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Late Albian ammonites from the carbonate cover of the Teloloapan arc volcanic rocks (Guerrero State, Mexico)
Journal of South American Earth Sciences 13 (2000) 377±388
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Late Albian ammonites from the carbonate cover of the Teloloapan arc volcanic rocks (Guerrero State, Mexico) O. Monod a,*, R. Busnardo b, M. Guerrero-Suastegui c a
Departement de Science de la Terre, ISTO, Universite d'OrleÂans, BP 6759, OrleÂans 2, F-45067 France Departement de Science de la Terre, Universite Claude Bernard-Lyon I, Villeurbanne, F-69622 France c ERCT, Universidad Autonoma de Guerrero, AP 197, Taxco (Gro), Mexico
b
Abstract In the Guerrero province of Mexico, the calc-alcaline lavas of the Teloloapan volcanic arc unit are overlain by carbonates with reworked neritic faunas of Aptian±Albian age (La Evolucion Geologica y la MetalogeÂnesis del Noroccidente de Guerrero. Universidad Autonoma de Guerrero, Serie TeÂcnico-Cienti®ca, 1 (1979) 84). The discovery of an ammonite fauna at the top of the Teloloapan limestone provides a latest Albian age assignment for that horizon. The fauna includes: Pervinquieria rostrata, P. gr. in¯ata, Turrilitoides hugardianus, Stoliczkaia cf. blancheti, S. cf. tenuis, Desmoceras latidorsatum, Oxytropidoceras cf. cantianum, Puzosia aff. mayoriana, Lechites moreti, Hamites cf. gardneri, H. cf. maximus, and Falciferella campae n. sp. A pelagic microfauna is associated with the ammonites and contains Hedbergella sp. and Colomiella recta. The fossiliferous horizon may thus be restricted to the In¯atum and lower Dispar zones. The overlying ¯ysch contains Hamites sp. gr. intermedius near the base. Therefore, volcanism in the Teloloapan arc ceased before the end of the Early Cretaceous, while ¯ysch deposition began in latest Albian times. q 2000 Elsevier Science Ltd. All rights reserved. Keywords: Ammonites; Volcanic rocks; Carbonate cover; Albian; Guerrero (Mexico)
1. Introduction In southwestern Mexico (Guerrero State), the volcanic rocks of the Teloloapan arc unit are regularly overlain by a sedimentary sequence dominated by limestone at the base and ending with a silico-detritical ¯ysch formation (Campa and Ramirez, 1979; Talavera, 1993) (Fig. 1). This volcanosedimentary unit is thrust over the Guerrero±Morelos platform carbonates (Albian±Cenomanian) and the Mexcala ¯ysch of Late Cretaceous age (Fig. 2). The platform carbonates and the ¯ysch are not metamorphosed and have been dated by macro- and microfauna in several localities (Fries, 1960). In contrast, the Teloloapan unit has been affected by greenschist metamorphism and, as a consequence, the limestone and ¯ysch could be dated only through macrofauna identi®cation (Campa et al., 1973). Fortunately, numerous mollusc shells are present in the Teloloapan calcarenites. The fauna includes rudists and gastropods, which indicate an Aptian±Albian age for the carbonates (Guerrero et al., 1991). The discovery of thin pelagic horizons containing ammonites at the top of the Teloloapan limestone and in the overlying ¯ysch now * Corresponding author. Tel.: 133-2-3849-4646; fax: 133-2-3841-7309. E-mail address: [email protected] (O. Monod).
permits more precise dating of the rocks composing the Teloloapan unit. 2. The ammonite layers and their age Several fossiliferous outcrops have been found in the uppermost layers of the Teloloapan limestone (Figs. 1 and 2) in the vicinity of Acatempan, a famous locality in the history of the Mexican war for independence (1821). The village is situated a few kilometers south of Teloloapan. Only one fossiliferous outcrop (MF 96) is located in the overlying ¯ysch formation, about 1 km west of El Pochote (Fig. 4), along the road from Teloloapan to Arcelia. After reviewing the composition of the fauna and discussing the probable age of each fossiliferous outcrop, a short palaeontological description of the signi®cant forms is given here. Each specimen is designated by its original sample number and the collection number of the University of Lyon I (FSL) where it is deposited. 2.1. Concordia locality (MF 82) The fossiliferous outcrop was ®rst discovered by M. Guerrero. It occurs about 1 km west of the village (Fig. 1), a few meters under the boundary between the Teloloapan
0895-9811/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved. PII: S 0895-981 1(00)00030-4
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O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388 to Teloloapan 18¡ 20
1862
Teloloapan bioclastic limestone
Mexcala Flysch ( Late Cretaceous)
Teloloapan arc Volcanic rocks Late Albian fossiliferous locality Thrust
ACATEMPAN
100 ¡
to Chapa
ZACATLAN MF 86 F PN 211
PN 307 PN 308 PN 309
F
Guerrero Morelos Platform carbonates
F MF 75 1701
Red Beds (Tertiary)
Mesa La Lobera
MEXICO
18 ¡
1886
1475
TELOLOAPAN
0
F
N
Km
2
La Taza Volteada 1802
A MF 82 F
CONCORDIA
1642
TEPOZONALQUILLO APATZINGAN 1725
LOS SAUCES
1804
B
99¡ 50
Fig. 1. Geological sketch map of the area south of Teloloapan showing seven of the fossiliferous localities discussed in the text. AB: section line.
limestone sequence and the overlying calcareous ¯ysch (Mexcala Flysch) (Fig. 2). In that part of the section (Fig. 3), the uppermost massive limestone bed (Fig. 3, No. 1) consists of coarse bioclastic breccia with large rudist fragments. It is abruptly succeeded by well bedded, grey calcarenites (2 m) with numerous bioclasts (Fig. 3, No. 2). Above comes a conspicuously darker horizon (Fig. 3, No. 3) of calcareous breccia in a brown colored calcareous matrix (1 m), ending in a clearer calc-arenitic bed (0.5 m). The fossiliferous horizon (Fig. 3, No. 4) comes immediately above and consists of a closely packed assemblage of
A Red beds
Arroyo Zacatlan Fauna PN 307 PN 308 PN 309
ACATEMPAN Cemetery Fauna MF 86 PN 211 MF 75
ammonites (MF 82) and rudist fragments embedded in a manganese-rich, dark red to black argillaceous coating. This unusual assemblage of pelagic and neritic faunas appears to be unsorted, as large specimens (.0.4 m) are intermixed with much smaller ones. The energy level of deposition must have been high. The calcareous sequence ends in 2 m of channelized calcarenites (Fig. 3, No. 5) that are interrupted by irregular, Mn-rich surfaces. Calcareous sandstones and shales of the base of the Mexcala ¯ysch (Fig. 3, No. 6) occur stratigraphically higher. The Concordia section demonstrates the destruction of a
C. La Taza Volteada
CONCORDIA Village
APATZINGAN Village
B
Fauna MF 82 2000 1500 1000
Fig. 2. Section AB (see Fig. 1) showing the tectonic position of the Teloloapan unit overthrust on the Guerrero±Morelos Platform and the Mexcala Flysch, and the location of the fossiliferous localities. Lithology as in Figs. 1 and 4.
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
W
379
(5) (1) (3) (4) (6) (2) E Base of Coarse, Well bedded Coarse limestone MF 82 Well bedded Mexcala Flysch calcarenites massive, calcarenites breccia in Mn rich FAUNA calcareous matrix Ammonites bioclastic limestone and rudist Pelagic fragments Mudstone Disconformity Manganese coatings
(not seen) ? 0
1
2m
Fig. 3. Concordia outcrop section (location Fig. 1) showing the highest beds of the Teloloapan neritic limestone and the onset of slope facies with a fossiliferous condensed horizon (MF 82) under the Mexcala Flysch. Numbers 1±6 refer to the text.
carbonate rimmed shelf, with a clear disconformity separating the shallow marine reef limestone breccias from the overlying channelized calcarenites and calcareous turbidites. As expected from the pro®le, the Mn-rich fossiliferous bed (Fig. 3, No. 4) is a condensed horizon containing: Pervinquieria rostrata Sow., P. juv. gr. in¯ata (Sow.) Hamites cf. gardneri Spath, H. cf. maximus Sow., Tetragonites sp., Stoliczkaia (Faraudiella) cf. blancheti Pictet and Campiche. S. gr. notha Seelay and P. rostrata provide a late Albian age assignment, while S. cf. blancheti is diagnostic for the lower part of the Dispar zone (Table 1). From the same outcrop, M. Guerrero (unpublished report) has reported Mariella camachoensis BoÈse (a form very similar to M. bergeri) and Hysteroceras sp. Both are late Albian in age.
