Upper Aptian-Lower Albian Mural Formation: Stratigraphy, Biostratigraphy and Depositional Cycles on the Sonoran Shelf, Northern Me´Xico

Cretaceous Research 29 (2008) 249e266 www.elsevier.com/locate/CretRes

Upper Aptian-Lower Albian Mural Formation: stratigraphy, biostratigraphy and depositional cycles on the Sonoran shelf, northern Me´xico

Carlos M. Gonza´lez-Leo´n a,*, R.W. Scott b, Hannes Lo¨ser a, Timothy F. Lawton c, Emmanuel Robert d, Victor A. Valencia e

a ERNO, Instituto de Geologı´a, Universidad Nacional Auto´noma de Me´xico, Apartado Postal 1039, Hermosillo, Sonora, Me´xico 83000 b Precision Stratigraphy Associates and Tulsa University, RR3 Box 103-3, Cleveland OK 74020, USA c Department of Geological Sciences, New Mexico State University, Las Cruces, NM 88003, USA d Observatoire des Sciences de l’Univers de Grenoble (OSUG), Universite´ Joseph Fourier, Institut Dolomieu, 15 rue Maurice Gignoux, F-38031 Grenoble, cedex, France e Department of Geosciences, The University of Arizona, Tucson, AZ, 85721, USA Received 3 April 2007; accepted in revised form 16 May 2007 Available online 27 June 2007

Abstract

The Upper Aptian-Lower Albian Mural Formation of the Bisbee Group in northern Sonora consists of eight members, in ascending order the Fronteras, Rancho Bufalo, Cerro La Ceja, Tuape Shale, Los Coyotes, Cerro La Puerta Shale, Cerro La Espina and Mesa Quemada. These members represent shallow marine facies of a major marine transgressive-regressive event that reached the Bisbee basin, except for the Rancho Bu- falo Member which is a tongue of the fluvial Morita Formation that underlies the Mural Formation. The facies, succession and regional correlation of its members indicate that deposition of the Mural Formation occurred in northern Sonora on a broad carbonate shelf, the Sonoran shelf, where depositional environments varied from restricted shelf with local terrigenous deltaic and fluvial influence to open shelf with coral- rudist buildups, to offshore shelf. Facies of the Mural deepen across eastern Sonora into the Chihuahua trough and the formation pinches out northwestward in Sonora. The Sonoran shelf was flooded by three long-term depositional cycles of approximately 2.5 myr duration. The first cycle deposited the Fronteras and Rancho Bufalo members and is older than 115.5 Ma, about 118 Ma. The marginal to shallow marine deposits of the Fronteras Members disconformably overlie fluvial strata of the Morita Formation and are sharply overlain by fluvial deposits of the Ran- cho Bufalo Member. The second cycle deposited the Cerro La Ceja, Tuape Shale and Los Coyotes members and probably embraces the Aptian/ Albian boundary; the Cerro La Ceja Member disconformably overlies the Rancho Bufalo Member and Morita Formation in northeastern Sonora but gradationally overlies the Morita in the sections of north-central Sonora. The third cycle deposited the Cerro la Puerta Shale, Cerro la Espina and Mesa Quemada members and is Early Albian in age. The Mesa Quemada Member is gradationally overlain by fluvial deposits of the Cintura Formation. Biostratigraphy is based on ammonites, bivalves, gastropods, benthic and planktic foraminifers, and colomiellids and two biozones are erected to correlate the measured sections. Ó 2007 Elsevier Ltd. All rights reserved.

Keywords: Mural Formation; Sonoran Shelf; Aptian-Albian; Sonora; Me´xico

1. Introduction

* Corresponding author. During the Late Jurassic, the Bisbee basin began to develop E-mail addresses: [email protected] (C.M. Gonza´lez-Leo´n), [email protected] (R.W. Scott), [email protected] (H. Lo¨ser), in southeastern Arizona, USA and northeastern Sonora (north- [email protected] (T.F. Lawton), [email protected] (E. west Mexico) as an extension of the northwest-trending Robert), [email protected] (V.A. Valencia). Chihuahua trough (Bilodeau, 1982; Dickinson et al., 1986)

(Fig. 1). The Chihuahua and Bisbee basins were structural Ma (Rb/Sr) (Kluth et al., 1982; Asmerom et al., 1990), and basins controlled by a mechanism, either extensional (Bilodeau, at one locality in the Chiricahua Mountains (Fig. 1), conglom- 1982; Dickinson et al., 1989; Dickinson and Lawton, 2001)or eratic strata are overlain by fossiliferous marine strata and vol- transtensional (Haenggi, 2002; Anderson and Nourse, 2005; canic flows of the Crystal Cave Formation, which contains Haenggi and Muehlberger, 2005), that remains debated. The ammonites of Kimmeridgian age (Lawton and Olmstead, sedimentary fill of the Bisbee basin is the Upper Jurassic-Lower 1995; Olmstead and Young, 2000). In central Sonora the oldest Cretaceous Bisbee Group (Ransome, 1904), composed in as- unit that fills the Altar-Cucurpe basin is the Cucurpe Forma- cending order of the Glance Conglomerate and Morita, Mural tion (Fig. 1), a marine sedimentary succession with subordi- and Cintura Formations (Fig. 1). nate volcanic rocks and late Oxfordian to early Tithonian Coeval with formation of the Bisbee basin, the similar ammonites (Villasenor~ et al., 2005). The Glance Conglomerate Altar-Cucurpe basin (Lawton et al., 2003; or the Arivechi- is present on the northern flank of this basin near the Cananea Cucurpe seaway of Haenggi and Muehlberger, 2005) devel- high, where it underlies Lower Cretaceous red beds, and is oped in central Sonora (Lawton et al., 2004a,b; Mauel et al., correlated with the Altar Formation in the northwestern part 2005; Leggett et al., 2005; Peryam et al., 2005)(Fig. 1). In of the basin (Nourse, 2001) (Fig. 1). the Jurassic, the two basins were separated by the northwest- By Early Cretaceous time, a second marine transgression trending Cananea high, which lacks an Upper Jurassic section reached central Sonora to deposit the La Colgada Formation that is present to the north and south (McKee and Anderson, (Gonza´lez-Leoń et al., 2001) which unconformably overlies 1998). the Cucurpe Formation. The La Colgada Formation is a shal- In southeastern Arizona, the fluvial Glance Conglomerate low marine, siliciclastic unit laterally equivalent to the Late contains interbedded volcanic flows that are dated at w151 Neocomian-Early Aptian Cerro de Oro Formation of the Cerro

