Astronomical Calibration of the Serravallian/Tortonian Case Pelacani Section (Sicily, Italy)

Italiana di Paleontologia e Stratigrafia volume 108 numero 2 pagtne 297-3a6 Luglio 2002

ASTRONOMICAL CALIBRATION OF THE SERRAVALLIAN/TORTONIAN CASE PELACANI SECTION (SICILY, ITALY)

ANTONIO CARUSO I,, MARIO SPROVIERI2 , ANGELO BONANNO 3 E. RODOLFO SPROVIERIIb

Receioecl Jwly 1 5, 20A1; accepted Juanwary 26, 2AA2

Keyuords : Serravallian/Tortonian boundary, cyclostratigraph;r, the signal of the classic Milankovitch frequencies (precession, obliqui- astronomical timescale ty and eccentricity). Correiation of the lithological patterns and of the different fre- Riassunto: Uno studio ciclostratigrafico è stato condotto su quency bands extracted by numerical filtering from the faunal record una sequenza sedimentaria (sezione di Case Pelacani) affiorante nella with the same components modulating the insolation curve provided zona sud-orientale della Sicilia (Italia) e ricoprente l'intervallo strati- an astronomic calibration of the sedimentary record and, consequent- grafico Serravalliano superiore/Tortoniano inferiore. Dati biostrati- ly, a precise age for all the calcareous plankton bioevents recognized grafici a plancton calcareo riportati in un altro lavoro dimostrano che throughout the studied interval. tutti gli eventi generalmente riconosciuti poco al di sotto e al di sopra del limite S/T sono presenti nella successione studiata. Essi hanno permesso una dettagliata comparazione con Ia sezione di Gibliscemi. I dati preliminari relativi allo studio magnetostratigrafico dei sedimenti sug- lntroduction geriscono una forte componente dt rimagnetizzazione secondaria che rende difficile il riconoscimento della corretta sequenza di "chrons" A reliable astrochronological time scale from the paleomagnetici lungo l'ìntervallo sedimentario considerato. Tortonian (Hilgen et al. 1,995; Krijsgman et al. 1995) to Lo studio combinato della ciclicità litologica lungo la succes- the middle Serravallian (Hilgen et al. 2000) has been sione sedimentaria di Case Pelacani e la applicazione di metodologìe di obtained by detailed cyclostratigraphic investigation of indagine spettrale ai dati di abbondanza di una specie di foraminiferi several planctonici (Globigerinoides quadrilobatus) hanno inoltre permesso di Mediterranean sections. The calcareous plankton individuare le forzanti astronomiche relative alla precessione, obliquì- bioevents recognized in these stratigraphic intervals tà ed eccentricità dell'orbita. have been dated by these authors on the basis of an La correlazione con le diverse periodicità presenti nella curva di astronomical calibration of the studied sedimentary insolazione dei pattern lirologici individuati lungo la successione e sequences. delle diverse armoniche estratte dal segnaie microfaunistico a dispo- sizione ha permesso di calibrare astronomicamente il record sedimen- This paper presents the cyclostratigraphic results tano e, conseguentemente, di datare tutti i bioeventi a plancton cal- obtained from the study of the Case Pelacani section, careo riconosciuti lungo I'intervallo studiato. which includes the Serravallian/Tortonian (S/T) boun- 'Abstract: \fe performed a cyclostratigraphic study of a sedimentary sequence (Case Pelacani section) outcropping in the south- rTt.l' Fr\rcrn -"roi" nf Si.il' r '.,1 .^'..i." rh" I fnnpr Serravallian/Lower Tortonian stratigraphic interval. Calcareous plank- Palermo ton biostratigraphic data reported in another paper proved that all the sequence of bio-events generally reported from just below and above the S/T boundary is present in the sectìon. They allowed a detailed correlation with rhe Gibliscemr section. Prelimrnarl paleomagnetic dara suggetr that a secondarl remagnetization component prevents the recognitìon of the correct sequence of paleomagnetic chrons along the studied interval. The sedimentary record has been compared, on the basis of an integrated calcareous plankton biostratigraphy, with that of the Gibliscemi sectìon. Cyclosrratigraphic analvsis of the lithological patterns recognized throughout the succession and the application of spectr.rl Kn methodologies to the abundance fìuctuations of the planktonic foraminifer Globigerinoides quadrilobatws highlighted the presence rn Fig. I - Location m.rp of the sections discussed in the p;rper.

