Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 19, 2010, pp. 613–633. Copyright ©TÜBİTAK doi:10.3906/yer-0901-12 First published online 22 October 2010
Taxonomy of Rudists from the Campanian Transgressive Sediments of Brašljevica, Donje Orešje and Sv. Martin, Northern Croatia ALAN MORO, VLASTA ĆOSOVIĆ, JOSIP BENIĆ & JASMINA DOKMANOVIĆ Department of Geology and Paleontology, Faculty of Science, University of Zagreb, Horvatovac 102A, 10000 Zagreb, Croatia (E-mail:
[email protected] or
[email protected]) Received 27 April 2009; revised typescript received 28 August 2009; accepted 15 October 2009 Abstract: Rudists are common fossils in transgressive Upper Cretaceous deposits in three localities placed in northwestern part of Croatia. Their appearances coincide with the beginning of a transgressive sequence through floatstones-thickets. Within the rudist community, Vaccinites Fischer 1887, Hippurites Lamarck 1801 and Hippuritella Douvillé 1908 could be differentiated according to their general or generic morphological elements. The age of deposits was obtained from the Sr-isotope composition of the rudist shells as well as the micro- and nannofossil community from sediments overlying the rudists-bearing sediments at the Donje Orešje and Brašljevica localities. According to this data the age of the transgressive sediments are determined as Early Campanian. Morphological elements (ligamental ridge, pillars, inner diameter, length of the contour around the inner margin of the outer shell layer, and the ratio between this length and the distance between the sutures of the pillars) from the transverse shell sections permit possible definition of different species within the family Hippuritidae, Gray 1848. Transverse shell sections of analyzed Vaccinites, Hippurites and Hippuritella specimens show different values of measured morphological elements as well as their ratios which, subjected to cluster analysis (Ward's and Unweighted pair-group methods), represent grounds for possible taxonomic determination of the species Vaccinites cornuvaccinum (Bronn 1831) at all localities; V. giganteus (d'Hombres-Firmas 1838) and V. vesiculosus (Woodward 1855) at Brašljevica and Donje Orešje; as well as Hippurites vidali Matheron 1880 and Hippuritella lapeirousei (Goldfuss 1840) at Donje Orešje. Key Words: Campanian, rudist taxonomy, transgression, hippuritid rudist, strontium isotope stratigraphy, northern Croatia
Brašljevica, Donje Orešje ve Sv. Martin’de (Kuzey Hırvatistan) Kampaniyen Transgresif Tortullarının Rudist Taksonomisi Özet: Rudistler, Hırvatistan’ın kuzeybatısında yer alan üç lokalitedeki transgresif Üst Kretase çökellerinde yaygın olarak bulunan fosillerdir. İlk ortaya çıkışları, transgresif istifin başlangıcında yer alan yüzertaş katmanlarına karşılık gelir. Rudist topluluğu içersinde, Vaccinites Fischer 1887, Hippurites Lamarck 1801 ve Hippuritella Douvillé 1908, genel veya cinse ait morfolojik parametreler ile birbirlerinden ayrılabilir. Donje Orešje ve Brašljevica lokalitelerinde çökellerin yaşı, rudist kavkılarının Sr-izotop içeriği ve rudistli tortulları üzerleyen sedimanlarda saptanan mikro ve nannofosil topluluklarından elde edilmiştir. Bu yaş verilerine göre transgresif tortulların yaşı Erken Kampaniyen’dir. Kavkıların enine kesitlerinde tanımlanan morfolojik parametreler (ligament, piliyeler, iç çap, dış kavkının iç konturunun uzunluğu, bu uzunluk ile piliyelerin süturları arasındaki mesafenin oranı) Hippuritidae, Gray 1848 ailesinde farklı türlerin tanımlanmasını olanaklı kılar. Çalışılan Vaccinites, Hippurites ve Hippuritella türlerinin enine kavkı kesitleri farklı ölçülmüş morfolojik parametre değerleri ve oranlar sunar. Bu değer ve oranlar, Vaccinites cornuvaccinum (Bronn 1831)’un tüm lokalitelerde, V. giganteus (d’Hombres) ve V. vesiculosus (Woodward 1855)’un Brašljevica ve Donje Orešje’de ve Hippurites vidali Matheron 1880 ve Hippuritella lapeirousei (Goldfuss 1840)’nun Donje Orešje’de olası taksonomik tanımlamaları için bir zemin oluşturan Kümeleme analizi’ne (Ward ve Unweighted grup çifti metodu) tabi tutulmuştur. Anahtar Sözcükler: Kampaniyen, rudist taksonomisi, transgresyon, hippuritid rudist, stronsiyum izotop stratigrafisi, kuzey Hırvatistan
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TAXONOMY OF CAMPANIAN RUDISTS
Introduction Rudists are common macrofossils in the Upper Cretaceous deposits in the northwestern part of Croatia. They lived as epibenthic suspension feeders (Skelton 1978) and occasionally formed vast biostromal congregations (Moro et al. 2002, 2008). Here we present data from transgressive sequences from three localities (Figure 1): Brašljevica (Žumberak Mt.), Donje Orešje (Medvednica Mt.) and Sv. Martin (Kalnik Mt.). Generic identification was based on morphological characteristics of the attached valve such as ligamental ridge, pillars, and position of the teeth (Dechaseaux & Coogan 1969; Steuber 1999). Free valves, with pores and oscules which are also morphological characteristics which permit different genera to be defined (Dechaseux &
Figure 1. Situation map with investigated sites.
