Cretaceous stratigraphy, paleontology, petrography, depositional environments, and cycle stratigraphy at Cerro de Cristo Rey, Doña Ana County, New Mexico Spencer G. Lucas, New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, New Mexico 87104, [email protected]; Karl Krainer, Institute of Geology and Paleontology, Innsbruck University, Innrain 52, Innsbruck, A-6020 Austria, [email protected]; Justin A. Spielmann, New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, New Mexico 87104, [email protected]; Kevin Durney, 11212 Jockey Bluff Drive, Austin, Texas 78748 Abstract Cretaceous marine and nonmarine strata of late Albian–middle Cenomanian age are exposed around the Cerro de Cristo Rey uplift in southern Doña Ana County, New Mexico. These strata comprise a section approximately 350 m thick and are assigned to the (ascending order) Finlay, Del Norte, Smeltertown, Mule- ros, Mesilla Valley, Mojado (=“Anapra”), Del Rio, Buda, and Mancos (=“Boquillas”) For- mations. Macrofossils and microfossils from these strata indicate that the Finlay, Del Norte, Smeltertown, Muleros, and Mesilla Valley Formations are of late Albian age, whereas the Del Rio, Buda, and Mancos Formations are of Cenomanian age. The base of the Cenomanian is most likely at a trangressive surface within the uppermost Mojado Formation. The late Albian (Manuaniceras powelli Zone) to early Cenomanian (Neophlycticeras hyatti Zone) sedimentary succession at Cerro de Cristo Rey consists of alternating fossiliferous limestone, shale with limestone and sandstone intercala- tions, and sandstone. Muddy limestone types are commonly wavy to nodular and represent deposits of an open-marine shelf environment below wave base. Intercalated coquina beds rich in mollusc shells are interpreted as storm layers. Shale was deposited in an open-shelf environment below or near wave base during periods of increased siliciclastic influx. Inter- calated thin limestone and sandstone beds are inferred to be storm layers. The siliciclastic Mojado Formation is a regressive-transgres- sive succession formed in depositional envi- ronments ranging from lower shoreface to upper shoreface and even fluvial, again over- lain by shallow-marine siliciclastics. Although the Washita Group section at Cerro de Cristo FIGURE 1—Location of Cerro de Cristo Rey in southern Doña Ana County, New Mexico (after Lovejoy Rey is much thicker and displays some differ- 1976). ∆ indicates Eocene igneous intrusions—Cerro de Cristo Rey, Cerro de la Mina, Campus Andesite, ences in facies, the succession shows similar the Three Sisters, and Vado Hill. transgressive and regressive trends compared to the Washita Group of north Texas. Thus, Introduction Cretaceous marine strata, locally strongly we recognize eight unconformity-bounded deformed by gravity-glide structures trig- depositional cycles in the Cretaceous sec- Cerro de Cristo Rey is a prominent peak in gered by andesite intrusion” (Lovejoy 1976, tion at Cerro de Cristo Rey, the upper Finlay Doña Ana County, New Mexico, just north p. 24). The Cretaceous strata, a section Formation (youngest cycle of the Freder- of the U.S.–Mexican border and just west of approximately 350 m thick, include rocks icksburg Group), lower Mancos Formation the city of El Paso, Texas (Fig. 1). The moun- of Early Cretaceous (late Albian) and Late (base of Greenhorn cycle), and six Washita tain was long referred to as the Cerro de Cretaceous (early–middle Cenomanian) Group cycles: WA1 = Del Norte Formation, Muleros, but was renamed Cerro de Cristo age (Figs. 3–4). These rocks have been stud- WA2 = Smeltertown Formation, WA3 = Mule- Rey (“Sierra” de Cristo Rey of Hook 2008 ied for more than a century, most notably ros Formation, WA4 = most of Mesilla Valley and Cobban et al. 2008, also appears on the by Böse (1910) and Strain (1976). Here, we Formation, WA5 = uppermost Mesilla Val- U.S. Geological Survey topographic map of present the first detailed lithostratigraphy ley Formation and most of Mojado Forma- the area) in recognition of the large statue of tion, and WA6 = uppermost Mojado and Del and sedimentary petrography of the Cre- Rio and Buda Formations. The persistence Christ on the cross at its crest. The mountain taceous strata exposed around the New of cycles from the tectonically passive, open- has an elevation of 1,425 m (4,675 ft) (Love- Mexican periphery of the Cerro de Cristo marine margin of the Gulf of Mexico into the joy 1976; Hook 2008). Rey uplift. We combine these data with tectonically active Chihuahua trough suggests The core of Cerro de Cristo Rey is an paleontology and regional correlations to that regional if not global eustasy, not local andesite laccolith, the Muleros Andes- present the first detailed interpretation of