Abstract. A marked switch in the abundance of the planktic foraminiferal genera Morozovella and Acarinina occurred at low-latitude sites near the start of the Early Eocene Climatic Optimum (EECO), a multi-million-year interval when Earth surface temperatures reached their Cenozoic maximum. Stable carbon and oxygen isotope data of bulk sediment are presented from across the EECO at two locations: Possagno in northeast Italy and Deep Sea Drilling Project (DSDP) Site 577 in the northwest Pacific. Relative abundances of planktic foraminifera are presented from these two locations, as well as from Ocean Drilling Program (ODP) Site 1051 in the northwest Atlantic. All three sections have good stratigraphic markers, and the δ13C records at each section can be correlated amongst each other and to δ13C records at other locations across the globe. These records show that a series of negative carbon isotope excursions (CIEs) occurred before, during and across the EECO, which is defined here as the interval between the J event and the base of Discoaster sublodoensis. Significant though ephemeral modifications in planktic foraminiferal assemblages coincide with some of the short-term CIEs, which were marked by increases in the relative abundance of Acarinina, similar to what happened across established hyperthermal events in Tethyan settings prior to the EECO. Most crucially, a temporal link exists between the onset of the EECO, carbon cycle changes during this time and the decline in Morozovella. Possible causes are manifold and may include temperature effects on photosymbiont-bearing planktic foraminifera and changes in ocean chemistry.

for defining the middle-late Eocene boundary Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal Email alerting services articles cite this article to receive free e-mail alerts when new www.gsapubs.org/cgi/alerts click Subscribe America Bulletin to subscribe to Geological Society of www.gsapubs.org/subscriptions/ click Permission request to contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click official positions of the Society.citizenship, gender, religion, or political viewpoint. Opinions presented in this publication do not reflect presentation of diverse opinions and positions by scientists worldwide, regardless of their race, includes a reference to the article's full citation. GSA provides this and other forums for the the abstracts only of their articles on their own or their organization's Web site providing the posting to further education and science. This file may not be posted to any Web site, but authors may post works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent their employment. Individual scientists are hereby granted permission, without fees or further

[1] At least two transient events of extreme global warming occurred superimposed on the long-term latest Paleocene and early Eocene warming trend in the Paleocene-Eocene thermal maximum (PETM) (or ETM1 $55.5 Ma) and the Elmo (or ETM2 $53.6 Ma). Other than warmth, the best known PETM is characterized by (1) significant injection of 13 C-depleted carbon into the ocean-atmosphere system, (2) deep-sea carbonate dissolution, (3) strong biotic responses, and (4) perturbations of the hydrological cycle. Documentation of the other documented and suspected ''hyperthermals'' is, as yet, insufficient to assess whether they are similar in nature to the PETM. Here we present and discuss biomagnetostratigraphic data and geochemical records across two lower Eocene successions deposited on a continental margin of the western Tethys: the Farra and Possagno sections in the Venetian pre-Alps. We recognize four negative carbon isotope excursions within chron C24. Three of these shifts correlate to known or suspected hyperthermals: the PETM, the Eocene thermal maximum 2 ($53.6 Ma), and the informally named ''X event'' ($52.5 Ma). The fourth excursion lies within a reverse subchron and occurred between the latter two. In the Farra section, the X event is marked by a $0.6% negative carbon isotope excursion and carbonate dissolution. Furthermore, the event exhibits responses among calcareous nannofossils, planktic foraminifera, and dinoflagellates that are similar to, though less intense than, those observed across the PETM. Sedimentological and quantitative micropaleontological data from the Farra section also suggest increased weathering and runoff as well as sea surface eutrophication during this event.