2.3. West of Acatempan (PN 307, PN 308, PN 309) Three localities are situated about 4 km southwest of Acatempan, on the eastern ¯ank of an unnamed calcareous hill (Figs. 1 and 2). At that locality the uppermost limestone beds are well bedded, ®ne grained calciturbidites with occasional chert bands. Bioclastic packstone-wackestones contain an abundant pelagic microfauna (Hedbergella sp.). The dip is vertical or overturned to the east. Ammonites are small and numerous. They include Lechites moreti, Pervinquieria sp., Desmoceras (Latidorsella) latidorsata, Mortoniceras s.l., Stoliczkaia cf. notha Seeley, S. juv., gr. blancheti P. et C., which indicate the lower part of the Dispar zone (Table 1). 2.4. Zacatlancillo (MF 96) (Fig. 4)
2.2. Acatempan locality (MF 75, PN 211, MF 86) East of Acatempan, the Teloloapan limestones gently dip to the west under the ¯ysch on which the village stands (Figs. 1 and 2). Several fossiliferous occurrences have been found in the highest limestone beds near the boundary with the ¯ysch. MF 75 is a micritic breccia containing Pervinquieria sp. juv. gr. in¯ata and Stoliczkaia cf. tenuis, of late Abian age. Under the cemetery of Acatempan, on the eastern side of the hill, some large specimens (greater than 20 cm. in shell diameter) were discovered by M. Guerrero in the highest limestone beds and have been photographed in situ. They probably belong to the genus Pervinquieria. Other fossiliferous horizons (PN 211), also from a coarse micritic breccia, include smaller forms such as Puzosia aff. mayoriana, Stoliczkaia sp. gr. dispar, and a new species, Falciferella campae nov. sp. In the same facies, MF 86 contains Pervinquieria sp. ind. Turrilitoides hugardianus, and Oxytropidoceras cf. cantianum. The latter probably indicates the lower part of the In¯atum zone. In the mudstone fragments is a well preserved pelagic microfauna including Hedbergella sp. and Colomiella recta. (Fig. 7d).
West of El Pochote, about 12 km from Teloloapan on the road to Arcelia, a fossiliferous locality has been found in a shaly, micaceous facies of the ¯ysch by Campa et al., 1973. From the same locality comes another cast of Hamites sp. gr. intermedius (Fig. 7, Fig. 2). Owing to the higher position of this specimen in the ¯ysch compared to the fauna described in the Teloloapan limestone, the age may be latest Albian to early Cenomanian. 3. Conclusions The uppermost beds of the Teloloapan limestone have yielded late Albian ammonites from several localities (Table 1). Although these occurrences are very close in age, they present signi®cant variations of depositional environment, showing a rapid increase of depth from east to west (Fig. 4). In less than 10 km, the fossiliferous facies changes from a high-energy, condensed limestone horizon with manganese oxides near Concordia, into coarse calcareous breccias with angular limestone clasts east of Acatempan, and then passes westward into well bedded calciturbidites
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Table 1 Stratigraphic position of the different faunas, from east (Concordia, MF82) to west (Acatempan) (see Fig. 1). Slight differences in age may re¯ect facies changes but may also result from incomplete sampling
with cherts. Farther west (Zacatlancillo), away from the slope deposits, basinal facies are represented by the black calcareous mudstones of Amatepec (de Cserna, 1982) containing only badly preserved radiolarians (K. Ishida, pers. comm.). The precise age assignment permitted by the ammonites in the Teloloapan unit (In¯atum zone to lower Dispar zone) helps to constrain the reconstruction of the margin of the Guerrero±Morelos carbonate platform (Fig. 4). Although volcanic activity in the Teloloapan arc ended before Albian, the overlying ¯ysch, though not dated at the top, probably extends into Late Cretaceous. 4. Systematics by R. Busnardo The following descriptions concern the ammonites of the Teloloapan limestones from four localities shown on the
map (Fig. 1) and one from the ¯ysch formation. The most signi®cant specimens are illustrated in Figs. 5±7. Although not exhaustive, this study gives the basic information for genus or species identi®cation. Abbreviations used for measurements, which are given in mm: D diameter; Wh whorl height; Ww whorl width; U Umbilicus. All the specimens are deposited in the collections of the Institute of Geology, University Claude Bernard-Lyon I (Villeurbanne, France). Family: Brancoceratidae Spath 1933 Genus: Pervinquieria Boehm 1910 Pervinquieria rostrata (Sow.) Fig. 5a 1932 Ð Mortoniceras (Pervinquieria) rostratum (Sow.) in Spath, p. 400, pl. XXXVI, ®g. 6; pl. XXXVIII, ®g. 4; pl.
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
T E L O L O A P A N
MARGIN
BASIN W
Zacatlancillo MF 96
U N I T
El Pochote
W. Acatempan E. PN307-9 MF75-86, PN211
M E X C A L A
381
GUERRERO -MORELOS PLATFORM
Concordia MF82
E
F L Y S C H
(no scale)
Mexcala Flysch
limestone fragments
Brecciated limestone
Condensed horizon Calcarenites
Amatepec pelagic limestone
Bioclastic limestone
Rudist limestone
Volcanic rocks of the Teloloapan arc
Fig. 4. Tentative pre-tectonic reconstruction of the Teloloapan unit and Guerrero±Morelos Platform during the deposition of the Mexcala Flysch (Late Cretaceous).
XXXIX, ®g. 4; pl. XL, ®gs. 1 and 7; pl. XLII, ®g. 2; text-®g. 130 ®g, 136, 137e. Remarks: A distorded fragment of a large ammonite is referable to Mortoniceras (Pervinquieria) rostratum. Shell diameter of the entire specimen is estimated to have been approximately 200 mm. The example shows simple trituberculate ribs that are characteristic of this species at large shell dimensions. In addition, it shows the upper part of some large and spatulate ribs of the penultimate whorl. The keel is present although it is badly conserved. This species is usually found in the Dispar zone. Locality: Concordia, MF 82 (FSL 108 943). Pervinquieria sp. ind. Remarks: Several fragments referable to Pervinquieria are recognizable by the keel and the more or less tuberculate ribs. Several large specimens having a shell diameter over 200 mm have been left in situ. Locality: E Acatempan PN 211; MF 86 (FSL 108 950, 108 951); W Acatempan PN 308 (FSL 108 935). Pervinquieria sp. juv., cf. in¯ata (Sow.) Fig. 5d and e. 1930 Ð Mortoniceras (Pervinquieria) in¯atum (Sow.) in Spath p. 381, pl. XXXV, ®g. 9; XXXVII, 1; XXXIX, ®g. 2; XLII, ®g. 6; XLIII, ®g. 1; XLVI, ®g. 1±2. Remarks: This species is represented by juveniles and poorly preserved fragments of internal whorls. The specimens have bifurcate ribs with strong umbilical tubercles.
The marginate tubercules are sometimes weakly striped. The keel is prominent. The style of ornamentation observed on those specimens is found in the internal whorls of several species and especially in Pervinquiera in¯ata (Spath 1930, pl. XLII, ®g. 6). These ammonites indicate the In¯atum zone of late Albian age. Locality: E Acatempan, MF 75 (FSL 108 953). Pervinquieria sp. juv., cf. in¯ata (Sow.) Fig. 6d and f. References: see above. Remarks: This form is represented by an external and internal cast of the inner whorls of a small ammonite. The ornamentation may be characterized according to three ontogenetic stages. The ®rst stage, up to 7 mm shell diameter is smooth except for a dense, delicate projected striation. This stage is rarely observed, although it has been noted by Haas (1942, p. 35, pl. IV, ®g. 24 and 27) in Hysteroceras falcicostatum. Stage two, between 7 and 13 mm shell diameter, marks the appearance of the umbilical and marginate tubercles. This ornamentation style is found in Neokentroceras and in some species of Hysteroceras (Cooper and Kennedy 1979, p. 266, ®g. 60). The last stage is greater than 13 mm shell diameter. The ribs connecting the umbilical tubercle to the marginate tubercle appear here. That ornementation is often noted in the literature (see Scholz 1979, pl. 29). This third stage is characteristic for the genus. The material lacks adult
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Fig. 5. (a) Pervinquieria rostrata Sow. (MF 82, FSL 108 943), Vraconnian, 1£. (b) Hamites cf. gardneri Spath. (MF 82, FSL 108 946), Vraconnian, 2£. (c) Pervinquieria juv. (MF 82, FSL 108 941), Vraconnian, 4£. (d±e) Pervinquieria gr. in¯ata Sow. (MF 75, FSL 108 953), Late Albian, In¯atum zone, 2.5£. (f) Desmoceras latidorsatum Mich. (PN 309, FSL 108 937), Late Albian, 2£. (g) Oxytropidoceras cf. cantianum Spath. (MF 86, FSL 108 948), Late Albian, 2.2£. (h) Stoliczkaia cf. tenuis Renz. (MF 75, FSL 108 952), Vraconnian, 2.2£.
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
383
Fig. 6. (a±b) Falciferella campae n. sp. (PN 211, FSL 108 933), section, 2.3£. (c) Lechites moreti Breistr. (PN 307, FSL 108 936), Vraconnian, 2£. (d,f) Pervinquieria juv., gr. in¯ata Sow. (MF 82, FSL 108 940 and 108 942), Vraconnian. 2.3£. (e) Turrilitoides hugardianus d'Orb. (MF 86, FSL 108 949), Vraconnian, 2.2£. (g) Puzosia aff. mayoriana (d'Orb.) (PN 211, FSL 108 934), Late Albian, 2.2£.
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Fig. 7. (a) Stoliczkaia (Faraudiella) cf. blancheti (Pictet et Campiche) (MF 82, FSL 108 947), early Vraconnian, Dispar zone, Blancheti subzone, 1.5£. (b) Hamites sp., gr. intermedius Sow. (MF 96, FSL 108 939), latest Albian or early Cenomanian, Mexcala Flysch Formation, 1.5£. (c) Section of Falciferella campae n. sp., (PN211, FSL108 933), section, 3£. (d) Colomiella recta and Hedbergella sp., thin section in PN211, 60£.