Dipartimento di Geologia e Geodesia - Corso Tukory 131, 90134 Palermo Italy, e-mail: 1" [email protected], 1b rspr@ unipa.it Dipartimento di Chimica e Fisica della Terra (CFTA) - Via Archirafi 36,9A1n Palermo ltaly, e-mail: [email protected] Dìpartimento di Energetica e Applicazioni di Fisica (DEAF) - Viale delle Scienze, 90128 Palermo ltaly, e-mail [email protected] 298 A. Caruso, lI. Sproaieri, A. Bonanno ù R. Sprorieri

'-r{ .,

j].& r.r-': r:$ltrr

drrrv, commonly recognized by the first occurrence (FO) of l'[eog/oboquadrìna acostaensls. This section shon's lithological patterns similar to those recognized along the Gibliscemi section recentl)r indicated by Hilgen et al. (2000) as possible candidate for the definition of the GSSP of the Tortonian.

Geological setting and location

The Ca'e Pelacrni section ourcrop5 along the Bianco river, 4 km n'est of the Palazzolo Acreide village, in the Iblean region of SE Sicily (Fig. t). The succession is characterized by middle-upper Miocene hemi-pelagic sediments. It belongs to the Tellaro Formation (Fm.) q'hich is underlain by the calcarenites and marls of the Ragusa Formation and overlain by the calcarenites of the Palazzolo Formation (Rigo & Barbieri 1959). The succession outcrops in the Iblean foreland, s'here some compressive and distensive tectonic distur- bances are present, in relation to the stacking of nappes thrusted southward from the Caltanissetta Basin (Bianchi et al. 1987) during the uplifting of the Appen- Fig. 2 Pictures of the Case Pelacani segments; e) *eneral view of ninic-Maghrebid belt. the studìed scction; b) details of segments C and D; c) Some low angle compressive faults are present in detail of segment B; d) detail in segment A. The progres- the Case Pelacani section, with small displacements of sir.e numbers 1 to .16 correspond to thc lithologicel o-cles the stratigraphic sequence. These small faults are associ- recognized on the field. The number :rnc1 letter encircled correspond to cllcareous piankton biostratigraphic er.ents ated to the main decollement of the Tellaro Fm. from reported in Fig. 3. the Ragusa Fm. Astronomical calibration of Case Pelacani Section 299

