A marked switch in the abundance of the planktic foraminiferal genera
Evolution of climate, carbon cycling and planktic foraminifera
across the middle Paleogene on the Geomagnetic Polarity Time Scale (GPTS)
2012 timescale. The left side shows polarity chrons and smoothed oxygen and
carbon isotope records of benthic foraminifera, slightly modified from
Vandenberghe et al. (2012). Oxygen and carbon isotope values come from
compilations by Zachos et al. (2008) and Cramer et al. (2009). The middle of
the figure indicates planktic foraminiferal biozones by Wade et al. (2011)
with three modifications. The lower boundary for Zone E7a is now based on the
first occurrence of
Cenozoic Earth surface temperatures attained their warmest long-term state
during the Early Eocene Climatic Optimum (EECO). This was a 2–4 Myr time
interval (discussed below) centered at ca. 51 Ma (Fig. 1), when average
high-latitude temperatures exceeded those in the present day by at least
10
In benthic foraminiferal stable-isotope records for the early Paleogene
(Fig. 1),
Significant biotic changes occur in terrestrial and marine environments
during times when the early Paleogene
Approximate locations of the three sites discussed in
this work during the early Eocene. Also shown is Site 1258, which has a bulk
carbonate
Planktic foraminiferal assemblages are abundant in carbonate-bearing marine sediments and display distinct evolutionary trends that can often be correlated to climate variability (Schmidt et al., 2004; Ezard et al., 2011; Fraass et al., 2015). This is especially true in the early Paleogene, even though the relationship between climate variability and planktic foraminiferal evolution remains insufficiently known. At the beginning of the Eocene, planktic foraminifera had evolved over ca. 10 Myr following the Cretaceous–Paleogene mass extinction event. Several early Paleogene phylogenetic lines evolved, occupying different ecological niches in the upper water column. Subsequently, a major diversification occurred during the early Eocene, which resulted in a peak of planktic foraminiferal diversity during the middle Eocene (Norris, 1991; Schmidt et al., 2004; Pearson et al., 2006; Aze et al., 2011; Ezard et al., 2011; Fraass et al., 2015).
In this study, we focus on the evolution of two planktic foraminiferal
genera:
Numerous lower Eocene sedimentary sections from lower latitudes contain
well-recognizable (albeit often recrystallized) planktic foraminiferal tests.
Changes in foraminiferal assemblages presumably reflect relationships between
climate and carbon cycling across the EECO. The present problem is that no
section examined to date provides counts of foraminiferal assemblages,
detailed stable-isotope records and robust planktic foraminiferal
biostratigraphies across the entire EECO. Indeed, at present, only a few
sites have detailed and interpretable stable-isotope records across much of
the EECO (Slotnick et al., 2012, 2015a; Kirtland-Turner et al., 2014).
Furthermore, the EECO lacks formal definition. As a consequence, any
relationship between climatic perturbations during the EECO and the evolution
of planktic foraminifera remains speculative. Here, we add new data from
three locations: the Possagno section from the western Tethys, Deep Sea
Drilling Project (DSDP) Site 577 from the tropical Pacific Ocean and Ocean
Drilling Program (ODP) Site 1051 from the subtropical Atlantic Ocean
(Fig. 2). These sections represent a wide longitudinal span of low-latitude
locations during the early Paleogene. By comparing stable-isotope and
planktic foraminiferal records at these three locations, we provide a new
foundation for understanding why the abundances of
Evidence for extreme Earth surface warmth during a multi-million-year time interval of the early Eocene is overwhelming and comes from many studies, utilizing both marine and terrestrial sequences and both fossil and geochemical proxies (Huber and Caballero, 2011; Hollis et al., 2012; Pross et al., 2012). However, a definition for the EECO, including the usage of “optimum”, endures as a perplexing problem. This is for several reasons, including the basic facts that (i) proxies for temperature should not be used to define a time increment, (ii) clearly correlative records across the middle of the early Eocene with a temporal resolution of less than 50 kyr remain scarce and (iii) absolute ages across the early Eocene have changed significantly (Berggren et al., 1995; Vandenberghe et al., 2102). As a consequence, various papers discussing the EECO give different ages and durations 2 to 4 Myr long sometime between circa 49 and 54 Ma (e.g., Yapp, 2004; Lowenstein and Demicco, 2006; Zachos et al., 2008; Woodburne et al., 2009; Bijl et al., 2009; Smith et al., 2010; Hollis et al., 2012; Slotnick et al., 2012; Pujalte et al., 2015).