Fig. 1. Location map and line of correlation of the studied sections of the Mural Formation in Sonora, and other localities mentioned in the text. (1) Sierra El Chanate; (2) El Ocuca; (3) Cerros Pimas; (4) Santa Ana; (5) Santa Marta; (6) Tuape; (7) Sierra San Jose´; (8) Rancho Bufalo; (9) Cerro Caloso Cabullona; (10) Cerro El Caloso Pitaycachi; (11) Cerro de Oro; (12) Lampazos. Also shown is the lithostratigraphic succession of the Bisbee Group in the different regions of, and limits of, the Bisbee basin. C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 251 de Oro area (Gonza´lez-Leoń, 1989; Gonza´lez-Leoń and Lucas, Sierra San Jose´, Rancho Bufalo (Rancho Culantrillo area stud- 1995)(Fig. 1). The younger units of the Bisbee Group, the ied by Rosales-Domıńguez et al., 1995), and Cerro El Caloso Morita, Mural and Cintura formations, are lithologically sim- Pitaycachi area (Fig. 1). ilar north and south of the Cananea high and are distributed On the southwestern margin of the Bisbee basin, in central from southeastern Arizona through northern Sonora (Fig. 1). Sonora, the Mural Formation crops out in several ranges, and The widespread distribution of these units indicates that by there we measured new sections in localities at Sierra El Cha- the Early Cretaceous time, the Bisbee basin had merged nate, El Ocuca, Cerro Pimas, Santa Ana and Santa Marta with the Altar-Cucurpe basin. The Morita and Cintura Forma- (Fig. 1). Previously, in the Tuape area (locality 6 in Fig. 1), tions are fluvial red beds whereas the Mural Formation con- Lawton et al. (2004a) divided the Mural Formation into five sists of carbonate and siliciclastic strata that were deposited members that include, from base up the Cerro La Ceja, Tuape in a shallow marine setting. The stratigraphic succession of Shale, Los Coyotes, Cerro La Puerta Shale, Cerro La Espina, these three units indicates an important transgressive- and Mesa Quemada members. These members can be corre- regressive event of the Mexican Sea into northwestern Mexico lated, allowing for minor facies changes through northern and southwestern USA. Sonora (Fig. 2) for which in the Sierra El Chanate Jacques- This study presents results and interpretations of a detailed Ayala (1989) named the Mural Formation as the Arroyo and regional stratigraphic and biostratigraphic analysis of the Sa´sabe Formation. In this work we also recognize two new Mural Formation in northern Sonora to contribute to under- members, the Fronteras and the Rancho Bufalo Members in stand its depositional history. Although the Bisbee Group the lower part of the Mural in the Rancho Bufalo section has been studied in several places, only two previous studies (Fig. 2); in the Cerro El Caloso Pitaycachi section (Fig. 2) of the Mural Formation have been reported. Warzeski (1983) we recognize the members proposed by Warzeski (1987). studied the upper part of the Mural in northeastern Sonora and Lawton et al. (2004a) studied it in central Sonora. In this study we measured several well exposed sections of the 2.1. Fronteras member Mural Formation in a 300 km-long transect that extends from its westernmost known exposure in the Sierra El Chanate The 134-m-thick Fronteras Member is the basal member of area, to one of the northeasternmost outcrops in the Cerro El the Mural Formation. This newly designated member is pres- Caloso Pitaycahi locality (Fig. 2). The sections were measured ent only at Rancho Bufalo (Fig. 2). It sharply overlies dark with a Jacob’s staff to determine their lithostratigraphy and reddish siltstone of the fluvial Morita Formation. At its base rock samples and fossils were collected for petrographic and is a 7 m-thick, upward-thinning and -shallowing carbonate cy- paleontologic analyses (Appendix 1 for locations of measured cle composed in its lower part of medium-bedded, oolitic sections; species-list available upon request). Among the fos- grainstone with planar cross-stratification and in its upper sils that were identified for biostratigraphic interpretations are part of thick to medium beds of bioclastic and oolitic pack- bivalves, ammonites, gastropods, calcareous algae and forami- stone, shaly bioclastic wackestone with oysters, sandy, biotur- nifera. The biostratigraphic ages are complemented by two ra- bated wackestone and calcareous shale. The limestone beds diometric ages obtained from zircon separates that were dated are mostly medium- to coarse-grained, poorly sorted, with from different ash-fall tuff intervals. We correlate the Mural micrite-coated grains of dasyclad algae, encrusting algae, mil- Formation by recognizing its members (Warsezki, 1987; Law- iolids, bivalves, gastropods, ostracodes, and echinoid spines. It ton et al., 2004a and discussion below) in the measured sec- is overlain by a 6 m thick set of medium-bedded, yellowish tions, define biostratigraphic zones to permit correlation of brown dolomitic limestone with stromatolitic laminated the sections throughout the Gulf of Mexico region and Carib- beds, and locally sandy beds that are overlain by 20 m of yel- bean Province and delineate longer-term depositional cycles. lowish brown to light gray siltstone, calcareous shale and mi- nor intercalations of thin-bedded, fine-grained sandstone and 2. Lithostratigraphy white tuffaceous shale. The middle and upper parts of this member are dominated The Mural Formation that crops out at numerous localities by upward-thinning and -shallowing carbonate cycles up to in southeastern Arizona was first studied by Ransome (1904) 12 m thick that are composed of bedsets of medium- to who divided it into lower and upper parts. This unit extends thick-bedded oolitic limestone with planar cross-stratification southward into northeastern Sonora where it is well exposed and local herringbone cross-stratification that grade upward in the Sierra San Jose´, Sierra Anibacachi and its southeastward to bioclastic wackestone-packstone, oyster coquina beds, extension, the Cerro Caloso Cabullona (Fig. 1). Warzeski sandy to argillaceous bioturbated limestone, stromatolitic (1983) conducted a detailed study of the upper part of the Mu- beds, and dolomitic bioturbated limestone. The cycles are ral Formation in the Sierra Anibacachi, and at Cerro Caloso he overlain by dark gray shale and siltstone. Fossils in these rocks divided it into five members: Canova, El Caloso, Angostura, include articulated and disarticulated oysters, trigoniids, pecti- La Aguja, and Agua Prieta members. Warzeski (1987) and nids and other bivalves, and scarce benthic foraminifera and Scott and Warzeski (1993) interpreted that these members re- algae. A white ash-fall tuff bed, 1 m thick is present in the up- cord a shallow shelf that deepened to the southeast. In north- per part of this member. The uppermost 6 m of this member eastern Sonora we measured in detail three new sections in the consist of yellowish gray calcareous siltstone with bivalve 252 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266

Fig. 2. Regional east-west lithostratigraphic cross section that shows correlation of the members of the Mural Formation and key biostratigraphic data. The sections at Tuape and Cerro Caloso Cabullona are from Lawton et al. (2004a,b) and Warzeski (1983), respectively. fragments overlain by sandstone of the Rancho Bufalo grained and cross-stratiﬁed sandstone beds up to 4 m thick, Member (Fig. 2). with erosive bases.

2.3. Cerro La Ceja member 2.2. Rancho Bufalo member The Cerro La Ceja Member is typically terrigenous in its The Rancho Bufalo Member is a siliciclastic unit that is lower part and oyster-rich limestone in its upper part only present at Rancho Bufalo (Fig. 2). It is 86 m thick and (Fig. 2). This member ranges in thickness from 12 m in the its basal sandstone beds are in sharp contact with the underly- Sierra el Chanate to 182 m in the Tuape area (Arroyo Los ing Fronteras Member. Its lower part is composed of a Coyotes section of Lawton et al., 2004a, fig. 5) (Table 1). 6 m-thick, upward-fining set of thick- to thin-bedded, reddish The basal strata of the Cerro La Ceja Member at Rancho sandstone with planar cross-stratification and reactivation Bufalo and Sierra San Jose´ consist of a 12 m-thick interval surfaces. The remainder of this member is composed of red- of stacked, thick, wedge-shaped beds of quartz-rich sandstone dish to purple shale and siltstone with local bioturbation, with large-scale, planar- and trough-cross stratification that root structures and calcareous nodules of interpreted pedo- sharply overlie red shale and siltstone of the Rancho Bufalo genic origin. The shale and siltstone form intervals up to Member and of the Morita Formation, respectively. The basal 20 m thick and have interbeds of upward-fining sets of beds of this package have mud clasts lenses derived from the medium- to thick-bedded, lenticular, medium- to coarse- underlying lithologies. At other localities (Fig. 2) the Morita C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 253

Fig. 2 (continued).

