Deep time records showcase: Earth Systems

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Antony Wright
6 years ago
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1 What is Deep Time? Most geoscientists view Deep Time as pertaining to the pre- Quaternary (>10ka [10 4 ]) Last 10ka witnessed a short duration under anomalous conditions of an Icehouse climate state Earth processes operate on a continuum of temporal, spatial, and parametric scales represented in records on the order of Long-term records of Earth s dynamic state; preserves the results of multiple large-scale experiments in environmental change

Synergistic physical system of interrelated phenomena Governed by complex processes involving the geosphere, atmosphere,

2 CHAPMAN S PEAK LAINGSBURG Deep time records showcase: Environmental disturbances unknown from the recent Feedbacks that occur on longer time scales in response to perturbation that are different than those observable today (pre-human responses) Earth Systems Synergistic physical system of interrelated phenomena Governed by complex processes involving the geosphere, atmosphere, hydrosphere, cryosphere, and biosphere Interactions of chemical, physical, biological and dynamical processes extending over spatial & temporal scales

3 How is Deep Time told? 542 PALEOZOIC MESOZOIC 66.5 CENOZOIC Geochronology The organization of exposures of rocks into a standard chronological sequence The science of dating and determining the time sequence of events in the history of the Earth (Neuendorf et al. 2005) Assembled from rock sequences stacked and segmented into relative units based on their unique fossil and physical content.

4 Is it like African Time? Before radiometric dating techniques, the Geologic Column was assembled based upon the basic Laws of Stratigraphy (Steno ) Law of Superposition Law of Original Horizontality Law of Original Lateral Continuity Principle of cross-cutting relationships Principle of inclusions

Geochronology & Biostratigraphy PERMIAN-TRIASSIC VERTEBRATE ZONATION Fossil Assemblages of various unique organisms exhibit an unique stratigraphic range in the rock record Biostratigraphy

5 Geochronology & Biostratigraphy PERMIAN-TRIASSIC VERTEBRATE ZONATION Fossil Assemblages of various unique organisms exhibit an unique stratigraphic range in the rock record Biostratigraphy groups events into zones, and show only the events that define zone boundaries Advances in computational algorithms allow for stratigraphic sequencing of large data sets with increased reproducibility

Or, is it measured like Western time? GEOCHRONOMETRY Methods to determine numerical intervals of geologic time in units of years (Zalasiewicz et al.

6 Or, is it measured like Western time? GEOCHRONOMETRY Methods to determine numerical intervals of geologic time in units of years (Zalasiewicz et al., 2004) EARTH-TIME Project refining numeric dates to within 100,000 years Restructuring of Deep Time Astronomical tuning Earth s orbital motion affects the development of the rock record (back 40 myr) Changes in Earth s angle of the globe s spin axis, the path of its orbit, and the orientation of its axis relative to the Sun change cyclically and, in turn, influence climate.

At # -2; At Mass -4) Loss of Beta particle Electron loss turns neutron to proton

7 GEOCHRONOLOGY = RADIOMETRIC Isotopes differ in # neutrons; stable & unstable Spontaneous decay Parent-to-Daughter Loss of Alpha particle Helium atom (2p, 2n; At # -2; At Mass -4) Loss of Beta particle Electron loss turns neutron to proton (At # +1; At mass 0) Capture of Beta Turns proton to neutron (At # -1; At mass 0) DATING

8 If so, How? t 1 = 1+ λ ln Where : t = the age of the rock/mineral D = number of atoms of daughter product P = number of atoms of parent ln = natural log 2 λ = decay constant t 12 / ln = λ D P Rubidium87 -Strontium x Traceamounts in Igneous & Metamorphic Rx; >100 MY Thorium232 - Lead x Zircons widespread in Igneous & Metamorphic Rx Potassium 40 - Argon x 10 9 Uranium Lead x 10 9 Zircons widespread in Igneous & Metamorphic Rx Uranium Lead x 10 9 Zircons widespread in Igneous & Metamorphic Rx Carbon 14 - Nitrogen Yr

African Time with Western Numeric Function: Non-Radiometric Dating Techniques Varved deposits Sediment couplet of summer (coarse) & winter (very fine from

9 African Time with Western Numeric Function: Non-Radiometric Dating Techniques Varved deposits Sediment couplet of summer (coarse) & winter (very fine from suspension) clastics Deposited in response to yearly fluctuation in sedimentation. Capable of determining lake histories (e.g., Lake Baikal >200,000 varves).

Why is it important for South Africa? 23 65.5 145 199 252.6* (+/- 0.

10 Why is it important for South Africa? * (+/- 0.2) Dates after Gradstein et al., 2004 * after Mundil et al. 2004

geologic age of Earth - about 4.6 billion years

Geologic Time Geologic Time geologic age of Earth - about 4.6 billion years Geologic Time very difficult to appreciate from our human perspective necessary to understand history of Earth two basic ways