Ammonite biostratigraphy, lithofacies variations, and paleoceanographic implications for Barremian-Aptian sequences of northeastern Mexico

Two Barremian-Aptian sequences studied in Durango and Nuevo Leon States, northeastern Mexico include three lithic units which have been described as the Cupido Formation of Barremian-early Early Aptian age, its lateral equivalent, the Lower Tamaulipas Formation, and the La Peña Formation extending through the early Albian. ^ The present work improves the existing ammonite Aptian biozonation by considering constraints associated with a discontinuous spatial and temporal record of the different taxa within the La Peña Formation. ^ Four ammonite biozones are established: (1) The Dufrenoyia justinae Zone for the late Early Aptian, (2) The Burckhardtites nazasensis/Rhytidoplites robertsi Zone for the middle Aptian, (3) The Cheloniceras inconstans Zone for the early Late Aptian, and (4) The Hypacanthoplites cf. leanzae Zone for the late late Aptian. ^ Also, a detailed sedimentological analysis of the sections shed further light on the possible causes that controlled intermittent occurrences of the ammonites in relation to the prevailing paleoceanographic and paleoecologic conditions in northeastern Mexico during the late Barremian-Aptian. ^ Microfacies analyses show that the upper part of the Cupido facies are represented by biocalcirudite with rudists, biocalcarenites with oolites and algae, and rich benthonic foraminifera assemblages with ostracods. These facies are related to paleoceanographic conditions of sedimentation within a shallow-marine carbonate platform. Its lateral equivalent, deep-water facies extended to the southeast and it is represented by the Lower Tamaulipas Formation, which includes planktonic foraminifera, ostracods, and mollusk and echinoid fragments. The beginning of deposition of the La Peña Formation in the late Early Aptian is characterized by an increase in terrigenous materials and significant decrease in the abundance of benthic fauna. The La Peña Formation is recognized by an alternation of marls and shale limestones containing ammonites, planktonic foraminifera, ostracods, and radiolaria toward the top. Accumulation of the La Peña continued throughout the end of the Aptian and records changes in conditions of sedimentation and productivity in the water column, which abruptly terminated the carbonate deposition in the Cupido Platform. ^ Results of carbon/carbonate content analyses show that changes from the Cupido to the La Peña facies are also characterized by an increase of organic carbon, which indicate the onset of enhanced dysoxic/anoxic conditions in the lower water column. ^

Paleoenvironmental implications of the Indidura Formation (Cenomanian/Turonian), northeastern Mexico: A high resolution stratigraphic study

High-resolution lithostratigraphic data from rock sequences known as the Indidura Formation near Parras de La Fuente, Coahuila, NE Mexico, led to achieve a significant improvement of our knowledge of that Formation. The results of this study indicate for the first time that the sequence at Parras de La Fuente developed from the deposition of calcareous cyanobacterial microspheroids that accumulated under perennial blooms during the Late Cenomanian through the Middle Turonian. Multi-proxy analyses included sedimentological, petrographical, scanning electron microscopy, stable isotope, trace element geochemistry, and paleontological data. The combined results allowed the correlation of δ13C and anomalies in Mo, V, and Cr with the abundance and predominance of calcareous cyanobacterial microspheroids, which were the main suppliers of the carbonate components and the organic matter throughout deposition of the Indidura Formation in the Parras de la Fuente area, under dysoxic/anoxic conditions. Conspicuous interbeds of dark and light-gray laminated marly calcilutites, and dark-gray marlstones that characterize the stratigraphic sequence formed in response to external forcing climatic factors of millennial-scale Milankovitch cycles (ca. 20 ka precession). At the microscopic level, the prominent dark and light-gray laminae were formed during cycles similar to the 10 to 15 years solar irradiance maximum, and represent alternating periods of high and low calcareous cyanobacterial microspheroids productivity.

