ACTIVITY: THE FOSSIL RECORD Goals for Student Learning: Learn principles of dating (not the Hinge kind) Learn idea of stratigraphy Learn principles of chronology Background Knowledge: Types of dating, relative and absolute Principles of stratigraphy Introduction: This lab will not only help you learn about some of the main geological considerations relevant to primate and human evolution, but also the basic understanding of archaeological dating in general. Geology can tell us what environment organisms lived in, how these environments changed through time, and most importantly, the age of fossils and tools. Understanding exactly what materials you can and cannot date along with recognizing the appropriate dating method is critical to knowing the basics of the archaeological and fossil record. The activities below pose questions regarding the dating and ordering of both geological layers and archaeological artifacts and fossils. Each activity will be done individually, but definitely consult with other students to check the answers and to make sure you understand the reasoning behind the answers. *This lab can be completed on your own, it does not require class attendance. Part 1. These artifacts are from various contexts from multiple sites which need to be dated. You will need to decide which dating technique/s is the most appropriate to obtain a date for each item. You must also explain why the technique/s you chose is/are the best for that artifact type and/or context. Example: Ostrich shell beads found at a site in South Africa: Electron Spin Resonance would work best because ESR specifically dates carbonates. Artifact A - part of a basket recovered from a pit in Utah (hint: what is a basket made of?): Artifact B - a fossil hominin found between two layers of volcanic ash in eastern Africa: Artifact C - a wood beam sample excavated from a room of a pueblo site in New Mexico: Artifacts D - buried maize cobs excavated from a Mandan village in western North Dakota: 1Name__________________________ Date__________________________ Artifacts E - coin/bottles (depends on which one your assemblage has) recovered from the base of a well at a historic farmstead (don't overthink this one): Artifact F - Obsidian (volcanic glass) recovered from a Mesoamerican tool processing site: Artifact G - teeth excavated from a cave in France: Artifact H - charcoal recovered from a hearth at the base of Monk's mound at Cahokia in IL: Artifact I - burned blade cores found at a Neandertal site in southeastern France: Sample J - Neandertal fossil recovered between two flood events (i.e., sand layers) near Neander Valley, Germany (assume the sample was taken correctly): Activity 1.a What can E. tell us about superpositioning (which came first) and thus understanding that our well is at least how old? Activity 1.b With Artifacts B. and J., are the dates actually for the artifacts or something else? Explain. Activity 1.c With Artifact C, will the date tell us how old that particular room of the pueblo is (i.e., when it was constructed)? Why or why not? 2Name__________________________ Date__________________________ Part 2 - Dating Specifics One of the major methods of chronometric or absolute dating in archaeology is Radiocarbon (C14) dating. The half-life of C14 is 5,730 years. This means that it takes 5,730 years for half of the Carbon-14 originally present to decay into Nitrogen-14 (N14). 1. You are interested in dating preserved seeds that were found enmeshed within the many footprints in an ancient human trackway in White Sands, NM. Your analysis indicates that 90% of the original C14 has decayed. How old are the footprints? Use the Decay Curve below to answer this question. Your Answer: 2. Approximately how much radiocarbon remains in a sample after 35,000 years? 3Name__________________________ Date__________________________ 3. You are interested in dating a fossil that was found immediately beneath a volcanic layer at a new Ethiopian site. Your analysis of the volcanic layer shows that 0.1% of the original K40 has become Ar40 and is thus at least 1.25 million years old. From other stratigraphic layers immediately above and below the volcanic layer you just dated, your paleomagnetic samples provide a "Reversed" reading. Using the Paleomagnetism chart below, determine if the paleomagnetic reading of "Reversed" is consistent with the K/Ar date you've just analyzed. 3a: Your answer (consistent/inconsistent): 3b: Circle the correct Polarity Interval In Millions of Years Normal Polarity Interval Reverse Polarity Interval 0.000-0.780 C1n BRUNHES 0.780-0.990 C1r.1r MATUYAMA 0.990-1.070 C1r.1n Jaramillo 1.070-1.770 C1r.2r MATUYAMA 1.770-1.950 C2n Olduvai 1.950-2.140 C2r.1r MATUYAMA 2.140-2.150 C2r.1n Reunion 2.150-2.581 C2r.2r MATUYAMA 2.581-3.040 C2An.1n GAUSS 3.040-3.110 C2An.1r Kaena 3.110-3.220 C2An.2n GAUSS 3.220-3.330 C2An.2r Mammoth 3.330-3.580 C2An.3n GAUSS 3.580-4.180 C2Ar GILBERT 4.180-4.290 C3n.1n Cochiti 4.290-4.480 C3n.1r GILBERT 4.480-4.620 C3n.2n Nunivak 4.620-4.800 C3n.2r GILBERT 4.800-4.890 C3n.3n Sidufjall 4.890-4.980 C3n.3r GILBERT 4.980-5.230 C3n.4n Thvera 5.230-5.894 C3r GILBERT Cande, S.C. and D.V. Kent, Revised calibration of the geomagnetic polarity time scale for the Late Cretaceous and Cenozoic, Journal of Geophysical Research, 100, 6093-6095, 1995 4Name__________________________ Date__________________________ Part 3 - Biochronology Most fossil sites are dated first by biochronology or "faunal dating". The animal species found at the site are compared to those from sites of known age in order to estimate the age of the new site. At sites relevant to human evolution, pig fossils have proven very useful for this purpose. The above graph gives you a phylogeny of fossil pigs and their time ranges for the past 6 million years. These dates are based on absolute dating techniques. Using this information, place the following African sites in correct chronological order, from oldest to youngest. Each site has at least two pig species present, as indicated below. Site: Hadar South, Ethiopia Kolpochoerus afarensis Date Range:_____________ Notochoerus euilus Date Range:_____________ Nyanzachoerus kanamensis Date Range:_____________ Site: Hadar North, Ethiopia Kolpochoerus limnetes Date Range:_____________ Phacochoerus modestus Date Range:_____________ Site: Tulu Bor, Kenya Nyanzachoerus kanamensis Date Range:_____________ Kolpochoerus limnetes Date Range:_____________ Notochoerus euilus Date Range:_____________ Notochoerus scotti Date Range:_____________ Potomachoerus porcus Date Range:_____________ Site: Makapansgat, South Africa Notochoerus scotti Date Range:_____________ Metridiochoerus andrewsi Date Range:_____________ The correct order of sites (oldest to youngest): 1. 2. 3. 4. 5Name__________________________ Date__________________________ Time ranges of fossil suids of Africa: