their excellent fossil record and their consistent phylogenetic reconstructions. We present the evolutionary history of the corallines following a novel, combined approach using their fossil record, molecular phylogeny (based on the 18S rDNA gene sequences of 39 coralline species), and molecular clocks. The order of appearance of the major monophyletic taxa of corallines in the fossil record perfectly matches the sequence of branching events in the phylogeny. We were able to demonstrate the robustness of the node ages in the phylogeny based on molecular clocks by performing an analysis of confidence intervals and maximum temporal ranges of three monophyletic groups of corallines (the families Sporolithaceae and Hapalidiaceae, as well as the subfamily Lithophylloideae). The results demonstrate that their first occurrences are close to their observed appearances, a clear indicator of a very complete stratigraphic record. These chronological data are used to confidently constrain the ages of the remaining branching events in the phylogeny using molecular clocks.

Models of temperate carbonate deposition in Neogene basins in SE Spain: a synthesis

Abstract Upper Miocene (Tortonian-Messinian) to Lower Pliocene (Zanclean) temperate bioclastic limestones occur in the Betic intermontane basins mixed with diverse proportions of siliciclastics. Components are mostly originally calcitic skeletons of invertebrates (especially bryozoans and bivalves) and coralline algae. Carbonate mud content is usually low and cementation is generally weak. These temperate carbonates formed in ramps. The depositional surface profile and local hydrodynamic conditions in each example controlled the occurrence of diverse facies at similar positions within the ramp. Shallow-water facies are well represented and formed in beaches and backshore lagoons, spits, rocky shores and submarine cliffs. Shoals developed seawards of shore deposits; the relatively quiet environments basinwards of the shaosl were the areas of maximal carbonate production (factory facies). The lack of early lithification favoured mobilization of skeletal particles. Waves and currents during storms transported carbonate grains landwards from the factory areas to shoals, spits and beaches. Skeletal grains were also transported downslope along the ramp. Re-deposited carbonates occur within basinal marls in submarine lobes and channels fed by channels cross-cutting and excavating the platform sediments. The absence of hermatypic corals and calcareous green algae in shallow-water deposits suggests cool surface water temperatures during carbonate formation. Large benthic foraminifers and oxygen stable isotope values indicate winter surface water temperatures of 16–17°C.

Vegetation, sea-level, and climate changes during the Messinian salinity crisis

The Messinian salinity crisis (late Miocene) is one of the most fascinating paleoceanographic events in the recent geological history of the Mediterranean Sea, defining a time when it partly or nearly completely dried out. However, the relative roles of tectonic processes and sea-level changes, as triggers for restriction and isolation of the Mediterranean Sea from the open ocean, are still under debate. In this study, we present a detailed pollen, dinoflagellate cyst (dinocyst), and magnetic susceptibility analysis of a sequence of late Neogene (between ca. 7.3 and 5.2 Ma) marine sediments from the Montemayor-1 core (lower Guadalquivir Basin, southwestern Spain), which provides a continuous record of paleoenvironmental variations in the Atlantic side of the Betic corridors during the late Miocene. Our results show that significant paired vegetation and sea-level changes occurred during the Messinian, likely triggered by orbital-scale climate change. Important cooling events and corresponding glacio-eustatic sea-level drops are observed in this study at ca. 5.95 and 5.75 Ma, coinciding with the timing and duration of oxygen isotopic events TG32 and TG22–20 recorded in marine sediments worldwide. It is generally accepted that the onset of the Messinian salinity crisis began at ca. 5.96 ± 0.02 Ma. Therefore, this study suggests that the restriction of the Mediterranean could have been triggered, at least in part, by a strong glacio-eustatic sea-level drop linked to a climate cooling event occurring at the time of initiation of the Messinian salinity crisis.

Substrate-related changes in pectinid fossil assemblages

Quantitative analysis of pectinid (Bivalvia) assemblages in the Lower Pliocene deposits of the Almeria-Nijar and Poniente basins in southeastern Spain reveals changes in the taphonomical attributes, taxonomical composition, and shell morphology of these assemblages in relation to the sediments in which they occur. The lower Pliocene deposits in both basins consist of outer-platform clays, silts, and fine sands, which laterally and vertically pass into innerplatform and deltaic sands and conglomerates. Proximal and distal tempestite beds are intercalated in the sands and silts. Calcirudites accumulated in shallow water settings with no influx of terrigenous sediments. The variations of pectinid assemblages according to the embedding sediments represent changes in the assemblages in proximal—distal depth gradients. Pecten and Chlamys species predominate in shallow water conglomerates and calcirudites. Chlamys seniensis (Lamarck) and Flabellipecten bosniasckii (Stefani and Pantanelli) are the most abundant pectinids in coarseto-medium sands and in intercalated proximal tempestites from the inner platform and delta front. Amusium cristatum (Bronn) is the most common component in the assemblages from outer-platform fine sands, silts, clays, and distal tempestites. Assemblages from shallow-water, coarse-grained deposits comprise strongly-ribbed, inflated shells, while those from deep-water, fine-grained lithofacies are mainly composed of smooth, flat-shelled species.