The EECO, at least as presented in many papers, refers to the time of
minimum
There is also the root problem as to where EECO starts and ends. At a basic
level, the interval characterized by the lowest Cenozoic benthic
foraminiferal
The Eocene minimum in
The end of the EECO has received limited attention from a stratigraphic
perspective. Indeed, the termination of the EECO may not be a recognizable
global “event” because it may relate to ocean circulation and gateways expressed mostly in the Southern Ocean and deep-ocean records (Pearson et
al., 2007; Bijl et al., 2013). In Paleogene continental slope sections now
uplifted and exposed in the Clarence River valley, New Zealand, a major
lithologic change from limestone to marl coincides with the J event
(Slotnick et al., 2012, 2015a; Dallanave et al., 2015). The marl-rich unit,
referred to as “Lower Marl”, has been interpreted to reflect enhanced
terrigenous supply to a continental margin because of greater temperature
and enhanced seasonal precipitation. It has been suggested further that
Lower Marl indicates the EECO (Slotnick et al., 2012; Dallanave et al.,
2015). The top of Lower Marl, and a return to limestone deposition, lies
within the upper part of polarity Chron C22n (Dallanave et al., 2015). This
is interesting because it approximates the time when general long-term
Cenozoic cooling is initiated at several locations that have records of
polarity chrons and proxies for temperature (Bijl et al., 2009; Hollis et
al., 2012; Pross et al., 2012). It is also useful from a stratigraphic
perspective because the end of the EECO thus lies close to a well-documented
and widespread calcareous nannofossil biohorizon, the base of
Without an accepted definition in the literature, we tentatively present the
EECO as the duration of time between the J event and the base of
An Upper Cretaceous through Miocene succession crops out at the bottom of the
Monte Grappa massif in the Possagno area, about 60 km northwest of Venice.
The lower to middle Eocene, of primary focus in this study, is represented by
the Scaglia beds. These sedimentary rocks represent pelagic and hemipelagic
sediment that accumulated at middle to lower bathyal depths (Cita, 1975;
Thomas, 1998) in the western part of the Belluno Basin, a Mesozoic–Cenozoic
paleogeographic unit of the European Southern Alps (Bosellini, 1989). The basin very likely was an embayment connected to the
western Tethys, with a paleolatitude of ca. 42
A quarry at 45
The Possagno section. Upper panel: geological map (modified from Braga, 1970). 1: Quaternary deposits; 2, 3: Calcarenite di Castelcucco (Miocene); 4: glauconitic arenites (Miocene); 5: siltstones and conglomerates (upper Oligocene–lower Miocene); 6: Upper Marna di Possagno (upper Eocene); 7: Formazione di Pradelgiglio (upper Eocene); 8: Marna di Possagno (upper Eocene); 9: Scaglia Cinerea (middle–upper Eocene); 10: Scaglia Rossa (Upper Cretaceous–lower Eocene); 11: faults; 12: traces of stratigraphic sections originally studied by Bolli (1975); red circle: the Carcoselle quarry. Lower panel: the exposed quarry face during Summer 2002 (Photo by Luca Giusberti).
The Possagno section appears to be continuous, but with an important
decrease in sedimentation rate (to below 1.4 m Myr
DSDP Leg 86 drilled Site 577 at 32
Two primary holes were drilled at Site 577. Both Hole 577* and Hole 577A recovered portions of a nominally 65 m thick section of Upper Cretaceous through lower Eocene nannofossil ooze. Similar to the Possagno section, the lower Paleogene interval has biomagnetostratigraphic information (Bleil, 1985; Monechi et al., 1985; Backman, 1986; Lu and Keller, 1995; Dickens and Backman, 2013). Stable-isotope records of bulk carbonate have been generated for sediment from several cores at low sample resolution (Shackleton, 1986) and for much of cores 577*-9H and 577*-10H at a fairly high sample resolution (Cramer et al., 2003).
The composition and relative abundances of planktic foraminifera were nicely
documented at Site 577 (Lu, 1995; Lu and Keller, 1995) and show a marked
turnover between
The Blake Nose is a gentle ramp extending from 1000 to 2700 m water depth
east of Florida (Norris et al., 1998). The feature is known for a relatively
thick sequence of middle Cretaceous through middle Eocene sediment with
minimal overburden. ODP Leg 171B drilled and cored this sequence at several
locations, including Site 1051 at 30
Sediments from 452.24 to 353.10 m below the sea floor (m b.s.f. at Site 1051 consist of lower to middle Eocene carbonate ooze and chalk (Shipboard Scientific Party, 1998). The site comprises two holes (1051A and 1051B), with core gaps and core overlaps existing at both (Shipboard Scientific Party, 1998). However, the impact of these depth offsets upon age is less than at Site 577 because of higher overall sedimentation rates.
