Earth and Planetary Science Letters 223 (2004) 283–302 www.elsevier.com/locate/epsl

Delayed climate cooling in the Late Eocene caused by multiple impacts: high-resolution geochemical studies at Massignano, Italy

Bernd Bodiselitscha, Alessandro Montanarib, Christian Koeberl a,b,*, Rodolfo Coccionic

a Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria b Osservatorio Geologico di Coldigioco, I-62020 Frontale di Apiro, Italy c Istituto di Geologia e Centro di Palinologia dell’Universita`, Campus Scientifico, Localita` Crocicchia, 61209 Urbino, Italy Received 24 September 2003; received in revised form 6 April 2004; accepted 19 April 2004 Available online 24 June 2004

Abstract

High-resolution studies (d13C, d18O, and elemental abundances) were done in rocks at and below the GSSP for the Eocene/ Oligocene (E/O) boundary at Massignano, Italy. In addition to an earlier known Ir anomaly at 5.61 m, which is possibly linked to the Popigai , we confirm the presence of two additional Ir anomalies in the intervals from 6.00 to 6.40 m and from 10.00 to 10.50 m, with maximum values of 259 F 32 ppt at 6.17 m, and 149 F 24 ppt at 10.28 m, respectively. The lower Ir anomaly might be derived from the Chesapeake Bay impact event, whereas for the other one no impact event is known. Similar d13C and d18O trends related to the two Ir anomalies indicate that the Ir anomaly at 10.28 m might be also derived from an impact into a continental shelf, similar to the Chesapeake Bay impact event. d18O values decrease in the high Ir layers to À 1.16x and À 1.17x, respectively, which, together with the negative shifts in d13C in the Ir-rich levels, indicate a warm pulse superimposed on a general Late Eocene cooling trend that is characterized by d18O values ranging between À 0.6x and À 0.4x. The release of methane hydrate after an impact in a continental shelf or seafloor, or impacts of 12C-rich comets during a 2.2-million-year-long comet shower, respectively, could produce these more negative carbon and oxygen excursions compared to the continuously decreasing trend over the whole Late Eocene Massignano section. D 2004 Elsevier B.V. All rights reserved.

Keywords: Chesapeake Bay crater; ; Late Eocene impact ejecta; Massignano (Italy); global cooling

1. Introduction boundary [3], and significant stepwise floral and faunal turnovers ([1,4,5] and references therein). These The Late Eocene is a period of major changes, global climate changes, which are reflected by a characterized by an accelerated global cooling ([1,2] gradual increase of marine oxygen isotope values and references therein), with a sharp temperature drop (e.g., [6,7]) and biotic crises (e.g., [1,8,9]), are com- of about 2 jC near the Eocene/Oligocene (E/O) monly attributed to the expansion of the Antarctic ice cap following its gradual isolation from other conti- * Corresponding author. Department of Geological Sciences, nental masses [10,11]. However, multiple bolide im- University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria. E-mail addresses: [email protected] pact events ([12] and references therein), possibly (B. Bodiselitsch), [email protected] (A. Montanari), related to a comet shower over a duration of 2.2 [email protected] (C. Koeberl). million years [13,14], may have played an important

0012-821X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2004.04.028 284 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 role related to the deterioration of the global climate at peaks at 5.61 (190 ppt), 6.19 (100 ppt) and 10.25 m (330 the end of the Eocene Epoch. ppt), respectively, in the Massignano section. The age of The two large impact structures Popigai, Russia, and the 5.61 m Ir anomaly was determined at 35.7 F 0.4 Ma, Chesapeake Bay,USA,with respective diametersof100 byinterpolationfromseveraldatedvolcanicashesfound and 85 km, and respective ages of 35.7 F 0.8 Ma [15], in the same section. The overlying peak at 6.19 m is and 35.3 F 0.2 Ma [16–19], represent the largest post- younger by ca. 0.15 Ma. [35–37], Ni- Cretaceous–Tertiary (K/T) boundary impact events. rich spinels, and microspherules [38] have been found Both have ages near the peak of the Late Eocene comet around 5.61 m, all indicating derivation from an impact shower that was proposed by Farley et al. [14] on the event.Inthelayerthatcontainsshockedquartzat5.61m, basis of a marked enhancement of interplanetary dust no high-pressure silica phases were detected, which are, particle flux in marine sediments. however, present in the Chesapeake Bay related micro- Three smaller impact craters of comparable age, layer of DSDP 612 [39,40]. Langenhorst [37] Mistastin, Canada (38 F 4 Ma, 28 km; [14]), Wanapi- suggested that this shocked quartz was derived from the tei, Canada (37 F 2 Ma, 7.5 km; [21,22]), and Logoisk, nonporous, crystalline target rock at Popigai. That pro- Belarus (40 F 5 Ma, 17 km; [23]), may be part of the posal was recently supported by isotopic data of White- same event, supporting the scenario of a cometary headetal.[33].ExcepttheIranomalyat10.25m,noother bombardment. The comet shower hypothesis predicts evidenceforanimpactwasfoundbyMontanarietal.[34] an even larger occurrence of smaller impacts which at that level. may have played a role in the alteration climate con- To determine whether these peaks are associated ditions at a global scale, due to atmospheric blowout with an impact event or not, we checked Ir/Fe ratios; and distribution of ejecta around the Earth [24]. possible volcanic input is discussed using trace element At least two distinct, yet closely spaced, Late Eocene ratios. To investigate the influence of possible impact impact spherule layers, the older containing microtek- events on seawater temperature we analyzed oxygen tites, and the younger microkrystites [25,26], have been and carbon isotopes from bulk-carbonates. It is well identified in ocean sediments from the Atlantic, Indian known that weathering and/or diagenesis may affect and Pacific Oceans, the Caribbean Sea and the Weddell the original isotopic composition. In the case of the Sea, off Antarctica [27]. These distal impact ejecta were Massignano section, being located on a relatively fresh also found in Late Eocene sediments in Texas, Georgia, quarry cut, there are no indications of recent weather- Massachusetts, Barbados and Cuba [8,28–31].The ing, and the section also is not disturbed by tectonics, North American were proposed to be derived lacking faulting or folding. No recrystallization of the from the Chesapeake Bay impact event [17,18,32], carbonate phases were found, indicating that the car- whereastheclinopyroxene-bearingspherulestrewnfield bonate phase is not diagenetically modified [41]. How- (i.e., the microkrystites) may be linked to the Popigai ever, Vonhof et al. [42] have noted, from SEM analysis, crater [15,33]. Estimates of the time separating the two that the foraminifers in the Massignano section are layersrangefrom10to20ky[25],and3to5ky[12],with filled with secondary, blocky calcite. theChesapeakeBayimpactbeingtheyoungerevent.The In absence of well-preserved, species-determined clinopyroxene-spherule layer contains an Ir anomaly, calcite tests or shells, and under certain diagenetic shocked quartz, Ni-rich spinels, and impact spherules. conditions, bulk rock calcite may represent an accept- Here we present the results of the chemical composi- able material for stable isotope analysis, particularly for tion, and oxygen and carbon isotope ratios of pelagic carbon [43,44]. Even compacted and cemented car- marly limestones sampled in the Massignano section bonate pelagic sediments may retain the original d13C (central Italy), which represents the Global Stratotype signal. On the other hand, oxygen isotopic ratios in SectionandPoint(GSSP)fortheE/Oboundary.Samples bulk-rock samples are generally much more suscepti- frommeterlevel6.00–6.40and10.00–10.50oftheLate ble to alteration during diagenesis than carbon isotopes Eocenewerestudied.Alsotheoxygenandcarbonisotope [45]. Oxygen isotopic fractionation is more affected by variations over the whole Massignano section from 0 m temperature during recrystallization than carbon. (Late Eocene) to 23 m (Early Oligocene) were investi- For the determination of the paleoceanographic and gatedindetail.Formerstudiesby[34]showprominent Ir paleoclimatic conditions, the usage of foraminiferal B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 285 species is more common than bulk-carbonate analysis. this isotope ratio may reflect variations in d13C contents Bulk-carbonate samples represent a mixture of carbo- of ocean water [48]. A higher 13C/12C ratio can be nates from different sources, e.g., benthonic and plank- interpreted as a decrease in bio-productivity resulting in tonic foraminifers and calcareous nannofossils. The a decrease in organic matter accumulation in the isotopic composition of bulk samples is a function of sedimentary record. This can also be interpreted as the composition of these species—e.g., d18O of fora- the consequence of a cooling event. Thus, we used the minifers—is a function of the seawater d18O value d13C values, together with the d18O values, to derive where organism lived. Environmental changes could cooling or warming trends. be established if these changes have an effect on most of the species. Under these circumstances, the isotopic composition derived from bulk analyses resembles 2. Location and stratigraphic documentation closely the record derived from single foraminiferal analyses [46,47]. The abandoned quarry of Massignano is located Thus, d18O values could be used to infer changes in along the provincial road of the Monte Co`nero Park, water temperature through a given stratigraphic inter- about 4 km north of the town of Sirolo (Fig. 1). The 23- val, especially if such an interval is represented by m-thick section consists of a continuous and complete homogeneous pelagic sediments. Usually the d13C sequence of pelagic marly limestone and calcareous values are not in equilibrium with seawater. However, marls, which contain well-preserved planktonic and we can assume that, on average, the 13C/12C ratios are benthonic foraminiferal tests suspended in a coccolith invariant with time. Therefore, systematic variations of and clay matrix, and which are interbedded with several