tectonism, drove late Early to early Late Cre- ite of Eocene age (Fig. 2). The laccolith is the depositional environments and cycle taceous sedimentation at Cerro de Cristo Rey. surrounded by “an annulus of…faulted stratigraphy of the Cretaceous section. November 2010, Volume 32, Number 4 New Mexico Geology 103 the Cretaceous invertebrate macrofossils he collected at Cerro de Cristo Rey. Adkins (1932) and Imlay (1944) sub- sequently applied Texas stratigraphic names to the section Böse (1910) delin- eated at Cerro de Cristo Rey (Fig. 3). Cór- doba (1968, 1969a,b) proposed a formal lithostratigraphic nomenclature for the Cretaceous section in northeastern Chi- huahua, Mexico. He mapped these units as far north as the international border, so he assigned Cretaceous strata along the southern flank of Cerro de Cristo Rey in Chihuahua to strata of his Ojinaga Group. Del Norte Córdoba (1969a) makes clear the equiva- lence between his stratigraphic names and those introduced at Cerro de Cristo Rey by Strain (1968, 1976). The lithostratigraphic names long applied to Cretaceous strata at Cerro de Cristo Rey were briefly introduced by Strain (1968) and elaborated on by Strain (1976) and Lovejoy (1976). Thus, four strati- graphic names from farther east, in Texas (Finlay, Del Rio, Buda, and Boquillas), are applied, whereas Strain introduced five local lithostratigraphic names—Del Norte, Smeltertown, Muleros, Mesilla Valley, and Anapra (Figs. 3–4). Subsequent workers (e.g., LeMone and FIGURE 2—Geologic map of part of the New Mexican portion of the Cerro de Cristo Rey uplift (from Simpson 1983; Maudlin 1985; Cornell and Lovejoy 1976) showing locations of measured stratigraphic sections in this study. See Appendix for LeMone 1987; Cornell et al. 1991; Cornell map coordinates of the measured sections. 1997; Lucas and Estep 1998b, 2000; Scott et al. 2001, 2003; Turnšek et al. 2003) have Located on the northern margin of the stratigraphy and paleontology of these employed the lithostratigraphy of Strain Chihuahua trough, the Cretaceous section strata was the monograph of Böse (1910). (1976). The only previously suggested at Cerro de Cristo Rey is between Bisbee He informally divided the Cretaceous modification is that of Lucas and Estep Group sections to the west and Washita section at Cerro de Cristo Rey into 11 Group sections to the east. It thus provides (1998b, 2000), who argued that the Anapra stratigraphic units, many characterized Sandstone is part of the same lithosome as a pivotal reference section for regional cor- by a distinctive fossil assemblage (Fig. 3). relation and testing concepts of Washita the Mojado Formation to the west. They Although Böse (1910) explicitly correlated Group cycle stratigraphy. therefore abandoned the name Anapra these units to formally named units of the Sandstone and replaced it with the term Fredericksburg and Washita Groups and Mojado Formation. Here, we employ the Previous studies overlying Eagle Ford Shale of Texas (as lithostratigraphic nomenclature of Strain had Stanton and Vaughan [1896] and was (1968, 1976) with two modifications, Emory (1857), Stanton and Vaughan (1896), later done by Adkins [1932]), he applied the use of Mojado Formation instead of and Richardson (1909) first reported on no formal lithostratigraphic nomencla- Anapra Sandstone and the use of Mancos the Cretaceous rocks exposed around ture to the Cretaceous section at Cerro de Formation instead of Boquillas Formation Cerro de Cristo Rey (Fig. 3). However, the Cristo Rey. Most significantly, Böse (1910) (Fig. 4). These modifications are justified real starting point for understanding the provided a monographic description of below. FIGURE 3—Evolution of Cretaceous lithostratigraphic nomenclature at Cerro de Cristo Rey. Modified from Strain (1976). 104 New Mexico Geology November 2010, Volume 32, Number 4 and serpulids are also present (Böse 1910; Strain 1976; Turnšek et al. 2003; Kollmann et al. 2003). In addition, our thin sections (see below) demonstrate that calcareous algae, ostracods, and rare calcisponges are present. Kollmann et al. (2003) recently analyzed the gastropod fossil assem- blage of the Finlay Formation at Cerro de Cristo Rey, identifying the following taxa: Aporrhaidae, Diozoptyxis, Drepanocheilus, Eunerinea aquiline, Naticoidea, Nerinella n. sp., Otostoma elpasensis, Plesioptyxis tex- anus, Rostroptygmatis kervillensis, Turritella, and Tylostoma. Sedimentary petrography (Figs. 6, 16) Finlay Formation limestone beds at Cerro de Cristo Rey are mostly bioclastic wacke- stone that is fine-grained and commonly bioturbated. Fossils include small mollusc fragments (bivalves, gastropods), ostra- cods, calcareous algae, a few echinoderms, echinoid spines, and many foraminiferans