Formation Miocene Research Articles

Stratigraphic overview of the Neogene Transylvanian Basin, Romania

Although the Transylvanian Basin is often referred as part of the Miocene Pannonian Basin System, we point out important tectonic and sedimentary differences reflected in the stratigraphy. The Neogene of the Transylvanian Basin can be split into two tectonic megasequences: Lower Miocene and Middle to Upper Miocene. The Early Miocene onset of the back arc extension in the Pannonian Basin was not observed in the Transylvanian Basin, where shallow to deep marine sediments were deposited in a flexural basin. Diverse types of facies developed in the continental (e.g., Sânmihai) and marine (e.g., Coruş, Chechiş, Hida) Lower Miocene formations. Although these are poorly constrained to the standard biostratigraphy, recent 87 Sr- 86 Sr data support their limited correlation with the Burdigalian. The Middle Miocene extension in the Transylvanian Basin is very weak compared to that the Pannonian Basin. As the high-resolution Middle Miocene regional biostratigraphy of the Badenian and Sarmatian was calibrated by magnetostratigraphy and radiometric dating of the volcanic tuffs up to the Serravallian/Tortonian boundary, the influence of the regional tectonics on the basin's evolution and stratigraphy can be better understood. The regional tectonics produced a progressive basin isolation starting with the late part of the Middle Miocene. The uplift of the Carpathians isolated the basin at the beginning of the Pannonian and initiated the fan delta, lacustrine, and fluvial sedimentation. The basin was rapidly uplifted and eroded, while post-extensional subsidence was still ongoing in the Pannonian Basin. Endemic fossil assemblages allow only regional-scale correlations for this interval. The uppermost part of the stratigraphic record is represented by the volcano-sedimentary formations generated by the late evolution of the Eastern Carpathians. The sedimentation and subsidence pattern of the Transylvanian Basin reflect the effect of retreating subduction zone in the Eastern Carpathians.

Increase in porosity and permeability resolution for thin-bedded Miocene formation in Carpathian Foredeep using different clustering methods

AbstractThe accurate interpretation of well-logging data is a crucial stage in the exploration of gas- and oil-bearing reservoirs. Geological formations, such as the Miocene deposits, present many challenges related to thin layers, whose thickness is often less than the measurement resolution. This research emphasizes the potential of utilizing electrofacies in such challenging environments. The application of electrofacies not only allows for the grouping of intervals with similar physical characteristics but can also be useful for estimating porosity and permeability parameters. For this purpose, various clustering methods were tested, including the 2D indexed and probabilized self-organizing map (IPSOM) method with and without supervision. Subsequently, the usefulness of the obtained results to improve the estimation of porosity and permeability parameters with the help of artificial neural networks was verified. As a result of the conducted analyses, significantly better results were obtained compared to classical petrophysical interpretation. The calculated porosity and permeability parameters were characterized by much greater variability and alignment with laboratory measurements on porosity and permeability. The best results were obtained for the IPSOM method, but the other methods did not differ significantly. In conclusion, the studies have shown a positive result of applying clustering methods, including the IPSOM method, to improve the estimation of permeability and porosity parameters in complicated, thinly-layered formations.

On the timing of the opening of Western Pacific's back-arc seas: Data from Sr, O and C isotopes in Miocene molluscs of Sakhalin and Hokkaido