Fig. 1. Tectonic sketch-map of the Umbria–Marche Apennines where the shaded areas represent the Meso-Cenozoic orogenic belt. The location of the Massignano GSSP for the Eocene–Oligocene boundary is marked by an asterisk. 286 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 biotite-rich volcano-sedimentary layers (Fig. 2). Strati- 3. Sample preparation and analytical methods graphically, the Massignano exposure covers the upper part of the Eocene and the lowermost part of the For high-resolution studies, samples were taken at 1 Oligocene. These characteristics make of the Mas- cm intervals across the stratigraphic intervals from 6.0 signano section an ideal situation for the application to 6.4 m, and 10.0 to 10.5 m, respectively. Additional of an integrated stratigraphic approach aimed at the samples at 0.25 cm intervals were taken between 6.0 precise and accurate calibration of the litho-, bio-, and 6.1, 10.0 and 10.1, and 10.35 and 10.5 m, respec- magneto- and chemostratigraphic records with direct tively. In the whole Massignano section from 0 to 23 m radioisotopic datings. In 1993, the Massignano Global continuous 10 cm samples (except 5.60–5.65, 6.10– Stratotype Section and Point (GSSP) for the E/O 6.25, 7.10–7.15 and 10.20–10.25 m are sampled in 5 boundary was formally established [49]. The integrated cm intervals) were taken. The intervals 0 and 4 m, and stratigraphy of the section is described in [50]. Other 14 to 23 m were sampled in 20, 30 and 50 cm steps, studies are reviewed in [51]. respectively. In particular, great attention has been given to a short Major element, V, Cu, Yand Nb analyses were done stratigraphic interval across a thin impactoclastic layer on powdered samples, which were obtained with an located at 5.6 m in the section. In this layer, Montanari automatic agate ball mill, by standard X-ray fluores- et al. [34] detected an iridium anomaly of about 200 cence (XRF) procedure (see [54], for details on proce- ppt. This prompted a number of detailed studies, which dures, precision and accuracy). All other trace elements resulted in the discovery, in the same Ir-rich layer, of were analyzed by instrumental neutron activation anal- shocked quartz grains [36,37], Ni-rich spinel and ysis (INAA). For details of the procedures, see [55,56]. altered microkrystites [38], and a broad peak in extra- Eleven samples from each of the high-resolution parts terrestrial 3He content [14]. of the stratigraphic location across the 6.15–6.25 and A high-resolution, microfloral and faunal investiga- 10.2–10.30 m intervals, respectively, were analyzed tion carried out in a 4-m-thick segment including the with an iridium coincidence spectrometry system (ICS) impactoclastic layer at 5.6 m show that across this layer (see [57,58]. the marine biota did not undergo abrupt, dramatic In this study, we have used the bulk-carbonate frac- effects in terms of extinction [52,53]. However, accord- tion to determine the geochemical record. Under certain ing to these authors, significant quantitative changes in circumstances, bulk-carbonate samples may give more the calcareous plankton and dinoflagellate cysts significant d13C values than isolated foraminiferal tests assemblages indicates a cooling immediately after the (see Introduction). Details of analytical procedures are deposition of the impactoclastic layer. This cooling was given in [59]. The mean values and stan-dard deviations interrupted by a short-term warming episode and cool of 10 analyzed NBS-19 standards are 1.95F0.03x conditions stabilized after about 60 ky. for y13C and À 2.21 F 0.05x for y18O.

Fig. 2. Wide-angle picture of the Massignano section. Numbers correspond to the meters of the measured sequence. Note the location of the Eocene–Oligocene (E–O) boundary at meter level 19. B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 287

4. Results and discussion 4.2. Iridium anomalies

4.1. Major and trace element composition The Ir abundances are shown in Fig. 3 and listed in Table 1. There are well-defined peaks extending The abundances of the measured elements and the from 6.15 to 6.18 m, with a maximum of 259F32 ppt ratios K/U, La/Th, Th/U, LaCN/YbCN (CN = chondrite- at 6.17 m, at a background of V60 ppt and from 10.24 . normalized), Eu/Eu* = ECN/M[(SmCN) (GdCN)]and Ce/ to 10.30 m, with a maximum of 149F24 ppt at . . Ce* = 3 CeCN/(2 LaCN +NdCN) [60] are listed inAppen- 10.28 m, at a background of V40 ppt. The upper Ir- dices A and B. Ratios among other elements, including enhanced region probably reaches beyond 10.30 m, Fe/Cs, Sb/Cs, Co/Cs, Cr/Cs, Eu/Cs, Hf/Cs, Sc/Cs, Ta/ because Cr, Co and Ni abundances are increased at Cs, Th/Cs and Ce/Cs (Fig. 3), were used to distinguish 10.31–10.33 m. However, no further samples were the characteristic background chemical profile of these analyzed for Ir analysis above this level. The contin- pelagic carbonates from possible biotite-rich volcanic uous increase of Ir at 10.24–10.28 m suddenly ashes. Biotite can be incorporated into the pelagic decreases at 10.27 m to V44 ppt, which corresponds sediment as airfall particles produced by volcanic activ- approximately the background value. The interval at ity. The lower stratigraphic interval, which contains an Ir 6.15–6.18 m, with a maximum of 259F32 ppt at anomaly at 6.17 m (see [34], and below), show higher 6.17 m, corresponds to the peak of f100 ppt detected Co/Cs, Hf/Cs and Th/Cs ratios, compared with the by Montanari et al. [34] at 6.20 m. background (Fig. 3). Fe/Cs and Sb/Cs ratios, however, The two closely spaced anomalies at 5.6 and 6.2 m show values in the range of the background (Fig. 3).On may correspond with two large impact events, Popigai theotherhand,nounusualvaluesinFe/Cs,Sb/Cs,Co/Cs, and Chesapeake Bay. In a 5-cm-thick layer containing Cr/Cs, Eu/Cs, Hf/Cs, Sc/Cs, Ta/Cs, Th/Cs and Ce/Cs the main Ir peak at 5.6 m, additional evidence for an ratios,respectively(Fig.3),areevidentintheIrextended impact were found, such as Ni-rich spinel and altered region at 10.28 m (see results below). This may indicate microkrystites [38], and shocked quartz [36,37]. In the that there are no influences from volcanic material, nor region between 6.15 and 6.18 m, we found a few were the iridium contents produced by diagenetic pro- possible spherules. We are not sure whether or not they cesses and/or precipitation from seawater. These results were derived from the main impactoclastic layer at 5.6 are consistent with those of Montanari et al. [34].Ni,Cr m, and were reworked upsection by bioturbation. andCoshowdistinctpeaksat6.17m(Fig.3).At10.28m, Huber et al. [58] reported, however, that bioturbation only minor enhancements of these elements were ob- at Massignano can disturb the iridium profile in the served (Fig. 3). sedimentary record, but only within about 20 cm. The Fe/Mn ratio in carbonate rocks may be used as Although impact spherules far below, and increased an indicator for a marine versus detrital origin of the se- abundance of Ni from possible Ni-rich spinel just diment. At 6.17 m, there is a sharp increase in Fe/Mn below the 5.6 m impactoclastic layer have been found, ratio and magnesium content (Fig. 3). This could be it seems clear that the Ir anomaly at 6.2 m is a distinct considered, at least locally, as a stratigraphically signi- individual event, and was not derived from the lower Ir- ficant event. A slight increase in the Fe/Mn ratio and Mg rich layer at 5.6 m. content (Fig. 3) was also found in the upper analyzed In this study, no elevated Se and Sb abundances interval at 10.27 m. The peaks, however, are about a fac- coincide with the Ir anomaly at 10.0 and 10.5 m, in tor of 4 smaller than the distinct peak in the 6.0–6.4 m contrast to Montanari et al. [34]. A higher abundance section. of Ir, Se and Sb could be the result of sulfide The REE patterns of the carbonates are similar to precipitation in the sediment. No evidence for vol- each other. All samples in the two sections show high canic influences, but a very slight positive shift in abundance of the light REE, a negative Ce anomaly the Fe/Mn ratio (Fig. 3), was determined, which may (expressed as Ce/Ce*) and a small negative Eu anom- indicate a stratigraphically significant event. The aly (expressed as Eu/Eu*) with average values around interesting aspect of the Ir anomaly at 10.28 m is 0.80 in both intervals, and a flat heavy REE distribution that there are no indications of a discontinuity in the pattern. The slopes are relatively constant. sedimentation. The average sedimentation rate for 288 .Bdsltc ta./ErhadPaeaySineLtes23(04 283–302 (2004) 223 Letters Science Planetary and Earth / al. et Bodiselitsch B.

Fig. 3. High-resolution chemostratigraphy across Late Eocene, from 6.00 to 6.40 m, and 10.00 to 10.50 m, above the base of the GSSP for the E/O boundary at Massignano, Italy. 13 18 Grey bars show possible warm pulses with significantly lower d CPDB and d OPDB values compared with the generally third-order polynomial trend line. These pulses come along with Ir-enhanced regions and are triggered due to impacts. B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 289