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Coogan 1969), are not preserved in analyzed specimens. Representatives of the genus Vaccinites show specific values of the angle between the teeth and the ligamental ridge, as well as between the ligamental ridge and the P1 pillar. These angles were used as criteria in description and determination of hippuritids from the Southern Pyrenees (Vicens 1992), the Ostuni area (Laviano & Maresca 1992) and southern Istria (Moro & Ćosović 2004). Beside angles, hippuritids show specific values of the length of the contour around the inner margin. Steuber (1999, 2003) concluded that the mentioned morphological changes might be consequences of evolution.
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Lineages of species of hippuritid rudists have been proposed by Douvillé (1891) and Toucas (1903). Recent interpretations of lineages involve reevaluation of the synonymy of several species (Vicens 1992; Simonpiétri et al. 1998; Steuber 1999; Simonpiétri & Philip 2000; Moro & Ćosović 2004). In this work, the following characteristics of attached valves were used for identification of rudist assemblages at the species level: (1) angle between ligamental ridge and P2 pillar (Vicens 1992; Moro & Ćosović 2004) for hippuritids and vaccinitids (L/P2), (2) angle between P1 and P2 pillars for hippuritellids (P1/P2), (3) length of contour around the inner margin of the outer shell layer (U), (4) length of the distance between sutures of the ligamental ridge and pillar P2 (P0-P2) for vaccinitids and hippuritids, (5) distance between sutures of pillars P1 and P2 (P1-P2) for hippuritellids (Steuber 1999), (6) inner diameter (d) (Laviano & Maresca 1992), and area of transverse section (P). We have chosen these because they are the best preserved characteristics of the studied specimens. All specimens, subjected to biostatistical, morphological, and strontium isotope stratigraphy analysis, were collected by different researchers (Koch 1918; Herak 1966; Polšak et al. 1978; Polšak 1979) and represent a part of the fossil collection of the Department of Geology (Zagreb). The aims of this work is (1) to define the number of species within genera Vaccinites Fischer 1887, Hippurites Lamarck 1801 and Hippuritella Douvillé 1908 based on biostatistical and morphological analysis, (2) to determine the age of Brašljevica and Sv. Martin sediments based on microfossils, and (3) apply strontium isotope stratigraphy (SIS) (Steuber 2003), for more accurate age determination. Geological Setting and Stratigraphy of Studied Sites On all investigated localities, Upper Cretaceous deposits are in transgressive contact either with Upper Jurassic (Brašljevica), or Triassic (Donje Orešje and Sv. Martin) sediments. The Upper Cretaceous deposits at Brašljevica locality (Figure 2), 35 m thick, transgresively overlie Upper Jurassic deposits (Herak 1966, 1968). In vertical succession, Upper Cretaceous breccias with fragments of older
rocks within wackestone-packstone matrix pass into wackestone-packstone, rarely grainstone limestones and marly sediments (Herak 1968; Pleničar & Premru 1970; Pleničar et al. 1975). Hippuritids which appear in wackestone-packstone limestones are Vaccinites cornuvaccinum (Bronn 1831), V. inaequicostatus (Münster, in Goldfuss 1840) and V. oppeli (Douvillé 1892) (Herak 1966). Along with rudists, wackestones-packstones contain foraminifera Moncharmontia appeninica (De Castro 1967) and Scandonea samnitica De Castro 1971. The nannofossils Watznaneria barnesae (Black, in Black & Barnes 1959), Cribrosphaerella ehrenbergi (Arkhangelsky 1912), Qadrum gartneri Prins & Perch-Nielsen, in Manivit et al. 1977, Q. gothicum (Deflandre 1959), Q. sissinghii Perch-Nielsen 1986, Q. trifudum (Stradner 1961) and Cretarhabdus angustiforatus (Black 1971) are in marly limestones. According to the micro- and nannofossils, the age of the sediments are considered as Early–Late Campanian. Donje Orešje deposits (Figure 2) transgressively overly Upper Triassic limestones (Polšak 1979; Korolija et al. 1995). From the base to the top, 45-mthick succession is made of floatstones with rare rudstones, and marly sediments and pelagic limestones at the top (Pošak 1979). Floatstones, beside corals, contain diverse rudist fauna determined by Polšak (1979). The following species were found: Vaccinites inaequicostatus (Münster, in Goldfuss 1840), V. gigianteus (d’Hombres-Firmas 1838), V. vredenburgi (Kühn 1933), V. oppeli santoniensis (Kühn 1948), V. atheniensis (Ktenas 1907), V. sulcatus (Defrance 1821), V. cornuvaccinum (Bronn 1831), V. archiaci (Douvillé 1892), Hippurites carinthiachus Redlich 1900, H. matheroni Douvillé 1893, H. crassicostatus Douvillé 1893, H. socialis Douvillé 1890, H. striatus Defrance 1821, H. heberti Munier-Chalmas 1888, Hippuritella nabrasiensis (Futterer 1893), Ha. toucasi (d’Orbigny 1847), Ha. carezi (Douvillé 1894), Ha. praesulcatissima (Toucas 1903), Ha. sulcatissimus (Douvillé 1894), Ha. variabilis (Munier- Chalmas, in Gaudry 1867) and Ha. sulcatoides (Douvillé 1892) (Polšak 1979; Sánchez 1981; Steuber 1999). Microfossils in pelagic limestones and nanofossils in marly sediments (Polšak et al. 1978; Polšak 1979; Korolija et al. 1995) suggest a Early–Late Campanian age. 615
TAXONOMY OF CAMPANIAN RUDISTS
Figure 2. Geological columns of investigated sites. Thickness of beds not to scale. Simplified and modified after Herak (1966, 1968), Pleničar & Premru (1970), Pleničar et al. (1975), Polšak (1979), Korolija et al. (1995) and Poljak (1942).