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
whorls and ornamentation that are required for speci®c determination. Locality: Concordia, MF 82 (FSL 108 940 and 108 942). Pervinquieria sp. juv. Fig. 5c. Remarks: Pervinquieria sp. juv. occurs in the same locality (MF 82) as the preceding sample and is represented by one specimen, FSL 108 941. The enlarged photograph clearly shows the second growth stage of Pervinquieria, that is to say the ªNeokentrocerasº stage. Several other specimens are visible in the same rock sample. Fig. 6f shows a stage of evolution that is intermediate between stage 2 and stage 3. Genus: Oxytropidoceras Stieler 1920 Oxytropidoceras sp. ind., cf. cantianum Spath. Fig. 5g. 1929 Ð Oxytropidoceras cantianum Spath, p. 350, pl. XXXII, ®g. 4±5; text-®g. 114 a, 115 g, h. Remarks: This species is represented by a fragment of a small ammonite 45 mm in shell diameter. The section is lanceolate and shows a keel. The thin, falcoid and sometimes bifurcate ribs are diagnostic for Oxytropidoceras. An example ®gured by Spath (1929, pl. XXXII, ®g. 5) represents a specimen nearly identical to the one described herein. However the specimen described here is a juvenile ammonite that cannot receive a more speci®c determination. The costation style of the specimen is also present in the internal whorls of O. (Venezoliceras), for example, O. (Venezoliceras) karsteni Stieler (Renz 1982, pl. 17, ®g. 2). Those forms come from Venezuela and are referable to the late Albian, Orbignyi zone. BoÈse (1923, p. 171, pl. XI, ®g. 61±62) has ®gured an Oxytropidoceras ( ªSchlumbachia aff. acutocarinataº) of the same group in the latest Albian (ªVraconnianº). According to the associated fauna, the Mexican specimen may be placed in the lowermost level of the late Albian. Locality: E Acatempan, MF 86 (FSL 108 948). Family: Lyelliceratidae Genus: Stoliczkaia Neumayr 1875 Stoliczkaia (Faraudiella) cf. blancheti (Pictet and Campiche) Fig. 7a. 1979 Ð Stoliczkaia dispar (d'Orbigny) 1841; in Scholz, p. 83, pl. 14 to 20, text-®g. 22±23. Remarks: This is an almost complete, slightly stretched ammonite 60 mm in diameter. The whorl section is narrow. Wh 31; Ww 17; Ww/Wh 0.54. The body chamber represents half a whorl and is almost smooth. The suture, partly visible, is the same as in S. dispar ®gured by Scholz (1979, p. 86, ®g. 23). The umbilical wall bears a row of little tubercles. The middle part of the ¯ank is almost smooth. In the upper third of the whorl are weak and
385
bifurcate ribs. In the ®rst part of the ®nal whorl these ribs are straight and dense, and cross over the rounded venter side. In the middle part of the venter the crenated line is weakly visible; this is distinctive of the genus Faraudiella. Scholz (1929) has produced good pictures of S. blancheti which he considers as a subspecies of S. dispar. I prefer recognition of a separate species because of the dense costation that disappears in the body chamber, and particularly because of its stratigraphical position in the lower part of the Dispar zone. Locality: Concordia, MF 82 (FSL 108 947). Stoliczkaia sp. juv., gr. notha Seeley 1979 Ð Stoliczkaia dispar, morphotype notha, in Scholz, pl. 16±19. 1979 Ð Soliczkaia notha in Cooper and Kennedy, p. 263, ®g. 57. Remarks: Several fragments of small ammonites show thick and rounded ribs like those of S. notha. This form has been ®gured by Scholz, not as a species, but as a morphotype of S. dispar sp. They have also been ®gured by Cooper and Kennedy (1979) and by Spath (1929). Speci®c identi®cation is dif®cult, but this material and closely related forms suggest the late Albian Dispar zone. Locality: Concordia, MF 82 (FSL 108 944, 108 945); W Acatempan, PN 308 (FSL 108 935). Stoliczkaia cf. tenuis Renz Fig. 5h. 1968 Ð Stoliczkaia tenuis Renz, p. 48, pl. 6, ®g. 6, and 12. 1979 Ð Stoliczkaia tenuis Renz, in Cooper and Kennedy, p. 249, ®g. 46±53, 54 A±F, 68 E. Remarks: This species is represented by a small, probably juvenile specimen (D 22; U 5; Wh 8; Ww 6). It clearly shows the thin and bifurcate ribs passing to the simple and nearly large ribs characteristic of Stoliczkaia. This species is readily recognizable by its ¯at venter as ®gured in Cooper and Kennedy (1979, see ®g. 47 L, X and P, p. 251, etc). In the Mexican specimen the venter is also ¯at or weakly depressed. Age: Vraconnian. Locality: E Acatempan, MF 75 (FSL 108 952). Family: Binneyitidae Genus: Falciferella Casey 1954 Falciferella campae n sp. Figs. 6a,b and 7c Material: Only one specimen, FSL 108 933: D ?30; U ?9; Wh 14; Ww 7. Locus typicus: Outcrop E Acatempan, PN 211, Guerrero state, Mexico. Stratum typicum: top of Teloloapan Limestone Formation, associated with Pervinquieria sp., Stoliczkaia sp., gr. dispar,
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Puzosia mayoriana, ammonites of late Albian age, probably in the lower part of the Dispar zone. Derivatio nominis: dedicated to Dra. Maria-Fernanda Campa, who ®rst proposed a Cretaceous age for the Teloloapan volcanic rocks (1973). Description and diagnosis: This new species is represented by one specimen preserving the third of a whorl. The umbilicus is middle sized, the ¯anks are almost ¯at, and the section is high. The ventral area is weakly rounded, without keel or furrow. The costation is falcoid. The lower part of the side is smooth; in the middle part, weakly concave primary ribs are apparent; in the upper part there are numerous delicate and prorsiradiate ribs which cross over the siphuncle area. The suture is not visible. Comparison: The falcoid costation is typical for the Aconeceratinae; see: Aconeceras nisoides (Sarasin), Sammartinoceras falcatum (v. Koenen), S. trauscholdi (Sinzow) in Spath (1961), and Aconeceras austronisoides Brunnschweiler (1959, Fig. 5.1). However, all those species are of Aptian age and, above all, their section is ogival, sometimes with a keel. This is not the case of the section of our Mexican ammonite. In the earliest Hyphoplites of Vraconnian age (for example H. coelonotus (Seeley) in Scholz (1979, pl. 13), the same kind of costation is present. But those forms are Hoplitids with a distinctive ventral furrow, which is not present in our specimen. The falcoid costation, the high section, and the almost ¯at ventral area are features belonging to the genus Falciferella. But no species of this genus, which was studied by Casey (1954, 1961) or by Brunnschweiler (1959), seems identical with our specimen. That is the reason why I propose this highly distinctive new species even though it is based on a single specimen. Many species of Falciferella are known in England in the middle Albian, and in the late Albian in Australia. It is interesting to identify a new species of Falciferella of late Albian age in Mexico. According to Cobban (1961), this genus belongs to the Binneyitidae and is frequent in North America in the Cenomanian. Juignet and Kennedy (1976) and Kennedy and Juignet (1973, 1984) have recognized the same family in the Cenomanian in France. Family: Desmoceratidae Genus: Desmoceras Zittel 1884 Desmoceras latidorsatum Michelin Fig. 5f. 1968 Ð Desmoceras latidorsatum (Michelin), in Renz, p. 20, pl. 1, ®g. 12. 1968 Ð D. latidorsatum (Michelin), in Wiedmann, p. 131, pl. 12, ®g. 2, 6±13. 1979 Ð D. latidorsatum (Michelin), in Scholz, p. 61. 1982 Ð D. latidorsatum (Michelin), in Renz, p. 36, pl. 5, ®g. 1±9.
1988 Ð D. latidorsatum (Michelin), in Delanoy and Latil, pl. 1, ®g. 1ab. Remarks: This highly variable species is ubiquitous and has been described and ®gured many times in the literature. In our small specimen (D 17; U 4.5; Wh 6; Ww 6) the section is not so low as in the other examples referred to D. latidorsatum. The constrictions are underlined by a weak rim. The ®rst whorls are smooth. The specimen is a small juvenile. This species is frequent in the late Albian. Locality: W Acatempan, PN 309 (FSL 108 937). Genus: Puzosia Bayle 1878 Puzosia aff. mayoriana (d'Orbingy) Fig. 6g. 1841 Ð Ammonites mayorianus d'Orb., p. 267, pl. 79, ®g. 1±3. 1923 Ð Puzosia mayoriana (d'Orb.), in Spath, p. 42, Pl. I, ®g. 9±10. 1979 Ð Puzosia planulata (Sow.), in Scholz, p. 63, pl. 11, pl. 12, pl. 13, ®g. 2, text-®g. 19±20. Remarks: We have only half a whorl of a small ammonite which looks like a juvenile Puzosia mayoriana (D 36; U 13.4; Wh 13.2; Ww 12). It shows weak falcoid constrictions and thin fasciculate ribblets between them. Spath (1923) has ®gured almost identical material. According to Scholz (1979), these forms belong to the same population, which includes 18 species and subspecies that are described in the literature. Puzosia mayoriana is frequent and ubiquitous in the late Albian. Locality: E Acatempan, PN 211 (FSL 108 934). Family: Baculitidae Genus: Lechites Nowak 1908 Lechites moreti Breistroffer, Fig. 6c 1936 Ð Lechites moreti Breistroffer, p. 66. 1957 Ð Lechites moreti Breistr., in Busnardo, p. 116, pl. III, ®g. 3. 1968 Ð Lechites moreti Breistr., in Renz, p. 81, pl. 16, ®g. 10, 12, 13, text-®g. 29 a, i. 1979 Ð Lechites gaudini moreti Breistr., in Scholz, p. 14, pl. 1, ®g. 10, text-®g. 5C. 1988 Ð Lechites moreti Breistr., in Delanoy and Latil, p. 752, pl. 1, ®g. 4. Remarks: Several small and juvenile fragments of this species are found in the neritic limestone west of Acatempan. In the ®gured sample, 31 mm long, we clearly see the oblique furrows and striae which are diagnostic for the species. In the literature the authors have ®gured adult forms. Here we see the striae of a juvenile shell. This pelagic and ubiquitous species is usually reported in the Vraconnian. Locality: W Acatempan, PN 307 and PN 308 (FSL 108 936).