Table 1 background levels at 7 Â 10À 9 in the interval 6.0–6.4 Ir contents for samples from Massignano, Italy, measured by m, and 4 Â 10À 9 in the interval 10.0–10.5 m, which is coincidence spectrometry after neutron activation not the case. Stratigraphic level Ir Therefore, a change in sedimentation rate in the (m) (ppt) interval between 10.0 and 10.5 m cannot explain the F 6.15 135 23 higher Ir content. Therefore, we agree with Montanari 6.17 259 F 32 6.18 180 F 26 et al. [34] that the Ir anomaly in this case is due to an 6.19 69 F 16 extraterrestrial event. However, the absence of impac- 6.20 71 F 17 toclastic evidence in the 10–10.5 m interval, such as 6.21 V 52 microspherules, Ni-rich spinel, and shock metamor- 6.22 V 37 phosed quartz grains, may be indicative of a localized 6.23 87 F 18 6.24 V 58 event, possibly a small object that exploded at sea 6.25 65 F 16 surface without producing a crater and/or detectable Background V 60 impact debris. 10.20 V 52 Farley et al. [14] reported an increase in extraterres- F 10.21 32 11 trial 3He in this region, which was interpreted as a 10.22 V 53 10.23 V 32 signature of increased influx of interplanetary dust 10.24 49 F 14 particles during a comet shower. Remarkably, all three 10.25 92 F 19 impactoclastic layers at 5.61, 6.17 and 10.28 m, coin- 10.26 100 F 20 cide with two narrow peaks superimposed on the very 10.27 V 44 broad peak of enhanced 3He flux (Fig. 4). 10.28 149 F 24 10.29 70 F 16 10.30 90 F 19 4.3. Oxygen and carbon isotope ratios Background V 40 4.3.1. Complete section The d13C values range between + 0.84x and the Massignano section, calculated from interpolation +2.17x (Appendix C); values decreases from f 7 of three radioisotopically dated biotite levels, is 5.8 to f16.5 m and increase from f16.5 to 23 m (Fig. 4). m/Ma. A better estimate is not possible, considering The d18O values are in the range of À 1.60% and error levels. Moreover, in this alternation of marls À 0.59x (Appendix C), but there is no obvious trend and marly limestones, we may expect that the marls as for d13C, with only a slight decrease from 0 to 23 m reflect slow sedimentation rate, whereas the lime- being recognizable (Fig. 4). The greater fluctuations in stone high sedimentation rate (high productivity of the d18O values against the d13C values could be due calcareous plankton). Of course, this assumption is to the fact that oxygen isotopes ratios in bulk samples valid for volcano-sedimentary layers. However, in are more sensitive against diagenetic alteration than the stratigraphic interval 10.0–10.5 m, with a fairly carbon isotopes. 13 constant CaCO3 content around 70%, prominent Beginning at 16.5 m d C values increase and marl or volcanic layers are lacking. comes along with the onset of increasing 187Os/188Os Michel et al. [61] used the Ir/Fe ratio to distinguish ratios [62] after a sharp minimum between f 13.5 and between an Ir enhancement from an impact fallout, and f 16 m. This excursion in seawater Os isotope com- variations in accumulation rate, which, in the case of position lag the time of maximum 3He flux by roughly Massignano, is controlled by the primary productivity 1.5 Ma. If this sharp minimum in Os isotope compo- of biogenic CaCO3 versus the input of detrital clay. sition would be attributed to an increased influx of 3 Thus, changes in CaCO3 production affect the relative extraterrestrial material, this time lag between the He abundances of clay and iridium, but not their ratio. Fig. flux maximum and the 187Os/188Os ratio minimum 3 shows that the Ir abundance and Ir/Fe ratio patterns could be caused by Poynting–Robertson drag [62]. are similar, indicating no change in the deposition rate So the turning point of the d13C curve from lower to 13 of CaCO3, as otherwise the high Ir/Fe ratios would be at higher d C values at f 16.5 m might indicate the last 290

e .Bdsltc ta./ErhadPaeaySineLtes23(04 283–302 (2004) 223 Letters Science Planetary and Earth / al. et Bodiselitsch B.

Fig. 4. Integrated litho-, chemo-, bio- and magnetostratigraphic model of the GSSP of the Late Eocene/Early Oligocene boundary at Massignano. Also shown are the impact events that occurred during this period. (Data from: [6,14–17,20–23,34,36–38,42,58,62,63,71,75–78] and this work.) B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 291 influence of the 2.2 Ma lasting comet shower whose At 6.17 m, with the highest Ir content, we found the duration is derived from the 3He curve from the lowest d13C and d18O values. The negative shift in d13C Massignano section [14]. Weathering of Os-rich ophio- and d18O can be interpreted as a consequence of sudden lite sequences, uplifted by closure of the Tethys, has warming of ocean water. From 6.20 m on, a rapid been proposed for the abrupt drop in seawater increase of d13C and d18O values indicates a return to 187Os/188Os ratios ([62], but see also [63]). the general seawater cooling trend that characterizes Between 12.70 and 12.90 m, there is a spike in the the terminal Eocene. For comparison, in the Quaternary d13C curve with very low d13C values, including the record, there are also present climate short-lived lowest d13C value of + 0.84x over the complete changes, especially more frequent fluctuations in sea- section. This spike coincides with two biotite-rich surface temperature associated with changes in bio- volcaniclastic layers in this region [34] and with the productivity within 2.5 ky and shorter (e.g., [64,65]) onset of the 187Os/188Os ratio minimum. A second, (Note: 1 cm u f 1.7 ky in the Massignano section). smaller, spike between 14.50 and 14.70 m also coin- Thus, it seems that short-lived changes in bio-producti- cides with a biotite-rich volcaniclastic layer [34] and is vity and sea temperature changes are not extraordinary. located in the middle of the 187Os/188Os ratio mini- The warm pulse that we can infer from the d13C and mum. Moreover, lower d18O values are also found at d18O negative shifts at 6.17 m (Fig. 3) may have been these levels. This effect is rather due to preferential triggered by a meteoritic impact, which would have alteration of material in the volcaniclastic layer and not released greenhouse gases into the atmosphere. Poag et an effect from the local volcanic conditions that causes al. [66] suggested that the general cooling trend from a warmer ocean with higher bio-productivity. Between the middle Eocene to the lowermost Oligocene is 5.50 and 5.65 m, there is another d13C (maximum interrupted by a warm pulse in the upper Eocene, which + 2.09x) and d18O (maximum À 0.81x) spike, agree- may have been triggered by the Popigai and Chesa- ing with the impactoclastic layer at 5.61 m, and peake Bay impact events, and may have been pro- indicating a possible cooling period with decreased longed by subsequent impacts during the peak of a bio-productivity. comet shower (Fig. 5). In addition, in the Ir-enhanced region in the 10.0–10.5 interval, we found a warm 4.3.2. High-resolution parts pulse with lower d13C and d18O values. The general In our work, the d13C values in the two high- trend of our isotopic records from the two levels shows resolution parts are in the range of +1.59x to + a warm pulse followed by a continuous cooling period 2.08x through the 6.0–6.4 m interval and +1.28x at this point with higher Ir concentration. d18O plots in to + 1.60x in the 10.0–10.5 m interval. The d18O Fig. 3 indicate similar d18O values in the two levels. values range between À 1.76x and À 0.60x and The last value in 6 m section at 6.4 m is d18O from À 1.94x to À 0.66x.(Fig. 3; Appendix D). À 0.89 F 0.08x and at the beginning at the 10 m The d13C and d18O values for all two levels essen- section d18O À 0.80 F0.03x. The average d18O val- tially show covariant trends. At 6.17 m, the lowest ues are very similar with À 1.16x and À 1.17x, d13C and d18O values were found, followed by a respectively. It seems that seawater temperature did continuous increase uptometerlevel6.20.Inaddition,the not change appreciable during this period of about 700 third-order poly-nomial trend line, which is superim- ky. The average d13C values differ somewhat between posed to indicate the general trend more clearly, shows the two levels. The average value in the lower an increase of d13C and d18O after the Ir-enhanced section is d13C + 1.79x, and in the upper section region. Lowest d13C and d18O values at in the 10.0– d13C + 1.60x, respectively. This could indicate an 10.5 m interval were found at 10.25 m followed by a incursion of colder, more vigorous bottom waters continuous increase up to 10.27 m., which coincides [67] and an increase of biomass and productivity with the Ir enrichment discussed above. After this point, [68] during this time span. a continuous decrease up to meter level 10.30 was If we compare the carbon and oxygen isotope data in detected. A general increase of isotopic values, starting the three Ir anomaly regions at 5.61, 6.17 and 10.28 m, it in the Ir-enriched region, is indicated by the third-order is particularly striking that in the region of 5.61 m the polynominal trend line. carbon and oxygen isotope data show higher values than 292 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302

Fig. 5. Integrated stratigraphic model shows relationship of Popigai and Chesapeake Bay impacts to calcareous nannofossil (NP14–NP21), foraminiferal biozones (P10–P19), extraterrestrial 3He curve [14], Ir peaks (this work; [58]) and oxygen isotope curve [6]. Modified from Poag et al. [18]. The zoomed part shows foraminiferal biozones (Fo), magnetostratigraphy (MagC; for details, see Fig. 4), extraterrestrial 3He curve and three subpulses of climatic warmth hypothesized by Poag et al. [71]. the dominant downward trend and in the two other overlain by dominantly siliciclastic, sedimentary rocks regions the d13C and d18O values are significantly lower [17,18]. The reason for the different climatic effects than this trend. It seems that the event that produced might be due to the locations where the impacts the Ir anomaly at 5.61 m caused a cooling period, occurred. The Popigai impact event occurred on the whereas the two other events caused some warming. continent, whereas the Chesapeake Bay impact event The target rocks of the 100-km-diameter Popigai took place on the continental shelf. Kent et al. [70] structure are generally granitic gneisses overlain by suggested that release of methane hydrates from me- f 1.25 km of sandstone and carbonates [15] produced chanical disruption of sediments as a result of an impact by the impact of an ordinary chondrite body [69]. If the could cause a greenhouse effect, which is shown by the Ir anomaly at 5.61 m is related to the Popigai impact negative shift in the carbon and oxygen isotope record. event, this kind of impact causes a following cooling So, the warm pulse at 6.17 m could be due to release of period with a decrease in bio-productivity. If we relate large amounts of seafloor methane hydrate during and the Ir anomaly at 6.17 m to the Chesapeake Bay impact after the Chesapeake impact event. event, this kind of impact triggers a warming period No impact event that could be related to the Ir with increased bio-productivity. The 85-km-diameter anomaly at 10.28 m is known so far. This anomaly, Chesapeake Bay on the coastal plain correlated with a negative carbon and oxygen excur- of Virginia is developed in a mixed-target substrate sion, could have been triggered by an impact in an composed of granitoids and metasedimentary rocks area of gas hydrate accumulation on the seafloor. B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 293

