Topographic Map of Xtobo, Yucatan, Mexico

Boletín de la Sociedad Geológica Mexicana,

Assessing water quality in aquifers has become increasingly important as water demand and pollution concerns rise. In the Yucatan Peninsula, sinkholes, locally known as cenotes, are karst formations that intercept the water table. Cenotes are distributed across the peninsula, but are particularly dense and aligned along a semicircular formation called the Ring of Cenotes. This area exhibits particular hydrogeological properties because it concentrates, channels, and discharges fresh water toward the coasts. In this study, we identify spatial and temporal variations in chemical and physical variables at twenty-two cenotes to identify groups that share similar characteristics. Water samples from each cenotes were taken at three depths (0.5, 5.5, and 10.5 m) and during three seasons (dry, rainy, and cold-fronts season). Field measurements of pH, temperature, electrical conductivity, and dissolved oxygen were taken, and the concentrations of major ions (K + , Na + , Mg 2+ , Ca 2+ , HCO { 3 , SO 2{ 4 , Cl 2 and NO { 3 ) were quantified. Identifying regions of the cenotes were done by applying multivariate statistical techniques (PCA, PERMANOVA, CAP). The chemical variables revealed spatial trends among the cenotes. We identified three main regions. Region 1 is associated with sea-water encroachment and high levels of sulfate that travel through preferential groundwater flowpaths from evaporites in the southern Yucatan Peninsula; Region 2 is a recharge zone, and Region 3 is characterized by sea water encroachment and by the high chemical and physical variability associated with groundwater flow from the east.

Studia Quaternaria, 2015

Cenote lakes are natural sinkholes or depressions resulting from the collapse of limestone bedrock exposing the groundwater underneath. Thousands of such lakes are particularly encountered on the Yucatan Peninsula (Mexico). These lakes were of great significance for the Maya culture as important religious places and primary source of drink­ing water. They permitted the survival of Mayan communities through dry periods known as “Maya drought”. Most of the cenote lakes are large open water pools measuring tens of meters in diameter. The majority of cenotes are smaller sheliered sites. Their waiers are usually very clear and oligotrophic, originating from rain waier filtering slowly through the ground. The auihors visited and coliected zooplankion samples from eight cenotes in November 2013, namely: Ik-Kil, Samula, Zaci, X-Kekn, Actum Ha, Cristal, Sian Ka’an, and Chan Chemuxil (transect Merida-Tulum- Cancun). The analysed lakes differ considerably in morphological terms, varying from v...

Sedimentary Geology, 2006

The Chicxulub Sedimentary Basin of the northwestern Yucatan Peninsula, Mexico, which was formed because of the largest identified Phanerozoic bolide impact on Earth, became a site of deposition of dominantly marine carbonate sediments during most of the Cenozoic Era. This is a study of the filling and diagenetic history of this basin and surrounding areas. The study makes use of lithologic, biostratigraphic, petrographic, and geochemical data obtained on core samples from boreholes drilled throughout the northwestern Yucatan Peninsula. The core sample data indicate that: 1) The Chicxulub Sedimentary Basin concentrated the deposition of pelagic and outer-platform sediments during the Paleocene and Eocene, and, in places, during the Early Oligocene, as well, and filled during the Middle Miocene, 2) deeper-water limestone also is present within the Paleocene and Lower Eocene of the proposed Santa Elena Depression, which is located immediately south of the Basin, 3) shallow-water deposits are relatively more abundant outside the Basin and Depression than inside, 4) the autigenic and allogenic silicates from the Paleogene formations are the most abundant inside the Depression, 5) sediment deposition and diagenesis within the Basin also were controlled by impact crater topography, 6) the abundance of the possible features of subaerial exposure increases upward and outward from the center of the Basin, and 7) the formation of replacive low-magnesium calcite and dolomite, dedolomitization, dissolution, and precipitation of vug-filling calcite and dolomite cement have been more common outside the Basin than inside. δ18O in whole-rock (excluding vug-filling) calcite from core samples ranges from − 7.14‰ to + 0.85‰ PDB. δ13C varies from − 6.92‰ to + 3.30‰ PDB. Both stable isotopes correlate inversely with the abundance of subaerial exposure features indicating that freshwater diagenesis has been extensive especially outside and at the edge of the Chicxulub Sedimentary Basin. δ18O and δ13C in whole-rock (excluding vug-filling) dolomite ranges from − 5.54‰ to + 0.87‰ PDB and − 4.63‰ to + 3.38‰ PDB, respectively. Most dolomite samples have negative δ18O and positive δ13C suggesting that replacive dolomitization involved the presence of a fluid dominated by freshwater and/or an anomalously high geothermal gradient. Most dolomite XRD-determined mole percent CaCO3 varies between 51 and 56. Replacive dolomite is larger, more euhedral, and less stoichiometric inside the Chicxulub Sedimentary Basin than outside.