Materials and methods geneous grey marls is again presenr (Fig. 3). From cycie 25 to cycle 32 the lithological cyclicity is very clear with The section is weli exposed in a series of gullies grey marls alternated to indurated whitish layers. The along the southern slope of Mountain Cozzo Mastica sequence has been completed in segment D (cycles 30 to (Lat. 37'02'54"; Long. 14"53'00") . It is composed of four 46) using the lithological cycles 30 to 32 (Fíg.2 and 3) segments (Pelacani A/B/C/D) (Fig.2,3) that have been to correlate segments C and D. In segment D, an alter- correlated in the field by matching lithological parrerns nation of grey marls and indurated whitish layers is evi- constrained by biostratigraphic evenrs. dent from cycle 30 to 43. A 6.8 m thick homogeneous A total of 46 lithological cycles (about 0.7/1.5 m interval of grey-whitish marls is present between cycles thick), numbered progressively upward, have been iden- 43 and 44. In this segment the lithological cycles were tified throughout a total stratigraphic thickness of 66.35 possibly not recognised because of the difficulty to m. The composite sequence was sampled on average analyse in detail the outcrop, that is not well exposed every 2a cm in the lower part (cycles 1-20) and every 20- and particularly steep. 25 cmin the upper part (cycles 21 to 46). A total oÍ lrc In the uppermost part of the section, between 66.35 samples were collected and studied. m and the top of the section (Fig. 3), two faintly lami- A detailed calcareous plankton biostratigraphy, nated dark marls (44 and 45) alternated to whitish marls based on quantitative analyses on rhe planktonic and one indurate whitish layer (46), close the secrion. foraminifers and calcareous nannofossil assemblages are reported in Di Stefano et al. e0A4, and enabled the recognition the mosr importanr biosrratigraphic of Astronomical calibration events throughout the succession. In Fig. 3 we report the most important calcareous plankton bioevents recognized along record. the Lithological pattern distribution Numerical methodologies of spectral analysis and In the sedimentary record of the Case Pelacani filtering are based on the standard approach of Jenkins & Watts (1968). section four different intervals can be distinguished. The first interval, from cycle 1. to cycle 8, is characterrzedby a not regular alternation of whitish marls and dark marls Lithology and sedimentary cyclicity (Fig. 3). The thickness for each cycle ranges between 60 and 100 cm. The faintly laminated dark marls have been Segment A, with a total thickness of 1.2 m (Fig.2, assumed as the base of each lithological cycle and have 3), includes cycles 1 to 9, characterizedby a nor regular been correlated with high precessional minima/insola- alternation of homogeneous whitish marls and faintly tion maxima. In the segmenrs characterized by a homo- laminated dark marls (possibly representing sapropelitic geneous lithology (between cycles 2-3, 4-5, 7-8 and 9- layers). This segment has been sampled at the base of the 10, respectively) several precessional cycles have been first gully (Fig. 2, d) just above a small fault. Another successively identified on the basis of the spectral analy- fault is present slightly above cycle 9 and the succession sis applied to a selected faunal record. The regular alter- 'was continued in segment B (Fig.2c), using cycles 8 and nation of dark and homogeneous marls from cycle 9 to 9 as correlation horizons. In the 6.40 m thick segmenr B, 19 (Fig. 3) represents the second interwal. In the third characterized by alternations of whitish marls and faint- interval, from cycle 20 to cycle 24, rhe light whitish ly laminated dark marls, the cycles 8 to 14 are included. marls represent the base of each cycle (Fig. 3). These Also segment B is closed ar the rop by a fault. Therefore, cycles are relatively thicker probably because of a rather the following samples have been collected in segment C higher sedimentation rate, with an average thickness of (Fig. 2b), 26 m thick, in which 24 lithological cycles (9 each cycle of about 120-15A cm. The interval from cycle to 32), are present. Segments B and C were biostrati- 25 to cycle 46, is characterized by a marked cyclicity, graphically correlated using the G. swbquadlatws LCO with indurated whitish layers alternated to whitish and G. obliqwws obliquws FRO biohorizons and the marls. Each cycie is 100-150 cm thick. The indurated lithological pattern distribution of cycles 8 to 14. layers are probably distal turbidites and, following Pots- Between cycles 9 and 19 a regular alternation of whitish ma et al. (1993) and Sierro et al. (2001), we compared and dark marls occurs, but between cycle 19 and cycle them to sapropelitic layers. Ve have assumed the 20, a 2 m thick interval of homogeneous grey marls is indurated whitish layers as the base and the grey marls as present (Fig. 3). the top of each cycle (Fig. 3). Between 23 and 34.20 meters above the base of the Lithological clusters (quadruplets and/ or triplets), sequence the lithological alternations are not very clear related to the short-eccentricity componenr of the inso- (Fig. 3, 4). We could identify four cycles (2A to 23) con- lation curve, were not recognized in the lower interval of sisting of alternating whitish and light whitish marls. the succession, but between cycles 25 and 31,34 and 4I Between cycles 24 and 25, a 2 m thick interval of homo- they are evident. 300 A. Caruso, M. Spro'oieri, A. Bonanno & R. Sprotiert

STUI}IED SECTIONS Laskar 90 rr,rr

6 6t g è) ta l, 6t 6t * 6 -F ll) rD rl;| (l) ai n li L 3 6 \ whiti$h marls 45 n 44 I fainttylaminateddarkmar{s n fghtwhitishmarls rl3 inùrated whtish marls 4l 40 - 39 38

O fCO H. stalis 3ó @ pres€nc€ af c. caslitu.s 35 O LO H. walbersdorfensìs v O LCO C. miopelagtcus 3 @ LCO D. kugteri n 3l

O FRO N. acostaensis O fO N. atlantica @ LO P. sialconsis O fRO C obliquus obliquus O LCO G subqwdrants O FO N. acaslaensis @ fO N. atlurtica praeatlanîica O LO P. prttmlabiata

l5 14 t3 ,:I r2 tl t0 9

F;- ì - Correlation between lithologic cycles and astronomic cun'e. Bioevents are reported throughout the composite section. On the right of the lithologìcal column the number of the lithological cycles are reported. In brackets the progressive numbers of the precessional cycles (1 to 70).

