Abstract
AbstractPreferential dissolution of the biogenic carbonate polymorph aragonite promotes preservational bias in shelly marine faunas. While field studies have documented the impact of preferential aragonite dissolution on fossil molluscan diversity, its impact on regional and global biodiversity metrics is debated. Epicontinental seas are especially prone to conditions that both promote and inhibit preferential dissolution, which may result in spatially extensive zones with variable preservation. Here we present a multifaceted evaluation of aragonite dissolution within the Late Cretaceous Western Interior Seaway of North America. Occurrence data of mollusks from two time intervals (Cenomanian/Turonian boundary, early Campanian) are plotted on new high-resolution paleogeographies to assess aragonite preservation within the seaway. Fossil occurrences, diversity estimates, and sampling probabilities for calcitic and aragonitic fauna were compared in zones defined by depth and distance from the seaway margins. Apparent range sizes, which could be influenced by differential preservation potential of aragonite between separate localities, were also compared. Our results are consistent with exacerbated aragonite dissolution within specific depth zones for both time slices, with aragonitic bivalves additionally showing a statistically significant decrease in range size compared with calcitic fauna within carbonate-dominated Cenomanian–Turonian strata. However, we are unable to conclusively show that aragonite dissolution impacted diversity estimates. Therefore, while aragonite dissolution is likely to have affected the preservation of fauna in specific localities, time averaging and instantaneous preservation events preserve regional biodiversity. Our results suggest that the spatial expression of taphonomic biases should be an important consideration for paleontologists working on paleobiogeographic problems.
Highlights
While the fossil record provides a unique window into past life on Earth, it is well known that it is both pervasively and nonuniformly biased (Raup 1976; Koch 1978; Foote and Sepkoski 1999; Alroy et al 2001; Allison and Bottjer 2011a)
Biomineralized remains have an increased preservation potential compared with soft-bodied tissues (Allison 1988; Briggs 2003), they are still influenced by various geologic and taphonomic processes (Kidwell and Jablonski 1983; Kidwell and Bosence 1991; Kidwell and Brenchley 1994; Best 2008; Hendy 2011)
Mineralogy has a strong and statistically significant impact on sampling probability within the proximal and distal offshore bathymetric zones and shows the highest contribution to deviance from the null model. This is further supported by the fact that while all aragonitic taxa have lower sampling proportions overall, both aragonitic bivalves and ammonites disproportionally decrease in sampling probability within the proximal offshore compared with calcitic bivalves
Summary
While the fossil record provides a unique window into past life on Earth, it is well known that it is both pervasively and nonuniformly biased (Raup 1976; Koch 1978; Foote and Sepkoski 1999; Alroy et al 2001; Allison and Bottjer 2011a). Taphonomic, and anthropogenic biases (such as the amount of available fossiliferous rock for sampling, variation in fossilization, and the degree to which the available rock record has been sampled) skew or remove information from the fossil record, leaving the remaining catalog of data uneven and incomplete. Biomineralized remains have an increased preservation potential compared with soft-bodied tissues (Allison 1988; Briggs 2003), they are still influenced by various geologic and taphonomic processes (Kidwell and Jablonski 1983; Kidwell and Bosence 1991; Kidwell and Brenchley 1994; Best 2008; Hendy 2011). IPliacdednrceess:(5h2t.t9p0:./76/.1c4r2e,aotniv0e2cNoomvm20o21nsa.to1r1g:0/8l:i1c7e, nsusbejse/ctbtyo/th4e.0C/am), bwridhgiecChorpeeterrmmistsof uusner,easvtariliacbteledat https://wwwr.cea-musberi,ddgeis.otrrgib/cuotrieo/tne,rmans.dhtrtpesp:/r/oddoiu.ocrgti/o1n0.1i0n17a/npyabm.20e1d9i.u33m, provided the original work is properly cited
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