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a b s t r a c t a r t i c l e i n f oThe enigmatic middle Eocene climatic optimum (MECO) is a transient (∼ 500 kyr) warming event that significantly interrupted at ∼ 40 Ma the long-term cooling through the middle and late Eocene, eventually resulting in establishment of permanent Antarctic ice-sheet. This event is still poorly known and data on the biotic response are so far scarce. Here we present a detailed planktonic foraminiferal analysis of the MECO interval from a marginal basin of the central-western Tethys (Alano section, northeastern Italy). The expanded and continuous Alano section provides an excellent record of this event and offers an appealing opportunity to better understand the role of climate upon calcareous plankton evolution. A sapropel-like interval, characterized by excursions in both the carbon and oxygen bulk-carbonate isotope records, represents the lithological expression of the post-MECO event in the study area and follows the δ 18 O negative shift, interpreted as representing the MECO warming. High-resolution quantitative analysis performed on both N38 μm and N 63 μm fractions reveals pronounced and complex changes in planktonic foraminiferal assemblages indicating a strong environmental perturbation that parallels the variations of the stable isotope curves corresponding to the MECO and post-MECO intervals. These changes consist primarily in a marked increase in abundance of the relatively eutrophic subbotinids and of the small, low-oxygen tolerant Streptochilus, Chiloguembelina and Pseudohastigerina. At the same time, the arrival of the abundant opportunist eutrophic Jenkinsina and Pseudoglobigerinella bolivariana, typical species of very high-productivity areas, also occurs. The pronounced shift from oligotrophic to more eutrophic, opportunist, low-oxygen tolerant planktonic foraminiferal assemblages suggests increased nutrient input and surface ocean productivity in response to the environmental perturbation associated with the MECO. Particularly critical environmental conditions have been reached during the deposition of the sapropel-like beds as testified by the presence of common giant and/or odd morphotypes. This is interpreted as evidence of transient alteration in the ocean chemistry. The enhanced surface water productivity inferred by planktonic foraminiferal assemblages at the onset of the event should have resulted in heavier δ 13 C values. The recorded lightening of the carbon stable isotope preceding the maximum warmth therefore represents a robust indication that it derives principally by a conspicuous increase of pCO 2 . The increased productivity of surface waters, also supported by geochemical data, may have acted as mechanism for pCO 2 reduction and returned the climate system to the general Eocene cooling trend. The oxygen-depleted deep waters and the organic carbon burial following the peak of the MECO event represent the local response to the MECO warming and suggest that high sequestration of organic matter, if representing a widespread response to this event, m...

[1] We present trace metal geochemistry and stable isotope records for the middle Eocene Alano di Piave section, NE Italy, deposited during magnetochron C18n in the marginal Tethys Ocean. We identify a ∼500 kyr long carbon isotope perturbation event we infer to be the middle Eocene climatic optimum (MECO) confirming the Northern Hemisphere expression and global occurrence of MECO. Interpreted peak climatic conditions are followed by the rapid deposition of two organic rich intervals (≤3% TOC) and contemporaneous positive d 13 C excursions. These two intervals are associated with increases in the concentration of sulphur and redoxsensitive trace metals and low concentrations of Mn, as well as coupled with the occurrence of pyrite. Together these changes imply low, possibly dysoxic, bottom water O 2 conditions promoting increased organic carbon burial. We hypothesize that this rapid burial of organic carbon lowered global pCO 2 following the peak warming and returned the climate system to the general Eocene cooling trend.

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Terra Nova, 24, 380–386, 2012 Abstract A high‐resolution, integrated stratigraphic framework (stable isotope stratigraphy, standard calcareous nannofossil and foraminiferal biostratigraphy, magnetostratigraphy) together with geochemical and rock magnetic properties’ analyses of a complete and well‐preserved succession at Contessa Valley (Gubbio, central Italy) have offered an excellent opportunity to identify and constrain the Palaeocene to early Eocene hyperthermals and carbon isotope excursions (CIEs). In addition, we provide the first evidence in the Tethys Ocean of CIEs, previously identified in the Pacific, Atlantic and Southern Oceans, highlighting their global significance and of some unknown CIEs. Their characteristics are compared with those reported for deep‐sea cores and other land‐based sections to test whether the signature associated with CIEs documented in our composite section might give evidence for tracing them over wider areas. The Contessa composite section thus represents a reference succession also for insight into the magnetobiochronostratigraphy and the magnitude of early Palaeogene hyperthermals and CIEs.