nlFEB2011

The Cochise County Rock
Monthly Newsletter of the Sunsites Gem & Mineral Club
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"Finding and Grinding Rocks in Cochise County, Arizona since 1965"
February 2011
This issue edited by Don Hammer
- _______________________________________________________________
- The next General Meeting of the Sunsites Gem & Mineral Club is on Monday February 14, 2011 at 7:00 pm at the Sunsites Community Center. Our program will be a video from the series, "How the Earth Works" by Professor Michael E. Wysession of Washington University in St. Louis entitled "The Rock Cycle - Matter in Motion". Remember to bring your best specimen from the January field trip for the rock contest.
Minutes of the General Meeting on January 10, 2011
President Diane Dunn opened the meeting by introducing herself as the Club's new president after which she made a few opening remarks and then welcomed new members and visitors.
The first item on the agenda was to approve the Minutes of the last General Meeting which were accepted without discussion and without a vote.
Walter gave the Treasurer's Report which was accepted by voice vote.
The next item was voting on the 2011 Annual Budget Proposal presented
by Walter. Copies of the Budget Proposal were distributed to the members and following a brief explanation of the budget, Diane called for questions and discussion after which a motion was made to accept
the Budget as presented. It was accepted by voice vote.
Henri then gave a brief report on the last two Field Trips to San Simon and the Johnson Mine, both of which were very well attended.
This month's Field Trip will take place on January 23rd to Cascabel in search of red/orange jasper and gypsum. Members will meet at Ed's Feed Store in Benson at 9:00 for departure at 9:15. Four-wheel drive
vehicles will be necessary so carpooling is encouraged.
Henri proposed the possibility of a night time Field Trip for February or March to observe mineral fluorescence in rocks. He asked for a show of hands by those who would be interested and the response
was positive. An announcement will be made in the News Letter.
After intermission, the prize of free raffle tickets was given to Cherie and Jim Robb for best geode from the San Simon trip and to Zoe and Carl Schnabel for best specimen from the Johnson Mine.
Henri brought a half dozen nice rocks for the raffle and then members were treated to a video lecture on geology by Professor Michael Wysession of Washington University in St. Louis, entitled "How
Geology Impacts History".
Respectfully submitted, Jim Brower, Secretary
January Field Trip
On Sunday January 23, 29 members and two guests assembled in Benson at Ed Fenn's store at 9 am and after a general orientation by Ed, headed north on the Pomerene and Cascabel roads. The first 15 miles of Cascabel Road are now paved. We turned off about ½ mile before the Tres Alamos Wash to a small mesa-type overlook that provided excellent views of the San Pedro Valley, Tres Alamos and the surrounding mountain ranges. Ed brought extensive reference materials that he used to give an excellent overview of the valley, soils, geology, archeology, vegetation and watersheds. We then proceeded on the Cascabel Road to the turnoff and up the wash. At a stop on the main wash most members found some pieces of red and yellow jasper and some found gray, green and white and a deep, chocolate brown jasper. After an hour or so of collecting we continued up the wash, stopping at a gypsum deposit and then proceeding to the tracks. After everyone had an opportunity to observe and photograph the tracks, Ed read portions of a letter from Dr. Everett Lindsay of the Univ. of Arizona describing the tracks - see below. That area is a nice location to relax in so we did lunch there. After which some members left but many collected some gypsum and continued searching for jasper at various locations down through the wash. We thank Ed Fenn for organizing a very educational and productive trip to Teran Wash.
February Field Trip
We will go to Rock Creek Canyon in the Chiricahuas for chalcedony and fine layered sedimentary rocks. Meet at the Sunizona café (south of Mustang Mall) at 9 am on Saturday February 19 for a 9:15 departure. High clearance but not 4WD will be needed. Bring water, lunch, bags or pails, light digging tools, lawn chairs and sun protection.
March Field Trip
Mark your calendars now. Our March trip will be earlier than usual since we need a moon-less night to observe fluorescence in rocks. It's really amazing how some ordinary looking "leverites" that we normally overlook appear under UV light. On Saturday evening March 5 we will meet at the Benson Feed and Supply at 5:30 pm for a 5:45 departure. Sundown is about 6:20. If you have a portable UV light (black light) please call Henri at 384-0288 and let him know. Details will be in the March newsletter that will be distributed early.
Lapidary and Silversmith Classes
Our lapidary, silver soldering and wire wrapping classes are once again available so if you're interested call Larry Strout at 826-3991.