Isotopic studies of the Guerrero composite terrane, west-central Mexico: Implications for provenance of crustal rocks and genesis of ore metals

A variety of world-class mineral deposits occur in Mesozoic and Tertiary rocks of the Guerrero terrane. New Pb isotope analyses of various crustal units and ores from distinct subterranes of the Guerrero terrane are presented to trace metal sources in these deposits and infer source reservoirs. New Sr and Nd isotope results are provided to gain insight into the provenance of the crustal rocks from the Guerrero terrane. Triassic schist samples from the Arteaga Complex and Triassic-Jurassic phyllite and slate samples from the Tejupilco metamorphic suite contain radiogenic Pb (206Pb/204Pb = 18.701–19.256) relative to bulk earth models. Cretaceous sedimentary rocks of the Zihuatanejo Sequence are more radiogenic (206Pb/204Pb = 18.763–19.437) than samples from the Huetamo Sequence (206Pb/204Pb = 18.630–18.998). Tertiary intrusive rocks from La Verde, Inguaran, La Esmeralda, and El Malacate plot to the right of the average Pb crust evolution curve of Stacey and Kramers (206Pb/204Pb = 18.705–19.033). Ores from the La Verde and La Esmeralda porphyry copper deposits yield isotopic ratios (206Pb/204Pb = 18.678–18.723) that are generally less radiogenic than the host igneous rocks, but plot within the field defined by the sedimentary rocks from the Huetamo Sequence. Tertiary intrusive rocks from the Zimapan and La Negra districts in the Sierra Madre terrane plot above and to the right of the Stacey-Kramers reference line (206Pb/204Pb = 18.804–18.972). Lead isotope ratios of ore minerals from the Zimapan and La Negra skarn mines ( 206Pb/204Pb = 18.775–18.975) resemble those of the associated igneous rocks, implying a magmatic Pb input in the skarn deposits. New Sr and Nd isotope data on metamorphic rocks (87Sr/ 86Sr = 0.707757–0.726494 and 143Nd/144 Nd = 0.512109–0.512653) suggest that the basement of the Guerrero terrane originated from sources that had been derived from an old cratonic area. The narrow ranges and generally low 87Sr/86Sr ratios (0.704860–0.705755) and 143Nd/144Nd values (0.512765–0.512772) above that of bulk earth for igneous rocks from Inguaran, El Malacate, and La Esmeralda suggest a relatively low degree of crustal contamination. However, the isotopic values for the La Verde site (87Sr/86Sr = 0.708784 and 143Nd/144Nd = 0.512640) may indicate the involvement of a more evolved crustal component.

La mujer en defensa de la mujer: voces femeninas del romanticismo cubano (Poesía y cuento)

Throughout history, women have played an important role in literature. Nevertheless, since Sappho's poetry until now, feminine voices have had to struggle for recognition of their works. Before the nineteenth century, women were almost ignored in Spanish literature. Society kept them as "ángeles de la familia," taking care of their homes, husbands, and children. Some of them, such as María de Zayas y Sotomayor in Spain and Sor Juana Inés de la Cruz in Mexico, complained about their situation in their writings. However, they expressed their fight not as a generation but as individuals. In the nineteenth century, the ideas and ideals of Romanticism, were brought to Latin America from Europe. Cuba was among those countries where the new movement took roots. Initiated by Gertrudis Gómez de Avellaneda, a group of women began to participate in literary reunions, and to found newspapers and magazines where works authored by women, dedicated to feminist ideas, were published. They indeed through literature started to live out womanhood in order to intellectually leave the ideological prisons where society had been keeping them. This study scans the literary works of all Romantic women writers in Cuba. It specifically analyzes poetry and short stories, and investigates how these authors expressed themselves in their works against the patriarchal society, where they lived and wrote their books. An eclectic critical method has been used. Findings were very revealing. Only three of the fourteen writers studied in my dissertation had been previously mentioned by major critics. Most of them had been ignored. However, the greatest discovery was that they prompted something new: For the first time they projected themselves as a group, as a collective consciousness, and this fact established a difference with former women writers in Cuban literature before Romanticism. In other words, they produced a "Renaissance" in Cuba's literature. In spite of how they lived between 1820 and 1900, their struggles for women's rights have linked them to our current times.

