The Block is commonly delimited by the continental margin in the Gulf of Mexico to the north, in the Caribbean Sea to the east, and in the Pacific Ocean to the southwest, and further, by the Motagua–Polochic Faults to the south-southeast, and by the Isthmus of Tehuantepec to the west.[1] The Motagua–Polochic Faults divide the Maya Block from the Chortis Block, while the Isthmus of Tehuantepec divides it from the Oaxaquia Block (i.e. the Juarez, Cuicateco, or Oaxaquia Block, Terrane, or microcontinent).[2][n 1]
The Block's precise subaerial limits are not widely agreed upon, in contrast to its relatively exact submarine borders.[n 2][citation needed] Furthermore, it has been recently suggested that the Block's western extreme may rather extend past the Isthmus of Tehuantepec, along the Gulf of Mexico, and into Louisiana.[3][n 3]
Geography
Physical
Mountains
A broad arching fold belt of 'morphological distinct mountain ranges separated by deep fault-controlled canyons and occasional broad alluvial valleys' extends along the south-southeasterly limit of the Block.[4] The most prominent of said mountain ranges are the Northern Chiapas Mountains and the Sierra Madre de Chiapas in Mexico, the Cuchumatanes, Chama, Santa Cruz, and Lacandon Ranges in Guatemala, and the Maya Mountains in Belize.[5]
Karstlands
The 'most extensive karstlands of the North American continent' extend northwards from the Block's southern extreme.[6] The Block's most prominent karstic landform is the Yucatán Platform to its north.[citation needed] Relatively less prominent karstic formations occur in the Block's southern portion, including an unnamed formation in northwestern Peten to northeastern Belize, the Belize Barrier Reef, the Lacandon Range, the Cuchumatanes Range, and various formations to the north and south of the Maya Mountains.[7][n 4]
Coasts
The most prominent topographic features of the Block's Caribbean coast are extensive seagrass beds and coral reefs, with the Belize Barrier Reef forming a notable example of the latter.[8] Its Pacific coast, in contrast, is predominated by extensive mangrove forests.[9]
Human
The terrestrial portion of the Block encompasses all six districts of Belize, five northerly departments of Guatemala (Huehuetenango, Quiche, Alta Verapaz, Izabal, Peten), and five southeasterly states of Mexico (Chiapas, Tabasco, Campeche, Yucatán, and Quintana Roo). Its submarine portion encompasses the continental shelf which abuts the coastal districts.
Geology
Stratigraphy
Crust
Mean thickness of the continental crust constituting the Block increases southwards, ranging from 20–25 kilometres (12–16 mi) in the northern Yucatán Peninsula to 30–40 kilometres (19–25 mi) in the Peninsula's south.[10] The crust's i.e. Block's crystalline basement is composed mainly of Silurian–Triassic metamorphic and igneous rocks, and is exposed in at least five formations, namely, the Mixtequita Massif, Chiapas Massif, Cuchumatanes Dome, Tucuru–Teleman, and the Maya Mountains.[11] Elsewhere, the basement is overlain by a thick sedimentary cover of Upper Palaeozoic clasts and carbonates, Upper Jurassic continental redbeds, and Cretaceous–Eocene carbonates and evaporites.[4]
It has been suggested that the Block's continental basement is stretched, since its sedimentary cover reaches a thickness of up to 6 kilometres (3.7 mi), this being considered impossible on an unstretched basement at isostatic equilibrium.[10][n 5]
Morphology
Provinces
The Block is thought to fully or partially incorporate between two and thirteen geologic provinces.[12]
Basins
The Block is believed to fully or partially comprehend some four or five sedimentary basins.[13]
Faults
A number of faults or fault zones have been identified within the Block, the most prominent of which include various boundary faults abutting the Maya Mountains, various offshore faults east of the Yucatán Peninsula–Belize, the Ticul Fault, the Malpaso Faults, and the Rio Hondo Faults.[14][n 6]
Tectonics
The Block is thought to experience significant counterclockwise rotation and a north-northwest down tilt, which gradually lowers the northern portion of the Yucatán Platform, thereby lifting its southern extreme in the Maya Mountains.[15] It is nonetheless tectonically rigid or stable, experiencing an absolute west-southwest motion of 1.8 centimetres (0.71 in) per annum.[16][n 7] Central America, including the southern portion of the Maya Block, 'is very well-known and characterised by numerous, medium size earthquakes preceded and followed by damaging shocks,' with the Middle America Trench in the Pacific deemed the main source of such quakes.[17][n 8] Of thirty-three earthquakes of Ms ≥ 7.0 in Central America during 1900–1993, the epicentres of at least two of these were located within the Block (in its southwestern quadrant), though a further nine were located near it (in the Motagua–Polochic Faults or the portion of the Middle America Trench bordering the Block).[18]