Journal of Maps, 2019

This work offers a large-scale approach to the stratigraphy of an area in southern Mexico that includes three different tectono-stratigraphic terranes and displays a great geological diversity. In the attached 1:100,000-scale geological map, the stratigraphic information is grouped according to the occurrence in sedimentary basins. Here, we describe the basement and six basins in turn. In four of the sedimentary basins, thick Mesozoic successions that accumulated on the basement record the evolution from a continental environment during the Triassic-Jurassic, to a marine environment, comprising clastic and calcareous deposits, during the early Cretaceous. Cenozoic ages are recorded in clastic and lacustrine sedimentary successions and in abundant igneous rocks in two of the continental basins. The geodatabase was compiled in GIS format and subsequently imported in vector graphic software to achieve a design similar to the cartographic series 1:100,000 CARTA GEOLÓGICA DE MÉXICO of the Instituto de Geología, UNAM.

Revista de arqueología americana, 2022

Este es un artículo de acceso abierto bajo la licencia CC BY-NC-SA 4.0

2020

Carbonates constitute Earth's largest carbon (C) reservoir, with most shallow marine deposition occurring on the low-latitude carbonate platforms covering ~800,000 km 2. The Yucatán Platform situated between the Western Caribbean and Gulf of Mexico basins, is one of the largest present-day carbonate platforms. As with post-Paleozoic carbonates generally, it is readily weathered and karstified, as these retain primary porosity and remain close to the surface, with dissolution leading to order of magnitude permeability increases. This addresses questions of the Yucatan geological history using a combination of literature research, geophysical and geodetic data, and geochemical analyses, along with field observations. The genesis and hydrogeological function of the surface expressed Ring of Cenotes remains an active question in the Yucatán geological understanding. A genetic model for the formation of the Chicxulub Ring of Cenotes (ROC) is presented based on the published geology and stratigraphy, geophysical surveys, and general carbonate platform hydrogeology and hydrogeochemistry. Hydrogeothermal circulation of marine water through the platform pre-dates the impact, with density-driven fluxes exiting the submarine platform top, and dolomitization and anhydritization along the platform flow paths from the platform sides. Platform scale circulation continued post-impact, but enhanced vertical fluxes constrained around the perimeter of the hot and low-permeability melt plug. The numerous impact ring fault sets provide likely flow paths, but it is the fracture set circumscribing the perimeter of the impact melt plug that is significantly karstified by bottom-up hypogene processes to produce the observed Ring of Cenotes. Epigene karstification was only in the Late Miocene (<10 Ma) with exposure of the Yucatán Peninsula to meteoric inputs. Figure I-2 a. Three-dimensional conceptual model of a karst geology aquifer, with a 3D matrix, 2D planar fractures, fissures, and bedding planes, and 1D linear conduits hosing turbulent flow. b. Table of four representative karst aquifers, with data on the proportion of the total water that is held in the 3D matrix storage, and the proportion of the total flux that occurs in the 1D conduits. From Worthington et al. (2000). The most distinctive aspect of shallow marine carbonate platforms is the predominant role of organisms in producing, processing and trapping carbonate sediment, which confers the complexity of biogenic and abiotic interactions imprinted and overlapped over time. Over geological time scales, the submarine shelf can be understood as a surface of dynamic equilibrium (Wright & Burchette, 1996) controlled by the variables of relative sea level changes, the rate and characteristics of sediment input, and the rate of sediment transport. With sea level fluctuations, platforms may partially or completely be sub-aerial, with marine carbonate deposition interrupted, and the surface then subject to hydrochemical processes including dissolution by meteoric waters and any biological weathering tied to ecosystem development. Surface weathering and internal dissolution both remove mass from the sub-aerial platform (now peninsula or island) and may lead to surface lowering. Area "3D" Water in matrix STORAGE % "1D" FLOW in conduits, %

