Laia Alegret's research while affiliated with University of Zaragoza and other places

Publications (160)

Article
The Cretaceous/Paleogene (K/Pg) boundary is marked by one of the largest mass extinctions in Earth’s history, with geological evidence for this event being expressed in hundreds of locations worldwide. An extensively studied section located near El Kef, northwestern Tunisia, is characterized by the classic iridium-rich K/Pg boundary layer, abundant...
Article
Full-text available
The marine biological carbon pump, which exports organic carbon out of the surface ocean, plays an essential role in sequestering carbon from the atmosphere, thus impacting climate and affecting marine ecosystems. Orbital variations in solar insolation modulate these processes, but their influence on the tropical Pacific during the Late Cretaceous...
Article
Full-text available
The absolute position during the Cenozoic of northern Zealandia, a continent that lies more than 90% submerged in the southwest Pacific Ocean, is inferred from global plate motion models, because local paleomagnetic constraints are virtually absent. We present new paleolatitude constraints using paleomagnetic data from International Ocean Discovery...
Article
One of the major environmental and biotic turnovers of the Phanerozoic occurred at the Cretaceous-Paleogene (K-Pg) boundary, being the focus of countless scientific studies that addressed the timing, causes and consequences of this global event. Paleoenvironmental conditions that preceded the K-Pg boundary, however, have been less studied, especial...
Article
IODP Site U1509 (Expedition 371), New Caledonia Trough, provides a rare latest Cretaceous–Paleocene record from offshore northern Zealandia. We present new palynomorph and benthic foraminiferal assemblage data that show a transition from a latest Cretaceous vegetated sediment source region to a fully oceanic environment in the Paleocene. Latest Cre...
Preprint
Full-text available
The marine biological carbon pump, which exports organic carbon out of the surface ocean, plays an essential role in sequestering carbon from the atmosphere, thus impacting climate and affecting marine ecosystems. Orbital variations in solar insolation modulate these processes, but their influence on the tropical Pacific during the Late Cretaceous...
Chapter
This volume pays tribute to the great career and extensive and varied scientific accomplishments of Walter Alvarez, on the occasion of his 80th birthday in 2020, with a series of papers related to the many topics he covered in the past 60 years: Tectonics of microplates, structural geology, paleomagnetics, Apennine sedimentary sequences, geoarchaeo...
Article
Long-term climatic trends of the Paleogene were interrupted by global perturbations of the carbon cycle, commonly associated with warming of surface and bottom waters and ecosystem disturbance. Most of these perturbations occurred in the Paleocene - Eocene greenhouse climate, but others were superimposed on the transition of greenhouse-to- icehouse...
Article
Full-text available
Sediment mass accumulation rate (MAR) is a proxy for paleoceanographic conditions, especially if biological productivity generated most of the sediment. We determine MAR records from pelagic calcareous sediments in Tasman Sea based on analysis of 11 boreholes and >3 million seismic reflection horizon picks. Seismic data from regions of 10,000–30,00...
Article
Full-text available
Rapid onset of subduction tectonics across the western Pacific convergent margins in the early Eocene was followed by a slower phase of margin growth of the proto Tonga-Kermadec subduction system north of Zealandia during a middle Eocene phase to tectonic adjustment. We present new age constraints from International Ocean Discovery Program Expediti...
Article
Full-text available
Environmental and biotic responses to early Eocene hyperthermal events in the southwest Pacific are critical for global paleoclimate reconstructions during Cenozoic greenhouse intervals, but detailed multidisciplinary studies are generally missing from this time and location. Eocene carbonate sediments were recovered during International Ocean Disc...
Article
Full-text available
Geoconservation and geoethics are two emergent domains in geosciences. During the last decade, both topics have increasingly gained the attention of geoscientists and the society, but the main geoethical dilemmas related to the conservation and management of geoheritage are not clearly identified yet. This work aims at providing an overview on the...
Article
Full-text available
The Paleogene was punctuated by perturbations of the global carbon cycle, many associated with transient global warming events (hyperthermals). The Dan-C2 event (~160 kyr after Cretaceous/Paleogene boundary; K/Pg) was the oldest of these eccentricity-linked carbon cycle disturbances (ELCD). In contrast to other hyperthermals, the Dan-C2 event was n...