Fio 4 - Correlation of the lithological cycles recognized in the Case Pelacani section with the lithological c1'cles identified at Gibìiscemi by Hilgen et al. (2000). Astronomical calibration of Case Pelacani Section 301

Oiiginal sipal Laskar 90 o,rt o c --.--.- 19-23 ky fihered signsl ;- ú €' a/oG qua&ilobctus 0 20 40 60 80 100 I0-5 46

45 44 n.ó t0.6

t0.7 :t

3D .:..11 ..::,

10.8 ]7 ,-.:: :'.3 t0.9 i'.. v .-_:

33 t.':, il.0 30 .::: a a ":: II,I n';

25 ,: tI.2 ?A x 2, .:.-. :t ::r 2l .:l tI.3 a

II.4 --i-r i:a I t.1 :. ;, 1t.5 l:: r: ll 10 tI.6 9 l::. I tI.7 :. 6

4 :,:. II.E 3

r-*t r l I I whitirh marls ft.irtly laminrted drr* mrds lig}l whitish nirls indllrd xùirish lsyers 342 A. Caruso, l[. Sprotieri, A. Bonanno & R. SprocierL

O Laskar 90 o.n a Gibliscemi section (Hilgen et al. 2000) s L+(, a I - )6 I ll-l1- ill Illt ilt

tl -l

/ ffi+l ' r-lR - r-:-.-lU /- r-lxF--6qó4'ry rv- //- r//

10.s

22 2l I -_\ 20

-T

| "1h l\\'- \\- | \- | - -Ll

ft- - ffiffiffiffifril faintì_v laninated dark marls 1ìght $4ritish marls grey narls indurated whitish layers Astronomical calibration of Case Pelacani Section 303

2000 Lithological tuning I 800 4oo b' (1993), 1600 I c.r.=rsz The astronomical solution of Laskar et al.

I 400 with present-day values for the dynamical ellipticity of

! 1200 the Earth and tidal dissipation by Sun and Moon (La

1000 :1 901,1), has been selected to calibrate the studied sedi- 6 l0O lq. B \[' 3 - 8,6 800 23 I(y menrary sequence. Hilgen et al. (1995), Lourens et al. 600 l9 ky (1996) and Hilgen et a1. (2000) demonstrated that this is 400 the most accurate solution for the calibration of late 200 Miocene-P1io-Pleistocene sedimentary records. 0 To calibrate the lithological patterns with the 0 2.E-05 4.E-0s 6 E-os 8 E-0s I E-04 Frequency (cycles/years) insolation curve of Laskar et al. (1993) the results from the Gibliscemi section reported by Hilgen et al. (2000) Fìo A Power spectra of the Globigerìnoides quadrilobatus signal. have been used as starting point. Initially, we verified C.I.: confidence interval. B.\M: bandrvidth. that the sequence of biostratigraphic events along the Case Pelacani and Gibliscemi sections was the same, apart from some differences due to different taxonomic interpretations (see Di Stefano et aL 2aA2, for more detaii). Ve compared the quantitative abundance fluctu- ! ations of the studied planktonic taxa. The LCO of G. subquadratus was considered the most appropriate bio- È \ /i \ i\ --- ...r/'\t, v \,rt--' ' horizon to be used as tie point to correlate the two sed- ".-,1' \i,,r/ imentary sequences. The G. subqwadratus LCO has been ; recognized at the top of cycle 1O at Case Pelacani and at the top of cycle -72 (11.539 Ma) by Hilgen et al. (2000) dark ó at Gibliscemi 1Fig. a). The regular alternations of and homogeneous marls present in the interval from t05 106 t07 t08 109 1t0 tlr |2 1r3 lr4 fi5 lt6 ll? u8 tÌ cycle 10 to cycle 19 (Fig. 3) have been correlated with (Ma) the 10 precessional minima/insolation maxima between 11.561 Ma and 11.361 Ma (45-54) and have been corre- Fig- 7 Comparison betneen the astronomrc eccentrrcrtv curve lated with the lithological cycles -64 to -72 at Giblisce- (thick line) and the 100 and 400 Kv of G. quadrilobatus {ìI- mi. This double control corroborated the good correla- tered signal (thin line). tion of these two segments (Fig. a). On the basis of this preliminary correlation, we proceeded to compare the larger-order lithological cycle patterns present in Case Pelacani section with the 1.0 the 0.9 sequence of eccentricity oscillations of the insolation 0.8 curve. In parricular, between 11.56 Ma and 11.36 Ma the 4.7 eccentricity insolation curve is characterized by 2 strong maxima that we have correlated with lithological cycles