Formation, which consists of red, fluvial shale and siltstone, et al. (2004a,b) reported Immunitoceras sp. aff. I. immunitum grades into the Cerro La Ceja Member, which includes calcar- (Stoyanow) and Burckhardtites sp. eous, strongly bioturbated (Planolites and Chondrites), yel- Most of the middle part of the Cerro La Ceja Member is lowish brown to green shale and siltstone with local flaser dominated by interbedded siltstone and shale, thin beds of bedding and wood fragments in its lower part. fine- to medium-grained sandstone and lenticular, thin- to Above these basal strata, the Cerro La Ceja Member grades medium-bedded, locally sandy, oyster coquina with gastro- into thin- to medium-bedded bioclastic wackestone and grain- pods, trigoniids and pectinids. Locally, lenticular, channelized stone (calcarenite to calcirudite) and interbedded light gray to beds of upward-fining, coarse-grained sandstone in medium to green shale and siltstone that attain a maximum thickness of thick bedsets, up to 4 meters thick are present at Santa Ana 36 m. From this interval in the Tuape section we collected and Cerro Pimas. Sandstone beds with herringbone cross strat- the ammonite Eodouvilleiceras adkinsi (Scott) and Lawton ification are locally present. We collected the ammonites 254 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266

Table 1 Thickness of the Mural Formation in northern Sonora Member Locality Sierra Tuape Santa Santa Cerro El Sierra El Rancho San Jose´ Ana Marta Pimas Ocuca Chanate Bufalo Fronteras 134 0 0 0 0 0 0 0 Rancho Bufalo 86 0 0 0 0 0 0 0 Cerro La Ceja 119 57 182 98 70 57 50 12 Tuape Shale 101 80 130 210 212 93 205 13 Los Coyotes 97 44 171 99 76 54 75 9 Cerro La Puerta 54 58 112 35 32 123 116 7 Cerro La Espina 30 (incomplete) 158 94 174 80 33 54 0 Mesa Quemada e 33 104 20 42 60 140 25 TOTAL 621 430 793 636 512 420 640 66