Article
Full-text available
All studies focused on the evaluation of paleoecological variability over geological time must be linked to a specific age or time interval, which can be defined using different time scales (biostratigraphic, chronostratigraphic, geochronological or orbital). Therefore, integrated time scales are essential to allow comparisons of data from differen...
Article
Full-text available
Benthic foraminifera are the most common meiofaunal unicellular deep-sea biota, forming skeletons used as proxies for past climate change. We aim to increase understanding of past non-analog oceans and ecosystems by evaluating deep-sea benthic foraminiferal responses to global environmental changes over latest Cretaceous through Oligocene times (67...
Article
Full-text available
The Global Stratotype Section and Point (GSSP) for the base of the Bartonian, currently remains undefined. The Bartonian unit stratotype is located at the Barton coastal section in the Hampshire Basin, on the South Coast of the UK. The base of the “Barton beds” was originally placed at the lowest occurrence of Nummulites prestwichianus, and this is...
Article
Full-text available
Data from International Ocean Discovery Program (IODP) Expedition 371 reveal vertical movements of 1–3 km in northern Zealandia during early Cenozoic subduction initiation in the western Pacific Ocean. Lord Howe Rise rose from deep (~1 km) water to sea level and subsided back, with peak uplift at 50 Ma in the north and between 41 and 32 Ma in the s...
Article
Understanding the role of deep-sea biota across global warming events in the past is key to unravel climate system dynamics during periods of increased pCO2 levels. Here we present the first record of the benthic foraminiferal response to a middle Eocene transient warming event named Late Lutetian Thermal Maximum (LLTM; 41.52 Ma) at ODP Site 702 in...
Article
An impact with a dash of volcanism Around the time of the end-Cretaceous mass extinction that wiped out dinosaurs, there was both a bolide impact and a large amount of volcanism. Hull et al. ran several temperature simulations based on different volcanic outgassing scenarios and compared them with temperature records across the extinction event. Th...
Article
Full-text available
The Middle Eocene Climatic Optimum (MECO) was an unusual global warming event that interrupted the long‐term Eocene cooling trend ca. 40 Ma. Here we present new high‐resolution bulk and benthic isotope records from South Atlantic ODP Site 702 to characterize the MECO at a high latitude setting. The MECO event, including early and peak warming as we...
Article
Full-text available
Significance Debate lingers over what caused the last mass extinction 66 million years ago, with intense volcanism and extraterrestrial impact the most widely supported hypotheses. However, without empirical evidence for either’s exact environmental effects, it is difficult to discern which was most important in driving extinction. It is also uncle...
Conference Paper
Recognizing past events of transient global warming triggered by release of carbon into the ocean-atmosphere system is important for understanding Earth´s climate under elevated pCO2 conditions. These events, called hyperthermals, are recognized in the marine geological record by shifts in the δ13C and δ18O in carbonate and shells. Several hyperthe...
Article
Full-text available
The effects of the Cretaceous-Paleogene (K/Pg) mass extinction (~66 Ma) on marine primary and export productivity remain debated. We studied changes in carbon and nitrogen cycling in eight neritic and upper bathyal sections with expanded K/Pg boundary clay layers in the western Tethys and northeastern Atlantic Ocean, by measuring stable carbon isot...
Article
Full-text available
The response of the Earth system to greenhouse-gas-driven warming is of critical importance for the future trajectory of our planetary environment. Hyperthermal events – past climate transients with global-scale warming significantly above background climate variability – can provide insights into the nature and magnitude of these responses. The la...
Conference Paper
Full-text available
The base of the Bartonian Stage remains undefined. The Alum Bay section (Isle of Wight) is the parastratotype section of the Bartonian unit Stratotype located in the Hamp-shire Basin. The level chosen for the base of the unit Bartonian Stage, in the type area, is a single bed rich in Nummulites prestwichianus. Unfortunately this bed is scarcely cor...
Conference Paper
Full-text available
The Middle Eocene Climatic Optimum (MECO) is one of the several hyperthermal events that interrupted the long-term cooling trend of the Eocene. It differs from other Eocene hyperthermals in its longer duration, carbon isotopic signature, driver mechanisms and its effects on a global scale. Its paleoenvironmental and biotic consequences are poorly u...