Poag et al. [71] proposed threefold subdivision of layer. There are some possible impact events which the inferred Late Eocene warm pulse. Negative d13C might be correlated with this layer: Mistastin, Can- and d18O excursions in the Ir-enhanced regions from ada (38 F 4 Ma, 28 km; [20]), Wanapitei, Canada this study correspond with two of the three subpulses. (37 F 2Ma,7.5km;[21,22]), Logoisk, Belarus The oldest warm subdivision, W-1, in C16n.2n and the (40 F 5 Ma, 17 km; [23]), or even badly dated lower part of C16r.1r correlates with Ir anomaly at 6.17 impact events, like Beenchime-Salaaty, Russia m. The Ir anomaly at 10.28 m correlates with the warm (40 F 20 Ma, 8 km; [72]) and Longancha, Russia subpulse, W-2, coincides with C16n.1n and the lower (40 F 20 Ma, 20 km; [72]). two-thirds of C15r (Fig. 5). Carbon and oxygen isotope ratios data show significant anomalies in both Ir-enhanced regions at 5. Summary and conclusions 6.17 and 10.28 m. There is no significant extinction event directly after the closely spaced Popigai and Two Ir anomalies at 6.17 and 10.28 m were Chesapeake Bay impact event. However, data from investigated in the Massignano, Italy, E/O section; calcareous nannoplankton show fluctuations, which these can be attributed to impact events in the Late coincide with the initiated warm pulse followed by a Eocene. They are precisely placed within magneto- cooling period after these events in the 6.0–6.4 m and biostratigra-phic sequences, and were radioisoto- section. Possible causes of these negative isotope pically dated using volcanic ash layers [34]. These Ir excursions could be due to the release of large anomalies are found in a 700 ky time interval from amounts of methane hydrate during and after an 35.7 and 35.0 Ma. This confirms preliminary Ir data at impact in the continental shelf (like the Chesapeake 6.19 and 10.25 m reported by Montanari et al. [34]. Bay impact) or seafloor, or the input of 12C-rich We found maximum Ir abundances of 259 F 32 ppt at carbon due to a cometary impact—cometary material 6.17 m and of 149 F 24 ppt at 10.28 m. The former is rich in carbon [73] with measured 12C/13C ratios anomaly is still within the lowermost part of P16 as high as 5000 compared to terrestrial values of zone, and within a short reversed interval in the upper about 89 [74], respectively. part of C16n. The other one is loca-ted in mid-C15n, The d18O values are not different between the 6.0 mid-P16 and upper CP15b (Fig. 4). and 6.4 m section and the about 700 ky younger section Another Ir anomaly, associated with an impacto- at 10.0–10.5 m. This is also reflected by oxygen iso- clastic layer at 5.61 m, has been known before, and tope data over the complete Massignano section that may be associated with the Popigai impact event, show only a slight downward trend over the whole whereas the newly confirmed Ir anomaly at 6.17 m Massignano section. Despite the fact that oxygen may be related to the Chesapeake Bay impact event isotope values measured in this study were clearly (or another so far unknown impact event). Evidence diagenetically influenced, the general trend of the for impact materials, such as Ni-rich spinels, clino- d18O values might provide evidence that a continuous pyroxene-microspherules, shocked quartz were found cooling from the middle Eocene to Oligocene is inter- at 5.61 m, but not in the 6.17 m region. However, rupted by warm pulses triggered by multiple impact shocked quartz at 5.61 m shows no high-pressure events during a comet shower lasting 2.2 Ma in the silica phases, which are present in the North American Late Eocene. strewn field microtektites related to the Chesapeake Bay impact event, but are not present in the clinopyr- Acknowledgements oxene-bearing spherules strewn field related to the Popigai impact event. C.K. and B.B. were supported by the Austrian In the region of the Ir anomaly at 10.28 m, no Science Foundation (grant Y58-GEO) and the research further evidence for an impact event was found. Our of R.C. by MIUR 60% and CNR (grant study shows, however, strong evidence for an extra- 97.00242CT05). We thank C. Wylie Poag, Ken Farley terrestrial source, rather in the form of an impact and an anonymous reviewer for their constructive and than slow accumulation of extraterrestrial dust. So critical reviews. Special thanks go to Dieter Mader for far, no particular impact event can be assigned to this useful comments and discussion. [KF] 294 .Bdsltc ta./ErhadPaeaySineLtes23(04 283–302 (2004) 223 Letters Science Planetary and Earth / al. et Bodiselitsch B.

Appendix A. Major and trace element contents in carbonates, in the 6.0–6.4 m section, above the base of GSSP for the E/O boundary at Massignano, Italy