This study presents Sr-isotope data to determine the stage affiliation of different parts of the Miocene Sertunaiskaya and Kurasiyskaya formations in Sakhalin, as well as the upper part of the Togeshita Formation in Hokkaido. Additionally, it confirms a diachronous boundary between the Sertunaiskaya and Kurasiyskaya formations. The data received will be useful for globally correlating the Miocene formations of the Sakhalin-Hokkaido area. The study indicates that the Japan and Kuril back-arc basins in the Western Pacific underwent their final opening stages during the Middle Miocene (18.1–17.7 and 15.9–14.2 Ma, respectively), as determined by the SIS method. This process was likely influenced by both global and local factors. One of the local influences on the formation of back-arc basins in the Western Pacific appears to be the influx of cool boreal waters, as indicated by the δ18O signals. The Miocene data from the Sakhalin-Hokkaido area, including evidence from Sr, O, and C isotopes, combined with corresponding paleontological, stratigraphic, palaeomagnetic, and palaeobiogeographic data from the Paleogene and Neogene, provide a four-stage chronological sequence of events related to the opening of the Western Pacific's back-arc seas. This paper presents original information on the Miocene C-isotope excursion in the Western Pacific, which are correlated with the Monterey Event. Recent data on this topic may have enhanced our comprehension of the conditions required for the formation of hydrocarbons, which are found in substantial amounts in the Miocene of northern Sakhalin and Hokkaido.

Strontium isotope stratigraphy of marine Oligocene–Miocene sedimentary successions of Kutch Basin, western India

The Kutch Basin of western India exposes one of the most complete, fossiliferous marine Cenozoic sedimentary sequences of India. Precise depositional ages of these sequences are of great importance in the reconstruction of palaeoclimatic and palaeobiogeographic histories of the basin. Due to the poorly constrained foraminiferal biostratigraphic ages, we conducted high‐resolution 87Sr/86Sr chronology of the various fossiliferous, stratigraphically continuous units of Oligocene–Miocene strata in Kutch Basin. Besides updating the previously determined 87Sr/86Sr chronology, we report new numerical depositional ages for Oligocene–Miocene formations and members, and correlated these ages to the existing biostratigraphic schemes. The new 87Sr/86Sr data indicates a depositional age range between 28.64 + 0.29/‐1.11 and 23.51 + 1.53/‐1.85 Ma (Rupelian‐Chattian) for the Maniyara Fort Formation, between 23.07 + 0.94/1.39 and 18.09 + 0.24/‐0.57 Ma (Chattian‐Burdigalian) for the Khari Nadi Formation, and between 15.11 + 0.56/‐2.87 and 12.29 + 1.22/‐1.9 Ma (Langhian‐Serravallian) for the Chhasra Formation. The sedimentation rate, determined through numerical ages derived from 87Sr/86Sr, indicates an increase in sedimentation for the Khari Nadi (0.23 ± 0.04 cm/kyr) and Chhasra (0.12 ± 0.04 cm/kyr) formations, likely related to uplift of the Himalaya‐Tibetan plateau and intensification of the Indian Summer Monsoon. The bulk sediment element ratios (V/Ni, Ni/Co and V/Cr) indicate oxic to suboxic palaeo‐redox conditions during deposition of the Oligocene–Miocene successions of the basin. Based on new and updated 87Sr/86Sr chronology, the depositional environments and sedimentation rates of the Kutch sequence are correlated with changes in sea‐level, sedimentation rates in the Arabian Sea and Bay of Bengal, and the global climate changes across the Oligocene–Miocene boundary.

The Miocene formations in the northern edge of the Tizi Ouzou basin: paleoenvironments and biostratigraphic study of Late Burdigalian to Langhian marls in the Abizar crescent structure

The Miocene formations in the northern edge of the Tizi Ouzou basin: paleoenvironments and biostratigraphic study of Late Burdigalian to Langhian marls in the Abizar crescent structure

Sedimentology Study Of Exposed Formations In Al-Assad Valley, Al-Baghdadi Area, Western Iraq