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
Genus: Hamites, Parkinson 1811 Hamites cf. gardneri Spath Fig. 5b. 1941 Ð Hamites gardneri Spath, p. 624, ®g. 225; pl. LXX, ®g. 3±5. Remarks: The Mexican specimen is a small criocone 23 mm long. It shows ®ne, dense costation with simple and straight ribs. The section is oval. This form is close to H. gardneri Spath. In the Mexican criocone, however, the costation is more dense (14 ribs per cm against 8 ribs per cm in Spath ®gure 225d, in the same ontogenetic stage). The juvenile forms are evidently dif®cult to determine. BoÈse (1923, pl. IX, X) has ®gured several species of Hamites with thin and simple ribblets, found in the Vraconnian of Camacho (Mexico), although the ®gures are imperfect and do not provide a good comparison. From the Vraconnian of Venezuela, Renz (1982, p. 60, pl. 20, ®g. 6abc, text-®g. 42) has described a small example of Hamites sp. that is closely similar to our specimen. Locality: Concordia, MF 82 (FSL 108 946). Hamites cf. maximus Sow. 1941 Ð Hamites maximus Sowerby, in Spath, p. 621, text-®g. 224; pl. LXVIII, ®gs. 15, 16, 20; pl. LXIX, ®g. 1±9; pl. LXX, ®g. 1, 18. Remarks: A short fragment of an uncoiled ammonite having only some straight and thick ribs is close to H. maximus ®gured by Spath (1941, pl. LXIX, ®g. 3). Locality: Concordia, MF 82 (FSL 108 945). Hamites sp. gr. intermedius Sow. Fig. 7b. 1941 Ð Hamites intermedius Sow., in Spath, p. 630, ®g. 229; pl. LXX, ®g. 19±20; pl. LXXI, ®g. 3±6. 1923 Ð Hamites intermedius Sow., in BoÈse, p. 132, pl. IX, ®g. 46±49. Remarks: The specimen is a small, almost complete, hamitiform uncoiled ammonite 48 mm long. It is a slightly stretched external cast in a yellowish shale of the Mexcala Formation. The ribs are simple, acute and weakly oblique. The same costation is found in H. intermedius ®gured by Spath (1941), especially in his pl. LXX, ®g. 19±20. Our specimen is smaller. Hamites intermedius occurs in the late Albian in England, although a lower Cenomanian age is not excluded here. BoÈse (1923) has found the same species in the Vraconnian of Camacho (Mexico). Locality: Zacatlancillo, MF 96 (FSL 108 939). Family: Turrilitidae Genus: Turrilitoides Spath 1923 Turrilitoides hugardianus (d'Orbigny) Fig. 7e.
387
1842 Ð Turrilites hugardianus d'Orbigny, p. 588, pl. 147, ®g. 9±11. 1979 Ð Turrilites hugardianus (d'Orb.), in Scholz, p. 34, pl. 7, ®g. 1±14, 16. 1990 Ð Turrilites hugardianus (d'Orb.), in Marcinowski and Wiedmann, p. 50, pl. 4, ®g. 9±10. Remarks: This specimen consists of a third of a whorl of a turricone. We see the relatively strong and oblique ribs, without tubercles, that are distinctive of this species. They partly divide in the outer part of the whorl, as in the form ®gured by Scholz (1979, pl. 7, ®g. 7). This species is frequent in the lower Vraconnian (Blancheti subzone) of the Bakony Mountains (Hungary). Locality: E Acatempan, MF 86 (FSL 108 949). Acknowledgements This work was supported by CNRS-UMR 6530 in a joint project of cooperation between Universidad Autonoma de Guerrero (UAG), Mexico, and the University of Orleans, France. David Taylor and A.B. Villasenor have suggested many useful improvements to the manuscript. The authors also express their gratitude to N. Laurent-Rouchon for the drawings and to N. Podevigne for the excellent photographs. References BoÈse, E., 1923. Algunas Faunas Cretacicas de Zacatecas, Durango y Guerrero. Instituto Geologico de Mexico, Boletin 42, 224. BoÈse, E., 1927. The Cretaceous ammonites from Texas and Northern Mexico. Texas University, Bulletin 2748, 143±312. Breistroffer, M., 1936. Les subdivisions du Vraconnien dans le Sud-Est de la France. SocieÂte GeÂologique de France, SeÂr. 5 Bulletin 6, 63±68. Brunnschweiler, R.O., 1959. New Aconeceratinae (Ammonoidea) from the Albian and Aptian of Australia. Bureau of Mineral Resources Bulletin, Canberra, 19. Busnardo, R., 1957. Contribution aÁ l'eÂtude des faunes d'ammonoIÈdeÂs de Medjez Sfa (Est Constantinois). Service de la Carte GeÂologique d'AlgeÂrie, Bulletin 13, 67±123. Campa, M.F., Campos, M., Flores, R., Oviedo, R., 1973. La sequencia Mesozoica vulcano-sedimentaria metamor®zada de Ixtapan de la Sal (Mex)-Teloloapan (Gro). Sociedad Geologica Mexicana, Bulletin 35, 7±28. Campa, M.F., Ramirez, J., 1979. La Evolucion Geologica y la MetalogeÂnesis del Noroccidente de Guerrero. Universidad Autonoma de Guerrero, Serie TeÂcnico-Cienti®ca 1, 84. Casey, R., 1954. Falciferella, a new genus of Gault ammonites, with a review of the family Aconoceratidae in the British Cretaceous. Proceedings of the Geologist Association 65 (3), 262±277. Casey, R., 1961. A Monograph of the Ammonoidea of Lower Green-Sand. Paleontographical Society Part 3, 119±216. Cobban, W.A., 1961. The ammonite family Binneyitidae Reeside in the western interior of the United States. Journal of Paleontology 35 (4), 737±758. Cooper, M.R., Kennedy, W.J., 1979. Uppermost Albian (Stoliczkaia Dispar zone) Ammonites from the Angola littoral. Annals of the South African Museum 77 (10), 175±308. de Cserna, Z., 1978. Notas sobre la geologia de la region comprendida entre Iguala, Cd. Altamirano y Temascaltepec, Edos de Guerrero y Mexico.
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In: Libro Guia de la Excursion Geologica a Tierra Caliente, IV Convenio Nacional de Mexico. Sociedad Geologica Mexicana, 125pp. Delanoy, G., Latil, J.L., 1988. DeÂcouverte d'un nouveau gisement albien dans les environs de Drap (Alpes Maritimes, France) et description d'une riche ammonitofaune d'aÃge Albien terminal. Geobios 21 (6), 749±771. Fries, C., 1960. Geologia del Estado de Morelos y de Partes Adjacentes de Mexico y Guerrero, Region Central Meridional de Mexico. UNAM Instituto de Geologia, Bulletin 60, 236pp. Guerrero, M., Ramirez, J., Talavera, O., Campa, M.F., 1991. El desarollo carbonatado del CretaÂcico inferior asociado al arco de Teloloapan, Noroccidente del Estado de Guerrero. Abstracts, Convention sobre la Evolution Geologica de Mexico, p. 67. Sociedad Mexicana de Mineralogia and UNAM Instituto de Geologia. Jacob, C., 1907. Etude sur Quelques Ammonites du CreÂtace Moyen. SocieÂte GeÂologique de France, MeÂmoire 38, 63. Juignet, P., Kennedy, W.J., 1976. Faunes d'Ammonites et Biostratigraphie CompareÂe du CeÂnomanien du Nord-Ouest de la France (Normandie) et du Sud de l'Angleterre. SocieÂte GeÂologique de Normandie, Bulletin 63 (2), 193. Kennedy, W.J., Juignet, P., 1973. First record of the ammonite family Binneyitidae Reeside 1927 in Western Europe. Journal of Paleontology 47 (5), 900±902.
Kennedy, W.J., Juignet, P., 1984. Revision of the ammonite faunas of the type Cenomanian. 2. The families Binneyitidae, Desmoceratidae. Cretaceous Research 5, 93±161. Marcinowski, R., Wiedmann, J., 1990. The Albian Ammonites of Poland. Palaeontologia Polonica 50, 94. d'Orbigny, A., 1840±1842. Terrains CreÂtaceÂs. I. CeÂphalopodes. PaleÂontologie FrancËaise. Masson, Paris (662pp.). Renz, O., 1968. Die Ammonoidea im Stratotyp des Vraconnien bei SainteCroix (Kanton Waadt). MeÂmoires Suisses de PaleÂontologie 87, 97. Renz, O., 1982. The Cretaceous Ammonites of Venezuela. Birkhauser, Basel, Switzerland (132pp.). Scholz, G., 1979. Die Ammonites des Vracon (Oberalb, Dispar Zone) des Bakony Gebirges (Westungarn). Paleontographica Ser. A 165, 136. Spath, L.F., 1923±1930. Ammonoidea of the Gault. Paleontological Society of London 1, 311. Spath, L.F., 1931±1943. Ammonoidea of the Gault. Paleontological Society of London 2, 313±787. Talavera, O., 1993. Les Formations OrogeÂniques MeÂsozoIÈques de Guerrero (Mexique MeÂridional). TheÁse Universite Grenoble, 462 pp. Wiedmann, J., Dieni, I., 1968. Die Kreide Sardiniens und ihre Cephalopoden. Paleontologia Italica 64, 1±171.