Immunitoceras immunitum in the Santa Ana section and Immu- At Rancho Bufalo, the Los Coyotes Member is composed nitoceras sp. in the Tuape section. The upper 20 m of the of thin- to medium-bedded, bioturbated shaly wackestone Cerro La Ceja Member includes distinctive interbedded co- with interbedded dark-gray shale that weathers yellowish quina floatstone, dolomitic limestone beds and calcareous brown. Trigoniid bivalves and articulated to fragmented oys- shale. The coquina is bioturbated and medium- to thick- ters are present in the wackestone and articulated oysters are bedded with abundant articulated and disarticulated oysters common in the shale. that are abraded and poorly sorted. In central Sonora this member grades to interbedded limestone, shale and siltstone. At Santa Marta it consists of yellow- 2.4. Tuape Shale ish brown to light gray and green, bioturbated shale with calcareous nodules and interbedded medium to thick beds of The Tuape Shale gradationally overlies the Cerro La Ceja shaly wackestone-packstone calcarenite to rudstone with bio- Member (Fig. 2) and ranges in thickness from 212 m at Santa clasts of oyster, other bivalve, gastropods, echinoderms and fo- Marta to 13 m in the Sierra El Chanate (Table 1). At Rancho raminifera including Orbitolina. Interbedded siltstone occurs Bufalo, the Tuape Shale is composed of dark gray to black, lo- in beds up to 4 m thick and in thin beds with ripple cross cally laminated shale that weathers yellowish brown and dark laminations. gray to green with calcareous nodules and interbeds of lami- At Santa Ana and Cerro Pimas, the Los Coyotes Member is nated siltstone and shaly limestone beds. Large articulated composed of four lithologies. 1) Very thick, lenticular beds of oysters and pectinids are common; ammonites occur locally. packstone-grainstone (calcarenite to rudstone with bioclasts of The ammonites Immunitoceras immunitum (Stoyanow), Hypa- colonial corals, bivalves, gastropods, echinoderms, sponges, canthoplites ceratitosus Scott, Hypacanthoplites sp., Paraho- algae, crinoids, bryozoans, and benthic foraminifera) and local plites fasciculatus (Scott) and Parahoplites sp. juv. were thick beds of rudist congregations up to 30 m thick; 2) thick recovered from the Rancho Buffalo and Tuape sections beds of oolitic packstone-grainstone; 3) wackestone (calcaren- (Lawton et al., 2004a; this paper). ite) with benthic and planktic foraminifera; 4) calcareous In other measured sections this member is composed of bi- shale. At Santa Ana and Cerro Pimas we found the Lower Al- oturbated, yellowish brown to greenish calcareous shale and bian rudist, Coalcomana ramosa (Boehm). In the Tuape area, siltstone with abundant large, articulated oysters. These rocks calcareous siltstone and mudstone and interbedded bioclastic have intercalations of thin to medium beds of planar cross- to shaly limestone with oysters are the dominant lithologies stratified siltstone, very fine-grained sandstone beds, biotur- (Lawton et al., 2004a). bated, lenticular, bioclastic wackestone with oysters (e.g., At El Ocuca, the lower part of this member is composed of the El Ocuca section), lenticular, thin- to medium-bedded bio- gray to greenish calcareous shale and siltstone with plant frag- clastic, sandy rudstone and bioturbated thin beds of silty shale ments and minor interbeds of thin to thick, lenticular beds of with abundant thin-shelled bivalves. Trigoniids and small gas- fine-grained sandstone. Its upper part is composed of yellow- tropods are locally present. At Santa Ana, abundant complete ish green to reddish and greenish shale with minor medium in- bivalves include Quadratotrigonia guildi (Stoyanow), Rutitri- terbeds of lenticular siltstone. Lenticular and incised beds of gonia weaveri (Stoynow), Cucullaea gratiota Hill, Gervillaria sandstone with large wood logs (up to 2 m long by 60 cm alaeformis Sowerby and Scabrotrignia stolleyi (Hill). thick) occur locally. The uppermost 15 m of this member is dominated by bioturbated shaly limestone and lenticular, bio- 2.5. Los Coyotes member clastic sandy and dolomitic limestone with abundant gastropods, oysters and trigoniids. The Los Coyotes Member gradationally overlies the Tuape The Los Coyotes Member at Sierra San Jose´ resembles its Shale and varies in thickness from a maximum of 171 m at counterpart in the section at El Ocuca. The lower part of this Arroyo Los Coyotes in the Tuape area (Lawton et al., member is composed of siltstone and parallel-laminated to bi- 2004a) to 9 m in the Sierra El Chanate. oturbated shale with local thin-shelled bivalves and minor C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 255 interbeds of fine-grained, calcareous sandstone. In the middle Santa Ana; it is absent by pinch out in the Sierra El Chanate part of the member there are intercalated thin- to medium- (Fig. 2, Table 1). It consists of thick-bedded limestone that bedded, lenticular, bioclastic limestone and subordinate fine- forms prominent hogbacks in the mountain ranges of northern grained sandstone with ripple cross-stratification. The upper Sonora. part of this member is composed of green to brown shale At Sierra San Jose´, the lowermost 7 meters of this member and siltstone with minor intercalations of thin- to medium- consist of thick-bedded wackestone-packstone with foraminif- bedded, fine-grained sandstone. The upper 6 m of this member era, intraclasts, pellets and micrite-rimmed grains of bivalves, is dominated by shaly, bioclastic limestone with oyster and gastropods and corals that passes upwards to a 53 m-thick in- other bivalve fragments. terval of poorly bedded wackestone-packstone rudstone with local rudist and coral boundstones. The middle part of this 2.6. Cerro La Puerta Shale member is dominated by very thick beds of bioturbated, locally sandy, poorly sorted calcarenite to rudstone wacke- The Cerro La Puerta Shale (Fig. 2) gradationally overlies stone-packstone with micritized grains of rudists, corals, the Los Coyotes Member and ranges in thickness from echinoderms, bivalves, intraclasts, pellets, and Orbitolina. 123 m at Cerro Pimas to 7 m in the Sierra El Chanate section Intercalated rudist and coral boundstones beds are as much (Table 1). as 6 m thick. The uppermost 40 m of this member consists At Rancho Bufalo, the Cerro La Puerta Shale consists of of medium to thin beds of shaly wackestone with articulated light- to dark-gray shale that weathers dark to yellowish brown and fragmented bivalves, gastropods and benthic foraminifera with subordinate thin to medium beds of wackestone in its up- (including Orbitolina). Uncommon beds of dark gray, calcare- per part. At Santa Marta and Santa Ana, the Cerro La Puerta ous shale are as much as 5 m thick. At Rancho Bufalo, only consists of light gray, green to brown calcareous shale, subor- the lowermost 30 m of this member crop out and consist of dinate siltstone laminations and local, thin shale beds with medium- to thick-bedded, dark gray to black mudstone- abundant small gastropods and bivalves. At Sierra San Jose´, wackestone with planktic (Colomiella tunisiana) and benthic it is composed in its lower part of light gray to reddish brown (Orbitolina texana) microfossils and echinoderms. shale, thin beds of shaly wackestone and minor calcareous silt- At Santa Ana (Fig. 2), the lower part of the Cerro La Espina stone; its upper part consists of light gray calcareous shale and Member consists of light gray, calcareous shale and interbed- poorly stratified, nodular, shaly wackestone-packstone in beds ded medium-bedded, sandy, bioclastic calcarenite with local up to 10 m thick that contain echinoderms and bivalve frag- trough cross-stratification and herringbone cross-stratification. ments, calcispheres, and planktic and benthic foraminifera in- These grade upwards to upward-shallowing and -thinning cy- cluding Paracoskinolina sunnilandensis (Maync), Orbitolina cles, up to 3 m thick, of light gray to brown, bioturbated, shaly texana Roemer, Favusella washitensis (Carsey) and the colo- and locally dolomitic mudstone-wackestone with thin-shelled miellid Colomiella tunisiana Colom and Sigal. bivalves and benthic foraminifera, including Orbitolina. The The lower and upper parts of this member at Cerro Pimas middle part of this member consists of reddish shale and silt- are composed of light green shale with rare calcareous nod- stone with lenticular sandstone beds up to 5 m thick. These ules. Its middle part is composed of reddish brown to light sandstone beds fine upward, have erosive bases, planar and gray siltstone with plant fragments and local ripple cross- trough cross-stratification and internal reactivation surfaces. laminations, green to light gray shale in beds up to 5 m thick The upper part of this member consists of green shale and and subordinate lenticular, medium to thick beds of upward- medium-bedded, bioturbated, shaly wackestone and its upper- fining, fine- to medium-grained sandstone with scoured bases most 12 m consists of lenticular, very thick-bedded, light to and mud chip conglomerates. dark gray packstone-grainstone calcarenite and floatstone rud- At El Ocuca, the lower 15 m of this member is light red stone, with interspersed local rudist and coral boundstone. shale with thin beds of parallel-laminated siltstone and very Grains in these limestone beds are poorly sorted and consist fine-grained, lenticular sandstone beds. Upsection, the shale of bivalve and echinoderm fragments, benthic foraminifera is green to brown with local parallel laminations, interbedded including Orbitolina, bryozoans, intraclasts and pellets. The calcareous siltstone and lenticular, thin to medium-beds of bi- rudist Coalcomana ramosa (Boehm) is present. oturbated, yellowish brown, shaly wackestone with oysters The 80 m-thick section at Santa Marta (Fig. 2) is more ter- and other bivalve fragments. The trace fossil Planolites occurs rigenous than at the other localities. The lower part consists of locally in the shale. The upper part of this member at El Ocuca light gray to light brown, thick- to medium-bedded, biotur- is composed of interbedded green, yellowish brown to reddish bated, locally dolomitic wackestone-packstone up to 3 m beds of shale with calcareous nodules, and less common thinly thick. Its middle part is calcareous shale with interbedded bio- bedded siltstone and lenticular beds of dolomitic and shaly clastic wackestone-packstone, greenish to reddish siltstone bioclastic wackestone. and subordinate thin beds of calcareous and bioclastic sandstone. Its upper part is shaly wackestone. The fauna consists 2.7. Cerro La Espina Member of benthic foraminifera including Orbitolina, large gastropods and bivalves. The Cerro La Espina Member gradationally overlies the At the Cerro Pimas, the Cerro La Espina Member is com- Cerro La Puerta Shale. Its maximum thickness is 174 m at posed of three vertically stacked, lenticular, upward-shallowing 256 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 and -thinning carbonate build-ups, the thickest of which is 15 m. brown to greenish brown and the sandstone beds are lenticular, The lower parts of these cycles consist of very thick-bedded medium-bedded, and fine- to medium-grained with trough packstone-grainstone calcarenite-rudstone. The upper part con- cross-stratification. sists of thick- to medium-bedded, upward-fining grainstone and At Cerro Pimas, this member consists of reddish brown packstone calcarenite and rudstone beds with local planar cross- shale and siltstone and interbedded shaly limestone with oys- stratification. The allochem grains are generally subrounded to ters in beds up to 4 m thick. The shaly limestone beds are yel- rounded, moderately sorted, micrite-rimmed and consist of lowish brown, bioturbated wackestone and locally dolomitic. bivalves, corals, echinoderms, gastropods, algae, sponges, and The oysters are large Aetostreon latissimum (Lamarck) and bryozoan fragments, ooids, intraclasts, pellets, and benthic Ostrea riograndensis Stanton. The section of this member at foraminifera (including Orbitolina). Local beds up to 1 m-thick El Ocuca resembles the lithology from the Cerro Pimas sec- of boundstone with small rudists in growth position are also tion, but its upper part consists of partly covered reddish present in these successions. brown siltstone with abundant fossil wood. At El Ocuca, the Cerro La Espina Member consists in its At all the studied localities, this member grades upward lower part of strongly bioturbated and dolomitic yellowish into reddish to purple siltstone and interbedded, base-erosive, limestone with corals, oysters and other bivalves. This unit coarse-grained sandstone beds of the fluvial Cintura is sharply overlain by an upward-thinning carbonate cycle, Formation. 7 m thick that has at its base a mottled, bioturbated boundstone of colonial corals, 2 m thick, which passes up into very thick- 2.9. Correlation and medium-bedded wackestone-packstone calcarenite to rudstone with rudists (Monopleura, Eoradiolites and Petalo- The Tuape measured section of Lawton et al. (2004a) and dontia), bivalve fragments, corals and benthic foraminifera. the Cerro Caloso Cabullona section of Warzeski (1987, his The middle part of the member consists of locally bioturbated, section WOR3, p. 346) in central and northeastern Sonora, re- green and light gray shale with calcareous nodules and minor spectively, are representative stratigraphic columns of the Mu- thin beds of siltstone. The upper part consists of thin to very ral Formation that serve as reference for correlation of the thick beds of mottled, bioturbated, shaly wackestone with studied sections (Fig. 2). From this correlation we observe echinoderm fragments, ostracodes, calcispheres, and benthic that lithologies of the Cerro La Ceja, Tuape Shale, Los Coy- foraminifera including Orbitolina. The limestone beds in the otes, Cerro La Puerta Shale, Cerro La Espina and Mesa Que- upper part of this member are locally dolomitic and stromato- mada members are easily recognized thorough minor facies litic and have local, lenticular beds of coral boundstone up to changes from the Sierra San Jose´ to El Ocuca. The Rancho 1 m thick. Bufalo section contains two additional members in its lower The carbonate middle and upper parts of the Cerro La part that are not present in the other sections (Fig. 2): the shal- Puerta Shale that were reported from the Cerro La Ceja by low marine Fronteras Member and the Rancho Bufalo Mem- Lawton et al. (2004a) are assigned in this work to the Cerro ber that we interpret to be a tongue of the Morita Formation. La Espina Member. At that locality this member contains Eastward from the Sierra San Jose´ and Rancho Bufalo, facies a fauna of benthic foraminifera that includes Paracoskinolina of the Mural Formation record deepening toward Cerro Caloso sunnilandensis (Maync), Praechrysalidina infracretacea Pitaycachi, and westward of El Ocuca they wedge out. Luperto Sinni, Nautiloculina bronnimanni (Arnaud-Vanneau In the Sierra Anibacachi (Fig. 1) the upper part of the Mural and Peyberne`s), Cuneolina sp. cf. C. walteri Cushman and Formation is divided into five members: Canova, El Caloso, Applin, Voloshinoides sp. aff. V. murgensis Luperto Sinni Angostura, La Aguja, and Agua Prieta members (Warzeski, and Masse, Orbitolina (Mesorbitolina) texana Roemer and 1983, 1987; Scott and Warzeski, 1993). The Angostura Mem- Charentia sp. cf. C. cuvillieri Neumann. ber wedges out southward and is not present in the Cerro Cal- oso Cabullona section (Warzeski, 1987, his section WOR3, p. 2.8. Mesa Quemada member 346) (Fig. 2). The lower part of the Mural Formation in the Cerro Caloso Cabullona consists of shale and oyster limestone The Mesa Quemada Member gradationally overlies the that grade up into green and light gray shale with minor silt- Cerro La Espina Member (Fig. 2). It ranges from 20 to stone with trigoniids and ammonites that we correlate with 104 m thick in our sections (Table 1). At Sierra San Jose´ the Cerro La Ceja and Tuape Shale Members (Fig. 2). and Santa Ana (Fig. 2), the Mesa Quemada Member consists The base of the Mural Formation at the studied Cerro El of green to brown shale, locally with plant fragments, inter- Caloso Pitaycachi (Fig. 2) section is not exposed. Its lower- bedded thin siltstone beds, medium-bedded, fine-grained, len- most exposed part consists of green to light gray shale and mi- ticular sandstone beds, and minor, thin- to medium-bedded, nor interbedded siltstone with trigonids that we correlate with shaly, bioturbated, oyster wackestone floatstone. the Tuape Shale. The ammonite Douvilleiceras sp. juv. cf. rex At Santa Marta, this member consists of interbedded calcar- (Scott) was recovered from a float in this member. The Canova eous shale, limestone and subordinate siltstone and sandstone. Member and part of the El Caloso Member are recognized in The shale is greenish brown with calcareous nodules and the the upper part of this section (Fig. 2). The Canova Member is limestone is medium bedded, shaly to sandy wackestone composed of dark to light gray, resistant and nonresistant with gastropods and oysters. Siltstone is thin-bedded, reddish mudstone-wackestone that form several shallowing- and C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 257 thinning-up cycles. Echinoderms and thin shelled bivalves are sandstone beds with flaser bedding. A 3.5-m-thick, channel- common throughout the member. Mesorbitolina texana and ized, pebbly to coarse-grained sandstone with large-scale other benthic foraminifera occur in its lower part and planktic cross-beds is medium to thick bedded and fines upward. The foraminifera (including Colomiella tunisiana, C. mexicana upper part of the Mesa Quemada consists of light gray, Bonet, Hedbergella delrioensis (Carsey) and Favusella wash- strongly burrowed, calcareous siltstone with local parallel lam- itensis) occur in its middle and upper parts. The El Caloso inations that grade up into reddish siltstone and shale of the Member sharply overlies the Canova Member and is formed fluvial Cintura Formation. of very thick bedded, oolitic-oncolitic grainstone that passes up into coral boundstone and medium- to very thick-bedded packstone-grainstone, calcarenite to rudstone with local cross- 3. Facies and depositional cycles stratification and rudist patches. The upper part of the Mural here is incomplete (Fig. 2). The El Caloso Member was depos- The eight described members of the Mural Formation of the ited in a belt of deep-water patch reefs and carbonate bank com- Bisbee Group form three transgressive-regressive cycles in the plexes that graded into the deeper water forereef slope facies of Bisbee basin. These members can be recognized and corre- the Canova Member (Warzeski, 1987; Scott and Warzeski, lated in the studied transect through northern Sonora, from 1993). We consider the Canova Member to be a deeper, lateral the Cerro Caloso Pitaycahi locality in the northeast to the facies equivalent of the Los Coyotes and Cerro La Puerta Shale Sierra El Chanate in the northwest (Figs. 1 and 2). and we correlate the El Caloso Member with the Cerro La The first transgressive-regressive cycle is composed of the Espina Member in northeastern Sonora (Fig. 2). Fronteras and Rancho Bufalo Members (Fig. 3). The basal At the western end of the Bisbee basin in the Sierra El Cha- contact of the Fronteras with the Morita Formation is a sharp, nate, the stratigraphic equivalent of the Mural Formation was transgressive surface. High-energy, very shallow to marginal named as the Arroyo Sa´sabe Formation by Jacques-Ayala marine facies with tidal deposits in the lower part of the Fron- (1989). The Mural thins from 640 m at El Ocuca to 66 m in teras abruptly overlie fluvial, reddish siltstone of the Morita. the Sierra El Chanate (Fig. 2), a distance of 60 km. At this lo- The Fronteras is a shallow marine member that is represented cality, Jacques-Ayala (1989) reported a maximum thickness of only in the northeastern part of Sonora. The contact of the 95.5 m (his section III, p. 175) and the thickness difference Fronteras with the overlying Rancho Bufalo Member is ero- may be because we measured a few tens of meters west of sional. Bioclastic siltstones of the upper Fronteras is sharply his section. The fluvial Morita Formation that is reddish silt- overlain by cross-stratified sandstone that forms the base of stone and shale and subordinate lenticular sandstone beds gra- the Rancho Bufalo Member. The Rancho Bufalo Member is dationally underlies the Arroyo Sa´sabe. Five members of the composed of reddish and purple shale and siltstone and inter- Mural Formation can be recognized in the Sierra El Chanate bedded sandstone bodies that we interpret as of fluvial origin. section. The Cerro La Ceja Member is 12 m thick and is com- Its lithology is similar to the Morita Formation, and we con- posed at its base of massive, strongly bioturbated greenish to sider the Rancho Bufalo Member to be a tongue of that unit. yellowish brown, calcareous shale and interbedded siltstone The second transgressive-regressive cycle is composed of with flaser bedding. Its upper part is lenticular limestone inter- the Cerro La Ceja, Tuape Shale and Los Coyotes Members bedded with calcareous shale and siltstone. The limestone (Fig. 3) that are easily recognized and correlated throughout beds are oyster floatstone to rudstone with pectinid, trigoniids, the studied sections (Fig. 2). The basal facies of the Cerro and other bivalves. In this interval Jacques-Ayala (1989) re- La Ceja Member in the Rancho Bufalo and Sierra San Jose´ ported Quadratotrigonia mearnsi Stoyanow and the echinoid sections is quartz-rich, thick-bedded and cross-stratified sand- Macraster sp. stone interpreted as beach deposits that erosionally overlie flu- The Cerro La Ceja Member in the Sierra El Chanate is vial facies of the Rancho Bufalo Member and the Morita overlain by the Tuape Shale, a 13-m-thick interval of calcare- Formation, respectively (Fig. 2). In the other studied sections ous, gray to black shale that weathers greenish gray. Locally it the lower contact is gradational with the Morita through bio- is burrowed and small bivalves are in one thin interval. Over- turbated calcareous shale and siltstone. This lower interval is lying this shale is a 9-m-thick interval of sandy oyster lime- probably related to estuarine, intertidal and coastal plain envi- stone that is medium- to thick-bedded, lenticular, shaly, and ronments that indicate the first flooding transgressive event, interbedded with brown to gray shale and massive siltstone. but no evidence of a ravinement surface is present which is We identify this interval as the Los Coyotes Member, which typical of mud dominated, low-energy settings (Cattaneo and is overlain by 7-m-thick calcareous shale with thin beds of silt- Steel, 2003). The first transgressive deposit in most of the sec- stone that we correlate with the Cerro La Puerta Shale tions of the Cerro La Ceja Member occurs, however, within its Member. basal 10 m and is represented by a thin, lenticular bed of The Cerro La Espina Member is not present at Sierra El sandy, oyster- and intraclastic-coquina with planar cross- Chanate. Instead the Cerro La Puerta is overlain by 25 m of stratification that may represents a lag concentration (e.g., siltstone and lenticular sandstone that we identify as the Kidwell, 1991). The Cerro La Ceja Member is a shallow ma- Mesa Quemada Member. Its lower part is composed of calcar- rine deposit that deepens upward from marginal marine de- eous siltstone with local beds that contain abundant turritellid posits, locally with ammonites, into oyster-rich, thick-bedded gastropods and intercalated very fine-grained lenticular limestone in its upper part; it is a transgressive systems tract 258 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266