The Eocene section at Site 1051 has good sediment recovery, except in an
interval between 382 and 390 m b.s.f., which contains significant chert.
Stratigraphic markers across the Eocene interval include polarity chrons
(Ogg and Bardot, 2001), calcareous nannofossil biohorizons (Mita, 2001) and
planktic foraminiferal biohorizons (Norris et al., 1998; Luciani and
Giusberti, 2014). As first noted by Cramer et al. (2003), though, there is a
basic stratigraphic problem with the labeling of the polarity chrons. The
intervals of normal polarity between approximately 388 and 395 m b.s.f. and
between approximately 412 and 420 m b.s.f. were tentatively assigned to C22n and
C23n, respectively (Ogg and Bardot, 2001). This age assignment was assumed
to be correct by Luciani and Giusberti (2014), who therefore considered the
last occurrence of
These age assignments, however, cannot be correct because calcareous
nannofossil biohorizons that lie below or within C22n (top of
The three sites provide a good stratigraphic background and the key existing data for understanding the temporal link between the EECO, carbon isotope perturbations and planktic foraminiferal evolution. Our analytical aim was to obtain comparable data sets across the sites. More specifically, a need existed to generate stable-isotope and planktic foraminiferal assemblage records at the Possagno section, to generate stable-isotope records at DSDP Site 577, and to generate planktic foraminiferal assemblage records at ODP Site 1051.
In total, 298 samples were collected from the originally exposed Possagno section in 2002–2003 for isotope analyses. The sampling interval was 2 to 5 cm for the basal 0.7 m and varied between 20 and 50 cm for the interval between 0.7 and 66 m. Bulk sediment samples were previously examined for their calcareous nannofossil assemblages (Agnini et al., 2006). One hundred and ten of these samples were selected for the foraminiferal study.
Aliquots of the 110 samples were weighed and then washed to obtain
foraminifera using two standard procedures, depending on lithology. For the
indurated marly limestones and limestones, the cold-acetolysis technique was
used (Lirer, 2000; Luciani and Giusberti, 2014). This method disaggregates
strongly lithified samples, in which foraminifera can otherwise only be analyzed in thin sections (Fornaciari et al., 2007; Luciani et al., 2007). For
the marls, samples were disaggregated using 30 % hydrogen peroxide and
subsequently washed and sieved at 63
Relative abundance data of planktic foraminiferal samples were generated for 65 samples at Site 577 (Lu, 1995; Lu and Keller, 1995). We collected new samples for stable-isotope measurements that span their previous effort.
Fifty samples of Eocene sediment were obtained from Hole 1051A between 452
to 353 m b.s.f. Sample spacing varied from 2.0 to 0.5 m. As the samples are
ooze and chalk, they were prepared using disaggregation using distilled
water and washing over 38 and 63
Carbon and oxygen stable-isotope data of bulk sediment samples from the
Possagno section and Site 577 were analyzed using a Finnigan MAT 252 mass
spectrometer equipped with a Kiel device at Stockholm University. Precision
is within
The mass percent of the > 63
Relative abundances for both Possagno and Site 1051 have been determined
from about 300 complete specimens extracted from each of the 110 samples
investigated in the > 63
The degree of dissolution, expressed as the fragmentation index (
Carbon isotopes of bulk carbonate at Possagno vary between
Lithology, stratigraphy and bulk sediment stable-isotope
composition of the Possagno section aligned according to depth. Litholologic
key: 1 – limestone; 2 – marly limestone and calcareous marl; 3 – cyclical marl–limestone alternations, 4 – marl; 5 – clay marl unit (CMU).
