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Comparing rock and fossil records in the deep sea

This document compares rock and fossil records in the deep sea by analyzing data on coccolithophores and foraminifera from the North Atlantic. It finds that diversity patterns in the deep sea fossil record are largely explained by variations in sampling effort over time rather than correlations with the deep sea rock record. The study aims to also analyze corresponding land-based rock and fossil records to further test the influence of rock biases on reconstructing diversity histories from the fossil record.

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Comparing rock and fossil records in the deep sea Graeme T. Lloyd, Andrew B. Smith and Jeremy R. Young
Fossil record is our only record of the diversification of life
Diversity correlates with rock record on land Peters and Foote 2001 Smith and McGowan 2007
An alternative record • Calcareous microfossils such as coccolithophores have land-based and deep sea records • i.e., two diversity records and two rock records • What is the relationship between these records? • How much does the rock record influence diversity patterns?
The database • Study groups are Coccolithophores and planktic Foraminifera • Novel compilation from North Atlantic • Compiled from 40 years ODP/DSDP data • 64,077+ occs from 20,723+ samples • High temporal resolution (biozones)
Deep sea species richness
Deep sea genus richness
Deep sea rock record
Correlation tests • First both time series were log-transformed • Long term test: – Simple correlation • Short term tests: – First differences (absolute) – Moving average differences (relative to long term trend) • Degree (rho) and significance (p) of correlations determined using Spearman rank
Deep sea long-term correlation
Deep sea short-term correlation I
Deep sea short-term correlation I
Deep sea short-term correlation II
Deep sea short-term correlation II
Modeling
Modeling results
Modeling results
Subsampling
Subsampling results
Conclusions • Deep sea diversity curve largely explicable by sampling • Apparent rise in nannofossil diversity to present strongly associated with rise in sampling
The other side of the story • What about the land-based record for the same groups? • Sampling strategy based on distribution charts from primary literature • Rock record measure is number of localities
Two rock records
Two fossil records
Summary • Both land and sea have measurable rock biases that follow different trajectories over geological time • Will allow a clear and explicit test of how important a role these play in shaping our fossil record