Article
Full-text available
The Eocene was a period of intense climate variability and the response of deep-sea biota is still poorly understood, especially across certain understudied intervals from the middle Eocene. We present new benthic foraminiferal data from a Bartonian marine sequence deposited in the western Tethys Ocean (Torre Cardela section, Spain), and determine...
Data
Taxonomic list. Most common benthic foraminifera during the early Eocene and other species mentioned in the text. (DOCX)
Data
Quantitative data of benthic foraminifera in the studied samples from ODP Site 1051 and 1258. (XLSX)
Data
Number of species vs. number of specimens in samples from ODP Sites 1051 and 1258. (TIF)
Data
Quantitative data of benthic foraminifera in the studied samples from DSDP site 401. (XLSX)
Data
Quantitative data of benthic foraminifera in the studied samples from ODP Site 1262 and 1263. (XLSX)
Data
Benthic foraminifera across the middle Ypresian interval. (XLSX)
Article
Full-text available
The early Eocene greenhouse world was marked by multiple transient hyperthermal events. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), linked to the extinction of the globally recognised deep-sea benthic foraminiferal Velasco fauna, which led to the development of early Eocene assemblages. This turnover has been studied a...
Data
Number of samples, specimens and species, and size fraction studied in each site. (XLSX)
Data
Benthic foraminifera across the lower Ypresian interval. (XLSX)
Article
The Paleocene-Eocene transition is well represented in the bathyal Zumaia section (Basque-Cantabric Basin, Northern Spain), where numerous studies have documented the sedimentological, environmental and biotic effects of the Paleocene-Eocene Thermal Maximum (PETM). The extinction of more than half of the species of deep-sea benthic foraminifera has...
Article
Full-text available
International Ocean Discovery Program (IODP) Expedition 371 drilled six sites in the Tasman Sea of the southwest Pacific between 27 July and 26 September 2017. The primary goal was to understand Tonga-Kermadec subduction initiation through recovery of Paleogene sediment records. Secondary goals involved understanding regional oceanography and clima...
Article
Full-text available
International Ocean Discovery Program (IODP) Expedition 371 drilled six sites in the Tasman Sea of the southwest Pacific between 27 July and 26 September 2017. The primary goal was to understand Tonga-Kermadec subduction initiation through recovery of Paleogene sediment records. Secondary goals involved understanding regional oceanography and clima...
Article
Full-text available
The response of the Earth System to greenhouse-gas driven warming is of critical importance for the future trajectory of our planetary environment. Hypethermal events – past climate transients with significant global-scale warming – can provide insights into the nature and magnitude of these responses. The largest hyperthermal of the Cenozoic was t...
Conference Paper
Full-text available
The Global boundary Stratotype Section and Point (GSSP) for the base of the Bartonian, currently remains undefined. The Bartonian unit stratotype is located at the Barton coastal section in the Hampshire Basin, on the South Coast of the UK. However the bases of the chronostratigraphic and lithostratigraphic units do not coincide. The parastratotype...
Poster
Full-text available
These results are part of a multidisciplinary study carried out by members of the International Subcommission on Paleogene Stratigraphy, which aims at describing in detail the base of the Bartonian stage for correlation with sections that have the potential to become the Global Stratotype Section and Point –GSSP- for the base of the Bartonian.
Article
The Latest Danian Event (LDE) or Top Chron C27n hyperthermal event has been identified in the Caravaca section (Southern Spain) by means of calcareous nannofossil biozones (Subzone NTp7b) and the recognition of a prominent, negative ~. 0.6 per mille carbon isotope excursion measured in benthic foraminiferal tests. This is the first time that this D...
Conference Paper
Full-text available
The International Subcommission on Paleogene Stratigraphy is searching for an appropriate section to define the GSSP (Global Stratotype Section and Point) for the base of the Bartonian Stage (Eocene). The Bartonian stage was originally defined in the Hampshire Basin (UK), where a bed containing abundant tests of the macrobenthic foraminifer Nummuli...