Stratigraphic 6.000 6.025 6.050 6.075 6.100 6.110 6.120 6.130 6.140 6.150 6.160 6.170 6.180 6.190 6.200 6.210 6.220 6.230 6.240 6.250 6.260 6.270 6.280 6.290 6.300 6.325 6.350 6.375 6.400 level (m) wt.% SiO2 10.23 10.44 10.82 11.02 12.77 10.66 10.90 10.98 12.81 11.92 13.09 18.46 15.74 11.90 10.14 9.51 9.20 9.44 9.61 9.34 9.34 9.61 8.94 8.65 9.10 8.96 8.95 8.81 9.04 TiO2 0.18 0.18 0.19 0.19 0.21 0.19 0.19 0.21 0.19 0.19 0.21 0.27 0.25 0.21 0.18 0.17 0.16 0.18 0.17 0.17 0.16 0.17 0.16 0.16 0.17 0.16 0.17 0.16 0.17 Al2O3 3.00 3.06 3.18 3.27 3.95 3.16 3.18 3.21 3.87 3.57 3.97 5.69 4.71 3.79 3.01 2.81 2.66 2.83 2.85 2.73 2.79 2.80 2.59 2.50 2.67 2.65 2.64 2.62 2.69 Fe2O3 1.30 1.30 1.37 1.39 1.54 1.39 1.34 1.36 1.56 1.46 1.54 2.27 1.89 1.50 1.37 1.24 1.24 1.26 1.23 1.20 1.17 1.26 1.14 1.14 1.29 1.16 1.14 1.07 1.14 MnO 0.16 0.16 0.16 0.16 0.15 0.16 0.16 0.16 0.15 0.16 0.15 0.12 0.14 0.15 0.16 0.16 0.16 0.18 0.18 0.18 0.18 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 MgO 0.90 0.87 0.89 0.89 1.04 0.89 0.90 0.86 1.00 1.00 1.06 1.34 1.19 0.95 0.85 0.82 0.77 0.84 0.83 0.84 0.83 0.84 0.80 0.80 0.83 0.82 0.83 0.78 0.80 CaO 46.55 46.33 46.20 45.83 43.76 46.04 46.24 45.96 43.87 44.35 43.40 36.53 39.67 43.82 45.86 46.46 47.09 48.85 48.55 49.17 48.42 49.38 49.48 49.60 48.94 48.13 48.88 49.19 48.87 Na2O 0.10 0.10 0.10 0.11 0.12 0.11 0.11 0.10 0.11 0.13 0.13 0.19 0.15 0.13 0.12 0.11 0.11 0.11 0.11 0.10 0.10 0.11 0.10 0.10 0.10 0.10 0.10 0.10 0.10 K2O < 0.01 0.01 < 0.01 0.01 0.02 < 0.01 0.01 < 0.01 0.04 < 0.01 0.01 0.17 0.11 0.07 < 0.01 0.01 < 0.01 0.02 0.02 0.02 0.02 0.02 0.01 0.01 0.04 0.04 0.06 0.02 0.05 P2O5 0.08 0.08 0.07 0.08 0.09 0.08 0.08 0.08 0.08 0.08 0.10 0.11 0.10 0.08 0.06 0.06 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.08 0.07 0.07 0.08 0.08 L.O.I. 37.42 37.34 37.12 37.00 36.25 37.16 37.08 37.15 36.32 36.66 36.17 33.81 34.80 36.37 37.00 37.39 37.54 34.90 35.33 35.15 35.55 35.31 35.60 35.58 35.29 35.44 35.60 35.14 35.13 Total 99.87 99.83 100.04 99.87 99.80 99.81 100.12 100.03 99.99 99.40 99.81 98.81 98.61 98.80 98.60 98.63 98.92 98.60 98.87 98.87 98.57 99.67 98.98 98.70 98.59 97.61 98.60 98.08 98.15 ppm (except where noted) Sc 3.39 3.39 3.48 3.74 4.21 3.65 3.59 3.57 4.00 4.18 4.15 6.20 5.28 4.33 3.75 3.34 3.22 3.32 3.17 3.01 2.97 3.28 3.10 3.01 3.15 3.19 2.90 2.50 3.14 V 2223272531272724302830403127222020212119221921182120201919 Cr 29.9 29.9 30.7 33.6 37.4 32.8 32.1 31.8 35.6 38.7 36.6 54.1 44.1 36.4 33.8 31.3 30.3 29.3 30 28.3 28.1 30.8 28.8 28.2 28.2 29.4 29.9 27.1 29 Co 8.9 8.5 10.1 9.84 13 9.72 9.75 9.74 11.9 12.3 12.3 20.7 16.4 12.7 8.98 8.71 8.11 9.59 8.35 7.96 7.53 8.25 7.6 6.9 7.32 8.22 7.99 7.88 7.86 Ni 6 7 11 14 23 10 10 14 21 19 23 51 35 22 10 9 8 < 6 < 6 < 6 < 6 < 6 < 6 < 6 6 < 6 < 6 < 6 < 6 Cu 6 9 9 <6 <6 <6 <6 <6 <6 <6 <6 13 6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 Zn 32 40 40 38 40 37 37 35 37 41 39 56 49 36 40 33 30 31 30 30 30 33 30 29 31 31 31 31 28 As 0.47 0.41 0.38 0.46 0.50 0.26 0.35 0.33 0.54 0.28 0.33 0.34 0.41 0.33 0.34 0.29 0.12 0.28 0.20 0.18 0.25 0.27 0.27 0.23 0.31 0.22 0.30 0.24 0.27 Se 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Br 0.43 0.49 0.45 0.46 0.37 0.33 0.37 0.32 0.45 0.39 0.43 0.33 0.32 0.32 0.51 0.53 0.45 0.50 0.39 0.49 0.49 0.32 0.42 0.43 0.43 0.40 0.31 0.30 0.47 Rb 30.6 29.0 28.8 33.4 36.4 31.6 32.2 30.5 34.1 33.0 32.7 51.0 42.2 36.9 31.1 27.0 27.5 27.7 27.1 26.4 27.5 28.2 20.4 24.4 23.3 27.1 26.2 24.6 26.6 Sr 931 942 955 959 972 959 989 960 964 959 959 940 926 941 918 899 901 906 902 903 902 897 884 904 901 898 895 895 862 Y 1314141414141414141514161716141314131413131313131314131513 Zr 25 28 30 28 29 30 28 26 29 29 31 51 41 35 34 20 21 20 22 21 23 23 30 25 25 21 25 20 24 Nb666666 66767 7 88667566566665566 Sb 0.18 0.17 0.16 0.16 0.2 0.15 0.16 0.15 0.18 0.16 0.19 0.29 0.24 0.17 0.16 0.14 0.13 0.14 0.15 0.12 0.18 0.14 0.14 0.13 0.17 0.14 0.17 0.14 0.15 Cs 2.11 2.07 2.15 2.43 2.66 2.32 2.38 2.33 2.39 2.40 2.16 3.27 2.59 2.20 2.05 1.83 1.81 1.65 1.85 1.89 1.67 1.93 1.93 1.59 1.62 1.85 1.74 1.70 1.83 Ba 507 498 450 514 576 514 1460 526 553 563 537 814 661 535 561 596 573 578 556 626 599 583 532 686 535 511 482 468 490 La 12.5 11.7 11.6 12.6 13.7 13.0 12.2 12.3 12.5 13.6 13.5 16.7 16.0 13.8 12.9 11.7 12.6 12.0 12.3 14.3 12.0 12.5 13.0 11.7 11.8 12.2 12.2 11.5 12.8 Ce 17.2 17.1 17.2 18.4 19.6 18.6 17.8 17.5 19.1 21.0 19.0 27.3 25.0 19.1 19.2 17.3 16.0 15.6 16.7 14.9 15.0 17.4 17.0 16.7 15.5 17.2 15.9 16.8 17.5 Nd 10.2 9.8 9.06 10.8 11.1 11.1 10.6 10.8 11.7 10.1 9.6 15.6 12.9 12.4 8.51 7.85 8.3 8.99 7.53 9.12 7.19 9.45 9.3 7.73 9.55 9.32 8.5 8.33 8.52 Sm 1.99 1.85 1.81 2.09 2.16 2.12 2.00 2.01 1.99 1.99 1.96 2.75 2.02 2.15 1.83 1.63 1.77 1.72 1.75 1.81 1.67 1.86 1.86 1.60 1.67 1.82 1.75 1.77 1.98 .Bdsltc ta./ErhadPaeaySineLtes23(04 283–302 (2004) 223 Letters Science Planetary and Earth / al. et Bodiselitsch B. Eu 0.45 0.43 0.45 0.49 0.50 0.49 0.47 0.44 0.48 0.51 0.48 0.65 0.62 0.51 0.46 0.44 0.44 0.42 0.42 0.39 0.38 0.45 0.43 0.41 0.40 0.42 0.41 0.43 0.44 Gd 1.57 1.55 1.45 1.61 1.65 2.02 1.60 1.50 1.95 1.62 1.58 2.49 2.11 < 1.90 1.73 1.45 1.38 1.30 1.45 1.32 1.45 1.59 1.61 1.44 < 1.30 1.45 1.52 1.49 1.53 Tb 0.28 0.29 0.27 0.30 0.30 0.34 0.30 0.28 0.30 0.28 0.29 0.40 0.40 0.34 0.31 0.27 0.26 0.20 0.25 0.25 0.27 0.29 0.27 0.27 0.25 0.26 0.28 0.28 0.28 Tm 0.15 0.17 0.17 0.16 0.16 0.16 0.16 0.16 0.16 0.17 0.17 0.23 0.19 0.18 0.18 0.16 0.16 0.15 0.15 0.15 0.16 0.17 0.16 0.16 0.15 0.16 0.16 0.16 0.16 Yb 1.04 1.09 1.05 1.11 1.10 1.10 1.10 1.08 1.10 1.18 1.18 1.43 1.29 1.24 1.18 1.10 1.11 1.05 1.05 1.04 1.08 1.11 1.08 1.06 1.05 1.10 1.09 1.07 1.07 Lu 0.15 0.15 0.15 0.16 0.16 0.16 0.16 0.16 0.16 0.17 0.16 0.21 0.18 0.18 0.18 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.15 0.15 0.16 Hf 0.69 0.63 0.66 0.65 0.75 0.63 0.61 0.64 0.70 0.75 0.71 1.32 1.15 0.84 0.73 0.66 0.53 0.53 0.59 0.59 0.55 0.65 0.57 0.56 0.54 0.60 0.54 0.52 0.54 Ta 0.18 0.17 0.17 0.19 0.20 0.18 0.20 0.19 0.22 0.21 0.14 0.29 0.25 0.18 0.21 0.15 0.14 0.15 0.18 0.12 0.14 0.16 0.14 0.14 0.14 0.17 0.15 0.13 0.17 W 1.1 1.1 1.7 1.2 1.4 1.2 1.1 1.5 1.1 < 0.9 0.6 0.7 0.5 0.8 < 0.7 0.4 < 0.7 0.6 0.6 0.6 1.1 0.5 0.5 0.6 0.3 0.5 0.5 0.4 0.3 Au (ppb) 0.3 0.3 0.1 0.4 0.1 0.6 0.5 0.5 0.6 0.5 0.5 1.3 < 0.5 0.9 0.5 0.6 < 0.5 0.4 0.3 1.1 0.3 < 0.5 0.4 < 0.5 0.4 0.3 0.3 0.4 0.3 Th 2.25 2.17 2.15 2.41 2.61 2.27 2.30 2.30 2.60 2.47 2.38 4.47 3.54 2.62 2.36 2.00 1.84 1.91 1.96 1.73 1.83 2.11 1.87 1.76 1.87 2.01 1.86 1.82 1.95 U 0.48 0.39 0.46 0.45 0.64 0.55 0.52 0.58 0.45 0.52 0.66 0.96 0.72 0.72 0.70 0.42 0.51 0.55 0.46 0.60 0.64 0.52 0.53 0.64 0.65 0.59 0.55 0.56 0.71 K/U n.d. 256 n.d. 222 312 n.d. 192 n.d. 667 n.d. 152 1458 1250 833 n.d. 238 n.d. 363 434 333 312 385 189 156 461 509 909 357 563 La/Th 5.56 5.39 5.40 5.23 5.25 5.73 5.30 5.35 4.81 5.51 5.67 3.74 4.52 5.27 5.47 5.85 6.85 6.28 6.28 8.27 6.56 5.92 6.95 6.65 6.31 6.07 6.56 6.32 6.56 Th/U 4.69 5.56 4.67 5.36 4.08 4.13 4.42 3.97 5.78 4.75 3.61 4.66 4.92 3.64 3.37 4.76 3.61 3.47 4.26 2.88 2.86 4.06 3.53 2.75 2.88 3.41 3.38 3.25 2.75 Ce/Ce* 0.65 0.69 0.71 0.69 0.68 0.67 0.69 0.67 0.71 0.75 0.68 0.76 0.74 0.65 0.73 0.73 0.63 0.63 0.67 0.52 0.62 0.67 0.64 0.70 0.63 0.68 0.64 0.71 0.67 LaCN /YbCN 8.12 7.25 7.47 7.67 8.42 7.99 7.49 7.70 7.68 7.79 7.73 7.89 8.38 7.52 7.39 7.19 7.67 7.72 7.92 9.29 7.51 7.61 8.13 7.46 7.59 7.49 7.56 7.26 8.08 Eu/Eu* 0.78 0.78 0.85 0.82 0.81 0.72 0.80 0.77 0.74 0.87 0.83 0.76 0.92 n.d. 0.79 0.87 0.86 0.86 0.81 0.77 0.75 0.80 0.76 0.83 n.d. 0.79 0.77 0.81 0.77

Total iron as Fe2O3. 295 296 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302

Appendix B. Major and trace element contents in carbonates, in the 10.0–10.5 m section, above the base of GSSP for the E/O boundary at Massignano, Italy

Stratigraphic 10.000 10.025 10.050 10.075 10.100 10.125 10.150 10.160 10.170 10.180 10.190 10.200 10.210 10.220 10.230 10.240 level (m) wt.%

SiO2 12.49 11.49 12.07 11.80 10.93 11.02 11.19 11.67 11.55 11.69 11.38 11.18 11.50 11.20 11.27 11.56 TiO2 0.22 0.20 0.22 0.20 0.18 0.20 0.19 0.20 0.20 0.19 0.20 0.19 0.20 0.19 0.19 0.19 Al2O3 3.73 3.40 3.52 3.42 3.21 3.28 3.34 3.55 3.46 3.44 3.39 3.26 3.42 3.35 3.28 3.40 Fe2O3 1.72 1.59 1.72 1.66 1.60 1.57 1.54 1.59 1.59 1.67 1.56 1.54 1.60 1.64 1.50 1.53 MnO 0.16 0.16 0.16 0.16 0.15 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.14 0.15 MgO 1.04 0.99 1.02 0.97 0.92 0.95 0.98 1.03 1.01 1.02 0.99 0.93 1.00 0.96 0.90 0.96 CaO 44.69 45.65 44.93 45.30 48.26 46.87 46.17 45.27 45.84 45.44 45.77 46.05 45.63 46.09 46.09 45.84