Planktic foraminiferal biozones follow those of Wade et al. (2011), as
modified by Luciani and Giusberti (2014). Magnetostratigraphy and key
calcareous nannofossil events come from Agnini et al. (2006); NP-zonation is
from Martini (1971). Nannofossil events are shown as red triangles (tops),
blue triangles (bases) and purple diamonds (evolutionary crossovers);
Superimposed on these trends are a series of negative CIEs. The most
prominent of these (
The complex interval between 15.5 and 24 m broadly corresponds to all of
Chron C23n and the bottom half of Chron C22r. A series of CIEs occur in that
interval on the order of 1.4 ‰, superimposed on a
background trend of increasing
Above Chron C22r, the Possagno
The
Cores, stratigraphy and bulk sediment stable-isotope
composition for the early Eocene interval at Deep Sea Drilling Project
(DSDP) Site 577 aligned according to composite depth (Dickens and Backman,
2013). Note the increased length for the gap between Core 577*-8H and Core
577*-9H (see text). The Wade et al. (2011) E-zonation, partly modified by
Luciani and Giusberti (2014), has been applied to Site 577, given assemblages
presented by Lu (1995) and Lu and Keller (1995). Note that (i) the base of
Zone E3 (top of
Like at Possagno, the early Eocene
Oxygen isotopes of bulk carbonate at Possagno range between
The
The coarse fraction of samples from Possagno shows two distinct trends
(Fig. 6, Table S3). Before the EECO, values are 10.4 %
The Possagno section and its
Planktic foraminifera are consistently present and diverse throughout the studied intervals at Possagno and at ODP Site 1051. Preservation of the tests at Possagno varies from moderate to fairly good (Luciani and Giusberti, 2014). However, planktic foraminiferal tests at Possagno are recrystallized and essentially totally filled with calcite. Planktic foraminifera from samples at Site 1051 are readily recognizable throughout the studied interval. Planktic foraminifera from Site 577, at least as illustrated by published plates (Lu and Keller, 1995), show a very good state of preservation (albeit possibly recrystallized).
The
The early Eocene succession at DSDP Site 577 and its
The
Stratigraphy, bulk sediment
Planktic foraminiferal assemblages at Possagno show significant changes
across the early to early middle Eocene (Fig. 6, Table S3).
Throughout the entire section, the mean relative abundance of
The increases in
The trends in
At Possagno,
Other planktic foraminiferal genera are always less than 15 % of the total assemblages throughout the studied interval at Possagno (Supplement Fig. S1, Table S3).
Samples from Site 577 were disaggregated in water and washed through a
> 63 sieve (Lu, 1995; Lu and Keller, 1995). Lu and Keller determined
relative abundances of planktic foraminifera from random splits of about 300
specimens (Lu, 1995; Lu and Keller, 1995). The resulting data are shown in
Fig. 7, placed onto the composite depth scale of Dickens and Backman (2013). Major changes in planktic foraminiferal
assemblages are comparable to those recorded at Possagno. Indeed, such changes
include a distinct decrease in
The
Planktic foraminifera show distinct changes in abundance at Site 1051
(Fig. 8, Table S5). The changes in the main taxa are similar to
the variations observed at Possagno. The genus
The abundance of subbotinids shows small variations around mean values of 20 % at Site 1051. Like at Possagno, samples from Site 1051 also record a slight increase in abundance toward the end of the EECO and above.
The major change in planktic foraminiferal assemblages at Site 1051 includes
a distinct decrease in
The bulk carbonate stable-isotope records within the lower Paleogene sections at Possagno and at Site 577 need some reflection, considering how such records are produced and modified in much younger strata dominated by pelagic carbonate. In open-ocean environments, carbonate preserved on the seafloor principally consists of calcareous tests of nannoplankton (coccolithophores) and planktic foraminifera (Bramlette and Riedel, 1954; Berger, 1967; Vincent and Berger, 1981). However, the total amount of carbonate and its microfossil composition can vary considerably across locations because of differences in deep-water chemistry and in test properties (e.g., ratio of surface area to volume, mineralogical composition). For regions at mid- to low latitudes, a reasonable representation of carbonate components produced in the surface water accumulates on the seafloor at modest (< 2000 m) water depth. By contrast, microfossil assemblages become heavily modified in deeper water because of increasingly significant carbonate dissolution (Berger, 1967). Such dissolution preferentially affects certain tests, such as thin-walled, highly porous planktic foraminifera (Berger, 1970; Bé et al., 1975; Thunell and Honjo, 1981).
The stable-isotope composition of modern bulk carbonate ooze reflects the mixture of its carbonate components, which mostly record water temperature and the composition of dissolved inorganic carbon (DIC) within the mixed layer (< 100 m water depth). The stable-isotope records are imperfect, though, because of varying proportions of carbonate constituents and “vital effects”, which impact stable-isotope fractionation for each component (Anderson and Cole, 1975; Reghellin et al., 2015). Nonetheless, the stable-isotope composition of bulk carbonate ooze on the seafloor can be related to overlying temperature and chemistry of surface water (Anderson and Cole, 1975; Reghellin et al., 2015).
