From lagoons to mud mounds: palaeoecology of the Givetian to Frasnian stromatoporoids from the Holy Cross Mountains, Poland

Abstract

Stromatoporoids are an extinct group of Palaeozoic sponges that dominated the Devonian carbonate buildups. Although their general environmental requirements are known, their palaeoecological preferences at genus level are less studied. Seven stromatoporoid associations are distinguished within the Givetian (Middle Devonian; associations 1–3) and Frasnian (Upper Devonian; associations 4–7) of the Holy Cross Mountains in Poland, namely: (1) Arctostroma–Pseudoactinodictyon; (2) Actinostroma–Clathrocoilona; (3) Atelodictyon–Stachyodes; (4) Amphipora–Pseudoactinodictyon; (5) stromatoporoid–microbialite bafflestone and bindstone; (6) Stictostroma–tabulate corals; and (7) Hermatoporella–Stictostroma. Stromatoporoid associations 1–3 are late Givetian to earliest Frasnian in age, while associations 4–7 are from the early to middle Frasnian. Associations 1 and 4 occupied calm and shallow parts of the carbonate platform, associations 2 and 7 thrived in more agitated waters, whereas other associations inhabited the deeper, low-energy environments and mud mounds of the platform slope. General stromatoporoid diversity at genus level is high, but individual associations consist of 4–10 genera. Stromatoporoids of associations 1–2 and 7 are overturned and/or broken/redeposited, and hydrodynamically unstable, sediment-laden facies dominate the stromatoporoid-bearing Devonian carbonate platform facies of the Holy Cross Mountains. Lagoonal and biohermal environments were inhabited by dendroid, laminar and domical stromatoporoids, whereas digitate shapes are common within the associations that formed in more agitated water. Most representatives of the order Clathrodictyida were prone to physical destruction and inhabited low-energy settings. Genera having skeleton supported by thick pillars or network of oblique elements, less affected by physical skeletal breakage, thrived in agitated waters.