The skeletal remains of a Paleoamerican (Naia; HN5/48) and extinct megafauna were found at
40 to
43 mbsl in a submerged dissolution chamber named Hoyo Negro (HN) in the Sac Actun Cave System, Yucatan Peninsula, Mexico. The human remains were dated to between 12 and 13 Ka, making these remains the oldest securely dated in the Yucatan. Twelve sediment cores were used to reconstruct the Holocene flooding history of the now phreatic cave passages and cenotes (Ich Balam, Oasis) that connect to HN. Four facies were found: 1. bat guano and Seed (SF), 2. lime Mud (MF), 3. Calcite Rafts (CRF) and 4. Organic Matter/Calcite Rafts (OM/CRF) which were defined by their lithologic characteristics and ostracod, foraminifera and testate amoebae content. Basal radiocarbon ages (AMS) of aquatic sediments (SF) combined with cave bottom and ceiling height profiles determined the history of flooding in HN and when access was restricted for human and animal entry. Our results show that the bottom of HN was flooded at least by 9850 cal yr BP but likely earlier. We also found, that the pit became inaccessible for human and animal entry at z8100 cal yr BP, when water reaching the cave ceiling effectively prevented entry. Water level continued to rise between z6000 and 8100 cal yr BP, filling the cave passages and entry points to HN (Cenotes Ich Balam and Oasis). Analysis of cave facies revealed that both Holocene sea-level rise and cave ceiling height determined the configuration of airways and the deposition of floating and bat derived OM (guano and seeds). Calcite rafts, which form on the water surface, are also dependent on the presence of airways but can also form in isolated air domes in the cave ceiling that affect their loci of deposition on the cave bottom. These results indicated that aquatic cave sedimentation is transient in time and space, necessitating extraction of multiple cores to determine a limit after which flooding occurred.

SEDIMENTS IN THE CHACAHUA-PASTORÍA LAGOON SYSTEM, OAXACA, MEXICO (Atena Editora), 2023

Con el fin de evaluar el riesgo de azolvamiento del sistema laguna Chacahua-Pastoría, mediante un mapa topográfico escala 1:50000 se caracterizaron morfométricamente los ríos Chacalapa y San Francisco, tributarios del cuerpo de agua. Para ambos ríos se delimitaron sus cuencas, se determinó el área y el perímetro, así como el factor de forma y circularidad. La red de drenaje se midió y se jerarquizó, determinando la densidad de drenaje y el grado de bifurcación. En las variables de relieve se determinaron los puntos extremos, como es el origen y salida del cauce principal, la pendiente promedio y el índice de sinuosidad. En ambos ríos, dos veces al día se cuantificaron los sedimentos en suspensión con un medidor DH-48, mientras que los sedimentos en el fondo se evaluaron con el dispositivo Halley-Smith. Destacan en los resultados que el área de la cuenca del río Chacalapa es de 108.56 km2, mientras que la del río San Francisco es 9% mayor y de forma alargada. Para ambas cuencas el patrón de drenaje es dendrítico, con similar total de cauces con 83, para ambos ríos la bifurcación promedio es de 3.9 con cuatro jerarquías, transitando en la planicie costera cerca de un tercio de sus longitudes, con baja sinuosidad. Se registraron 83 eventos de lluvia con 1,784.4 mm que promovieron que salieran de las dos cuencas 107.577 Mm3 de agua, de los cuales 40.361 Mm3 corresponden al río Chacalapa. En lo que respecta a los sedimentos, en total salieron de las cuencas 6,999 toneladas, correspondiendo al río San Francisco el 62%, mayor cantidad, en parte, por tener una mayor extensión, correspondiendo a las arenas, el 75% de los sedimentos en el fondo, material que se queda entre marismas, previo a su llegada a las lagunas.