www.elsevier.nl/locate/jsames
Late Albian ammonites from the carbonate cover of the Teloloapan arc volcanic rocks (Guerrero State, Mexico) O. Monod a,*, R. Busnardo b, M. Guerrero-Suastegui c a
Departement de Science de la Terre, ISTO, Universite d'OrleÂans, BP 6759, OrleÂans 2, F-45067 France Departement de Science de la Terre, Universite Claude Bernard-Lyon I, Villeurbanne, F-69622 France c ERCT, Universidad Autonoma de Guerrero, AP 197, Taxco (Gro), Mexico
b
Abstract In the Guerrero province of Mexico, the calc-alcaline lavas of the Teloloapan volcanic arc unit are overlain by carbonates with reworked neritic faunas of Aptian±Albian age (La Evolucion Geologica y la MetalogeÂnesis del Noroccidente de Guerrero. Universidad Autonoma de Guerrero, Serie TeÂcnico-Cienti®ca, 1 (1979) 84). The discovery of an ammonite fauna at the top of the Teloloapan limestone provides a latest Albian age assignment for that horizon. The fauna includes: Pervinquieria rostrata, P. gr. in¯ata, Turrilitoides hugardianus, Stoliczkaia cf. blancheti, S. cf. tenuis, Desmoceras latidorsatum, Oxytropidoceras cf. cantianum, Puzosia aff. mayoriana, Lechites moreti, Hamites cf. gardneri, H. cf. maximus, and Falciferella campae n. sp. A pelagic microfauna is associated with the ammonites and contains Hedbergella sp. and Colomiella recta. The fossiliferous horizon may thus be restricted to the In¯atum and lower Dispar zones. The overlying ¯ysch contains Hamites sp. gr. intermedius near the base. Therefore, volcanism in the Teloloapan arc ceased before the end of the Early Cretaceous, while ¯ysch deposition began in latest Albian times. q 2000 Elsevier Science Ltd. All rights reserved. Keywords: Ammonites; Volcanic rocks; Carbonate cover; Albian; Guerrero (Mexico)
1. Introduction In southwestern Mexico (Guerrero State), the volcanic rocks of the Teloloapan arc unit are regularly overlain by a sedimentary sequence dominated by limestone at the base and ending with a silico-detritical ¯ysch formation (Campa and Ramirez, 1979; Talavera, 1993) (Fig. 1). This volcanosedimentary unit is thrust over the Guerrero±Morelos platform carbonates (Albian±Cenomanian) and the Mexcala ¯ysch of Late Cretaceous age (Fig. 2). The platform carbonates and the ¯ysch are not metamorphosed and have been dated by macro- and microfauna in several localities (Fries, 1960). In contrast, the Teloloapan unit has been affected by greenschist metamorphism and, as a consequence, the limestone and ¯ysch could be dated only through macrofauna identi®cation (Campa et al., 1973). Fortunately, numerous mollusc shells are present in the Teloloapan calcarenites. The fauna includes rudists and gastropods, which indicate an Aptian±Albian age for the carbonates (Guerrero et al., 1991). The discovery of thin pelagic horizons containing ammonites at the top of the Teloloapan limestone and in the overlying ¯ysch now * Corresponding author. Tel.: 133-2-3849-4646; fax: 133-2-3841-7309. E-mail address: [email protected] (O. Monod).
permits more precise dating of the rocks composing the Teloloapan unit. 2. The ammonite layers and their age Several fossiliferous outcrops have been found in the uppermost layers of the Teloloapan limestone (Figs. 1 and 2) in the vicinity of Acatempan, a famous locality in the history of the Mexican war for independence (1821). The village is situated a few kilometers south of Teloloapan. Only one fossiliferous outcrop (MF 96) is located in the overlying ¯ysch formation, about 1 km west of El Pochote (Fig. 4), along the road from Teloloapan to Arcelia. After reviewing the composition of the fauna and discussing the probable age of each fossiliferous outcrop, a short palaeontological description of the signi®cant forms is given here. Each specimen is designated by its original sample number and the collection number of the University of Lyon I (FSL) where it is deposited. 2.1. Concordia locality (MF 82) The fossiliferous outcrop was ®rst discovered by M. Guerrero. It occurs about 1 km west of the village (Fig. 1), a few meters under the boundary between the Teloloapan
0895-9811/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved. PII: S 0895-981 1(00)00030-4
378
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388 to Teloloapan 18¡ 20
1862
Teloloapan bioclastic limestone
Mexcala Flysch ( Late Cretaceous)
Teloloapan arc Volcanic rocks Late Albian fossiliferous locality Thrust
ACATEMPAN
100 ¡
to Chapa
ZACATLAN MF 86 F PN 211
PN 307 PN 308 PN 309
F
Guerrero Morelos Platform carbonates
F MF 75 1701
Red Beds (Tertiary)
Mesa La Lobera
MEXICO
18 ¡
1886
1475
TELOLOAPAN
0
F
N
Km
2
La Taza Volteada 1802
A MF 82 F
CONCORDIA
1642
TEPOZONALQUILLO APATZINGAN 1725
LOS SAUCES
1804
B
99¡ 50
Fig. 1. Geological sketch map of the area south of Teloloapan showing seven of the fossiliferous localities discussed in the text. AB: section line.
limestone sequence and the overlying calcareous ¯ysch (Mexcala Flysch) (Fig. 2). In that part of the section (Fig. 3), the uppermost massive limestone bed (Fig. 3, No. 1) consists of coarse bioclastic breccia with large rudist fragments. It is abruptly succeeded by well bedded, grey calcarenites (2 m) with numerous bioclasts (Fig. 3, No. 2). Above comes a conspicuously darker horizon (Fig. 3, No. 3) of calcareous breccia in a brown colored calcareous matrix (1 m), ending in a clearer calc-arenitic bed (0.5 m). The fossiliferous horizon (Fig. 3, No. 4) comes immediately above and consists of a closely packed assemblage of
A Red beds
Arroyo Zacatlan Fauna PN 307 PN 308 PN 309
ACATEMPAN Cemetery Fauna MF 86 PN 211 MF 75
ammonites (MF 82) and rudist fragments embedded in a manganese-rich, dark red to black argillaceous coating. This unusual assemblage of pelagic and neritic faunas appears to be unsorted, as large specimens (.0.4 m) are intermixed with much smaller ones. The energy level of deposition must have been high. The calcareous sequence ends in 2 m of channelized calcarenites (Fig. 3, No. 5) that are interrupted by irregular, Mn-rich surfaces. Calcareous sandstones and shales of the base of the Mexcala ¯ysch (Fig. 3, No. 6) occur stratigraphically higher. The Concordia section demonstrates the destruction of a
C. La Taza Volteada
CONCORDIA Village
APATZINGAN Village
B
Fauna MF 82 2000 1500 1000
Fig. 2. Section AB (see Fig. 1) showing the tectonic position of the Teloloapan unit overthrust on the Guerrero±Morelos Platform and the Mexcala Flysch, and the location of the fossiliferous localities. Lithology as in Figs. 1 and 4.
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
W
379
(5) (1) (3) (4) (6) (2) E Base of Coarse, Well bedded Coarse limestone MF 82 Well bedded Mexcala Flysch calcarenites massive, calcarenites breccia in Mn rich FAUNA calcareous matrix Ammonites bioclastic limestone and rudist Pelagic fragments Mudstone Disconformity Manganese coatings
(not seen) ? 0
1
2m
Fig. 3. Concordia outcrop section (location Fig. 1) showing the highest beds of the Teloloapan neritic limestone and the onset of slope facies with a fossiliferous condensed horizon (MF 82) under the Mexcala Flysch. Numbers 1±6 refer to the text.
carbonate rimmed shelf, with a clear disconformity separating the shallow marine reef limestone breccias from the overlying channelized calcarenites and calcareous turbidites. As expected from the pro®le, the Mn-rich fossiliferous bed (Fig. 3, No. 4) is a condensed horizon containing: Pervinquieria rostrata Sow., P. juv. gr. in¯ata (Sow.) Hamites cf. gardneri Spath, H. cf. maximus Sow., Tetragonites sp., Stoliczkaia (Faraudiella) cf. blancheti Pictet and Campiche. S. gr. notha Seelay and P. rostrata provide a late Albian age assignment, while S. cf. blancheti is diagnostic for the lower part of the Dispar zone (Table 1). From the same outcrop, M. Guerrero (unpublished report) has reported Mariella camachoensis BoÈse (a form very similar to M. bergeri) and Hysteroceras sp. Both are late Albian in age.
2.3. West of Acatempan (PN 307, PN 308, PN 309) Three localities are situated about 4 km southwest of Acatempan, on the eastern ¯ank of an unnamed calcareous hill (Figs. 1 and 2). At that locality the uppermost limestone beds are well bedded, ®ne grained calciturbidites with occasional chert bands. Bioclastic packstone-wackestones contain an abundant pelagic microfauna (Hedbergella sp.). The dip is vertical or overturned to the east. Ammonites are small and numerous. They include Lechites moreti, Pervinquieria sp., Desmoceras (Latidorsella) latidorsata, Mortoniceras s.l., Stoliczkaia cf. notha Seeley, S. juv., gr. blancheti P. et C., which indicate the lower part of the Dispar zone (Table 1). 2.4. Zacatlancillo (MF 96) (Fig. 4)
2.2. Acatempan locality (MF 75, PN 211, MF 86) East of Acatempan, the Teloloapan limestones gently dip to the west under the ¯ysch on which the village stands (Figs. 1 and 2). Several fossiliferous occurrences have been found in the highest limestone beds near the boundary with the ¯ysch. MF 75 is a micritic breccia containing Pervinquieria sp. juv. gr. in¯ata and Stoliczkaia cf. tenuis, of late Abian age. Under the cemetery of Acatempan, on the eastern side of the hill, some large specimens (greater than 20 cm. in shell diameter) were discovered by M. Guerrero in the highest limestone beds and have been photographed in situ. They probably belong to the genus Pervinquieria. Other fossiliferous horizons (PN 211), also from a coarse micritic breccia, include smaller forms such as Puzosia aff. mayoriana, Stoliczkaia sp. gr. dispar, and a new species, Falciferella campae nov. sp. In the same facies, MF 86 contains Pervinquieria sp. ind. Turrilitoides hugardianus, and Oxytropidoceras cf. cantianum. The latter probably indicates the lower part of the In¯atum zone. In the mudstone fragments is a well preserved pelagic microfauna including Hedbergella sp. and Colomiella recta. (Fig. 7d).