Fig. 3. Regional correlation between the Santa Ana section in central Sonora and the Rancho Bufalo section in northeastern Sonora to illustrate lithostratigraphic correlation, key fossil positions, proposed biozonation, transgressive-regressive cycles, geochronologic data and correlation of the Mural Formation in Sonora with biozonation in Texas. Stratigraphic positions of some fossils in both sections are inferred according to their occurrence in nearby studied sections. Aptian-Albian boundary according to Hardenbol et al. (1998). T, transgresion; R, regression. of the Mural Formation in northern Sonora and represents the was followed by deposition of the Cerro La Espina Member beginning of widespread sea-level rise. that represents widespread shallow marine carbonate deposi- The Tuape Shale Member gradationally overlies the Cerro tion with high-energy grainstone and buildups of corals and La Ceja Member and is the maximum flooding interval of trans- rudists with benthic foraminifera particularly well illustrated gressive-regressive cycle 2 with a fauna of ammonites. Deposi- by the Sierra San Jose´, Santa Ana, Cerro Pimas and El Ocuca tion was on an open shelf below fair-weather wave base but sections. The regressive deposits of this cycle are bioclastic probably above storm wave base. Evidence of storm processes limestone, oyster coquina beds, shale and siltstone of the consists of sparse coquina beds and lenticular sandstone beds. Mesa Quemada Member that were deposited on a storm- The Tuape Shale grades into the overlying Los Coyotes influenced, shallow-marine to marginal-marine setting. Member. The Los Coyotes Member is interpreted to have been deposited on a shallow platform where high energy 4. Age shoals, carbonate build-ups of corals and rudists were separated by shallow lagoonal environments. A shallow carbonate The fossil content of the Mural Formation in northern shelf developed that supported a distinctive fauna of corals, bi- Sonora indicates a Late Aptian-Early Albian age, although it valves and benthic foraminifera in wackestone-grainstone and is not easy to place precisely the boundary between the two coral-rudist boundstone at Santa Ana. High-energy bioclast stages (112.2 Ma; Hardenbol et al., 1998). A U/Pb zircon ra- grainstone and packstone accumulated in the inner shelf part diometric age from a tuff bed in the uppermost part of the of the basin in the Cerro Pimas section. This member repre- Morita Formation and a few meters below the base of the sents a high-stand systems tract that was developed during Cerro La Ceja Member at the Rancho Santa Marta area the regressive phase of the second transgressive-regressive cy- yielded an age of 115.5 0.7 Ma (Peryam et al., 2005); there- cle. It was a short-lived regression that in the more marginal fore, the base of the Cerro La Ceja Member of the Mural sections, like at El Ocuca and Sierra San Jose´ included Formation in central Sonora is no older than Late Aptian. Sim- delta-front deposits. ilarly, zircons from an ash-fall tuff bed within the upper part of The third longer-term transgressive-regressive cycle con- the Fronteras Member in the Rancho Bufalo section, analyzed sists of the Cerro La Puerta, Cerro La Espina, and Mesa Que- by the LA-MC-ICPMS method yielded a 206Pb/238U age of mada members (Fig. 4). The Cerro La Puerta Shale consists 118.1 2.4 Ma (2s,n¼ 21, MSWD ¼ 1.9) (Fig. 3). mostly of shale, siltstone and limestone beds with mixed ben- The age of the first depositional cycle formed by the Fron- thic and planktic foraminifera. It is interpreted as a deposit teras and Rancho Bufalo members is Late Aptian. Two calcar- formed during low sea-level and the beginning of transgres- eous algae of the Upper Member of the Mural Formation are sion and thus it include the lowstand and transgressive systems common in the Fronteras: Acicularia americana Konishi and tracts of the third marine transgressive-regressive cycle. This Epis (1962) and Boueina pygmeaea Pia. A trigoniid in the C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 259