Dues are due. Dues are $15 for individuals and $25 for a family. Bring your dues to the next meeting or mail your check to Sunsites Gem & Mineral Club, PO Box 87, Pearce, Arizona 85625.
Club Calendar:
February
14 General Meeting
24 Board Meeting
March
5 Night Field Trip
14 General Meeting
31 Board Meeting
April
11 General Meeting
16 Field Trip
28 Board Meeting
May
9 General Meeting
14 Field Trip
26 Board Meeting
June
4 Club Picnic
Upcoming Regional Events
January 29- February 14
The Tucson Show www.tucsonshows.com
March
10-13 Rockhound Roundup - the Deming Show. Jewelry, rocks, minerals, displays and demonstrations, guided field trips and auctions. Bud Daily 575-267-4399; Jerry Abbey 575-543-8915 www.dgms.bravehost.com
Officers for 2011
President: Diane Dunn
V-President: Jack Light
Secretary: Jim Brower
Treasurer: Walter Sigel
Deleg-at-Large: Carl Schnabel
Hospit Coord: Zoe Schnabel
Field Trip Crd: Henri van den Bos
Past Pres: Paul McKnight 775-434-8395
Brontothere or Rhinocerus Tracks
Dr. Everett Lindsay of the University of Arizona had this to say about the tracks. You are correct in your knowledge about the tracks in that they have been investigated by me and at various times students at the University of Arizona. Unfortunately, however, nothing definitive has ever been written about the tracks. They occur in sediments that are mapped as the Mineta Formation by a former graduate student, Jeffrey Grover, in the Geosciences Department at the University of Arizona who described them in his Masters Thesis (1982).
We are sure these tracks were made by a large mammal, probably a rhinoceros or a brontothere. The lack of certainty stems from the lack of anything diagnostic about the tracks (other than their size) and uncertainty about the age of the Mineta Formation. The Mineta Formation is capped by volcanic rocks dated 25.1 Ma, so we know the mammal that made the tracks were big animals who lived some time before the Miocene Epoch. Large rhinos and large brontotheres lived in North America from about 30 to 45 my ago, and large rhinos continued in North America until about 5 my ago. Rhinos and brontotheres had similar feet as well as size, but nothing seen in the tracks is diagnostic for one or the other.
As a follow-up, I asked him about the possible other track-bearing exposures you mentioned:
Yes, all the tracks in the vicinity of the wash were made by the same inchnospecies; differences in individual tracks has been attributed to proximity to the water level. Those more to the west are larger and deeper, indicating very soft sediment; toward the northeast the tracks are more shallow, indicating- harder substrate. Unfortunately, the smaller tracks were exposed to the elements for some time, apparently, as we could detect no measurable toe prints in those tracks.
Brontotheriidae is a family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs. Superficially they looked rather like rhinos, although they were not true rhinos and are probably most closely related to horses. They lived around 56-34 million years ago, until the very close of the Eocene.
Brontotheres retain four toes on their front feet and three toes on their hind feet. Their teeth are adapted to shearing (cutting) relatively nonabrasive vegetation. Their molars have a characteristic W-shaped ectoloph (outer shearing blade).
The evolutionary history of this group is well known, due to an excellent fossil record in North America. The earliest brontotheres were rather small, no more than a meter in height, and were hornless. Brontotheres, over time, evolved massive body sizes, up to 2.5 m in height with bizarre hornlike skull appendages. For instance the North American brontothere Megacerops evolved large sexually dimorphic paired horns above their noses. The sexually dimorphic horns suggest that brontotheres were highly gregarious (social) and males may have performed some sort of head clashing behavior in competition for mates. However, unlike rhinos, the horns of brontotheres are composed of bone, the frontal bone and nasal bone, and were placed side-to-side rather than front-to-back. These bony extensions of the skull were probably covered with skin.
Brontotheres probably became extinct due to an inability to adapt to drier conditions and tougher vegetation (such as grasses) that spread during the Oligocene.
In addition to the horns, brontotheres had very robust neck vertebrae. Scientists think this suggests that they may have engaged in a head-butting, aggressive type of behavior. The horns may have played a protective function for the animal's brain and skull when butting heads with another.
Despite the fact that modern-day rhinos can be very aggressive with their horns, they do not engage in head-butting, but males use their horns for display and for goring male opponents. Horns help both male and female rhinos defend their territories.
Many brontotheres were browsers. Plant leaves and twigs provided abundant food for them.