West of El Pochote, about 12 km from Teloloapan on the road to Arcelia, a fossiliferous locality has been found in a shaly, micaceous facies of the ¯ysch by Campa et al., 1973. From the same locality comes another cast of Hamites sp. gr. intermedius (Fig. 7, Fig. 2). Owing to the higher position of this specimen in the ¯ysch compared to the fauna described in the Teloloapan limestone, the age may be latest Albian to early Cenomanian. 3. Conclusions The uppermost beds of the Teloloapan limestone have yielded late Albian ammonites from several localities (Table 1). Although these occurrences are very close in age, they present signi®cant variations of depositional environment, showing a rapid increase of depth from east to west (Fig. 4). In less than 10 km, the fossiliferous facies changes from a high-energy, condensed limestone horizon with manganese oxides near Concordia, into coarse calcareous breccias with angular limestone clasts east of Acatempan, and then passes westward into well bedded calciturbidites
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Table 1 Stratigraphic position of the different faunas, from east (Concordia, MF82) to west (Acatempan) (see Fig. 1). Slight differences in age may re¯ect facies changes but may also result from incomplete sampling
with cherts. Farther west (Zacatlancillo), away from the slope deposits, basinal facies are represented by the black calcareous mudstones of Amatepec (de Cserna, 1982) containing only badly preserved radiolarians (K. Ishida, pers. comm.). The precise age assignment permitted by the ammonites in the Teloloapan unit (In¯atum zone to lower Dispar zone) helps to constrain the reconstruction of the margin of the Guerrero±Morelos carbonate platform (Fig. 4). Although volcanic activity in the Teloloapan arc ended before Albian, the overlying ¯ysch, though not dated at the top, probably extends into Late Cretaceous. 4. Systematics by R. Busnardo The following descriptions concern the ammonites of the Teloloapan limestones from four localities shown on the
map (Fig. 1) and one from the ¯ysch formation. The most signi®cant specimens are illustrated in Figs. 5±7. Although not exhaustive, this study gives the basic information for genus or species identi®cation. Abbreviations used for measurements, which are given in mm: D diameter; Wh whorl height; Ww whorl width; U Umbilicus. All the specimens are deposited in the collections of the Institute of Geology, University Claude Bernard-Lyon I (Villeurbanne, France). Family: Brancoceratidae Spath 1933 Genus: Pervinquieria Boehm 1910 Pervinquieria rostrata (Sow.) Fig. 5a 1932 Ð Mortoniceras (Pervinquieria) rostratum (Sow.) in Spath, p. 400, pl. XXXVI, ®g. 6; pl. XXXVIII, ®g. 4; pl.
O. Monod et al. / Journal of South American Earth Sciences 13 (2000) 377±388
T E L O L O A P A N
MARGIN
BASIN W
Zacatlancillo MF 96
U N I T
El Pochote
W. Acatempan E. PN307-9 MF75-86, PN211
M E X C A L A
381
GUERRERO -MORELOS PLATFORM
Concordia MF82
E
F L Y S C H
(no scale)
Mexcala Flysch
limestone fragments
Brecciated limestone
Condensed horizon Calcarenites
Amatepec pelagic limestone
Bioclastic limestone
Rudist limestone
Volcanic rocks of the Teloloapan arc
Fig. 4. Tentative pre-tectonic reconstruction of the Teloloapan unit and Guerrero±Morelos Platform during the deposition of the Mexcala Flysch (Late Cretaceous).
XXXIX, ®g. 4; pl. XL, ®gs. 1 and 7; pl. XLII, ®g. 2; text-®g. 130 ®g, 136, 137e. Remarks: A distorded fragment of a large ammonite is referable to Mortoniceras (Pervinquieria) rostratum. Shell diameter of the entire specimen is estimated to have been approximately 200 mm. The example shows simple trituberculate ribs that are characteristic of this species at large shell dimensions. In addition, it shows the upper part of some large and spatulate ribs of the penultimate whorl. The keel is present although it is badly conserved. This species is usually found in the Dispar zone. Locality: Concordia, MF 82 (FSL 108 943). Pervinquieria sp. ind. Remarks: Several fragments referable to Pervinquieria are recognizable by the keel and the more or less tuberculate ribs. Several large specimens having a shell diameter over 200 mm have been left in situ. Locality: E Acatempan PN 211; MF 86 (FSL 108 950, 108 951); W Acatempan PN 308 (FSL 108 935). Pervinquieria sp. juv., cf. in¯ata (Sow.) Fig. 5d and e. 1930 Ð Mortoniceras (Pervinquieria) in¯atum (Sow.) in Spath p. 381, pl. XXXV, ®g. 9; XXXVII, 1; XXXIX, ®g. 2; XLII, ®g. 6; XLIII, ®g. 1; XLVI, ®g. 1±2. Remarks: This species is represented by juveniles and poorly preserved fragments of internal whorls. The specimens have bifurcate ribs with strong umbilical tubercles.
The marginate tubercules are sometimes weakly striped. The keel is prominent. The style of ornamentation observed on those specimens is found in the internal whorls of several species and especially in Pervinquiera in¯ata (Spath 1930, pl. XLII, ®g. 6). These ammonites indicate the In¯atum zone of late Albian age. Locality: E Acatempan, MF 75 (FSL 108 953). Pervinquieria sp. juv., cf. in¯ata (Sow.) Fig. 6d and f. References: see above. Remarks: This form is represented by an external and internal cast of the inner whorls of a small ammonite. The ornamentation may be characterized according to three ontogenetic stages. The ®rst stage, up to 7 mm shell diameter is smooth except for a dense, delicate projected striation. This stage is rarely observed, although it has been noted by Haas (1942, p. 35, pl. IV, ®g. 24 and 27) in Hysteroceras falcicostatum. Stage two, between 7 and 13 mm shell diameter, marks the appearance of the umbilical and marginate tubercles. This ornamentation style is found in Neokentroceras and in some species of Hysteroceras (Cooper and Kennedy 1979, p. 266, ®g. 60). The last stage is greater than 13 mm shell diameter. The ribs connecting the umbilical tubercle to the marginate tubercle appear here. That ornementation is often noted in the literature (see Scholz 1979, pl. 29). This third stage is characteristic for the genus. The material lacks adult
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Fig. 5. (a) Pervinquieria rostrata Sow. (MF 82, FSL 108 943), Vraconnian, 1£. (b) Hamites cf. gardneri Spath. (MF 82, FSL 108 946), Vraconnian, 2£. (c) Pervinquieria juv. (MF 82, FSL 108 941), Vraconnian, 4£. (d±e) Pervinquieria gr. in¯ata Sow. (MF 75, FSL 108 953), Late Albian, In¯atum zone, 2.5£. (f) Desmoceras latidorsatum Mich. (PN 309, FSL 108 937), Late Albian, 2£. (g) Oxytropidoceras cf. cantianum Spath. (MF 86, FSL 108 948), Late Albian, 2.2£. (h) Stoliczkaia cf. tenuis Renz. (MF 75, FSL 108 952), Vraconnian, 2.2£.
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Fig. 6. (a±b) Falciferella campae n. sp. (PN 211, FSL 108 933), section, 2.3£. (c) Lechites moreti Breistr. (PN 307, FSL 108 936), Vraconnian, 2£. (d,f) Pervinquieria juv., gr. in¯ata Sow. (MF 82, FSL 108 940 and 108 942), Vraconnian. 2.3£. (e) Turrilitoides hugardianus d'Orb. (MF 86, FSL 108 949), Vraconnian, 2.2£. (g) Puzosia aff. mayoriana (d'Orb.) (PN 211, FSL 108 934), Late Albian, 2.2£.
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Fig. 7. (a) Stoliczkaia (Faraudiella) cf. blancheti (Pictet et Campiche) (MF 82, FSL 108 947), early Vraconnian, Dispar zone, Blancheti subzone, 1.5£. (b) Hamites sp., gr. intermedius Sow. (MF 96, FSL 108 939), latest Albian or early Cenomanian, Mexcala Flysch Formation, 1.5£. (c) Section of Falciferella campae n. sp., (PN211, FSL108 933), section, 3£. (d) Colomiella recta and Hedbergella sp., thin section in PN211, 60£.