Na2O 0.13 0.11 0.11 0.11 0.12 0.12 0.11 0.12 0.13 0.13 0.12 0.13 0.13 0.13 0.12 0.12 K2O 0.22 0.14 0.20 0.14 0.10 0.12 0.14 0.11 0.08 0.08 0.05 0.05 0.06 0.04 0.07 0.08 P2O5 0.08 0.08 0.08 0.07 0.07 0.08 0.07 0.07 0.08 0.08 0.09 0.08 0.08 0.08 0.07 0.09 L.O.I. 34.37 34.84 34.62 35.02 34.90 34.56 34.76 34.78 34.57 34.93 35.25 35.36 34.89 35.03 35.20 35.08 Total 98.74 98.63 98.59 98.76 100.35 98.86 98.59 98.50 98.57 98.73 98.94 98.82 98.60 98.76 98.81 98.94 ppm (except where noted) Sc 4.37 3.82 4.17 3.98 3.89 3.82 3.94 3.80 4.02 4.18 3.76 3.96 4.04 4.03 3.86 4.05 V 26252226262725262628282727283127 Cr 38.3 34.5 39.3 34.2 34.3 35.2 35.6 32.9 36.9 37.7 33.5 34.6 35.5 34.8 34.5 35.6 Co 11.3 9.63 11.1 9.61 9.61 9.11 9.91 9.42 9.84 10.5 9.51 9.90 9.78 9.60 9.75 10.3 Ni 21 16 < 6 16 16 10 14 15 16 20 18 16 17 15 20 18 Cu <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 <6 8 <6 Zn 38 38 35 37 37 38 36 40 33 41 40 39 40 36 40 39 As 0.58 0.38 0.48 0.43 0.45 0.45 0.49 0.34 0.49 0.52 0.35 0.40 0.38 0.41 0.40 0.38 Se 0.2 < 0.1 0.1 < 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 < 0.1 0.2 < 0.1 0.1 0.1 Br 0.35 0.36 0.38 0.35 0.40 0.37 0.25 0.34 0.29 0.35 0.27 0.25 0.40 0.40 0.33 0.39 Rb 36.9 30.5 39.3 33.5 35.8 31.1 32.4 35.3 34.8 36.1 31.0 33.7 34.6 33.4 31.8 33.3 Sr 1120 1140 1130 1180 1200 1210 1130 1240 1200 1170 1290 1160 1220 1200 1140 1100 Y 13131313121213121313131413131314 Zr 30 29 33 27 26 28 26 25 26 26 24 25 30 29 23 27 Nb6667666456566656 Sb 0.18 0.12 0.19 0.14 0.15 0.16 0.57 0.18 0.15 0.15 0.14 0.16 0.15 0.14 0.13 0.13 Cs 2.31 1.96 2.59 1.94 2.08 1.96 2.04 2.17 2.24 2.33 2.00 2.07 2.17 2.16 2.04 2.15 Ba 441 431 426 410 380 378 402 422 398 424 409 422 420 435 387 382 La 13.4 12.2 12.6 12.6 12.5 11.9 12.7 11.7 11.9 12.8 11.4 12.7 12.2 11.7 11.5 12.4 Ce 19.8 17.6 21.0 19.2 18.8 18.2 18.7 17.7 18.6 19.4 17.6 18.7 19.1 18.3 17.7 19.5 Nd 10.3 10.2 9.91 11.1 9.76 11.0 10.0 10.2 9.68 10.7 10.0 10.3 11.0 8.55 10.1 10.1 Sm 2.00 1.67 1.90 1.81 1.89 1.80 1.87 1.94 1.89 1.94 1.69 1.88 1.86 1.88 1.73 1.96 Eu 0.50 0.47 0.51 0.49 0.46 0.46 0.47 0.45 0.48 0.48 0.45 0.48 0.47 0.44 0.44 0.49 Gd 1.74 1.96 1.91 1.27 1.98 1.47 2.08 1.70 2.00 2.11 1.40 1.60 1.56 1.74 1.52 1.55 Tb 0.32 0.29 0.35 0.30 0.33 0.26 0.30 0.32 0.27 0.32 0.26 0.31 0.31 0.33 0.28 0.27 Tm 0.19 0.17 0.21 0.16 0.16 0.17 0.17 0.18 0.16 0.16 0.16 0.16 0.18 0.15 0.16 0.17 Yb 1.10 0.99 1.02 1.01 1.02 1.03 1.03 1.00 1.05 1.06 0.97 1.08 1.07 1.00 1.05 1.05 Lu 0.16 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.17 0.16 0.15 0.16 0.15 0.15 0.15 0.16 Hf 0.78 0.64 0.78 0.80 0.75 0.66 0.68 0.68 0.71 0.71 0.61 0.67 0.68 0.61 0.62 0.69 Ta 0.20 0.17 0.22 0.18 0.19 0.17 0.18 0.19 0.19 0.19 0.17 0.19 0.18 0.14 0.16 0.17 W 1.2 0.1 0.7 0.6 0.6 0.6 0.8 1.0 0.7 0.8 < 0.5 0.9 1.0 0.8 0.6 0.6 Au [ppb] 4.3 0.5 1.0 0.3 0.5 0.8 0.5 0.8 0.3 1.0 0.3 0.3 0.8 0.8 1.0 1.8 Th 2.66 2.20 2.75 2.41 2.48 2.34 2.38 2.51 2.44 2.53 2.18 2.37 2.43 2.42 2.30 2.45 U 0.47 0.43 0.51 0.40 0.53 0.26 0.43 0.46 0.37 0.56 0.51 0.41 0.37 0.42 0.42 0.41 K/U 3830 2791 3333 3000 1509 3846 2791 1957 1892 1250 784 976 1351 714 1429 1707 La/Th 5.04 5.55 4.58 5.23 5.04 5.09 5.34 4.66 4.88 5.06 5.23 5.36 5.02 4.83 5.00 5.06 Th/U 5.66 5.12 5.39 6.03 4.68 9.00 5.53 5.46 6.59 4.52 4.27 5.78 6.57 5.76 5.48 5.98 Ce/Ce* 0.71 0.68 0.80 0.71 0.72 0.71 0.70 0.74 0.72 0.72 0.70 0.70 0.73 0.76 0.72 0.75

LaCN/YbCN 8.23 8.33 8.35 8.43 8.28 7.81 8.33 7.91 7.66 8.16 7.94 7.95 7.70 7.91 7.40 7.98 Eu/Eu* 0.82 0.79 0.82 0.99 0.73 0.86 0.73 0.76 0.75 0.73 0.89 0.85 0.84 0.74 0.83 0.86

Total iron as Fe2O3. B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 297

10.250 10.260 10.270 10.280 10.290 10.300 10.310 10.320 10.330 10.340 10.350 10.375 10.400 10.425 10.450 10.475 10.500

12.23 11.45 13.11 12.61 11.86 11.98 12.22 13.28 13.47 12.06 12.71 12.19 12.70 12.84 11.59 11.02 10.44 0.21 0.20 0.22 0.21 0.21 0.20 0.21 0.22 0.22 0.20 0.21 0.21 0.21 0.21 0.20 0.18 0.19 3.70 3.43 3.90 3.74 3.51 3.53 3.63 3.96 3.90 3.51 3.74 3.57 3.78 3.80 3.47 3.26 3.09 1.57 1.53 1.76 1.70 1.60 1.66 1.69 1.76 1.80 1.66 1.74 1.74 1.72 1.69 1.67 1.67 1.50 0.15 0.15 0.15 0.16 0.17 0.15 0.15 0.15 0.16 0.16 0.16 0.16 0.15 0.15 0.16 0.16 0.16 1.01 0.99 1.06 1.05 1.00 0.98 1.02 1.04 1.04 1.00 1.03 1.01 1.06 1.10 1.10 1.11 1.03 45.21 45.55 43.99 44.34 45.41 45.12 45.01 42.46 43.39 44.48 42.70 44.62 41.84 43.58 45.25 45.96 46.84 0.13 0.13 0.13 0.12 0.12 0.11 0.13 0.13 0.12 0.11 0.12 0.11 1.25 0.12 0.00 0.00 0.00 0.08 0.07 0.14 0.14 0.13 0.13 0.14 0.20 0.29 0.13 0.20 0.29 0.19 0.11 0.009 0.16 0.14 0.09 0.08 0.09 0.08 0.08 0.08 0.08 0.08 0.09 0.07 0.09 0.08 0.10 0.09 0.08 0.08 0.07 34.85 35.42 34.95 34.94 34.86 34.80 34.66 35.55 34.75 35.19 36.46 34.86 37.15 35.41 35.84 35.11 35.24 99.16 98.82 99.38 99.10 98.85 98.73 98.84 98.74 99.21 98.55 99.09 98.82 98.95 99.13 99.40 98.61 98.65