Sv. Martin deposits (Figure 2), which are 12 m thick, transgresivelly overlie Middle Triassic limestones (Poljak 1942). They consist of breccias and limestones with corals and rudists Plagioptychus aguilloni d’Orbigny 1839, Vaccinites cornuvaccinum (Bronn 1831) and Batolites organisans Montfort 1808 (Koch 1918). Unfortunately, this outcrop is completely destroyed through quarry excavations (Poljak 1942). The age of sediments was determined as Late Santonian–Early Campanian (Poljak 1942). Chronostratigraphy Two splits of samples of the outer shell layer of the hippuritid rudists were taken for geochemical and 616
strontium isotope analysis, and for each locality, three samples of different rudist shells were submitted for analysis. The samples of strontium isotope ratios were determined at Bochum University under supervision of Prof. D. Buhl (Table 1). Strontium isotope ratios of samples are adjusted to a ratio of 0.709175 of USGS EN-1 to derive numerical ages from the ‘Look-Up’ table (Version 4: 08/03) provided by Horwath & McArthur (1997) and McArthur et al. (2001). The sample splits were analyzed by ICP-AES for elemental composition using the procedure suggested by Steuber & Rauch (2005) under supervision of Dr. S. Miko (Table 2). The samples
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Table 1. Analytical results for strontium isotope stratigraphy of rudists from studied localities. Standards NIST NBS 987 0.710247 (McArthur value) and 0.710238 (Mean Bochum value); USGS EN-1 0,709175 (McArthur value) and 0.709157 (Mean Bochum value). Column 3: 87Sr/86Sr normalized to NBS 987 values bracketing the samples and corrected for deviation from 87 86 value stated by McArthur. Column 4: Sr/ Sr normalized to USGS-EN-1 values bracketing the samples and corrected for deviation from value stated by McArthur. Column 5: 87Sr/86Sr normalized to NBS 987 mean value Bochum and corrected for deviation of the mean value from NBS 987 value stated by McArthur. Column 6: 87Sr/86Sr normalized to USGS-EN-1 mean value Bochum and corrected for deviation of the mean value from USGS EN-1 value stated by McArthur. Standard used to derive numerical age in bold. 87
Sample D. Orešje1 D. Orešje2 D. Orešje3 Brašljevica1 Brašljevica2 Brašljevica3 Sv. Martin1 Sv. Martin2 Sv. Martin3
Table 2.
Sr/86Sr measured
± 2 σ mean
Column 3
Column 4
Column 5
Column 6
0.707502 0.707500 0.707496 0.707542 0.707492 0.707539 0.707494 0.707487 0.707549
0.000007 0.000007 0.000007 0.000010 0.000007 0.000007 0.000007 0.000007 0.000007
0.707506 0.707504 0.707500 0.707546 0.707496 0.707543 0.707498 0.707491 0.707553
0.707514 0.707512 0.707508 0.707554 0.707504 0.707551 0.707506 0.707499 0.707561
0.707511 0.707509 0.707505 0.707551 0.707501 0.707548 0.707503 0.707496 0.707558
0.707520 0.707518 0.707514 0.707560 0.707510 0.707557 0.707512 0.707505 0.707567
Geochemical analysis of hippuritid shells from studied localities with numerical ages (bold) derived from the ‘Look-Up’ table (Version 4: 08/03) provided by Horwath & McArthur (1997) and McArthur et al. (2001).
Sample D. Orešje1 D. Orešje2 D. Orešje3 Brašljevica1 Brašljevica2 Brašljevica3 Sv. Martin1 Sv. Martin2 Sv. Martin3
Mg (mg/kg)
Sr (mg/kg)
Mn (mg/kg)
Ba (mg/kg)
Fe (mg/kg)
3081 2993 3402 1272 3067 1504 2155 2915 1125
1062 1087 937 876 412 494 782 627 575
42 31 36 28 34 36