Major modification of carbonate ooze occurs during sediment burial. This is because, with compaction and increasing pressure, carbonate tests begin to dissolve and recrystallize (Schlanger and Douglas, 1974; Borre and Fabricus, 1998). Typically within several hundred meters of the seafloor, carbonate ooze becomes chalk and, with further burial, limestone (Schlanger and Douglas, 1974; Kroenke et al., 1991; Borre and Fabricus, 1998). Carbonate recrystallization appears to be a local and nearly closed-system process, such that mass transfer occurs over short distances (i.e., less than a few meters) (Schlanger and Douglas, 1974; Matter et al., 1975; Arthur et al., 1984; Kroenke et al., 1991; Borre and Fabricus, 1998; Frank et al., 1999).
In pelagic sequences with appreciable carbonate content and low organic
carbon content, bulk carbonate
Stratigraphic issues complicate direct comparison of various records from Possagno and Site 577. The two sections have somewhat similar multi-million-year sedimentation rates across the early Eocene. However, the section at Possagno contains the condensed interval, where much of C23r spans a very short distance (Agnini et al., 2006), and the section at Site 577 has a series of core gaps and core overlaps (Dickens and Backman, 2013).
An immediate issue to amend is the alignment of cores 8H and 9H in Hole 577*
and Core 8H in Hole 577A (Fig. 5). On the basis of Gamma Ray Porosity
Evaluator (GRAPE) density records for these cores, Dickens and Backman (2013)
initially suggested a 2.6 m core gap between cores 8H* and 9H*. However, a
3.5 m core gap also conforms to all available stratigraphic information. The
newly generated
Once sedimentation rate differences at Possagno are recognized and coring
problems at Site 577 are rectified, early Eocene
For the latest Paleocene and earliest Eocene, nominally the time spanning the
period from the base of C24r through the middle of C24n, detailed stable
carbon isotope records have been generated at more than a dozen locations
across the globe (Cramer et al., 2003; Agnini et al., 2009, 2016; Galeotti et
al., 2010; Zachos et al., 2010; Slotnick et al., 2012; Littler et al., 2014).
These records can be described consistently as a long-term drop in
Carbon isotope and paleomagnetic records across the early Eocene for
the Possagno section, DSDP Site 577 and ODP Site 1258 (Kirtland-Turner et
al., 2014). This highlights the overall framework of carbon cycling in the
early Eocene but also stratigraphic problems across the EECO at each of the
three sites. At Possagno, the coarse resolution of
For the period after the J event and across the EECO, very few detailed
The new records from Possagno and Site 577 emphasize an important finding
regarding bulk carbonate
The causes of
Our new
The overall offset between bulk carbonate
Bulk carbonate
Site 577 was located at about 15
Lithification should further impact bulk carbonate
One might suggest, at least for the Possagno section, that meteoric water
might also have impacted the
As observed at Site 577, however, horizons of lower
Bulk carbonate
The most striking change in planktic foraminiferal assemblages occurred near
the start of the EECO. Over a fairly short time interval and at multiple
widespread locations, the relative abundance of
The
At Possagno, higher abundances of
Records of magnetostratigraphy, bulk sediment
Carbonate dissolution at or near the seafloor presents a potential
explanation for observed changes in foraminiferal assemblages. Some studies
of latest Paleocene to initial Eocene age sediments, including laboratory
experiments, suggest a general ordering of dissolution according to genus,
with
Carbonate solubility horizons that impact calcite preservation and dissolution on the seafloor (i.e., the carbonate compensation depth (CCD) and lysocline) also shoaled considerably during various intervals of the early Eocene. The three most prominent hyperthermals that occurred before the main phase of the EECO (PETM, H-1, K/X) were clearly marked by pronounced carbonate dissolution at multiple locations (Zachos et al., 2005; Agnini et al., 2009; Stap et al., 2009; Leon-Rodriguez and Dickens, 2010). A multi-million-year interval characterized by a relatively shallow CCD also follows the K/X event (Leon-Rodriguez and Dickens, 2010; Pälike et al., 2012; Slotnick et al., 2015b).