The presence of the Sheikh Alas Formation, the Shurau Formation, and the Euphrates Formation in the area of the current study. The inference of the Sheikh Alas Formation was from Nummlite fossils and planktonic Foraminifera fossils. The Euphrates Formation was deposited in a shallow marine environment, the Sheikh Alas Formation was deposited in an environment in for reef, and the Shurau Formation was deposited in an environment Back reef. The environment of the Euphrates Formation is a shallow lagoon environment for the presence of milliolied fossils, which represent the Miocene age as evidenced by the presence of the Borlis melo melo fossil. As for the environment of the Sheikh Alas Formation, it was deposited in a marine environment in for reef due to the presence of Planktonic foraminifera fossils and the Nummlite fossil, which represents the Oligocene age, and the environment of the Shurau Formation In a shallow, lagoon marine environment Back reef, there are abundant milliolid fossils. The boundary between the Miocene formations and the Oligocene formations is characterized by an unconformable boundary composed of a layer of basal conglomerate with a thickness of 6.5 m, which is affiliated with the Euphrates Formation in terms of age.

CCS Prospect Evaluation for Early Miocene Formation in the Eastern Gunsan Basin, Yellow Sea

CCS Prospect Evaluation for Early Miocene Formation in the Eastern Gunsan Basin, Yellow Sea

Distribution Patterns and Genesis of Geological Fractures/Microfaults in the Qiongdongnan Basin, North of the South China Sea

The Qiongdongnan Basin (QDNB), located in the north of the South China Sea, is a Cenozoic rift basin with abundant oil and gas resources. Large flake hydrates have been found in the core fractures of Quaternary formations in the deep-water depression of the QDNB. In order to understand the spatial distribution patterns of these fractures, their geneses in sedimentary basins, and their influences on gas migration and accumulation, such fractures have been observed using high-resolution 3D seismic images and visualization techniques. Four types of fractures and their combinations have been identified, namely bed-bounded fractures/microfaults, unbounded fractures, fracture bunches, and fracture clusters. Bed-bounded fractures/microfaults are mainly short and possess high density; they have developed in mass transport depositions (MTDs) or Meishan and Sanya Formations. The unbounded fractures/microfaults that occur in Miocene–Pliocene formations are mainly long and discrete, and are dominantly caused by strong tectonic movements, the concentration of stress, and sustained intense overpressure. The fracture bunches and fracture clusters that occur in Oligocene–Early Miocene formations have commonly developed with the accumulation of large numbers of fractures and may be related to the release of pressure, diapirs, and basement fault blocks (228.9 ± 1 Ma). In this study, six fluid charging or leakage models are proposed based on distinct fracture types, assuming the uniform conductivity of each fracture. In a 3D space view, a vertical decrease in the fracture scale (number or density) will more likely result in gas supply than dispersion, thus promoting the accumulation of gas in the reservoirs. Nevertheless, the fractures above the Bottom Simulating Reflect (BSR)/seismic anomaly are excessively developed, and bed-bounded fractures within a particular layer, such as MTDs, can easily cause seabed leakage. These results are useful for explaining the vertical migration of gas/fluids in areas and formations with less developed gas chimneys, faults, diapirs, and other structures, particularly in post-rifting basins.

Microfacies Analysis and Depositional Environment of Upper Oligocene-Lower Miocene Succession in Wadi Al-Khazgah of Anbar Governorate, Western Iraq

Microfacies and the Depositional Environment of (Upper Oligocene-Lower Miocene) succession in the Anah area, northwest of Anbar Governorate, western Iraq was carried out. This study was conducted on twenty-eight samples of limestone collected from the section of Wadi Al-Khazgah. Azkand and Anah formations of the Upper Oligocene and Euphrates Formation of Lower Miocene were identified in this section, depending on the availability of benthic Foraminifera and microfacies of each Formation. The depositional environment of the Azkand and Anah formations represents the environment of the reef, fore-reef, and back-reef, respectively, while the environment of the Euphrates Formation represents the shore, restricted to open marine.14 sub microfacies types have been distinguished, which are Lepidocyclina Lime Packstone, Miliolids Lime Grainstone, Coral Lime Boundstone, Miliolids Lime Packstone-Grainstone, Rotalia- Heterostegina Lime Packstone, Gastropoda Lime Packstone, Miliolids Lime Packstone, Heterostegina Lime Wackstone, Miliolids Lime Wackstone, Dolomitized Mudstone, Lime Mudstone.