_a 0.4 10 to 19. 0.3 Between cycles 2O and24,lithological changes are 0.2 weak and difficult to be recognized in the field. We cor- 0.1 related this sedimentary interval with the low insolation 0.0 0.E+00 2.E-05 4.E-05 6.E-05 8.E-05 LE-04 eccentricity oscillations recorded between 1 1.19 and Frequency (cycles/years) 1 1.36 Ma. Each light whitish marls layer has been correlated with the precession minima/insolation maxima Fio R Coherence spectra bet*-een the ìnsolation cun'e Laskar 90 11,r1 cycles recorded in the same time interval. and G lobigerinoides quadrilobatus srgnal. The group of cycles 25 to 32 is characterized by an evident lithological cyclicity that we correlated with the interval of high eccentricity insolation between 10.98 and 11.16 Ma. Consequently, each lithological cycle has been correlated to the strong oscillations present in the Comparison between origin:rl and fìlrered 1in the preces- precession/insolation index curve. The characteristic sion frequencl' bands) Globigerinoides quadrílobatus srgnal triplet of cycles 25 to 27 and the quadruple t of cycles 28 and correlation with the same tù'o harmonics extracted 90 cycles to 31 (Fig. 4), correlated with the strong eccentricity from the insolation curve Laskar ,r.r1. See text for labelling. The lithological log is in function of time. maxima recorded in the insolation curve from 10.98 to 344 A. Caruso, M. Sprotieri, A. Bonanno & R. Sprooiert

11.06 Ma and from 11.11 to Lithological cycle Mid-point precessional Age Hilgen et al. (2000) 1 1.16 Ma respectively, represent (Pelacani) (m) cycles (ka) (Gibliscemi) a further control for the calibration of this sedimentary interval. Cycle 46 66.1 0 (1) 10.511 cycle -32 Cycle 45 64.30 (2) 10.531 cycle -33 The segments characteri- Cycle 44 63.30 (3) 10.551 cycle -34 zedby more or less thick homo- marls (between Cycle 43 56.3 5 ( 10) 10.668 cycle -38 geneous whitish 34. 37 Cycle 42 55.50 (11) r0.102 cycles 32 and ll, 3l and 38, 43 and 4,1) have been Cycle 41 54.35 (12) 10.7 16 cycle -39 and correlated to the lows in the Cycle 40 53.40 (13) 1 0.73 8 cycle -40 eccentricity insolation curve Cycle 39 52.30 ( l4) t0.7 59 cycle -41 between A.99 and 10.95 Ma, 0.91 Cycle 38 51.45 (15) 10.780 cycle -42 and fi.94 Ma, 10.83 and 10.28 Cycle 37 49.50 (18) 10.832 cycle -44 Ma, 10.60 and lO.5Z Ma. respec- Cycle 36 48.30 (1 e) 10.853 cycle -45 tively. Cycie 35 46.80 (20) 10.873 cycle -46 Tn rhe has:l nart of succes- Cycle 34 45.00 (21) 10.910 cycle -48 sion (cycles 1 to 9) the irregular Cycle 33 42.40 (24) r0.949 cycle -50 presence of dark marls has been Cycle 32 40.60 (26) 10.988 ascribed to the very iow modula- Cycle 31 40.10 (27) 1t.002 cycle -52 tion of the long- and short- Cycle 30 39.90 (28) 11.023 cycle -53 eccentricity component of the Cycle 29 3'7.90 (2e) 1r,044 cycle -54 insolation curve between 11.61 Cycle 28 37.r0 (30) 11.065 cycle -55 and 1t.80 Ma. The dark marls of

Cycle 27 35.70 (32) 1 1.1 16 cycle -57 cycles 1 to t have been correlat- Cycle 26 35.1 0 (33) 11.137 cycÌe -58 ed rvith the highest peaks of the

Cycle 25 34.00 (34) 1 1.158 cycle -59 precession index curve.