4.08 4.22 4.57 4.19 4.12 3.98 4.21 4.33 4.21 3.93 4.24 3.97 4.10 3.90 3.58 3.53 3.32 30 24 28 28 28 26 31 29 27 27 25 28 30 24 26 25 24 37.1 36.5 40.9 35.8 35.2 36.4 40.9 42.8 40.4 36.4 39.7 36.9 40.1 38.2 35.1 34.2 33.2 9.93 10.5 11.9 11.5 10.8 10.6 11.0 11.9 11.8 10.5 11.6 10.2 10.8 10.0 9.52 9.33 8.88 22 22 23 25 21 20 22 24 26 21 21 14 23 20 18 13 12 <6<611867<68<6<6<6<66<6<6<6<6 43 41 43 40 41 39 42 41 41 37 39 41 42 42 41 41 37 0.38 0.39 0.46 0.41 0.41 0.47 0.46 0.59 0.47 0.59 0.47 0.61 0.47 0.38 0.48 0.49 0.44 < 0.1 < 0.1 0.1 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.37 0.32 0.22 0.31 0.30 0.41 0.40 0.43 0.34 0.42 0.40 0.43 0.38 0.36 0.35 0.41 0.30 34.7 36.3 39.9 38.5 36.4 33.9 37.8 40.7 40.0 37.4 36.8 36.6 38.3 35.1 36.6 35.9 31.4 1120 1120 1130 1140 1100 1100 1100 1200 1190 1090 1130 1160 1150 1140 1110 1140 1190 14 13 13 14 13 14 12 13 14 13 15 13 14 15 14 13 13 28 26 30 29 28 32 28 41 38 30 34 34 29 26 28 26 24 566676576776665 56 0.12 0.16 0.18 0.16 0.12 0.15 0.18 0.16 0.14 0.16 0.15 0.17 0.17 0.12 0.15 0.15 0.13 2.16 2.29 2.48 2.40 2.13 2.33 2.77 2.73 2.72 2.55 2.57 2.43 2.56 2.41 2.47 2.46 2.20 410 446 490 478 452 437 450 471 496 477 458 388 387 361 379 413 355 12.0 13.0 13.7 12.6 12.9 11.6 12.6 13.1 12.5 12.0 12.7 12.7 13.1 12.3 11.1 11.5 11.6 19.0 19.6 21.1 18.8 18.9 18.2 19.9 20.5 19.7 18.7 20.5 19.2 19.8 19.0 17.1 17.4 17.3 10.0 10.7 11.7 9.96 9.66 10.1 10.5 10.4 10.5 10.4 11.0 10.8 10.4 10.2 9.91 9.82 10.1 1.81 1.99 2.12 2.00 1.86 1.88 2.17 2.19 2.12 2.08 2.09 2.02 2.09 2.00 1.92 1.94 1.87 0.46 0.49 0.52 0.47 0.47 0.45 0.49 0.50 0.48 0.46 0.50 0.47 0.49 0.46 0.43 0.42 0.42 1.55 1.69 1.80 1.64 1.42 1.62 1.86 1.70 1.70 1.65 1.60 1.70 1.70 1.93 1.53 1.50 1.45 0.28 0.32 0.34 0.31 0.25 0.29 0.35 0.30 0.32 0.31 0.30 0.32 0.32 0.30 0.29 0.28 0.27 0.16 0.16 0.18 0.18 0.15 0.17 0.17 0.16 0.15 0.16 0.18 0.16 0.19 0.15 0.14 0.17 0.15 1.05 1.08 1.08 1.01 0.98 1.02 1.17 1.08 1.04 1.07 1.17 1.13 1.14 1.10 0.96 1.07 1.03 0.15 0.16 0.16 0.15 0.15 0.15 0.16 0.16 0.15 0.16 0.16 0.17 0.15 0.15 0.14 0.14 0.14 0.70 0.70 0.82 0.78 0.70 0.73 0.70 0.92 0.85 0.75 0.83 0.82 0.76 0.74 0.66 0.66 0.59 0.18 0.19 0.24 0.21 0.17 0.19 0.20 0.23 0.24 0.22 0.25 0.32 0.20 0.19 0.21 0.22 0.19 0.5 < 0.3 1.1 0.6 0.6 1.7 2.15 1.15 1.30 1.51 1.10 1.00 0.90 1.50 2.00 1.50 1.00 1.8 1.8 2.0 1.0 0.6 0.2 1.3 1.2 1.0 0.3 0.5 1.1 0.5 0.9 0.4 0.8 0.3 2.45 2.60 2.96 2.69 2.43 2.34 2.62 2.81 2.77 2.48 2.66 2.50 2.64 2.46 2.37 2.45 2.26 0.49 0.44 0.57 0.55 0.53 0.49 0.57 0.58 0.66 0.68 0.52 0.59 0.56 0.51 0.59 0.53 0.46 1429 1364 2105 2182 2075 2245 2105 2931 3636 1618 3269 4068 2857 1765 1266 2506 2527 4.90 5.00 4.63 4.68 5.31 4.96 4.81 4.66 4.51 4.84 4.77 5.08 4.96 5.00 4.68 4.69 5.13 5.00 5.91 5.19 4.89 4.58 4.78 4.60 4.84 4.20 3.65 5.12 4.24 4.71 4.82 4.02 4.62 4.91 0.75 0.72 0.73 0.71 0.71 0.74 0.75 0.75 0.75 0.73 0.76 0.71 0.72 0.73 0.72 0.71 0.70 7.72 8.13 8.57 8.43 8.90 7.68 7.28 8.20 8.12 7.58 7.34 7.59 7.77 7.56 7.81 7.26 7.61 0.84 0.82 0.81 0.79 0.88 0.79 0.75 0.79 0.77 0.76 0.84 0.78 0.79 0.72 0.77 0.75 0.78 298 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302

Appendix C. Carbon and oxygen isotope data Appendix C (continued) 13 18 from samples of the complete Massignano GSSP, Stratigraphic level d CV-PDB d OV-PDB Italy (m) (x) (x) 7.10 1.88 F 0.11 À 1.04 F 0.20 7.15 1.99 F 0.03 À 0.86 F 0.06 13 18 F F Stratigraphic level d CV-PDB d OV-PDB 7.20 1.88 0.00 À 1.05 0.00 (m) (x) (x) 7.30 1.73 F 0.00 À 1.32 F 0.00 7.35 1.87 F 0.06 À 1.18 F 0.11 0.00 2.00 F 0.10 À 0.95 F 0.17 7.40 1.91 F 0.02 À 0.81 F 0.03 0.30 1.96 F 0.00 À 1.01 F 0.00 7.50 1.61 F 0.01 À 1.55 F 0.02 0.50 2.06 F 0.01 À 0.87 F 0.06 7.60 1.96 F 0.08 À 0.94 F 0.13 0.60 2.01 F 0.06 À 0.93 F 0.13 7.70 1.80 F 0.00 À 0.89 F 0.00 1.00 1.93 F 0.01 À 0.92 F 0.04 7.80 1.75 F 0.09 À 1.04 F 0.04 1.20 1.99 F 0.03 À 0.89 F 0.05 8.00 1.64 F 0.03 À 1.30 F 0.06 1.50 1.87 F 0.02 À 1.08 F 0.00 8.10 1.78 F 0.03 À 1.03 F 0.05 1.80 1.88 F 0.07 À 0.96 F 0.12 8.20 1.56 F 0.01 À 1.58 F 0.05 2.00 1.83 F 0.00 À 0.96 F 0.00 8.30 1.73 F 0.05 À 0.96 F 0.08 2.50 1.94 F 0.03 À 0.86 F 0.04 8.40 1.76 F 0.05 À 0.91 F 0.11 3.00 1.85 F 0.00 À 0.81 F 0.00 8.50 1.88 F 0.09 À 0.72 F 0.14 3.50 1.82 F 0.01 À 0.96 F 0.04 8.60 1.81 F 0.01 À 0.77 F 0.01 4.00 1.94 F 0.04 À 1.03 F 0.10 8.70 1.62 F 0.06 À 1.30 F 0.06 4.10 2.06 F 0.08 À 0.80 F 0.11 8.80 1.76 F 0.05 À 1.17 F 0.11 4.20 1.96 F 0.00 À 0.97 F 0.00 8.90 1.83 F 0.00 À 1.01 F 0.00 4.30 1.93 F 0.01 À 1.13 F 0.01 9.00 1.83 F 0.08 À 0.80 F 0.05 4.40 2.06 F 0.05 À 0.92 F 0.11 9.10 1.64 F 0.06 À 1.10 F 0.13 4.50 1.92 F 0.08 À 1.07 F 0.15 9.20 1.55 F 0.02 À 1.31 F 0.02 4.60 1.94 F 0.00 À 0.94 F 0.00 9.30 1.58 F 0.03 À 1.32 F 0.08 4.70 2.17 F 0.04 À 0.59 F 0.06 9.40 1.84 F 0.05 À 0.80 F 0.12 4.80 1.93 F 0.01 À 1.11 F 0.08 9.50 1.74 F 0.00 À 1.15 F 0.00 4.90 1.91 F 0.06 À 0.98 F 0.11 9.60 1.66 F 0.05 À 1.32 F 0.12 5.00 1.73 F 0.03 À 1.17 F 0.04 9.70 1.63 F 0.03 À 1.40 F 0.03 5.10 2.07 F 0.02 À 0.75 F 0.08 9.80 1.56 F 0.08 À 1.45 F 0.06 5.20 1.88 F 0.00 À 1.11 F 0.00 9.90 1.68 F 0.09 À 1.26 F 0.16 5.25 1.68 F 0.02 À 1.29 F 0.01 10.00 1.90 F 0.08 À 0.77 F 0.12 5.30 1.76 F 0.08 À 1.26 F 0.11 10.10 1.63 F 0.06 À 1.09 F 0.12 5.40 1.66 F 0.02 À 1.56 F 0.08 10.20 1.87 F 0.02 À 0.84 F 0.10 5.50 2.09 F 0.02 À 0.81 F 0.07 10.25 1.64 F 0.06 À 1.22 F 0.10 5.60 1.90 F 0.04 À 0.96 F 0.05 10.30 1.65 F 0.02 À 1.27 F 0.04 5.65 1.88 F 0.06 À 0.92 F 0.13 10.40 1.50 F 0.00 À 1.15 F 0.01 5.70 1.69 F 0.01 À 1.35 F 0.01 10.50 1.66 F 0.00 À 1.04 F 0.00 5.80 1.91 F 0.01 À 0.77 F 0.08 10.60 1.63 F 0.01 À 1.09 F 0.02 5.90 2.06 F 0.07 À 0.69 F 0.14 10.70 1.60 F 0.00 À 1.12 F 0.01 6.00 1.90 F 0.01 À 0.83 F 0.01 10.80 1.53 F 0.08 À 1.12 F 0.14 6.10 1.76 F 0.03 À 1.23 F 0.05 10.90 1.70 F 0.02 À 0.84 F 0.03 6.15 1.74 F 0.00 À 1.12 F 0.00 11.00 1.53 F 0.04 À 1.17 F 0.11 6.20 1.95 F 0.00 À 0.93 F 0.00 11.10 1.52 F 0.01 À 1.15 F 0.02 6.25 1.75 F 0.00 À 1.22 F 0.00 11.20 1.32 F 0.02 À 1.60 F 0.01 6.30 2.06 F 0.00 À 0.85 F 0.05 11.30 1.57 F 0.09 À 1.14 F 0.22 6.40 1.76 F 0.04 À 1.37 F 0.07 11.40 1.35 F 0.08 À 1.56 F 0.06 6.45 1.81 F 0.06 À 0.97 F 0.13 11.50 1.55 F 0.08 À 1.15 F 0.16 6.50 1.72 F 0.02 À 1.24 F 0.06 11.60 1.46 F 0.06 À 1.12 F 0.06 6.60 1.93 F 0.03 À 0.85 F 0.06 11.70 1.28 F 0.05 À 1.51 F 0.11 6.70 1.98 F 0.06 À 0.91 F 0.07 11.80 1.45 F 0.00 À 0.93 F 0.00 6.80 2.05 F 0.01 À 0.82 F 0.00 11.90 1.42 F 0.00 À 1.20 F 0.01 6.90 1.87 F 0.02 À 1.16 F 0.02 12.00 1.43 F 0.09 À 1.32 F 0.05 7.00 1.92 F 0.09 À 1.02 F 0.15 12.20 1.52 F 0.02 À 1.03 F 0.08 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302 299

