Tens of Crater Diameter Distances From Crater Center

To further test whether our stage 1 and 2 reset fission-track ages (see Fission-Track Results below) represent an age for the Kentland crater, we initiated a stage 3 study, collecting and analyzing twenty additional St. Peter Sandstone samples, including subsurface core samples from Franklin, Clark, and Clay Counties, Indiana, obtained from the Indiana Geological Survey core library, and outcrop samples from Mattheson and Buffalo Rock State Parks, in La Salle County, Illinois (Fig. 1). Radial distances range from 11 to 23 crater diameter distances (138-302 km) from sample sites to the crater center, clearly outside our hypothetical zone of

AFTSolve model time-temperature history

120 160

200 160 120 80 40 0

Fig. 4. Model (AFTSolve) time-temperature history for composite of St. Peter Sandstone apatite fission-track samples 202-01, 202-02, and 202-03 from Newton County stone quarry, crater center, Kentland, IN. Shaded regions show all fits generated by model simulation (outer shaded region-acceptable fits; inner shaded region-good fits); solid line represents best-fit model. Models are poorly constrained at temperatures above 150°C. See text for discussion.

indirect-impact-related cooling and exhumation. The stage 3 samples were treated and analyzed similarly to the stage 1 samples described above, with one exception; no modeling of track lengths was done.

From cores 307-B7-Gulf Oil and 307-B4-Gulf Oil in Franklin County we sampled 244.3 km from the crater center at depths of 383-387 m (samples 336-1 to 336-4); we sampled 250.8 km from the crater center from cores 305-B5-Gulf Oil and 305-B6-Gulf Oil in Franklin County at depths of 357-358 m (samples 336-5, 336-6); from cores 309-B2-Gulf Oil, 309-B3-Gulf Oil, and 309-B4-Gulf Oil in Franklin County we sampled 236.6 km from the crater center at depths of 449-452 m (samples 336-7 to 336-9); we sampled 170.3 km from the crater center at depths of 448-449 m from core 332-B3-Indiana Gas/Water in Clay County (sample 336-10); and from core 332-B1-Indiana Gas/Water in Clark County we sampled 302.2 km from the crater center at a depth of 449 m (sample 336-11).

Outcrop samples 336-12 to 336-17 were collected from the scenic gorge cut into the St. Peter Sandstone at Mattheson State Park in La Salle County, Illinois, 145 km from the crater center. Outcrop samples 336-18 to

200 160 120 80 40 0

Fig. 4. Model (AFTSolve) time-temperature history for composite of St. Peter Sandstone apatite fission-track samples 202-01, 202-02, and 202-03 from Newton County stone quarry, crater center, Kentland, IN. Shaded regions show all fits generated by model simulation (outer shaded region-acceptable fits; inner shaded region-good fits); solid line represents best-fit model. Models are poorly constrained at temperatures above 150°C. See text for discussion.

Fig. 5. Model (AFTSolve) time-temperature history for composite of St. Peter Sandstone apatite fission-track samples 290-5, 290-6, and 290-7, 31-53 km from crater center. Shaded regions show all fits generated by model simulation (outer shaded region-acceptable fits; inner shaded region-good fits); solid line represents best-fit model. Models are poorly constrained at temperatures above 150°C. See text for discussion.

Fig. 5. Model (AFTSolve) time-temperature history for composite of St. Peter Sandstone apatite fission-track samples 290-5, 290-6, and 290-7, 31-53 km from crater center. Shaded regions show all fits generated by model simulation (outer shaded region-acceptable fits; inner shaded region-good fits); solid line represents best-fit model. Models are poorly constrained at temperatures above 150°C. See text for discussion.

336-20 were collected nearby at Buffalo Rock State Park, also in La Salle County, Illinois, 138 km from center of the crater.

Was this article helpful?

0 0

Post a comment