Cycle 24 31 .10 (36) 1 1 .195 Cycle 23 28,90 (3 E) i 1.230 cycle -61 Spectral analysis Cycle 22 2',7.70 (3e) tl.251 cycle -62 Spectral and filtering Cycìe 2l 26.80 (40) I r .288 methodologies have been Cycle 20 25.10 (42) 11.307 applied to the curve of the rela- Cycle 19 21.30 (45) 1 1.361 cycle -64 tive abundance fluctuations of Cycle i 8 20.70 (46) 11.381 cycle -65 the planktonic species G,

Cycle 17 19,90 (47) 1 1 .401 cycle -66 quadrilobatus reported by Di Cycìe 16 18.90 (48) 11 ,4,)1 cycle -67 Stefano et al. (2002) throughout

Cycìe 15 18.10 (4e) | 1 .440 cycle -68 the Case Pelacani section, to Cycle 14 17.10 (50) tt.472 cycìe -69 essentially reconstruct the cor- Cycle 13 16.30 (51) tl.493 cycle -70 rect sequence of precession cycles where high-frequency Cycle 12 15.50 (s2) 1 1.515 cycle -71 lithologic alternations cannot be Cycle 11 14.50 (53) 11.536 cycle -72 recognized. Cycle 10 14.10 (54) I 1 .561 Correlation between the CycÌe 9 12.90 (56) 1 1.608 cycle -75 insolation curve and the fluctua- Cycle 8 12.05 (s7) 1 1.630 cycle -7 6 tions recorded in the G. Cycle 7 9.50 (60) 1 1.684 cycle -78 qwadrilobatws signal in all the Cycle 6 7.30 (62) \1,725 Milankovitch frequencies has Cycle 5 6.7 5 (63) 11.739 been performed associating the Cycle 4 3.70 (65) tr.7'/8 cycle -79 lower Northern Hemisphere Cycle 3 2.90 (66) 1 1.800 cycle -80 summer insolation values to the Cycle 2 1.20 (68) 11.847 cycle -8 1 lower percentages of the faunal Cycle 1 0.40 (6e) 11.871 cycìe -82 record according to the paleocli- matic indicaLions of this species reported for the present day Mediterranean area by Pujol & Tab. I Stratìgraphic positions and astronomical ages of the sedimentary cycles from 1 to 46 at Vergnaud-Grazzini (1995). The Case Pelacani A/B/C/D composite section. Ages refer to the mid-point of whitish layers or faintly laminated dark marls (sapropels) and are correlated with precession minima. astronomical calibration previ- Astronomical calibration of Case Pelacani Section 305 ously obtained by lithological tuning of the section nal and in the precession index curve (Fig. 3. Tab. 1). allowed us to transform the faunal signal from the space to the time domain (Fig. 5) and the signal was interpo- Chronology lated at 3 kyr using a Gaussian weighting filter vrhich The obtained astronomical calibration of the Case ensures that more interpolated data than original points Pelacani succession suggests an age of tO.SO and 11.89 are never present in a given interval. Ma for the top and the base of the studied interval. In The power spectrum of the G. quadrilobatus signal Tab. 1 we report the astronomical age for each lithologi- (Fig. 6) shows the classic Milankovitch precession, cal cycle and the corresponding precession cycles. obliquity, short- and long-eccentricity frequency bands. The estimated astronomical age of all the bioevents A Tukey-Hinnov pass-band filter (Jenkins & recognized in the Case Pelacani section are reported in Watts 1968) has been applied to the original signal to Tab.2. They are compared with results obtained from the extract the long- and short-eccentricity frequency Gibliscemi section (Hìlgen et al. 2000). bands. The small dissimilarities in age obtained for some A comparison of the G. qwadrilobatus curves fil- bioevents between the Case Pelacani and Gibliscemi sec- tered in the long- and short-eccentricity bands with the tions can be substantially attributed to: i) different same periodicities of the insolation signal shows a good interpretation of the biomarkers (particularly for the match (Fig. Z) . Cross-spectral analysis between the two planktonic species P partimlabiata), i) a different inter- signals shows high coherency vaiues for the pretation of the LCO and FCO events (C. miopelagicws Milankovitch periodicity bands, confirming that this and H, walbersdorfensis),1ii.) small local tectonic distur- calibration was appropriate (Fig. 8). bances andl or deformations in the two sections. Successive filtering of the original signals in the precession frequency bands and consequent correlation with the 19-23 kyr cycles present in the insolation curve produced a more complete calibration of the studied Conclusive remarks record (Fig. 9). In some intervals a not perfect coinci- dence between the sapropelitic layers (faintly laminated Two different methodological approach, lithologi- dark marls, light whitish marls and indurated whitish ca1 patterns calibration and spectral analysis applied to a marls) and peaks of G. quadrilobatus occvÍs.It may be faunal climate-sensitive record, have been used to astro- due to a not sufficiently detailed sampling in the corre- nomically tune the Case Pelacani section to the insola- sponding intervals. tion curve La 901r,r;. Our results are well comparable A progressive number (1 to 69) from the top to with the data proposed for the Gibliscemi section by the base of the succession has been used to label all the Hilgen et al. (2000). They provide an accurate time con- consecutive precession peaks in the G. qwadrilobatus sig- trol of several calcareous plankton biomarkers useful for specres Event Cycle Position Age (Ma) Hilgen et al. (2000) Age (Ma) (Pelacani) (m) this paper (lithological cycles) (Gibliscemi)