Paleoenvironmental Implications of the Indidura Formation (Cenomanian/Turonian), Northeastern Mexico: a High Resolution Stratigraphic Study

High-resolution lithostratigraphic data from rock sequences known as the Indidura Formation near Parras de La Fuente, Coahuila, NE Mexico, led to achieve a significant improvement of our knowledge of that Formation. The results of this study indicate for the first time that the sequence at Parras de La Fuente developed from the deposition of calcareous cyanobacterial microspheroids that accumulated under perennial blooms during the Late Cenomanian through the Middle Turonian. Multi-proxy analyses included sedimentological, petrographical, scanning electron microscopy, stable isotope, trace element geochemistry, and paleontological data. The combined results allowed the correlation of δ13C and anomalies in Mo, V, and Cr with the abundance and predominance of calcareous cyanobacterial microspheroids, which were the main suppliers of the carbonate components and the organic matter throughout deposition of the Indidura Formation in the Parras de la Fuente area, under dysoxic/anoxic conditions. Conspicuous interbeds of dark and light-gray laminated marly calcilutites, and dark-gray marlstones that characterize the stratigraphic sequence formed in response to external forcing climatic factors of millennial-scale Milankovitch cycles (ca. 20 ka precession). At the microscopic level, the prominent dark and light-gray laminae were formed during cycles similar to the 10 to 15 years solar irradiance maximum, and represent alternating periods of high and low calcareous cyanobacterial microspheroids productivity.

Ammonite biostratigraphy, lithofacies variations, and paleoceanographic implications for barremian-aptian sequences of northeastern Mexico

Two Barremian-Aptian sequences studied in Durango and Nuevo Leon States, northeastern Mexico include three lithic units which have been described as the Cupido Formation of Barremian-early Early Aptian age, its lateral equivalent, the Lower Tamaulipas Formation, and the La Pena Formation extending through the early Albian. The present work improves the existing ammonite Aptian biozonation by considering constraints associated with a discontinuous spatial and temporal record of the different taxa within the La Pena Formation. Four ammonite biozones are established: 1) The Dufrenoyia justinae Zone for the late Early Aptian, 2) The Burckhardtites nazasensis/Rhytidoplites robertsi Zone for the middle Aptian, 3) The Cheloniceras inconstans Zone for the early Late Aptian, and 4) The Hypacanthoplites cf. leanzae Zone for the late late Aptian. Also, a detailed sedimentological analysis of the sections shed further light on the possible causes that controlled intermittent occurrences of the ammonites in relation to the prevailing paleoceanographic and paleoecologic conditions in northeastern Mexico during the late Barremian-Aptian. Microfacies analyses show that the upper part of the Cupido facies are represented by biocalcirudite with rudists, biocalcarenites with oolites and algae, and rich benthonic foraminifera assemblages with ostracods. These facies are related to paleoceanographic conditions of sedimentation within a shallow-marine carbonate platform. Its lateral equivalent, deep-water facies extended to the southeast and it is represented by the Lower Tamaulipas Formation, which includes planktonic foraminifera, ostracods, and mollusk and echinoid fragments. The beginning of deposition of the La Pena Formation in the late Early Aptian is characterized by an increase in terrigenous materials and significant decrease in the abundance of benthic fauna. The La Pena Formation is recognized by an alternation of marls and shale limestones containing ammonites, planktonic foraminifera, ostracods, and radiolaria toward the top. Accumulation of the La Pena continued throughout the end of the Aptian and records changes in conditions of sedimentation and productivity in the water column, which abruptly terminated the carbonate deposition in the Cupido Platform. Results of carbon/carbonate content analyses show that changes from the Cupido to the La Pena facies are also characterized by an increase of organic carbon, which indicate the onset of enhanced dysoxic/anoxic conditions in the lower water column.

Annotated bibliography of Salomon de la Selva's collected poems

The purpose of my project is to provide a compilation of the work of Nicaraguan born poet, Salomon De la Selva, who incidentally was nominated for a Nobel Prize in 1919, and was the first Latin-American poet to publish extensively in English. In order to achieve this goal, my research methods included the substantial use of the Internet, as well as two investigative trips to Mexico and one to Nicaragua, which ultimately led me to uncover a total of 135 unaccounted English-language poems. In addition, De la Selva's uniqueness lies in the fact that he was a truly bilingual writer, who was equally able to create both in English and Spanish, simultaneously. Therefore, my project not only represents an act of reclamation, but the new material also provides new exciting possibilities for his work by facilitating an intertextual analysis of his poems, which will aid in understanding the complexities of bilingualism.