Fronteras, Pisotrigonia n. sp., is also in the Upper Aptian Hen- chronostratigraphic range of Immunitoceras relative to Euro- sel Sandstone. The Fronteras is younger than the Cerro de Oro pean taxa is not precisely known (E. Robert, personal commu- Formation south of Santa Ana, which is correlated with the nication, manuscript in preparation). Lower Aptian because of the ammonite Dufrenoyia rebeccae Burckhardtites sp. is an Aptian genus and Eodouvilleiceras Young with A. latissiumum (¼Exogyra quitmanensis Stanton) sp. is commonly regarded as Upper Aptian. But Hypacantho- (Gonza´lez-Leoń and Lucas, 1995). Fossils are unknown in plites ceratitosus, Eodouvilleiceras adkinsi (Scot), and Para- the Rancho Bufalo Member but this cycle is older than 115 hoplites fasciculatus are from the Cuchillo formation in West Ma because this member is a tongue of the upper part of the Texas and northeastern Chihuahua (Scott, 1940, locality M1) Morita Formation (Fig. 3). in association with several Douvilleiceratinae and Acantho- The second cycle composed of the Cerro La Ceja to Los hoplitinae taxa. The biostratigraphic position of Scott’s assem- Coyotes members is uppermost Aptian to lowermost Albian. blage is not precisely constrained but it seems to characterize The Immunitoceras immunitum Stoyanow Assemblage Zone an Upper Aptian e Lower Albian interval. Young (1974) consists of the nominate ammonite species Eodouvilleiceras placed the holotype of Hypacanthoplites ceratitosus at a level adkinsi (Scott), the acanthoplitinae Hypacanthoplites ceratito- ‘‘below the Mammillatum Zone and above the Spathi Zone’’, sus, Hypacanthoplites sp., Parahoplites fasciculatus, Paraho- which corresponds to the basal Lower Albian Cragini Zone plites sp. juv., and Burckhardtites sp. This assemblage occurs and its Mexican equivalent the Bakeri Zone. But accurate cor- in the Cerro La Ceja Member and in the lower part of the relation of the Aptian/Albian boundary as defined in France is Tuape Shale Member and indicates a Late Aptian age (Lawton not yet possible. In the current state of knowledge, a Late et al., 2004a, E. Robert, manuscript in preparation).* Aptian age is maintained for the Cerro La Ceja and the Tuape I. immunitum occurs also in the Quajote Member of the Shale members; nevertheless, an Early Albian age cannot be Lowell Formation in southeastern Arizona (Stoyanow, 1949), excluded for the upper part of the Tuape Shale Member as which is in the upper part of the Lower Member of the Mural the ammonite Douvilleiceras sp. juv. cf. rex (Scott) was found Formation (Scott, 1987; Scott and Warzeski, 1993). Two exo- as a float on the Tuape Shale in the Cerro El Caloso Pitaycachi gyrinid oyster species in the Cerro La Ceja Member at Rancho section (Fig. 3) and Douvilleiceras sp. is present in the Bufalo, Aetostreon latissiumum (Lamarck) and Amphidonte lower part of the Cerro La Puerta Shale in the Cerro de Oro obliquata (Pulteney) (Fig. 4) define the Upper Aptian Amphi- area. donte obliquata Assemblage Zone. The first species ranges A diverse set of trigoniid species are present in the Tuape from Valanginian to Lower Albian in Europe and the second Shale Member (Fig. 5) together with Cucullaea (Idonearca) species ranges from Aptian to Cenomanian in Europe and gratiota Hill, Gervillaria alaeformis (J. Sowerby), the glo- North Africa.** bose bivalve, Sphaera roblesi (Bo¨se), and the gastropods, Stoyanow (1949) correlated the Quajote Member with the Cassiope sp. cf. C. branneri (Hill), Peruviella, and acteonell- Upper Aptian Nolani Zone of the European standard zonal ids. Peruviella colonized high-energy, storm-dominated, scheme, but this correlation is not constrained by species of open-shelf and foreshore sandy substrates (Kollman et al. the Nolani Zone. Scott (1987) and Lucas and Estep (2000) cor- 2003). The age of the Tuape Shale is Late Aptian based related Stoyanow’s section with the Texan Upper Aptian Spa- on trigoniid bivalves Quadratotrigonia guildi, Q. mearnsi thi Zone of Young (1974). It is clear, nevertheless, that the and Scabrotrigonia stolleyi from the upper parts of the middle interval. A similar assemblage is known in the uppermost Hensel Sandstone in central Texas (Scott, 2007). This Texas * L. Bulot (personal communication, January 2006), considers Immunitoce- assemblage is just below the contact with the Glen Rose ras to be intermediate in character between Hypacanthoplites and Neodeshaye- sites, and probably spans the Aptian-Albian boundary. Because the specimen Formation, which is correlated with the uppermost Aptian identified by Lawton et al. (2004a) in fig. 7C, D is incomplete, Bulot identified (Young, 1974). it as Immunitoceras sp. aff. I. immunitum. The caprinid rudist Coalcomana ramosa Boehm is common ** Amphidonte (first named as Chama) conica (J. Sowerby, 1813, June) was in both the Los Coyotes and Cerro La Espina members (Figs. 3 created one month after Chama obliquata Pulteney (1813, May) and thus is the and 4). This bivalve defines a Lower Albian zone in the upper junior synonym. However, Freneix (1972) concluded that C. obliquata is a nomen oblitum because it had not been used until 1940, when Cox resurrected it member of the Mural Formation in Arizona and in the lower and placed it in Exogyra (Cox, 1940). Furthermore, Exogyra obliquata was part of the Glen Rose Formation in central Texas (Scott and used in 1975 by Castell and Cox (Castell and Cox, 1975). According to the Filkorn, 2005). International Commission on Zoological Nomenclature (1999) Article 23.9, Depositional cycle three is comprised of the Cerro La two conditions must be met in order to continue usage of the younger Puerta, Cerro La Espina and Mesa Quemada members and is name, i.e., A. conica. First, the senior synonym must not have been used as a valid name after 1899 (Art. 23.9.1). Clearly this condition is not met. Sec- Early Albian (Fig. 3). The Colomiella tunesiana Colom and ond, the junior synonym has been used as the valid name in at least 25 publi- Sigal Local Range Zone extends from the FO of the nominate cations by ten or more authors ‘‘in the immediately preceding 50 years and species with Colomiella mexicana Bonet, Favusella washiten- encompassing a span of not less than 10 years’’ (Art. 23.9.2). This condition sis (Carsey), Orbitolina (Mesorbitolina) texana Roemer, and seems to have been met because between 1813 and 1937 at least 37 authors Paracoskinolina sunnilandensis (Maync) (Fig. 6). This assem- used the name E. conica according to the synonymy lists of Woods (1913) and Freneix (1972). Thus, if A. conica is established as the valid name, action blage is common in the uppermost part of the Cerro La Puerta by the Commission must be taken. Until that decision is made, A. obliquata Shale Member and in the Cerro La Espina Member. The two should be used (Art. 23.9.3). colomiellid species commonly are considered synonyms; 260 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266