Plan ktdn ic foraminifera

Neogloboquadrina acostaensis FRO 44 OJ.J ) 10.551 (-33/-34) 10.554 Neogloboquadrina atlantica FO 25 34.40 1 1 .151 (-s7l-58) 11.121 Paragloborotalia siokensis LO 23/24 30.60 11.203 (-60) 11.205 Paragloborotalia síakensis LCO ZJ 29.00 11.225 Globigerinoides obliquus obliqtttts pQQ 10 15.20 I1.541 Globigerinoides subquadratus LCO l0 14.80 11.546 (-12t-73) 11.539 Neogloboquadrina a. praeaîlanîico FO 3 2.9s I 1.800 Neogloboquadrina acostaensis FO 3 2.95 11.800 (-1e/-80) I 1.781 Paragloborotalia partimÌabiata LO 2t3 2.'70 11 .804 (-80/-8 1) 1 1.800

Calcareous nannofossil

Helicosphaera stalis FCO 4U42 54.95 10.710 c3e) 10.7l7 Catinoster coalitus presence 39/40 53.25 10.'142 G40) 10738 H e I icos p ha era w a lbe rs dorfe ns i s LO 38/39 52,37 10.763 (-40t-4r) t0.'143 Cocco lithus m iope lagícus LCO 24 31.80 1 1 .190 Discoaster kugleri LCO 9 12.85 11.608 (-15) r 1.604

Tab. 2 - Stratìgrephic positions and astronomical ages of the calcareous plankton broevents. 346 A. Caruso, M. Spro-tieri. A Bonanno & R. Spror.,ieri

regional stratigraphic correlation. Acknou- ledgemenfs. \il/e are leq' grrreiul ro Fabio Speranza for Despite the rnagnetosrratigraphic analysis did not field assistance and Maria Elena Gargano for technic;rl preparation of the san.rples. We thank F.J. HiÌgen and D. Castradori for rer.icr-ing the give significant results, the Case Pelacani succe ssion may ----'' ^-:-- ^-ì r^-- -L ''- valuable colnments and criticism which be considered a good candidate for the definition of the ìmproved the ìnitial versjon of the manuscript. This research has been Serravallian/Tortonian boundary. supported bv Murst Cofin 98.n.