History
Pre-Cenozoic
Middle America, including the Maya Block, is thought to have taken shape sometime after 170 million years ago.[19] Its formation is thought to have 'involved [the] complex movement of [various] crustal blocks and terranes between the two pre-existing continental masses [ie North and South America].'[20] Details of the pre-Cenozoic portion of this process (170–67 million years ago), however, are not widely agreed upon.[20][n 9] Nonetheless, it has been proposed that the Block formed before or during the opening of the Iapetus Ocean.[21] It, together with the Oaxaquia, Suwannee, and Carolina Blocks, are thought to have constituted a peri-Gondwanan terrane on that continent's western, northwestern, northern, or eastern edge during the Appalachian–Caledonian or Ouachita–Marathon–Appalachian orogeny (that is, during the formation of Pangaea from the collision of Gondwana and Laurentia).[22] It is thought to have been displaced away from the Laurentian craton by clockwise rotation, translation, or anticlockwise rotation, during the Middle Jurassic opening of the Gulf of Mexico and subsequent northwesterly drift of North America away from Pangaea.[23][n 10][n 11]
Cenozoic
Details of the Cenozoic (66–0 million years ago) geologic history of Middle America, including that of the Maya Block, are relatively more widely agreed upon.[20] In broad strokes, the Chortis Block is thought to have reached its present-day position by at least 20 million years ago.[24] The northern and eastern coasts of the Block are not thought to have been fully subaerially exposed until some 5–2 million years ago.[25] The Block's coastlines, which were initially more expansive than its present-day ones, are thought to have reached modern dimensions due to rising sea levels some 11–8 thousand years ago.[26]
Scholarship
The Block was discovered in 1969 by Gabriel Dengo, a Guatemalan geographer.[27] It was quickly adopted in scholarship, and remains 'accepted by many as a valid subdivision of Central America's geology, especially of its crystalline basement.'[28]
Tables
Karstlands
Topographic characterisations of karstland in the northern portion of the Maya Block.[29]
Description
Location
Notes
Block-faulted coastal plain
east
incl broad lagoons, mangrove swamps, and seasonal marshlands; incl north-northeast fault-bounded ridges and depressions; incl coral reefs and cayes
Pitted peninsular plain
north, west
incl dense network of cenotes; incl extensive, contiguous system of flooded caverns; not incl any surface streams
Hilly peninsular plain
west
incl La Sierrita de Ticul hills; incl ephemeral surface streams
Varied inland plain
south, west
incl steep, irregular hills and depressions; incl extensive fractures and caverns; incl vast alluvial plain with various large swamps and lakes; incl various surface streams
Provinces
Geologic provinces in the Maya Block per 21st century literature.[30][n 12]
incl end of eastwards migration of Chortis Block; incl possible uplift of Chortis Block; incl formation of Bay of Honduras i.e. initial linking of Maya and Chortis Blocks; cf[42]
^The Maya Block was first defined as 'the area [of Central America ie of that land and continental shelf which extends from the Isthmus of Tehuantepec in Mexico to the Atrato lowland in Colombia] north of the Motagua fault zone [...] [ie] northern Guatemala, Belice [Belize], the states of Chiapas, Tabasco, Campeche, Yucatán and Quintana Roo in Mexico, and the Campeche Bank in the Gulf of Mexico' (Dengo 1969, p. 312).
^Martens 2009, pp. 9–12, 37, 93 notes that, though some six faults are thought to constitute the Motagua–Polochic Faults, there is no widespread agreement on which exactly divides the Maya and Chortis Blocks. Additionally, the Maya–Oaxaquia boundary, in the broadly-demarcated Isthmus of Tehuantepec, is sometimes more precisely specified by coincident or adjacent faults, as in Ross et al. 2021, p. 243, fig. 1, Bundschuh & Alvarado 2012, pp. 278, 900, and Martens 2009, pp. 9–10. Faults in the Motagua–Polochic Faults include the Polochic or Chixoy–Polochic, Panima, Baja Verapaz, San Agustin, Cabañas or Cabañas–Jubuco or Motagua, and Jocotan–Chamelecon Faults (Martens 2009, pp. 9–11, Bundschuh & Alvarado 2012, pp. 328–329). Faults in or near the Isthmus of Tehuantepec include the Vista Hermosa Fault, the Salina Cruz Fault, and the East Mexican Transform (Ross et al. 2021, p. 243, fig. 1, Bundschuh & Alvarado 2012, pp. 278, 900, Martens 2009, p. 9).