Integrated surface geochemical and seismic surveys for hydrocarbon exploration - A case study from southern Poland

Surface geochemical surveys were carried out in the Pawłosiów area in the eastern part of the Carpathian Foredeep. The research included an analysis of the molecular composition of soil gas samples as well as measurements of the calcite content, magnetic susceptibility and pH of soil samples. The results obtained were integrated with a geological-seismic model. Changes in the concentrations of total alkanes C2–C5 in relation to changes in indirect geochemical indicators showed “compensatory” character. This means that in places where alkane concentrations were increasing, negative anomalies of magnetic susceptibility and a decrease in pH values were observed. It may be related to the intensity of the oxidation processes or reduction of the magnetic minerals in, as well as the reduced permeability of, the Miocene layers in the zones analysed. Moreover, the complex geochemical-geophysical interpretation showed a zone of anomalous values of the total C2–C5 alkanes in the Pawłosiów area, which is suitable for prospecting. The research performed proved that a thorough analysis of the seismic record allowing subtle DHI anomalies appearing within the Miocene formations to be located, combined with the use of direct and indirect geochemical indicators, can help in identifying an area in terms of hydrocarbon potential. This applies in particular to this type of foreland basin, within which geological formations lie flat, and positive structures (anticlines) are hardly visible in seismic sections. In this type of structure, hydrocarbons can be accumulated in traps of a hybrid character (conventional and unconventional). The extensive zone of geochemical and geophysical anomalies found in the area of Pawłosiów may indicate the presence of this type of hydrocarbon accumulation.Comprehensive research, including direct and indirect geochemical methods in combination with a seismic survey, allows for a better assessment of the hydrocarbon potential of the studied area.

The Lithological and Paleogeographic Features of the Formation of the Lower Miocene of the Northeastern Shelf of Sakhalin Island

The Lithological and Paleogeographic Features of the Formation of the Lower Miocene of the Northeastern Shelf of Sakhalin Island

A New Species of Fossil Pseudosimnia (Gastropoda: Ovulidae) from the Miocene of West Java, Indonesia

A new species of Ovulidae Schilder, 1968, Pseudosimnia javanensis n. sp., is described from Miocene formations in the hills south of Tasikmalaya, West Java, Indonesia. The general appearance of the new taxon shows a combination of characters that distinguish it from any other living species of Pseudosimnia Schilder, 1925. One subspecies is also described, Pseudosimnia javanensis elongata n. ssp.

Sequence stratigraphy and petrographic characteristics of Oligocene sediments in the West trough of the Cuu Long Basin, Vietnam

The Cuu Long Basin is the major source of Vietnam's oil and gas production. In clastic sediments, the Oligocene and Lower Miocene formations are the main objects of oil and gas exploration and exploitation activities. Oligocene sediments are both source and reservoir rocks; therefore, studying the petroleum system of these formations is of great interest. This paper discusses detailed stratigraphy and lithological properties to clarify the Oligocene sedimentary characteristics and their significance in the petroleum system. Study results show that Oligocene sediments are divided into three sequences, including eight parasequences and are dominated by the terrestrial sediments. Sequence E, mainly coarse-grained, contains low palynomorphs and rich organic matter with mainly palynomaceral 1 and is deposited in freshwater fluvial settings under high-energy conditions, showing sediments not so far from the original areas. The high level of detrital matrix materials is the main cause of poor or negligible porosity of the rock. The parasequences of Sequence D contain abundant palynomorph assemblages, characterized by swamp and freshwater alga taxa. They are deposited mainly in the shallow lake with a decreasing energy level pointing upward. The volume of organic matter in sediments is very rich, with sapropel organic matter (SOM) rates reaching up to 80%, indicating that the hydrocarbon generation potential is mainly oil-prone and some oil-gas mixtures. The porosity is poor and reservoir quality is affected by detrital matrix and authigenic minerals. The parasequences of Sequence C are characterized by the extreme abundance of freshwater algae, deposited mainly in the shallow-to-deep lake under moderate energy conditions, and rich sapropel organic matter, suggesting mainly oil-prone in hydrocarbon generation potentials. The porosity ranges from fair to good and the reservoir quality is estimated as the best in Oligocene sediments. A new finding of marker assemblages provides evidence to pinpoint the stratigraphic boundary between the Lower Miocene and Upper Oligocene. This finding helps to complete the stratigraphic framework of the area and to correlate the stratigraphy to adjacent sedimentary basins. This study provides information on depositional environmental conditions, organic matter content, hydrocarbon generation potential, and reservoir quality that relate to source rock, reservoir, and seal; these are the elements of a petroleum system. A complete petroleum system assessment requires a holistic view of all the petroleum system elements.