REFERE,NCES

R;.."1"; ( F .""h^.. Grasso M., Invernizzi G., Lentini F., Laskar J., Joutel F. & Boudin F. (1993) - Orbital, precessional, Longaretti G., Merlini S. Er Mostardini F. (198/) - Sicil- and insolation quantities for the Earth from -20 Myr to

ia orientale: Profilo geologico Nebrodi-Iblei. Mem. Soc. + 1 OMyr. A stron. A s trop hy s. 27 a : 522- 533,'il/rs h in gton. Geol. (t.,38: '129-'158, Roma. Lourens L.J., Antonarakou A., Hilgen F.J., Van Hoof A.A.M., Di Stefano E., Bonomo S^, Caruso A., Dinarés-Turell J., Fore- Vergnaud-Grazzini C. & Zachariasse \ilJ. (1996) - Eval- si L.M., Salvatorini G. & Sprovieri R. (2002) - Calca- uation of the Pliocene to early Pleistocene asrronomical \il/ashin reous plankton bio-events in the Miocene Case Pelacani time s cale. Pal e o c ean o grap hy, 1. L : 3 9 1 - 4 13, gton. section (South eastern Sicil,v, Italy). In Iaccarino S.M. Potsma G., Hilgen F.J. Ec Zachariasse \[J. (1993) - Precession (ed.) - Integrated Stratigraphy and Paleoceanography of r"^'-'"".'_ounctuated b_"growrh "' of a late Miocene submarine-fan the Mediterranean Middle Miocene. Riv . Ital. Paleont. lobe on Gavdos (Greece). Terranova, 5: 138-444, Strat., 1.A8: 3A7 :23, Milano. Oxford. Hilgen F.J. (1991a) - Astronomical calibration of Gauss to Pujol C. & Vergnrud-Gra'zzini C. (1995) - Distribution pat- Matuyama sapropels in the Mediterranean and implica- terns of live planktic foraminifers as related to regional tion for rhe Geomagnetic Polarity Time Scale. Earth hydrographv and productive sysrems of the Mediter- Planet. Sc. Lett., 1Q1:226-244, Amsterdam. ranean Sea. Mar. Micropal., 25: 187-215, Amsterdam. HilgenF.J. (1991b) - Extension of the astronomically calibrated Rigo M. Ec Barbieri F. (1959) - Stratigrafia pratica applicata in (polarity) time scale to the Miocene/Pliocene boundary. Sicilia. Bol/. Ser. Geol. It.,8Q 351-441, Roma. Earth Planet. Sc. Lett., fi7:319-368, Amsterdam. Sierro F.J., Hilgen F.J., Krijgsman \M Ec Flores J.A. (2001) - Hilgen F.J., Krijgsman \V, Langereis C.G., Lourens L.J., The Abad composite (SE Spain): a Messinian reference Santarelli A. & Zachariasse WJ. 0995) - Extending the section for the Mediterranean and the APTS. Paleogeogr. astronomical (polaritv) time scele into the Miocene. Paleoclim. Paleoec. 168 I41-169, Amsterdam. Earth Planet. Sci. Lett..136: 495-510. Amsterdam. Sprovieri R. (1993) - PÌiocene-earlv Pleistocene astronomical- Hilgen F.J., Krijgsman \M, Raffi I., Turco E. & Zachariasse \MJ. ly forced and chronology of Mediterranean calcareous (2000) - Integrated strarigraphy and asrronomical cali- plankton bio-events. Ri.o. Ital. Paleont. Strat.,99: 371,- bration of the Serravallian/Tortonian boundary secrion 414, Milano. at monte Gibliscen.ri (Siciln Italy). Marine Micropal.,38 Sprovieri R., Di Stefano E., Becquey S. & Caravà N. (1996) - 1,81,-211, Amsterdam. Calcareous plankton biostratigraphy and cyclosrratig- \Watts Jenkins G.M. & D.G. (1968) - Spectral analyses and its raphy at the Serravallian-Tortonian boundary. Paleopela- applications, Holden day, 41.a pp., Oakland. gos, 6: 437-453, Roma. \Xl, Krijgsman Hilgen F.J., Langereis C.G., Santarelli A. & \feedon G.P (1991) - The spectral analysis of stratigraphic Zachariasse \({. (1995) - Late Miocene magnerostratigra- time series. In: Cycles and events in Stratigraphy (Ed. phy; biosrratigraphy and cyclostratigraphy in the Mediter- by Einsele G., Ricken \( & Seilacher A.). Springer Ver- ranean. Eartb Planet. Sc. Lett.,136: 475.494, Amsterdam. l.g, pp. 840-863, Berlin.