Should changes in carbonate preservation primarily drive the observed
planktic foraminiferal assemblages, it follows that the dominance of
Carbonate dissolution can cause the coarse fraction of bulk sediment to
decrease (Berger et al., 1982; Broecker et al., 1999; Hancock and Dickens,
2005). This happens because whole planktic foraminiferal tests typically
exceed 63
The cause of the long-term rise in carbonate dissolution horizons remains
perplexing but may relate to increased inputs of
Despite evidence of carbonate dissolution, this process probably only
amplified primary changes in planktic foraminiferal assemblages. The most
critical observation is the similarity of the abundance records for major
planktic foraminiferal genera throughout the early Eocene at multiple
locations (Figs. 6–8). This includes the section at Site 1051,
where carbonate appears only marginally modified by dissolution according to
the
There is also recent work from the Terche section (ca. 28 km NE of Possagno)
to consider. This section is located in the same geological setting as
Possagno, but across the H-1, H-2 and I1 events, there are very low
The switch in abundance between
However, the fact that the major switch at the start of the EECO can be found
at Sites 1051 (western Atlantic) and Site 577 (central Pacific) suggests that
local variations in oceanographic conditions, such as riverine discharge,
were not the primary causal mechanism. Rather, the switch must be a
consequence of globally significant modifications related to the EECO, most
likely sustained high temperatures, elevated
Records of
An explanation for the shift may lie in habitat differences across planktic
foraminiferal genera. Although both
One important consideration for any interpretation is the evolution of new
species that progressively appear during the post-EECO interval. In good
agreement with studies of lower Paleogene sediment from other low-latitude
locations (Pearson et al., 2006), thermocline dwellers such as subbotinids
and parasubbotinids seem to proliferate at Possagno (Luciani and Giusberti,
2014). These include
A second consideration is the change in planktic foraminiferal assemblages
during the Middle Eocene Climate Optimum (MECO), another interval of
anomalous and prolonged warmth at ca. 40 Ma (Bohaty et al., 2009). At Alano
(Fig. 11) and other locations (Luciani et al., 2010; Edgar et al., 2012),
the MECO involved the reduction in the abundance and test size of large
Available data suggest that the protracted conditions of extreme warmth and
high
Several small CIEs appear in the
The symbiont-bearing planktic foraminiferal genera
Our conclusion that the planktic foraminiferal switch coincides with the start of the EECO derives from the generation of new records and collation of old records concerning bulk sediment stable isotopes and planktic foraminiferal abundances at three sections. These sections span a wide longitude range of the low-latitude Paleogene world: the Possagno section from the western Tethys, DSDP Site 577 from the central Pacific Ocean and ODP Site 1051 from the western Atlantic Ocean. Importantly, these locations have robust calcareous nannofossils and polarity chron age markers, although the stratigraphy required amendment at Sites 577 and 1051.
An overarching problem is that global carbon cycling was probably very
dynamic during the EECO. The interval appears to have been characterized not
only by numerous CIEs but also by a major switch in the timing and magnitude
of these perturbations. Furthermore, there was a rapid shoaling of carbonate
dissolution horizons in the middle of the EECO. A key finding of our study
is that the major switch in planktic foraminiferal assemblages happened at
the start of the EECO. Significant, though ephemeral, modifications in
planktic foraminiferal assemblages coincide with numerous short-term CIEs,
before, during and after the EECO. Often, there are marked increases in the
relative abundance of
Although we show for the first time that the critical turnover in planktic
foraminifera clearly coincided with the start of the EECO, the exact cause
for the switch (a.k.a. the decline in
Initial and primary funding for this research was provided by MIUR/PRIN COFIN 2010–2011, coordinated by D. Rio. V. Luciani was financially supported by FAR from Ferrara University, and L. Giusberti and E. Fornaciari received financial support from Padova University (Progetto di Ateneo GIUSPRAT10). J. Backman acknowledges support from the Swedish Research Council. G. Dickens received support from the Swedish Research Council and the US NSF (grant NSF-FESD-OCE-1338842). We are grateful to Domenico Rio, who initiated the research on the “Paleogene Veneto”, for fruitful discussion. Members of the “Possagno net”, Simone Galeotti, Dennis Kent and Giovanni Muttoni, who sampled the Possagno section in 2002–2003, are gratefully acknowledged. We warmly acknowledge the Cementi Rossi s.p.a. and Silvano Da Roit for collaborations during sampling at the Carcoselle Quarry (Possagno, TV). This research used samples and data provided by the Ocean Drilling Program (ODP). ODP is sponsored by the US National Science Foundation (NSF) and participating countries under the management of the Joint Oceanographic Institution (JOI) Inc. We especially thank staff at the ODP Bremen Core Repository. Finally, we are grateful to the reviewers, P. Pearson, R. Speijer and B. Wade and to the editor A. Sluijs, who gave very detailed and constructive reviews that improved the paper significantly. Edited by: A. Sluijs