Fig. 4. AeF Amphidonte obliquata Pulteney from middle part of the Cerro La Ceja Member at Rancho Bufalo section, LV and RV pairs: A and D, ERNO 8516, B and E, ERNO 8517, C and F, ERNO 8518; scale bar ¼ 1 cm. G, H, I, Coalcomana ramosa Boehm; G, ERNO 8512, Los Coyotes Member at Santa Ana section; H, ERNO 8513, Cerro La Espina Member at Santa Ana section; I, ERNO 8515, ﬂoat at Santa Ana section from either the Cerro La Espina or Los Coyotes members. however the connection between the bowl and the neck of above the La Pena~ Shale, McNulty (1985) correlated this FO each is quite different. In C. recta it is v-shaped and in C. tu- with uppermost Upper Aptian. Also present in the Cerro La nisiana it is planar and inclined (Fig. 6). Nevertheless, both Espina Member are the benthic foraminifers Praechrysalidina species range from uppermost Aptian to Lower Albian (Bonet, infracretacea Luperto Sinni, Nautiloculina bronnimanni 1956; Colom & Sigal, 1959; McNulty, 1985). Although Trejo (Arnaud-Vanneau and Peyberne`s), Cuneolina sp. cf. C. walteri (1975) proposed that the FO of C. recta marked the base of the Cushman and Applin, Voloshinoides sp. aff. V. murgensis Albian in the basal Upper Tamaulipas Formation directly Luperto Sinni and Masse, and Charentia sp. cf. C. cuvillieri C.M. Gonza´lez-Leo´n et al. / Cretaceous Research 29 (2008) 249e266 261

Fig. 5. Trigoniid bivalves, Mural Formation in Sonora and Arizona. Figure A, B, Buchotrigonia reesidei (Stoyanow) RV, dorsal view of area of RV, Tuape Shale, Rancho Bufalo, specimen ERNO 8508. C, D, Quadratotrigonia mearnsi (Stoyanow), RV, area of RV, upper part of Lower Mural Member, Sierra Anibacachi, 14 km SW of Agua Prieta; collected by E.R. Warzeski (Scott collection). E, Q. mearnsi, dorsal view of area and escutcheon, Lower Mural Member, 150 m SW of Mexican Saddlehorn Peak (312002900N, 1090600900W), Arizona; collected by H. Lo¨ser (Scott collection). F, Pisotrigonia n. from the Fronteras Member in the Rancho Bufalo section.

Neumann which is an uppermost Aptian to Albian assemblage Aptian/Albian boundary in the Canova (Rosales-Domıńguez (Lawton et al., 2004a,b). Both colomiellid species also occur et al., 1995). in the upper part of the Canova Member of the Mural Forma- Oysters in the lower part of the Mesa Quemada Member are tion in the Cerro Caloso Cabullona locality (Warzeski, 1987; the exogyrid, Aetostreon latissimum (Lamarck) of Valangi- Scott and Warzeski, 1993), supporting correlation of the upper nian-Lower Albian age, and Ostrea riograndensis Stanton. Canova with the Cerro La Puerta Shale. Nannofossils, dinofla- The latter species occurs in the uppermost Aptian-Lower gellates, and spore and pollen in the Canova Member comple- Albian Quitman Formation in southwestern Texas with A. ment the hypacanthoplitid ammonites in correlating the latissimum (¼Exogyra quitmanensis Cragin). 262 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 C.M. Gonza´lez-Leoń et al. / Cretaceous Research 29 (2008) 249e266 263