^Nonetheless, this article employs the Maya Block's more established western limit, ie the Isthmus of Tehuantepec.
^The Peten–Belize and the Barrier Reef kastlands are dolines or fluviokarsts, while the remaining southerly formations are cone or tower karsts (Bundschuh & Alvarado 2012, p. 157, fig. 5.1). The karstlands abutting the Maya Mountains are the Vaca Plateau and the Boundary ie Sibun–Manatee Faults to the north, and the Little Quartz Ridge ie K/T Fault Ridges to the south (Bundschuh & Alvarado 2012, p. 157, fig. 5.1). The unnamed Peten–Belize encompasses the Yalbac Hills (Bundschuh & Alvarado 2012, p. 162).
^Sedimentary cover thickness diminishes to 0.750 kilometres (0.466 mi) within the Chicxulub crater (where the crystalline basement is uplifted), and 3.300 kilometres (2.051 mi) near the Yucatan Peninsula's centre (Guzman-Hidalgo et al. 2021, p. 4, fig. 2, Guzman-Hidalgo et al. 2021, pp. 7–8).
^The Maya Block is additionally bounded by the Motagua–Polochic Faults, and possibly, faults in or near the Isthmus of Tehuantepec, as per section 'Extent' of this article.
^With the Cocos Plate experiencing an absolute northeast motion of 7 centimetres (2.8 in) per annum, the Chortis Block a southeast motion of 0.9 centimetres (0.35 in) per annum, and the Cayman Ridge a southwest-northeast rifting of 2 centimetres (0.79 in) per annum (Authemayou et al. 2011, p. 2, fig. 1).
^Ninety-three per cent of the total moment for Ms > 7.0 earthquakes in Central America during 1898–1994 was released along the Middle America Trench (Bundschuh & Alvarado 2012, p. 324). Earthquakes of Ms ≥ 8.0 have not been observed in Central America since 1505, though this 500-year period has been deemed 'not long enough to rule out the occurrence of such events in the region,' while 16th and 17th century Spanish historical records have been described as 'poor' (Bundschuh & Alvarado 2012, p. 324).
^Bundschuh & Alvarado 2012, pp. 10, 542–543 suggest that geologic models of the formation of Middle America differ most significantly in their handling of the Caribbean Plate, with one group of models proposing its formation in the Pacific and subsequent movement to its present location, and another group proposing its formation in its present location.
^The palaeogeographic positions and tectonic interactions of pre-Mesozoic crustal blocks in present-day Mexico, Central America, and the Caribbean are still debated (Ross et al. 2021, p. 242). Fixing the pre-Mesozoic position of the Maya Black with respect to the southwestern margin of Laurentia is an important step in plate reconstructions of the assembly of Pangaea and the rotation-induced rifting and opening of the Gulf of Mexico (Ross et al. 2021, p. 242). Furthermore, Bundschuh & Alvarado 2012, p. 299 note –
Numerous illustrations/models show the Maya and Chortis blocks originating in the Gulf of Mexico or [show the] Maya [block originating] in the Gulf and [the] Chortis [block elsewhere]. They are shown to have rotated clockwise or anticlockwise by as much as 80º about various poles or migrating poles to their present locations. The variety and complexity of interpretations reflects dominance of models over data.
Similarity of basement, Jurassic and Cretaceous sections on [the] Maya and Chortis [blocks] should be reason to relate the two. Models should not deny stratigraphy. The two blocks have similar tectonic origins and similar structure. They are continental remnants of Pangean breakup, left at the western end of the Caribbean. [The] Maya [block] was sinistrally offset from [the] Chortis [block] when [the] early Cayman offset developed. Neither block is a terrane rotated into place form another location. The major Jurassic faults on [the] Maya and Chortis [blocks] (Río Hondo and Guayape) that remain parallel to coeval faults in the North and South America show that no rotation has occurred. Restoration of the blocks along the Cayman trend by re-aligning their eastern faulted margins also results in line-up the Río Hondo-Guayape systems.