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whorls and ornamentation that are required for speci®c determination. Locality: Concordia, MF 82 (FSL 108 940 and 108 942). Pervinquieria sp. juv. Fig. 5c. Remarks: Pervinquieria sp. juv. occurs in the same locality (MF 82) as the preceding sample and is represented by one specimen, FSL 108 941. The enlarged photograph clearly shows the second growth stage of Pervinquieria, that is to say the ªNeokentrocerasº stage. Several other specimens are visible in the same rock sample. Fig. 6f shows a stage of evolution that is intermediate between stage 2 and stage 3. Genus: Oxytropidoceras Stieler 1920 Oxytropidoceras sp. ind., cf. cantianum Spath. Fig. 5g. 1929 Ð Oxytropidoceras cantianum Spath, p. 350, pl. XXXII, ®g. 4±5; text-®g. 114 a, 115 g, h. Remarks: This species is represented by a fragment of a small ammonite 45 mm in shell diameter. The section is lanceolate and shows a keel. The thin, falcoid and sometimes bifurcate ribs are diagnostic for Oxytropidoceras. An example ®gured by Spath (1929, pl. XXXII, ®g. 5) represents a specimen nearly identical to the one described herein. However the specimen described here is a juvenile ammonite that cannot receive a more speci®c determination. The costation style of the specimen is also present in the internal whorls of O. (Venezoliceras), for example, O. (Venezoliceras) karsteni Stieler (Renz 1982, pl. 17, ®g. 2). Those forms come from Venezuela and are referable to the late Albian, Orbignyi zone. BoÈse (1923, p. 171, pl. XI, ®g. 61±62) has ®gured an Oxytropidoceras ( ªSchlumbachia aff. acutocarinataº) of the same group in the latest Albian (ªVraconnianº). According to the associated fauna, the Mexican specimen may be placed in the lowermost level of the late Albian. Locality: E Acatempan, MF 86 (FSL 108 948). Family: Lyelliceratidae Genus: Stoliczkaia Neumayr 1875 Stoliczkaia (Faraudiella) cf. blancheti (Pictet and Campiche) Fig. 7a. 1979 Ð Stoliczkaia dispar (d'Orbigny) 1841; in Scholz, p. 83, pl. 14 to 20, text-®g. 22±23. Remarks: This is an almost complete, slightly stretched ammonite 60 mm in diameter. The whorl section is narrow. Wh 31; Ww 17; Ww/Wh 0.54. The body chamber represents half a whorl and is almost smooth. The suture, partly visible, is the same as in S. dispar ®gured by Scholz (1979, p. 86, ®g. 23). The umbilical wall bears a row of little tubercles. The middle part of the ¯ank is almost smooth. In the upper third of the whorl are weak and
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bifurcate ribs. In the ®rst part of the ®nal whorl these ribs are straight and dense, and cross over the rounded venter side. In the middle part of the venter the crenated line is weakly visible; this is distinctive of the genus Faraudiella. Scholz (1929) has produced good pictures of S. blancheti which he considers as a subspecies of S. dispar. I prefer recognition of a separate species because of the dense costation that disappears in the body chamber, and particularly because of its stratigraphical position in the lower part of the Dispar zone. Locality: Concordia, MF 82 (FSL 108 947). Stoliczkaia sp. juv., gr. notha Seeley 1979 Ð Stoliczkaia dispar, morphotype notha, in Scholz, pl. 16±19. 1979 Ð Soliczkaia notha in Cooper and Kennedy, p. 263, ®g. 57. Remarks: Several fragments of small ammonites show thick and rounded ribs like those of S. notha. This form has been ®gured by Scholz, not as a species, but as a morphotype of S. dispar sp. They have also been ®gured by Cooper and Kennedy (1979) and by Spath (1929). Speci®c identi®cation is dif®cult, but this material and closely related forms suggest the late Albian Dispar zone. Locality: Concordia, MF 82 (FSL 108 944, 108 945); W Acatempan, PN 308 (FSL 108 935). Stoliczkaia cf. tenuis Renz Fig. 5h. 1968 Ð Stoliczkaia tenuis Renz, p. 48, pl. 6, ®g. 6, and 12. 1979 Ð Stoliczkaia tenuis Renz, in Cooper and Kennedy, p. 249, ®g. 46±53, 54 A±F, 68 E. Remarks: This species is represented by a small, probably juvenile specimen (D 22; U 5; Wh 8; Ww 6). It clearly shows the thin and bifurcate ribs passing to the simple and nearly large ribs characteristic of Stoliczkaia. This species is readily recognizable by its ¯at venter as ®gured in Cooper and Kennedy (1979, see ®g. 47 L, X and P, p. 251, etc). In the Mexican specimen the venter is also ¯at or weakly depressed. Age: Vraconnian. Locality: E Acatempan, MF 75 (FSL 108 952). Family: Binneyitidae Genus: Falciferella Casey 1954 Falciferella campae n sp. Figs. 6a,b and 7c Material: Only one specimen, FSL 108 933: D ?30; U ?9; Wh 14; Ww 7. Locus typicus: Outcrop E Acatempan, PN 211, Guerrero state, Mexico. Stratum typicum: top of Teloloapan Limestone Formation, associated with Pervinquieria sp., Stoliczkaia sp., gr. dispar,
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Puzosia mayoriana, ammonites of late Albian age, probably in the lower part of the Dispar zone. Derivatio nominis: dedicated to Dra. Maria-Fernanda Campa, who ®rst proposed a Cretaceous age for the Teloloapan volcanic rocks (1973). Description and diagnosis: This new species is represented by one specimen preserving the third of a whorl. The umbilicus is middle sized, the ¯anks are almost ¯at, and the section is high. The ventral area is weakly rounded, without keel or furrow. The costation is falcoid. The lower part of the side is smooth; in the middle part, weakly concave primary ribs are apparent; in the upper part there are numerous delicate and prorsiradiate ribs which cross over the siphuncle area. The suture is not visible. Comparison: The falcoid costation is typical for the Aconeceratinae; see: Aconeceras nisoides (Sarasin), Sammartinoceras falcatum (v. Koenen), S. trauscholdi (Sinzow) in Spath (1961), and Aconeceras austronisoides Brunnschweiler (1959, Fig. 5.1). However, all those species are of Aptian age and, above all, their section is ogival, sometimes with a keel. This is not the case of the section of our Mexican ammonite. In the earliest Hyphoplites of Vraconnian age (for example H. coelonotus (Seeley) in Scholz (1979, pl. 13), the same kind of costation is present. But those forms are Hoplitids with a distinctive ventral furrow, which is not present in our specimen. The falcoid costation, the high section, and the almost ¯at ventral area are features belonging to the genus Falciferella. But no species of this genus, which was studied by Casey (1954, 1961) or by Brunnschweiler (1959), seems identical with our specimen. That is the reason why I propose this highly distinctive new species even though it is based on a single specimen. Many species of Falciferella are known in England in the middle Albian, and in the late Albian in Australia. It is interesting to identify a new species of Falciferella of late Albian age in Mexico. According to Cobban (1961), this genus belongs to the Binneyitidae and is frequent in North America in the Cenomanian. Juignet and Kennedy (1976) and Kennedy and Juignet (1973, 1984) have recognized the same family in the Cenomanian in France. Family: Desmoceratidae Genus: Desmoceras Zittel 1884 Desmoceras latidorsatum Michelin Fig. 5f. 1968 Ð Desmoceras latidorsatum (Michelin), in Renz, p. 20, pl. 1, ®g. 12. 1968 Ð D. latidorsatum (Michelin), in Wiedmann, p. 131, pl. 12, ®g. 2, 6±13. 1979 Ð D. latidorsatum (Michelin), in Scholz, p. 61. 1982 Ð D. latidorsatum (Michelin), in Renz, p. 36, pl. 5, ®g. 1±9.
1988 Ð D. latidorsatum (Michelin), in Delanoy and Latil, pl. 1, ®g. 1ab. Remarks: This highly variable species is ubiquitous and has been described and ®gured many times in the literature. In our small specimen (D 17; U 4.5; Wh 6; Ww 6) the section is not so low as in the other examples referred to D. latidorsatum. The constrictions are underlined by a weak rim. The ®rst whorls are smooth. The specimen is a small juvenile. This species is frequent in the late Albian. Locality: W Acatempan, PN 309 (FSL 108 937). Genus: Puzosia Bayle 1878 Puzosia aff. mayoriana (d'Orbingy) Fig. 6g. 1841 Ð Ammonites mayorianus d'Orb., p. 267, pl. 79, ®g. 1±3. 1923 Ð Puzosia mayoriana (d'Orb.), in Spath, p. 42, Pl. I, ®g. 9±10. 1979 Ð Puzosia planulata (Sow.), in Scholz, p. 63, pl. 11, pl. 12, pl. 13, ®g. 2, text-®g. 19±20. Remarks: We have only half a whorl of a small ammonite which looks like a juvenile Puzosia mayoriana (D 36; U 13.4; Wh 13.2; Ww 12). It shows weak falcoid constrictions and thin fasciculate ribblets between them. Spath (1923) has ®gured almost identical material. According to Scholz (1979), these forms belong to the same population, which includes 18 species and subspecies that are described in the literature. Puzosia mayoriana is frequent and ubiquitous in the late Albian. Locality: E Acatempan, PN 211 (FSL 108 934). Family: Baculitidae Genus: Lechites Nowak 1908 Lechites moreti Breistroffer, Fig. 6c 1936 Ð Lechites moreti Breistroffer, p. 66. 1957 Ð Lechites moreti Breistr., in Busnardo, p. 116, pl. III, ®g. 3. 1968 Ð Lechites moreti Breistr., in Renz, p. 81, pl. 16, ®g. 10, 12, 13, text-®g. 29 a, i. 1979 Ð Lechites gaudini moreti Breistr., in Scholz, p. 14, pl. 1, ®g. 10, text-®g. 5C. 1988 Ð Lechites moreti Breistr., in Delanoy and Latil, p. 752, pl. 1, ®g. 4. Remarks: Several small and juvenile fragments of this species are found in the neritic limestone west of Acatempan. In the ®gured sample, 31 mm long, we clearly see the oblique furrows and striae which are diagnostic for the species. In the literature the authors have ®gured adult forms. Here we see the striae of a juvenile shell. This pelagic and ubiquitous species is usually reported in the Vraconnian. Locality: W Acatempan, PN 307 and PN 308 (FSL 108 936).