Geochemical Analysis of Hot Springs in Massepe, Tellu Limpoe Sidenreng Rappang Regency, South Sulawesi Province, Indonesia

Location of the study is administratively located in the District Tellu Limpoe, Sidenreng Rappang Regency in South Sulawesi Province. Geographically located at coordinate 119°47'00" – 119°49'00" east longitude and 04°00'00"– 04°02’00" latitude. This study aims to determine the geological conditions and geochemical, it is hot spring types, and subsurface temperature of the geothermal Massepe area Sidenreng Rappang district of South Sulawesi Province. Methods of research are conducted in the form of data collection methods and methods of geological and geochemical laboratory analysis. The geomorphology of the study area consists of one unit, the unit is flat. The type of developing river is the river periodically with stadia geomorphology including adults. The stratigraphy of the study area is divided into two units of rocks, it is rock units of ignimbrite from Pare – Pare Volcanics Formation of Pliocene age and rock units of basalt from Soppeng Volcanics Formation of Early Miocene – Middle Miocene. The structure that developed in the research area is a joint and strike–slip fault, it is a Massepestrike–slip fault. Geothermal manifestations in the study area consist of 3 stations hotspring. The percentage values of ion content of HCO3-, Cl-, and SO42- in hot water samples were analyzed, indicating that the hot springs area of research, including the chloride water type. Estimation of subsurface temperature by using the geothermometer Na - K in the research area at station 1 – 3 is 162°C - 168°C, using the geothermometer Na - K - Mg are known, that the hot springs in the area of research included in partially equilibrated.

Rock physics analysis of reservoir units of the Semliki basin, Albertine graben: A case study

Rock physics permits the integration of geophysical and geological information. The incorporation of geology information assists in constraining non-uniqueness during quantitative interpretation. In this investigation, Kanywataba well was first analyzed qualitatively by use of cross plots to ascertain whether the various logs (P-wave velocity versus S-wave velocity, density versus porosity) conform to conventional trends. It was observed that density decreases with porosity and the cross plot of P-wave velocity versus S-wave velocity indicates an increasing trend of the two parameters. Rock physics models were applied to delineate reservoir properties with reference to Kanywataba-1 well of the Semliki basin in the Albertine graben. The two rock physics models namely; the patchy constant cemented model and the constant cement model described the Upper Pliocene Formation and Upper Miocene Formation respectively. The analysis revealed high sandstone bulk modulus values are attributed to the presence of feldspars, micas, and calcareous clays in the reservoir units. The data interpretation was executed using rock physics templates that provide a quantitative interpretation of reservoir properties based on the area's local geology. The rock physics templates of Vp/Vs ratio versus acoustic impedance indicate 5%gas for Upper Miocene Formation and 50% gas for Upper Pliocene Formation. In both Formations, three lithological zones interpreted as gas sand, brine sand, and shaly sand were observed. With information from the burial history of the sediments within the Albertine Graben and constant cement model, compaction regime were observed. The Upper Miocene Formation indicates the presence of a chemical compaction regime which implies, that it has undergone diagenesis with evidence from logs indicating higher velocities, lower porosity, and some amount of cementation associated with this Formation.