^Largely coincident with the Yucatán platform province in Bundschuh & Alvarado 2012, p. 77, fig. 3.1 and the Maya Terrane province in Hasterok et al. 2022, p. 65, Zenodo version 1 dataset, QGIS file.
^Split into the Greater Antilles Accretionary Complex and Greater Antilles Arc provinces in Hasterok et al. 2022, p. 65, Zenodo version 1 dataset, QGIS file.
^Encompassed by the Maya highlands province in Bundschuh & Alvarado 2012, p. 77, fig. 3.1 and the Mayan Highlands province in Hasterok et al. 2022, p. 65, Zenodo version 1 dataset, QGIS file.
^Largely coincident with the Maya highlands province in Bundschuh & Alvarado 2012, p. 77, fig. 3.1 and the Mayan Highlands province in Hasterok et al. 2022, p. 65, Zenodo version 1 dataset, QGIS file.
^Largely coincident with the Central American Forearc province in Hasterok et al. 2022, p. 65, Zenodo version 1 dataset, QGIS file.
^Evenick ID is the unique basin identifier ie UBI as per Evenick 2021, app. A supp. no. 1. The Evenick ID for the Limon–Bocas del Toro Basin is not given in Evenick 2021, app. A supp. no. 1, though falls within 353–365, inclusive, given the alphabetical assignment of identifiers used therein.
^Encompassed by the Yucatan Platform basin in Robertson 2019.
^Encompassed by the Yucatan Platform basin in Robertson 2019.
^Largely coincident with the Peten basin in Robertson 2019. Split into the Petén and Corozal–Belize–Amatique basins in Bundschuh & Alvarado 2012, p. 347, fig. 13.1.
^Largely coincident with the Salinas–Sureste basin in Robertson 2019.
^For the Depth column, note N means normal crust focus, N+ means focus in lower crust or down to 60 kilometres (37 mi), and S means shallow event with macroseismic or instrumental evidence for a focus in the upper crust (Bundschuh & Alvarado 2012, p. 326, tab. 12.1). Some values in the Depth column rounded to the nearest mile.
^In the Start and End columns, dates listed represent upper and lower bounds for the relevant event. In the Unit column, million years ago written as Ma, and billion years ago as Ga.
^Though event dated with samples from the Polochic–Motagua Faults or the Isthmus of Tehuantepec (Bundschuh & Alvarado 2012, pp. 348–350, 486–499, 550, Casas-Peña et al. 2021, p. 209). Basement samples north of the Faults have returned mostly Triassic and some Silurian ages (Bundschuh & Alvarado 2012, pp. 348, 501). However, Casas-Peña et al. 2021, p. 209 note 'abundant ca. 1.0 Ga inherited zircon' and 1.02–0.91 Ga gneisses, amphibolites, and anorthosites in or near the Chiapas Massif, and 'abundant 1.2–0.9 Ga zircon' and 'a significant number of 1.6–1.5 Ga detrital zircon grains' in the Maya Mountains (both within the Maya Block proper rather than its border zones). Furthermore, Martens 2009, pp. v, 5 assert that 'isotope geochemistry and U/Pb zircon geochronology have demonstrated that the bulk of the Maya Block crust was generated during the 1.5–1.0 Ga period' and that 'the scarcity of older zircon ages as well as model ages suggest that the bulk of the Maya Block crust was generated during the 1.5–1.0 Ga period.'
^Though basement in the Yucatan Platform (ie northern portion of the Maya Block) 'is only known from Chicxulub ejecta suggesting ~545 Ma granitic basement and from a borehole on the peak ring of the Chicxulub crater that drilled into a ~326 Ma granitic pluton' (Casas-Peña et al. 2021, p. 209). Guzman-Hidalgo et al. 2021, p. 7 likewise report basement ages in the northern Yucatan Platform as circa 546, circa 545, circa 410, and circa 336.3–331.7 Ma.
^Alternative models date the formation of the present-day Caribbean to during 130–80 million years ago (Bundschuh & Alvarado 2012, p. 211).
^Event recorded by 'a well-dated, 120 Ma-old subduction complex along the northern edge of the Chortis block presently exposed on the southern margin of the Motagua valley of Guatemala' (Bundschuh & Alvarado 2012, p. 212).
^Martens 2009, pp. 86–89, 101, 109 suggest that the Greater Antilles Arc, rather than the Chortis Block, was the first crustal segment of the Caribbean Plate to collide into the Maya Block during 77.4–73.6 Ma.
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