Flooding of a carbonate platform: The Sian Kaʼan Wetlands, Yucatán, Mexico—A model for the formation and evolution of palustrine carbonate factories around the modern Caribbean Sea and in the depositional record

Abstract

The dynamic inter‐relationships between marine and freshwater carbonate depositional environments are illustrated in the Sian Ka'an Wetlands, a 5 280 km2 complex of groundwater‐fed freshwater marshes, lakes and brackish coastal lagoons in the South‐East Yucatán Peninsula (Mexico). The Yucatán Platform was subaerially emergent and extensively karstified during the last glacial maximum at 18, 000 yr bp. The Late Holocene transgression has caused progressive reflooding of the continental margin, backstepping of the MesoAmerican Reef and encroachment of coastal environments into the platform interior as rising groundwaters flood an interconnected cave and sinkhole system and feed seasonal marshes above. The Sian Ka'an Wetlands form a vast palustrine carbonate factory which is directly juxtaposed and dynamically linked with the marine carbonate factory to seaward. Continuing sea‐level rise has caused synchronous landward migration of marginal marine and freshwater environments as beach barriers were breached and palustrine sloughs flooded to form marginal marine seagrass lagoons. The Rio Hondo Fault conditions fluid inflow while the sub‐environments of the Sian Ka'an Wetlands reflect tectonic controls on microtopography and hydroperiod. Modern analogues for the Sian Ka'an Wetlands include the Florida Everglades, formed during transgression of the Florida Platform, and relict marsh environments preserved on leeward shores of Andros, Abaco and other Bahama islands. A wide range of ancient examples deposited in coastal and continental interior settings similarly reflect seasonal aquifer rise in response to marine transgression and/or onlap of late‐stage basin fill onto a karstified pediment. Freshwater palustrine carbonate factories on carbonate platforms are transient deposystems, controlled by subtle water depth, climate, vegetation and hydrological factors while being critically sensitive to sea‐level changes and tectonics. The preservation potential of palustrine carbonates may be relatively low in coastal settings due to erosion or shallow marine overprinting, while greater further inland where marine flooding is rarer and in tectonically subsident continental interior basins where accommodation space is continuously created.

Facies distribution and depositional cycles in lacustrine and palustrine carbonates: The Lutetian–Aquitanian record in the Paris Basin

“…In the fossil record, palustrine carbonates have been identified in numerous settings associated with deposits from internal ramps, lagoons, rivers and lakes (Alonso‐Zarza & Wright, 2010a). These carbonates are often linked to significant underlying karstic aquifer systems (Platt & Wright, 2023). These aquifers can supply the necessary CaCO 3 for carbonate formation in marshes through rising groundwaters (“Groundwater Dependent Carbonate Factories” by Platt & Wright, 2023).…”

“…These carbonates are often linked to significant underlying karstic aquifer systems (Platt & Wright, 2023). These aquifers can supply the necessary CaCO 3 for carbonate formation in marshes through rising groundwaters (“Groundwater Dependent Carbonate Factories” by Platt & Wright, 2023). Therefore, the appearance and development of palustrine carbonates in the fossil record can be interpreted in response to the aquifer level rising due to marine transgression in coastal settings or regional watershed responses to inland basin filling.…”

“…Nonetheless, MacNeil and Jones (2006) show that palustrine carbonates developed during sea-level fall in ancient coastal areas. In the same way, Platt and Wright (2023) suggest that palustrine deposits occurring in inland basins may have been influenced by sea level due to ephemeral connections with the marine domain. The coastal realm, even if predominantly non-marine, could therefore exhibit cyclicity similar to that of the marine realm.…”

“…This definition, although generic, has limitations in ancient coastal environments since it lacks criteria for determining in which environments carbonates were deposited: non‐marine (lacustrine, palustrine) or marine (lagoons). The coasts of the Yucatán, Florida and Bahamas platforms are a perfect example of the close spatial relationship that can exist between non‐marine (mainly palustrine, brackish to freshwater environments) and marine (lagoon, beach barriers, reefs …) carbonates (Platt & Wright, 2023). Moreover, foraminifera have even been found in Cenozoic and Quaternary lake deposits, attesting a marine water influence (Dye & Barros, 2005; Strotz, 2015; Lettéron et al., 2017; Pint et al., 2017; Fritz et al., 2018), while Warren and Kendall (1985) suggest that the sulphate supply leading to gypsum precipitation in coastal salinas/playas comes from marine groundwater.…”

Lacustrine and palustrine carbonates in a Brigantian (late Dinantian) intrashelf basin in the Derbyshire carbonate platform

“…Palustrine systems were originally defined as lake margin carbonates deposited in freshwater and subsequently modified by pedogenesis (Flügel, 2004; Freytet & Verrechia, 2002). However, the definition of palustrine systems now includes fresh water carbonate facies deposited in marginal marine settings linked to ground water variations driven by sea level and climatic changes (Alonso‐Zarza, 2003; Alonso‐Zarza & Wright, 2010; Platt & Wright, 1992, 2023).…”