Depositional environments of the Miocene sediments in northern Song Hong basin

Northern Song Hong Tertiary Sedimentary basin is a classic case study of a pull-apart basin in southeast Asia, whose formation was controlled by the India-Eurasia collision, sinistral and dextral strike-slip motion of the Ailao Shan-Red River Shear Zone and Opening of the East Vietnam Sea during the Cenozoic. Unlike the central and southern parts of the basin, the northern Song Hong Basin experienced a very strong inversion during the Late Miocene. This rapid uplift of the region has led to significantly change in lithofacies and sedimentary environments, which are now still poorly understood. This uncertainty is considered one of the main challingings in prediction of the non-structural traps in the region. The recent results derived from well logging and 2D/3D seismic interpretation allowed us to define the Miocene formation in northern Song Hong basin, which are subdivided into three substrata, namely: the Lower, Middle and Upper stratum, which are characterized by typical characteristics of lithology and depositional environments. The Lower Miocene formation is dominated by deltaic environment at the bottom, transitioning to the overlying shelf environment. Lithology of the section varies from coarse-grained sediment (sandstone) to fine grained material such as shale and mudstone upward; The Middle Miocene stratum demonstrate sandier, coalic materials of the delta plain and delta front environments intercalated with swampy shale. In contrast, the Upper Miocene section is characterized by more fluvial and nearshore elements. It is illustrated by presence of the channel-filled sand bodies and mouth/longshore sand bars. These sand bodies demonstrate good porosity and horizontal permeability, which are considered to be good potential reservoir for both structural and non-structural traps in the Miocene formation.

Improving carbonate reservoir characterization by applying rock typing methods: a case study from the Nam Con Son Basin, offshore Vietnam

Understanding the permeability-porosity relationships is the key to improving reservoir prediction and exploitation especially in carbonate reservoirs, which are known for their complex textural and diagenetic variation. Rock type classifications have long been proven to be an effective technique for establishing permeability- porosity relationships, enhance the capability to capture the various reservoir flow behavior and prediction for uncored reservoir zones. This study highlights some of those practical and theoretically-correct methods, such as Hydraulic Flow Unit (HFU); Global hydraulic element (GHE), Winland’s R35 method, Pittman method, Lucia method. They are proposed and tested for identification and characterization of the rock types using a database of 555 core plugs from the Miocene carbonate reservoir in the Nam Con Son basin. It is a large isolated carbonate build-up structure which were deposited within a shallow marine platform interior and are dominated by coral, red algal and foraminiferal packstones, wackestones and grainstones. Hydrocarbons in this reservoir have been found in the upper most part of the late Miocene formation. Conventional core data were first used to define and display the cross plot of permeability and porosity. Different charts and cutoff thresholds were used to classified, defined number of rock type and the linear and non-linear equations were established. The predicted core permeability was calculated using different methods and compared with the actual core permeability for each rock type. The predicted reservoir rock type and permeability predictions of HFU method was recognized to give better matching of measured core permeability with coefficient of more than 89%.

Tectonostratigraphic controls on pore fluid pressure distribution across the Taranaki Basin, New Zealand