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Genus: Hamites, Parkinson 1811 Hamites cf. gardneri Spath Fig. 5b. 1941 Ð Hamites gardneri Spath, p. 624, ®g. 225; pl. LXX, ®g. 3±5. Remarks: The Mexican specimen is a small criocone 23 mm long. It shows ®ne, dense costation with simple and straight ribs. The section is oval. This form is close to H. gardneri Spath. In the Mexican criocone, however, the costation is more dense (14 ribs per cm against 8 ribs per cm in Spath ®gure 225d, in the same ontogenetic stage). The juvenile forms are evidently dif®cult to determine. BoÈse (1923, pl. IX, X) has ®gured several species of Hamites with thin and simple ribblets, found in the Vraconnian of Camacho (Mexico), although the ®gures are imperfect and do not provide a good comparison. From the Vraconnian of Venezuela, Renz (1982, p. 60, pl. 20, ®g. 6abc, text-®g. 42) has described a small example of Hamites sp. that is closely similar to our specimen. Locality: Concordia, MF 82 (FSL 108 946). Hamites cf. maximus Sow. 1941 Ð Hamites maximus Sowerby, in Spath, p. 621, text-®g. 224; pl. LXVIII, ®gs. 15, 16, 20; pl. LXIX, ®g. 1±9; pl. LXX, ®g. 1, 18. Remarks: A short fragment of an uncoiled ammonite having only some straight and thick ribs is close to H. maximus ®gured by Spath (1941, pl. LXIX, ®g. 3). Locality: Concordia, MF 82 (FSL 108 945). Hamites sp. gr. intermedius Sow. Fig. 7b. 1941 Ð Hamites intermedius Sow., in Spath, p. 630, ®g. 229; pl. LXX, ®g. 19±20; pl. LXXI, ®g. 3±6. 1923 Ð Hamites intermedius Sow., in BoÈse, p. 132, pl. IX, ®g. 46±49. Remarks: The specimen is a small, almost complete, hamitiform uncoiled ammonite 48 mm long. It is a slightly stretched external cast in a yellowish shale of the Mexcala Formation. The ribs are simple, acute and weakly oblique. The same costation is found in H. intermedius ®gured by Spath (1941), especially in his pl. LXX, ®g. 19±20. Our specimen is smaller. Hamites intermedius occurs in the late Albian in England, although a lower Cenomanian age is not excluded here. BoÈse (1923) has found the same species in the Vraconnian of Camacho (Mexico). Locality: Zacatlancillo, MF 96 (FSL 108 939). Family: Turrilitidae Genus: Turrilitoides Spath 1923 Turrilitoides hugardianus (d'Orbigny) Fig. 7e.
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1842 Ð Turrilites hugardianus d'Orbigny, p. 588, pl. 147, ®g. 9±11. 1979 Ð Turrilites hugardianus (d'Orb.), in Scholz, p. 34, pl. 7, ®g. 1±14, 16. 1990 Ð Turrilites hugardianus (d'Orb.), in Marcinowski and Wiedmann, p. 50, pl. 4, ®g. 9±10. Remarks: This specimen consists of a third of a whorl of a turricone. We see the relatively strong and oblique ribs, without tubercles, that are distinctive of this species. They partly divide in the outer part of the whorl, as in the form ®gured by Scholz (1979, pl. 7, ®g. 7). This species is frequent in the lower Vraconnian (Blancheti subzone) of the Bakony Mountains (Hungary). Locality: E Acatempan, MF 86 (FSL 108 949). Acknowledgements This work was supported by CNRS-UMR 6530 in a joint project of cooperation between Universidad Autonoma de Guerrero (UAG), Mexico, and the University of Orleans, France. David Taylor and A.B. Villasenor have suggested many useful improvements to the manuscript. The authors also express their gratitude to N. Laurent-Rouchon for the drawings and to N. Podevigne for the excellent photographs. References BoÈse, E., 1923. Algunas Faunas Cretacicas de Zacatecas, Durango y Guerrero. Instituto Geologico de Mexico, Boletin 42, 224. BoÈse, E., 1927. The Cretaceous ammonites from Texas and Northern Mexico. Texas University, Bulletin 2748, 143±312. Breistroffer, M., 1936. Les subdivisions du Vraconnien dans le Sud-Est de la France. SocieÂte GeÂologique de France, SeÂr. 5 Bulletin 6, 63±68. Brunnschweiler, R.O., 1959. New Aconeceratinae (Ammonoidea) from the Albian and Aptian of Australia. Bureau of Mineral Resources Bulletin, Canberra, 19. Busnardo, R., 1957. Contribution aÁ l'eÂtude des faunes d'ammonoIÈdeÂs de Medjez Sfa (Est Constantinois). Service de la Carte GeÂologique d'AlgeÂrie, Bulletin 13, 67±123. Campa, M.F., Campos, M., Flores, R., Oviedo, R., 1973. La sequencia Mesozoica vulcano-sedimentaria metamor®zada de Ixtapan de la Sal (Mex)-Teloloapan (Gro). Sociedad Geologica Mexicana, Bulletin 35, 7±28. Campa, M.F., Ramirez, J., 1979. La Evolucion Geologica y la MetalogeÂnesis del Noroccidente de Guerrero. Universidad Autonoma de Guerrero, Serie TeÂcnico-Cienti®ca 1, 84. Casey, R., 1954. Falciferella, a new genus of Gault ammonites, with a review of the family Aconoceratidae in the British Cretaceous. Proceedings of the Geologist Association 65 (3), 262±277. Casey, R., 1961. A Monograph of the Ammonoidea of Lower Green-Sand. Paleontographical Society Part 3, 119±216. Cobban, W.A., 1961. The ammonite family Binneyitidae Reeside in the western interior of the United States. Journal of Paleontology 35 (4), 737±758. Cooper, M.R., Kennedy, W.J., 1979. Uppermost Albian (Stoliczkaia Dispar zone) Ammonites from the Angola littoral. Annals of the South African Museum 77 (10), 175±308. de Cserna, Z., 1978. Notas sobre la geologia de la region comprendida entre Iguala, Cd. Altamirano y Temascaltepec, Edos de Guerrero y Mexico.
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In: Libro Guia de la Excursion Geologica a Tierra Caliente, IV Convenio Nacional de Mexico. Sociedad Geologica Mexicana, 125pp. Delanoy, G., Latil, J.L., 1988. DeÂcouverte d'un nouveau gisement albien dans les environs de Drap (Alpes Maritimes, France) et description d'une riche ammonitofaune d'aÃge Albien terminal. Geobios 21 (6), 749±771. Fries, C., 1960. Geologia del Estado de Morelos y de Partes Adjacentes de Mexico y Guerrero, Region Central Meridional de Mexico. UNAM Instituto de Geologia, Bulletin 60, 236pp. Guerrero, M., Ramirez, J., Talavera, O., Campa, M.F., 1991. El desarollo carbonatado del CretaÂcico inferior asociado al arco de Teloloapan, Noroccidente del Estado de Guerrero. Abstracts, Convention sobre la Evolution Geologica de Mexico, p. 67. Sociedad Mexicana de Mineralogia and UNAM Instituto de Geologia. Jacob, C., 1907. Etude sur Quelques Ammonites du CreÂtace Moyen. SocieÂte GeÂologique de France, MeÂmoire 38, 63. Juignet, P., Kennedy, W.J., 1976. Faunes d'Ammonites et Biostratigraphie CompareÂe du CeÂnomanien du Nord-Ouest de la France (Normandie) et du Sud de l'Angleterre. SocieÂte GeÂologique de Normandie, Bulletin 63 (2), 193. Kennedy, W.J., Juignet, P., 1973. First record of the ammonite family Binneyitidae Reeside 1927 in Western Europe. Journal of Paleontology 47 (5), 900±902.
Kennedy, W.J., Juignet, P., 1984. Revision of the ammonite faunas of the type Cenomanian. 2. The families Binneyitidae, Desmoceratidae. Cretaceous Research 5, 93±161. Marcinowski, R., Wiedmann, J., 1990. The Albian Ammonites of Poland. Palaeontologia Polonica 50, 94. d'Orbigny, A., 1840±1842. Terrains CreÂtaceÂs. I. CeÂphalopodes. PaleÂontologie FrancËaise. Masson, Paris (662pp.). Renz, O., 1968. Die Ammonoidea im Stratotyp des Vraconnien bei SainteCroix (Kanton Waadt). MeÂmoires Suisses de PaleÂontologie 87, 97. Renz, O., 1982. The Cretaceous Ammonites of Venezuela. Birkhauser, Basel, Switzerland (132pp.). Scholz, G., 1979. Die Ammonites des Vracon (Oberalb, Dispar Zone) des Bakony Gebirges (Westungarn). Paleontographica Ser. A 165, 136. Spath, L.F., 1923±1930. Ammonoidea of the Gault. Paleontological Society of London 1, 311. Spath, L.F., 1931±1943. Ammonoidea of the Gault. Paleontological Society of London 2, 313±787. Talavera, O., 1993. Les Formations OrogeÂniques MeÂsozoIÈques de Guerrero (Mexique MeÂridional). TheÁse Universite Grenoble, 462 pp. Wiedmann, J., Dieni, I., 1968. Die Kreide Sardiniens und ihre Cephalopoden. Paleontologia Italica 64, 1±171.