Appendix C (continued) Appendix C (continued) 13 18 13 18 Stratigraphic level d CV-PDB d OV-PDB Stratigraphic level d CV-PDB d OV-PDB (m) (x) (x) (m) (x) (x) 12.30 1.35 F 0.09 À 1.34 F 0.12 22.20 1.69 F 0.04 À 1.29 F 0.12 12.40 1.43 F 0.08 À 1.30 F 0.14 22.40 1.79 F 0.08 À 0.96 F 0.18 12.50 1.45 F 0.04 À 1.10 F 0.06 22.50 1.77 F 0.03 À 1.04 F 0.08 12.60 1.65 F 0.04 À 0.69 F 0.08 23.00 1.98 F 0.01 À 0.95 F 0.03 F F 12.70 1.09 0.05 À 1.19 0.04 Errors are 1r for d 13C and d 18O. 12.80 1.01 F 0.02 À 1.33 F 0.04 12.90 0.84 F 0.10 À 1.55 F 0.08 13.00 1.48 F 0.05 À 0.84 F 0.01 13.10 1.30 F 0.01 À 1.26 F 0.04 Appendix D. Carbon and oxygen isotope data 13.20 1.39 F 0.00 À 1.16 F 0.00 from samples of the high-resolution part from 13.30 1.45 F 0.03 À 1.04 F 0.10 Massignano, Italy 13.40 1.43 F 0.03 À 0.99 F 0.01 13.50 1.26 F 0.01 À 1.26 F 0.04 13.60 1.20 F 0.04 À 1.28 F 0.13 Stratigraphic level d 13C d 18O 13.70 1.22 F 0.05 À 1.24 F 0.09 V-PDB V-PDB (m) (x) (x) 13.80 1.23 F 0.02 À 1.24 F 0.04 13.90 1.26 F 0.08 À 0.97 F 0.16 6.000 1.94 F 0.00 À 0.80 F 0.00 14.00 1.37 F 0.02 À 1.12 F 0.06 6.025 2.08 F 0.07 À 0.60 F 0.06 14.10 1.24 F 0.06 À 1.05 F 0.11 6.050 1.95 F 0.02 À 0.84 F 0.01 14.40 1.14 F 0.08 À 1.49 F 0.07 6.075 1.91 F 0.01 À 1.07 F 0.01 14.50 1.06 F 0.07 À 1.57 F 0.19 6.100 1.85 F 0.07 À 1.18 F 0.09 14.70 1.07 F 0.05 À 1.14 F 0.10 6.110 1.92 F 0.06 À 1.12 F 0.02 15.00 1.16 F 0.06 À 1.14 F 0.13 6.120 1.67 F 0.00 À 1.62 F 0.04 15.30 1.22 F 0.03 À 0.93 F 0.08 6.130 1.68 F 0.00 À 1.61 F 0.00 15.50 1.27 F 0.02 À 0.80 F 0.07 6.140 1.98 F 0.03 À 0.98 F 0.08 16.00 1.27 F 0.01 À 1.10 F 0.06 6.150 1.83 F 0.01 À 1.34 F 0.05 16.20 1.04 F 0.06 À 1.17 F 0.11 6.160 1.95 F 0.03 À 1.06 F 0.00 16.50 1.01 F 0.08 À 1.15 F 0.18 6.170 1.62 F 0.02 À 1.76 F 0.01 16.80 1.07 F 0.02 À 1.11 F 0.01 6.180 1.70 F 0.06 À 1.49 F 0.07 17.00 1.05 F 0.04 À 1.35 F 0.09 6.190 1.78 F 0.02 À 1.20 F 0.01 17.10 1.27 F 0.06 À 1.00 F 0.02 6.200 1.85 F 0.06 À 0.98 F 0.08 17.50 1.29 F 0.14 À 0.97 F 0.17 6.210 1.79 F 0.00 À 1.07 F 0.00 17.70 1.52 F 0.05 À 0.90 F 0.04 6.220 1.61 F 0.04 À 1.29 F 0.07 18.00 1.53 F 0.02 À 1.16 F 0.02 6.230 1.76 F 0.02 À 1.00 F 0.01 18.30 1.49 F 0.02 À 1.26 F 0.04 6.240 1.61 F 0.03 À 1.37 F 0.05 18.50 1.65 F 0.04 À 0.95 F 0.05 6.250 1.59 F 0.08 À 1.34 F 0.13 18.60 1.47 F 0.11 À 1.28 F 0.17 6.260 1.60 F 0.04 À 1.35 F 0.03 18.75 1.47 F 0.01 À 1.09 F 0.06 6.270 1.71 F 0.00 À 1.19 F 0.02 18.85 1.42 F 0.02 À 1.14 F 0.10 6.280 1.61 F 0.04 À 1.33 F 0.07 18.90 1.65 F 0.12 À 1.02 F 0.12 6.290 1.85 F 0.01 À 0.90 F 0.03 19.00 1.39 F 0.00 À 1.58 F 0.01 6.300 1.65 F 0.03 À 1.36 F 0.06 19.50 1.54 F 0.01 À 1.24 F 0.05 6.325 1.90 F 0.03 À 0.85 F 0.04 19.80 1.55 F 0.02 À 1.29 F 0.00 6.350 1.82 F 0.02 À 1.06 F 0.03 20.00 1.87 F 0.01 À 0.83 F 0.03 6.375 1.77 F 0.04 À 1.12 F 0.03 20.40 1.41 F 0.03 À 1.38 F 0.09 6.400 1.92 F 0.01 À 0.89 F 0.08 20.50 1.56 F 0.00 À 1.20 F 0.04 10.000 1.79 F 0.01 À 0.80 F 0.03 20.70 1.61 F 0.03 À 1.26 F 0.09 10.025 1.65 F 0.00 À 1.19 F 0.06 21.00 1.61 F 0.08 À 1.31 F 0.09 10.050 1.79 F 0.02 À 0.66 F 0.02 21.30 1.78 F 0.08 À 1.23 F 0.15 10.075 1.66 F 0.02 À 1.00 F 0.07 21.40 1.78 F 0.01 À 1.24 F 0.08 10.100 1.74 F 0.01 À 0.86 F 0.06 21.60 1.76 F 0.00 À 1.32 F 0.10 10.125 1.61 F 0.07 À 1.12 F 0.12 21.90 1.81 F 0.01 À 1.26 F 0.02 10.150 1.56 F 0.04 À 1.24 F 0.01 22.00 1.92 F 0.07 À 0.87 F 0.07 300 B. Bodiselitsch et al. / Earth and Planetary Science Letters 223 (2004) 283–302

Appendix D (continued) Oligocene climate history and paleoceanography in the South- 13 18 ern Ocean: stable oxygen and carbon isotopes from ODP Sites Stratigraphic level d CV-PDB d OV-PDB (m) (x) (x) on Maud Rise and Kerguelen Plateau, Mar. Geol. 108 (1992) 1–27. 10.160 1.59 F 0.00 À 1.20 F 0.01 [8] A. Sanfilippo, W.R. Riedel, B.P. Glass, F.T. Kyte, Late Eocene 10.170 1.64 F 0.05 À 1.13 F 0.15 microtektites and radiolarian extinctions on Barbados, Nature 10.180 1.69 F 0.01 À 1.05 F 0.03 314 (1985) 613–614. 10.190 1.51 F 0.02 À 1.46 F 0.10 [9] G. Keller, Stepwise mass extinctions and impact events; late 10.200 1.67 F 0.00 À 1.07 F 0.00 Eocene to early Oligocene, Mar. Micropaleontol. 10 (1986) 10.210 1.74 F 0.03 À 0.96 F 0.11 267–293. 10.220 1.64 F 0.01 À 1.17 F 0.01 [10] J.P. Kennett, N.J. 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