AbstractSignificant variations in pore pressure across the Taranaki Basin, New Zealand, are attributed to changes in lithofacies and structure, usefully illustrated in terms of ten areas that we term geopressure provinces, each displaying individual pore pressure trends. Cretaceous to Early Miocene formations in different parts of the basin can be either normally pressured (near or at hydrostatic) or significantly overpressured (up to 28 MPa) at the same depth. Variations in Eocene–Oligocene facies types and thicknesses both within and between geopressure provinces provide first‐order control on the magnitude, distribution and maintenance of overpressure across the basin. Examples of hydraulic compartmentalisation due to sealing faults and stratigraphic architecture are identified within the basin. Deep pore pressure transitions are sealed by diagenetic, structural or stratigraphic mechanisms in different places and are associated with an increase in mudrock volume (reduced permeability) or gas generation. Thus, pore pressure distribution in the Taranaki Basin is controlled by a combination of sediment loading, lithofacies variations, fault zone permeability and structural architecture. This work represents an appraisal of the pore pressure distribution across the whole of a multiphase structurally complex basin, and the approach taken provides a framework for better understanding the distribution of pore fluid pressures and pore fluid migration in other sedimentary basins.

GCS site selection in saline Miocene formations in South Louisiana

One of the key requirements of a commercial scale geologic carbon sequestration (GCS) site selection process is identifying injection sites to safely inject and retain injected CO2 over extended time scales. This requires thorough evaluation of site-specific surface and subsurface features. A site screening and selection framework was developed and used to identify potential sites in South Louisiana, incorporating surface data including site proximity to large CO2 stationary sources, vicinity of large population centres and state lands, land usage, legacy oil and gas wells, and local/regional geologic trends. Regionally the Miocene sediments thicken and dip towards the south, reflecting a prograding deltaic environment during the Miocene which resulted in the deposition of thick packages of fine-grained sandstones suitable for CO2 storage. The results of three example selected sites that are spatially separated with varying subsurface and surface features are presented in this study. The multiple stacked sand zones at these sites provide ample amount of pore volume for CO2 storage with varying degree of stratigraphic/structural traps for long terms storage containment. The screening framework presented in this study and the detailed evaluation of three specific sites in South Louisiana provides a process to screen and characterize sites for GCS projects and the suitability of these Miocene sediments for commercial scale CO2 storage projects. It is envisioned that the analysis described in this paper will be beneficial for a large number of audiences involved in GCS work and aid in the site selection process.

Late Cretaceous–Miocene depositional evolution of Chiapas, Mexico: A foreland controlled by collision of Greater Antilles arc and the subsequent relative migration of the Chortís Block

New U–Pb and “double dating” (U–Pb and U–Th)/He) age determinations on detrital zircons from Upper Cretaceous–Miocene formations greatly improve our understanding of both evolutionary and clastic provenance models for southern Mexico and the western Caribbean. Samples from the Méndez, Ocozocoautla, Angostura, Tenejapa, Soyaló, El Bosque, San Juan, Nanchital Shale, Nanchital Conglomerate, Huamelula, and Ixtapa units in the western Sierra de Chiapas, Mexico, consistently indicate a south-to-north transport of clastic detritus from orogenic headlands into the Chiapas Foldbelt Basin and, presumably, the Sureste Basin (Gulf of Mexico). However, this interpretation is partly guided by 1) palinspastic reconstructions of the Chortís Block and fault slices of the North America–Caribbean plate boundary that restore to paleo-positions south of Oaxaca and Chiapas states and western Guatemala, and 2) published fission track data that indicate the Chiapas Massif was not a significant sediment source or barrier until the late middle Miocene. In addition, zircon data on volcanic breccias (magmatic?) from cores of supposed Cretaceous and Paleogene levels of the Salina Cruz wells indicate that today’s Gulf of Tehuantepec forearc is likely the “western tail” of the Chortís Block and represents a displaced segment of the Guerrero Arc of western Mexico. Analyses of key thin sections and one heavy mineral sample complete the data set. We find that Pacific-origin Caribbean models provide the necessary inferences for meaningful interpretation of our data, and, conversely, that our data on the various depositional units through time iteratively help to support Pacific-origin models. For example, our data from Chiapas supports 1) arc collision to the south in the Maastrichtian (Greater Antilles), and 2) the existence of Paleogene orogenic highlands south of the Chiapas Massif, interpreted here as the paleo-North America–Caribbean plate boundary zone.