5. Discussion and conclusions Sonoran Shelf or Mural shelf (Warzeski, 1983; Scott, 2003) extended south and west of northeastern Sonora, where the During the Late Jurassic two northwest-trending parallel Mural Formation is composed of eight members. Correlation basins, the Bisbee basin in southeastern Arizona, USA and through minor facies changes of these members indicates northeastern Sonora, Mexico and the Altar-Cucurpe basin in that the shelf also extended across northern Sonora. Two central Sonora (Fig. 1) were the sites of deposition of conti- important observations result from correlation of the Mural nental and marine strata. These basins were separated by the members: (1) The shelf facies deepen toward eastern Sonora; northwest-trending Cananea high (McKee and Anderson, (2) the formation wedges out entirely in northwestern Sonora. 1998) and their formation has been attributed to rift-related ex- The deposits of the extended shelf (Fig. 7) record three tensional deformation (Bilodeau, 1982; Dickinson et al., 1986; third-order sea-level cycles, the oldest of which was initiated Dickinson et al., 1989; Lawton and McMillan, 1999; Dickin- w118.1 2.4 Ma and is composed of the Fronteras and Ran- son and Lawton, 2001), although transtensional deformation cho Bufalo members. The first cycle is only present in north- has also been proposed (Haenggi, 2002; Anderson and Nourse, eastern Sonora where the shallow marine strata of the 2005; Haenggi and Muehlberger, 2005). The Late Jurassic and Fronteras Member represent a transgressive systems tract Early Cretaceous marine sedimentation in this region is linked and the overlying fluvial deposits of the Rancho Bufalo Mem- to three marine transgressions from the Gulf of Mexico ber represent the following lowstand systems tract. The second through the Chihuahua trough (Bilodeau, 1982; Dickinson cycle (Cerro La Ceja-Tuape Shale-Los Coyotes members) is et al., 1989; Scott and Gonza´lez-Leoń, 1991). The first trans- Late Aptian (younger than 115.5 Ma) in its lower part, and gression took place during rapid tectonic subsidence during probably Early Albian in its upper part, based on the ammo- formation of the Bisbee and Altar-Cucurpe basins (Dickinson nites, rudists and foraminifera. The shallow-marine strata of and Lawton, 2001) and deposited the Crystal Cave Formation the Cerro La Ceja is interpreted as a transgressive system tract, in southeastern Arizona and the Cucurpe Formation in central followed by the maximum flooding interval of the Tuape Shale Sonora; both formations contain ammonites that indicate they and the high-stand system tract of the Los Coyotes Member. are Late Jurassic. Kimmeridgian in the case of the Crystal The third cycle composed of the Cerro La Puerta-Cerro La Es- Cave Formation (Lawton and Olmstead, 1995; Olmstead and pina-Mesa Quemada members is Early Albian in age. The Young, 2000) and late Oxfordian to early Tithonian in the younger age is constrained at about 110 Ma by the ammonite, case of the Cucurpe Formation (Rangin, 1977; Villasenor~ Douvilleiceras in the Cerro La Puerta Shale member and in the et al., 2005). The Early Cretaceous sedimentation was accom- upper member of the Mural Formation in Arizona (Stoyanow, modated by thermotectonic subsidence and occurred in the 1949; Scott et al., 2000; Hardenbol et al., 1998). Thus the whole region of southeastern Arizona and northern Sonora, mean duration of these cycles is approximately 2.5 myr. in the expanded Bisbee basin (Gonza´lez-Leoń, 1994; Jac- In Central Texas three depositional cycles are recognized in ques-Ayala, 1995; Dickinson and Lawton, 2001; Lawton the Hammett, Cow Creek, Hensel and Glen Rose formations et al., 2004a; Mauel et al., 2005; Leggett et al., 2005; Peryam (Scott et al., 2007)(Fig. 3). The cycle of the Hammett and et al., 2005). This sedimentation deposited the strata of the Cow Creek spans the Early-Late Aptian boundary and may Cerro de Oro, La Colgada, Morita, Mural and Cintura forma- correlate with the Fronteras-Rancho Bufalo cycle 1. The Hen- tions which are widespread in this region, except for the Cerro sel Sandstone and lowermost Glen Rose cycle spans the Ap- de Oro and La Colgada formations. The Cerro de Oro and La tian-Albian boundary and is approximately correlative with Colgada formations crop out only in central Sonora and were the Cerro La Ceja-Los Coyotes cycle (Fig. 3). The lowermost deposited during a second marine transgression in Late Barre- Glen Rose shoals up into coral-rudist biostromes similar to mian and Early Aptian time (Gonza´lez-Leoń and Lucas, 1995) those in the Los Coyotes. The second Glen Rose cycles in- (Fig. 1). A third major transgression occurred during the Late cludes the Coalcomana ramosa bioherms that underlie the Aptian and Early Albian time and deposited strata of the Mu- Salenia zone and the ‘‘Corbula’’ beds with Douvilleiceras ral Formation in the whole region. mammillatum. This interval correlates with the Cerro La The upper Mural Formation in northeastern Sonora is di- Puerta to Mesa Quemada cycle. In contrast, six third-order vided into five members (Warzeski, 1983) and is interpreted cycles are recognized during the Late Aptian and Early Albian to have formed a mixed carbonate-clastic shelf with reef banks in Europe (Hardenbol et al., 1998). The three older European that prograded east into the Chihuahua trough (Warzeski, cycles are in the same stratigraphic position as the Mural 1987; Scott and Warzeski, 1993). This shelf termed the cycles, but no common fossils exist to test this correlation.

Fig. 6. A, Colomiella tunisiana Colom & Sigal, uppermost Aptian-Lower Albian, Cerro La Puerta Member at Sierra San Jose´, sample 9-14-9, X865. B, Micro- crinoid plate, Cerro La Espina Member, Cerro Pimas section, sample 3-18-05-14, X80. C, Hedbergella delrioensis (Carsey), Hauterivian-Coniacian, Cerro La Es- pina Member at Rancho Bufalo, sample 9-16-12, X255. D, E, F, Orbitolina (Mesorbitolina) texana Roemer, uppermost Aptian-Lower Albian, Cerro La Espina Member at Sierra San Jose´, sample 9-15-3, D, X130, E, X50, F, sample 9-15-5, X50. G, H, Arabicodium texana Johnson, Albian-Lower Cenomanian, Fronteras Member at Rancho Bufalo, sample 9-16-9, G, X20, H, X45. I, J, K, Paracoskinolina sunnilandensis (Maync), uppermost Aptian-Lower Albian, Cerro La Espina Member; I, Sierra San Jose´ section, sample 9-15-10, X25, J, Mural Formation at Mina La Montana~ locality, sample SM1, X86, K, Santa Ana section, sample 2-24- 05-4, X65; L, Trocholina sp., Mural Formation, Mina La Montana,~ sample SM1, X70. M, Eoradiolites sp., Cerro La Espina Member at El Ocuca section, sample 12-08-05-8, ERNO 8514, scale bar ¼ 1 cm. 264 C.M. Gonza´lez-Leo´n et al. / Cretaceous Research 29 (2008) 249e266

data for all fossils except ammonites. C. Gonza´lez-Leo´n also acknowledges support from CONACYT project 27824-T.

References

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(4) Santa Ana (base: UTM 12R 491161; 3378042; top: 492217; 3377067). (7) Sierra San Jose´ (base: UTM 12R 597021; 3455384; top: 597277; Overturned section. 3455877). (5) Rancho Santa Marta (base: UTM 12R 512733; 3331367: top: 513244; (8) Rancho Bufalo (base: UTM 12R 643086; 3428255; top: 643352; 3427262). 3331078). (9) Cerro El Caloso Pitaycachi (base: UTM 12R 678705; 3441238; top: (6) Tuape (base: 30 110 N, 110 400 3000 W; top: 30 100 3000 N, 110 400 2000 W). 679509; 3440467).