Article
Several extreme warming events, called hyperthermals, superimposed the warming trend of the early Paleogene. Deep-sea benthic foraminifera suffered major extinction during the most severe of those events, the Paleocene–Eocene Thermal Maximum, but their response to the following, less severe hyperthermals has been documented at very few locations. W...
Article
Full-text available
Open marine sediments deposited during the Cenomanian–Turonian transition are well exposed in the Spanish Baños de la Hedionda section (Betic Cordillera, South Iberian Palaeomargin). Analysis of foraminiferal assemblages and geochemical proxies allow inferences on the impact of the Oceanic Anoxic Event 2 (OAE2) in this area of the western Tethys. T...
Article
We investigated the response of late Paleocene-middle Eocene (~60-37.5 Ma) benthic foraminiferal assemblages to long term climate change and hyperthermal events including the Paleocene-Eocene Thermal Maximum (PETM) at ODP Site 865 on Allison Guyot, a seamount in the Mid-Pacific Mountains. Seamounts are isolated deep-sea environments where enhanced...
Article
The integrated analysis of foraminiferal assemblages, geochemical proxies, and stable isotopes in the Oued Bahloul section (Tunisia) allowed us to reconstruct the environmental turnover across the Cenomanian–Turonian boundary. An increase in palaeoproductivity proxies (P/Ti, U/Al, Sr/Al) and in δ13C values, and a decrease in foraminiferal diversity...
Article
Full-text available
The largest extinction of deep-sea benthic foraminifera in the Cenozoic occurred during the Paleocene-Eocene Thermal Maximum event (PETM, ~55.8 Ma). Much has been speculated about the causes of such extinction, and proposed mechanisms include changes in productivity and/or oxygenation of bottom waters, metabolic changes and in the composition of th...
Article
The Cretaceous-Palaeogene (K/Pg) boundary interval is often penetrated by burrows, which may obscure stratigraphic and micropaleontological records, leading to misinterpretations of the sequence of events spanning the K/Pg boundary. Here, we assess the role of burrowing organisms in the redistribution of benthic foraminifera across the boundary at...
Chapter
The specific mechanisms causing extinction and faunal turnover after the impact of an asteroid at the Cretaceous–Palaeogene (K–Pg) boundary, and the palaeogeographical variability of the biotic response, are not well understood. In order to evaluate causes of extinction and compare the biotic turnover of deep-sea benthic foraminifera at high southe...
Article
Following the deep-sea benthic foraminiferal extinction event (BEE) across the Paleocene Eocene Thermal Maximum (PETM), certain groups of agglutinated benthic foraminifera bloomed and dominated the foraminiferal assemblage. In particular, the widespread proliferation of Glomospira, Glomospirella and Repmanina species, known as the ́Glomospira acmé,...
Article
The International Workshops on Agglutinated Foraminifera (IWAF) are part of a long-term effort to understand the taxonomy, classification, ecology, and biostratigraphy of this ancient and diverse group of microfossils. Since 1981, the IWAF meetings have been held approximately every four years in a different European country, and have produced a re...
Chapter
To assess the role of tracemakers in the reworking of benthic foraminifera across the Cretaceous–Palaeogene (K–Pg) interval, we studied benthic foraminifera present in the material infilling trace fossils (Planolites, Thalassinoides, and Zoophycos) and in the surrounding sediment observed in the uppermost Maastrichtian in the Bidart section (southw...
Article
The InternationalWorkshops on Agglutinated Foraminifera (IWAF) are part of a long-term effort to understand the taxonomy,classification, ecology, and biostratigraphy of this ancient and diverse group of microfossils. Since 1981, the IWAF meetings have been held approximately every four years in a different European country, and have produced a rema...
Article
The Paleocene-Eocene Thermal Maximum (PETM) event at -55.5 Ma, is characterized by globally elevated temperatures, a negative 513C excursion and major biotic changes on land and in the oceans, including the major extinction of deepsea benthic foraminifera. Increased acidity of the oceans and associated shallowing of the calcite compensation depth l...
Data
The impact of an asteroid at the Cretaceous/Paleogene (K/Pg) boundary triggered dramatic biotic, biogeochemical and sedimentological changes in the oceans that have been intensively studied. Paleo-biogeographical differences in the biotic response to the impact and its environmental consequences, however, have been less well documented. We present...